1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * kernel/workqueue.c - generic async execution with shared worker pool
   4 *
   5 * Copyright (C) 2002		Ingo Molnar
   6 *
   7 *   Derived from the taskqueue/keventd code by:
   8 *     David Woodhouse <dwmw2@infradead.org>
   9 *     Andrew Morton
  10 *     Kai Petzke <wpp@marie.physik.tu-berlin.de>
  11 *     Theodore Ts'o <tytso@mit.edu>
  12 *
  13 * Made to use alloc_percpu by Christoph Lameter.
  14 *
  15 * Copyright (C) 2010		SUSE Linux Products GmbH
  16 * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
  17 *
  18 * This is the generic async execution mechanism.  Work items as are
  19 * executed in process context.  The worker pool is shared and
  20 * automatically managed.  There are two worker pools for each CPU (one for
  21 * normal work items and the other for high priority ones) and some extra
  22 * pools for workqueues which are not bound to any specific CPU - the
  23 * number of these backing pools is dynamic.
  24 *
  25 * Please read Documentation/core-api/workqueue.rst for details.
  26 */
  27
  28#include <linux/export.h>
  29#include <linux/kernel.h>
  30#include <linux/sched.h>
  31#include <linux/init.h>
  32#include <linux/signal.h>
  33#include <linux/completion.h>
  34#include <linux/workqueue.h>
  35#include <linux/slab.h>
  36#include <linux/cpu.h>
  37#include <linux/notifier.h>
  38#include <linux/kthread.h>
  39#include <linux/hardirq.h>
  40#include <linux/mempolicy.h>
  41#include <linux/freezer.h>
  42#include <linux/debug_locks.h>
  43#include <linux/lockdep.h>
  44#include <linux/idr.h>
  45#include <linux/jhash.h>
  46#include <linux/hashtable.h>
  47#include <linux/rculist.h>
  48#include <linux/nodemask.h>
  49#include <linux/moduleparam.h>
  50#include <linux/uaccess.h>
  51#include <linux/sched/isolation.h>
  52#include <linux/sched/debug.h>
  53#include <linux/nmi.h>
  54#include <linux/kvm_para.h>
  55#include <linux/delay.h>
  56
  57#include "workqueue_internal.h"
  58
  59enum {
  60	/*
  61	 * worker_pool flags
  62	 *
  63	 * A bound pool is either associated or disassociated with its CPU.
  64	 * While associated (!DISASSOCIATED), all workers are bound to the
  65	 * CPU and none has %WORKER_UNBOUND set and concurrency management
  66	 * is in effect.
  67	 *
  68	 * While DISASSOCIATED, the cpu may be offline and all workers have
  69	 * %WORKER_UNBOUND set and concurrency management disabled, and may
  70	 * be executing on any CPU.  The pool behaves as an unbound one.
  71	 *
  72	 * Note that DISASSOCIATED should be flipped only while holding
  73	 * wq_pool_attach_mutex to avoid changing binding state while
  74	 * worker_attach_to_pool() is in progress.
  75	 */
  76	POOL_MANAGER_ACTIVE	= 1 << 0,	/* being managed */
  77	POOL_DISASSOCIATED	= 1 << 2,	/* cpu can't serve workers */
  78
  79	/* worker flags */
  80	WORKER_DIE		= 1 << 1,	/* die die die */
  81	WORKER_IDLE		= 1 << 2,	/* is idle */
  82	WORKER_PREP		= 1 << 3,	/* preparing to run works */
  83	WORKER_CPU_INTENSIVE	= 1 << 6,	/* cpu intensive */
  84	WORKER_UNBOUND		= 1 << 7,	/* worker is unbound */
  85	WORKER_REBOUND		= 1 << 8,	/* worker was rebound */
  86
  87	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_CPU_INTENSIVE |
  88				  WORKER_UNBOUND | WORKER_REBOUND,
  89
  90	NR_STD_WORKER_POOLS	= 2,		/* # standard pools per cpu */
  91
  92	UNBOUND_POOL_HASH_ORDER	= 6,		/* hashed by pool->attrs */
  93	BUSY_WORKER_HASH_ORDER	= 6,		/* 64 pointers */
  94
  95	MAX_IDLE_WORKERS_RATIO	= 4,		/* 1/4 of busy can be idle */
  96	IDLE_WORKER_TIMEOUT	= 300 * HZ,	/* keep idle ones for 5 mins */
  97
  98	MAYDAY_INITIAL_TIMEOUT  = HZ / 100 >= 2 ? HZ / 100 : 2,
  99						/* call for help after 10ms
 100						   (min two ticks) */
 101	MAYDAY_INTERVAL		= HZ / 10,	/* and then every 100ms */
 102	CREATE_COOLDOWN		= HZ,		/* time to breath after fail */
 103
 104	/*
 105	 * Rescue workers are used only on emergencies and shared by
 106	 * all cpus.  Give MIN_NICE.
 107	 */
 108	RESCUER_NICE_LEVEL	= MIN_NICE,
 109	HIGHPRI_NICE_LEVEL	= MIN_NICE,
 110
 111	WQ_NAME_LEN		= 24,
 112};
 113
 114/*
 115 * Structure fields follow one of the following exclusion rules.
 116 *
 117 * I: Modifiable by initialization/destruction paths and read-only for
 118 *    everyone else.
 119 *
 120 * P: Preemption protected.  Disabling preemption is enough and should
 121 *    only be modified and accessed from the local cpu.
 122 *
 123 * L: pool->lock protected.  Access with pool->lock held.
 124 *
 125 * K: Only modified by worker while holding pool->lock. Can be safely read by
 126 *    self, while holding pool->lock or from IRQ context if %current is the
 127 *    kworker.
 128 *
 129 * S: Only modified by worker self.
 130 *
 131 * A: wq_pool_attach_mutex protected.
 132 *
 133 * PL: wq_pool_mutex protected.
 134 *
 135 * PR: wq_pool_mutex protected for writes.  RCU protected for reads.
 136 *
 137 * PW: wq_pool_mutex and wq->mutex protected for writes.  Either for reads.
 138 *
 139 * PWR: wq_pool_mutex and wq->mutex protected for writes.  Either or
 140 *      RCU for reads.
 141 *
 142 * WQ: wq->mutex protected.
 143 *
 144 * WR: wq->mutex protected for writes.  RCU protected for reads.
 145 *
 146 * MD: wq_mayday_lock protected.
 147 *
 148 * WD: Used internally by the watchdog.
 149 */
 150
 151/* struct worker is defined in workqueue_internal.h */
 152
 153struct worker_pool {
 154	raw_spinlock_t		lock;		/* the pool lock */
 155	int			cpu;		/* I: the associated cpu */
 156	int			node;		/* I: the associated node ID */
 157	int			id;		/* I: pool ID */
 158	unsigned int		flags;		/* L: flags */
 159
 160	unsigned long		watchdog_ts;	/* L: watchdog timestamp */
 161	bool			cpu_stall;	/* WD: stalled cpu bound pool */
 162
 163	/*
 164	 * The counter is incremented in a process context on the associated CPU
 165	 * w/ preemption disabled, and decremented or reset in the same context
 166	 * but w/ pool->lock held. The readers grab pool->lock and are
 167	 * guaranteed to see if the counter reached zero.
 168	 */
 169	int			nr_running;
 170
 171	struct list_head	worklist;	/* L: list of pending works */
 172
 173	int			nr_workers;	/* L: total number of workers */
 174	int			nr_idle;	/* L: currently idle workers */
 175
 176	struct list_head	idle_list;	/* L: list of idle workers */
 177	struct timer_list	idle_timer;	/* L: worker idle timeout */
 178	struct work_struct      idle_cull_work; /* L: worker idle cleanup */
 179
 180	struct timer_list	mayday_timer;	  /* L: SOS timer for workers */
 181
 182	/* a workers is either on busy_hash or idle_list, or the manager */
 183	DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
 184						/* L: hash of busy workers */
 185
 186	struct worker		*manager;	/* L: purely informational */
 187	struct list_head	workers;	/* A: attached workers */
 188	struct list_head        dying_workers;  /* A: workers about to die */
 189	struct completion	*detach_completion; /* all workers detached */
 190
 191	struct ida		worker_ida;	/* worker IDs for task name */
 192
 193	struct workqueue_attrs	*attrs;		/* I: worker attributes */
 194	struct hlist_node	hash_node;	/* PL: unbound_pool_hash node */
 195	int			refcnt;		/* PL: refcnt for unbound pools */
 196
 197	/*
 
 
 
 
 
 
 
 198	 * Destruction of pool is RCU protected to allow dereferences
 199	 * from get_work_pool().
 200	 */
 201	struct rcu_head		rcu;
 202};
 203
 204/*
 205 * Per-pool_workqueue statistics. These can be monitored using
 206 * tools/workqueue/wq_monitor.py.
 207 */
 208enum pool_workqueue_stats {
 209	PWQ_STAT_STARTED,	/* work items started execution */
 210	PWQ_STAT_COMPLETED,	/* work items completed execution */
 211	PWQ_STAT_CPU_TIME,	/* total CPU time consumed */
 212	PWQ_STAT_CPU_INTENSIVE,	/* wq_cpu_intensive_thresh_us violations */
 213	PWQ_STAT_CM_WAKEUP,	/* concurrency-management worker wakeups */
 214	PWQ_STAT_REPATRIATED,	/* unbound workers brought back into scope */
 215	PWQ_STAT_MAYDAY,	/* maydays to rescuer */
 216	PWQ_STAT_RESCUED,	/* linked work items executed by rescuer */
 217
 218	PWQ_NR_STATS,
 219};
 220
 221/*
 222 * The per-pool workqueue.  While queued, the lower WORK_STRUCT_FLAG_BITS
 223 * of work_struct->data are used for flags and the remaining high bits
 224 * point to the pwq; thus, pwqs need to be aligned at two's power of the
 225 * number of flag bits.
 226 */
 227struct pool_workqueue {
 228	struct worker_pool	*pool;		/* I: the associated pool */
 229	struct workqueue_struct *wq;		/* I: the owning workqueue */
 230	int			work_color;	/* L: current color */
 231	int			flush_color;	/* L: flushing color */
 232	int			refcnt;		/* L: reference count */
 233	int			nr_in_flight[WORK_NR_COLORS];
 234						/* L: nr of in_flight works */
 235
 236	/*
 237	 * nr_active management and WORK_STRUCT_INACTIVE:
 238	 *
 239	 * When pwq->nr_active >= max_active, new work item is queued to
 240	 * pwq->inactive_works instead of pool->worklist and marked with
 241	 * WORK_STRUCT_INACTIVE.
 242	 *
 243	 * All work items marked with WORK_STRUCT_INACTIVE do not participate
 244	 * in pwq->nr_active and all work items in pwq->inactive_works are
 245	 * marked with WORK_STRUCT_INACTIVE.  But not all WORK_STRUCT_INACTIVE
 246	 * work items are in pwq->inactive_works.  Some of them are ready to
 247	 * run in pool->worklist or worker->scheduled.  Those work itmes are
 248	 * only struct wq_barrier which is used for flush_work() and should
 249	 * not participate in pwq->nr_active.  For non-barrier work item, it
 250	 * is marked with WORK_STRUCT_INACTIVE iff it is in pwq->inactive_works.
 251	 */
 252	int			nr_active;	/* L: nr of active works */
 253	int			max_active;	/* L: max active works */
 254	struct list_head	inactive_works;	/* L: inactive works */
 255	struct list_head	pwqs_node;	/* WR: node on wq->pwqs */
 256	struct list_head	mayday_node;	/* MD: node on wq->maydays */
 257
 258	u64			stats[PWQ_NR_STATS];
 259
 260	/*
 261	 * Release of unbound pwq is punted to a kthread_worker. See put_pwq()
 262	 * and pwq_release_workfn() for details. pool_workqueue itself is also
 263	 * RCU protected so that the first pwq can be determined without
 264	 * grabbing wq->mutex.
 265	 */
 266	struct kthread_work	release_work;
 267	struct rcu_head		rcu;
 268} __aligned(1 << WORK_STRUCT_FLAG_BITS);
 269
 270/*
 271 * Structure used to wait for workqueue flush.
 272 */
 273struct wq_flusher {
 274	struct list_head	list;		/* WQ: list of flushers */
 275	int			flush_color;	/* WQ: flush color waiting for */
 276	struct completion	done;		/* flush completion */
 277};
 278
 279struct wq_device;
 280
 281/*
 282 * The externally visible workqueue.  It relays the issued work items to
 283 * the appropriate worker_pool through its pool_workqueues.
 284 */
 285struct workqueue_struct {
 286	struct list_head	pwqs;		/* WR: all pwqs of this wq */
 287	struct list_head	list;		/* PR: list of all workqueues */
 288
 289	struct mutex		mutex;		/* protects this wq */
 290	int			work_color;	/* WQ: current work color */
 291	int			flush_color;	/* WQ: current flush color */
 292	atomic_t		nr_pwqs_to_flush; /* flush in progress */
 293	struct wq_flusher	*first_flusher;	/* WQ: first flusher */
 294	struct list_head	flusher_queue;	/* WQ: flush waiters */
 295	struct list_head	flusher_overflow; /* WQ: flush overflow list */
 296
 297	struct list_head	maydays;	/* MD: pwqs requesting rescue */
 298	struct worker		*rescuer;	/* MD: rescue worker */
 299
 300	int			nr_drainers;	/* WQ: drain in progress */
 301	int			saved_max_active; /* WQ: saved pwq max_active */
 302
 303	struct workqueue_attrs	*unbound_attrs;	/* PW: only for unbound wqs */
 304	struct pool_workqueue	*dfl_pwq;	/* PW: only for unbound wqs */
 305
 306#ifdef CONFIG_SYSFS
 307	struct wq_device	*wq_dev;	/* I: for sysfs interface */
 308#endif
 309#ifdef CONFIG_LOCKDEP
 310	char			*lock_name;
 311	struct lock_class_key	key;
 312	struct lockdep_map	lockdep_map;
 313#endif
 314	char			name[WQ_NAME_LEN]; /* I: workqueue name */
 315
 316	/*
 317	 * Destruction of workqueue_struct is RCU protected to allow walking
 318	 * the workqueues list without grabbing wq_pool_mutex.
 319	 * This is used to dump all workqueues from sysrq.
 320	 */
 321	struct rcu_head		rcu;
 322
 323	/* hot fields used during command issue, aligned to cacheline */
 324	unsigned int		flags ____cacheline_aligned; /* WQ: WQ_* flags */
 325	struct pool_workqueue __percpu __rcu **cpu_pwq; /* I: per-cpu pwqs */
 
 326};
 327
 328static struct kmem_cache *pwq_cache;
 329
 330/*
 331 * Each pod type describes how CPUs should be grouped for unbound workqueues.
 332 * See the comment above workqueue_attrs->affn_scope.
 333 */
 334struct wq_pod_type {
 335	int			nr_pods;	/* number of pods */
 336	cpumask_var_t		*pod_cpus;	/* pod -> cpus */
 337	int			*pod_node;	/* pod -> node */
 338	int			*cpu_pod;	/* cpu -> pod */
 339};
 340
 341static struct wq_pod_type wq_pod_types[WQ_AFFN_NR_TYPES];
 342static enum wq_affn_scope wq_affn_dfl = WQ_AFFN_CACHE;
 343
 344static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
 345	[WQ_AFFN_DFL]			= "default",
 346	[WQ_AFFN_CPU]			= "cpu",
 347	[WQ_AFFN_SMT]			= "smt",
 348	[WQ_AFFN_CACHE]			= "cache",
 349	[WQ_AFFN_NUMA]			= "numa",
 350	[WQ_AFFN_SYSTEM]		= "system",
 351};
 352
 353/*
 354 * Per-cpu work items which run for longer than the following threshold are
 355 * automatically considered CPU intensive and excluded from concurrency
 356 * management to prevent them from noticeably delaying other per-cpu work items.
 357 * ULONG_MAX indicates that the user hasn't overridden it with a boot parameter.
 358 * The actual value is initialized in wq_cpu_intensive_thresh_init().
 359 */
 360static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
 361module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
 362
 363/* see the comment above the definition of WQ_POWER_EFFICIENT */
 364static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
 365module_param_named(power_efficient, wq_power_efficient, bool, 0444);
 366
 367static bool wq_online;			/* can kworkers be created yet? */
 368
 369/* buf for wq_update_unbound_pod_attrs(), protected by CPU hotplug exclusion */
 370static struct workqueue_attrs *wq_update_pod_attrs_buf;
 
 
 371
 372static DEFINE_MUTEX(wq_pool_mutex);	/* protects pools and workqueues list */
 373static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
 374static DEFINE_RAW_SPINLOCK(wq_mayday_lock);	/* protects wq->maydays list */
 375/* wait for manager to go away */
 376static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
 377
 378static LIST_HEAD(workqueues);		/* PR: list of all workqueues */
 379static bool workqueue_freezing;		/* PL: have wqs started freezing? */
 380
 381/* PL&A: allowable cpus for unbound wqs and work items */
 382static cpumask_var_t wq_unbound_cpumask;
 383
 384/* PL: user requested unbound cpumask via sysfs */
 385static cpumask_var_t wq_requested_unbound_cpumask;
 386
 387/* PL: isolated cpumask to be excluded from unbound cpumask */
 388static cpumask_var_t wq_isolated_cpumask;
 389
 390/* for further constrain wq_unbound_cpumask by cmdline parameter*/
 391static struct cpumask wq_cmdline_cpumask __initdata;
 392
 393/* CPU where unbound work was last round robin scheduled from this CPU */
 394static DEFINE_PER_CPU(int, wq_rr_cpu_last);
 395
 396/*
 397 * Local execution of unbound work items is no longer guaranteed.  The
 398 * following always forces round-robin CPU selection on unbound work items
 399 * to uncover usages which depend on it.
 400 */
 401#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
 402static bool wq_debug_force_rr_cpu = true;
 403#else
 404static bool wq_debug_force_rr_cpu = false;
 405#endif
 406module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
 407
 408/* the per-cpu worker pools */
 409static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
 410
 411static DEFINE_IDR(worker_pool_idr);	/* PR: idr of all pools */
 412
 413/* PL: hash of all unbound pools keyed by pool->attrs */
 414static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
 415
 416/* I: attributes used when instantiating standard unbound pools on demand */
 417static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
 418
 419/* I: attributes used when instantiating ordered pools on demand */
 420static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
 421
 422/*
 423 * I: kthread_worker to release pwq's. pwq release needs to be bounced to a
 424 * process context while holding a pool lock. Bounce to a dedicated kthread
 425 * worker to avoid A-A deadlocks.
 426 */
 427static struct kthread_worker *pwq_release_worker __ro_after_init;
 428
 429struct workqueue_struct *system_wq __ro_after_init;
 430EXPORT_SYMBOL(system_wq);
 431struct workqueue_struct *system_highpri_wq __ro_after_init;
 432EXPORT_SYMBOL_GPL(system_highpri_wq);
 433struct workqueue_struct *system_long_wq __ro_after_init;
 434EXPORT_SYMBOL_GPL(system_long_wq);
 435struct workqueue_struct *system_unbound_wq __ro_after_init;
 436EXPORT_SYMBOL_GPL(system_unbound_wq);
 437struct workqueue_struct *system_freezable_wq __ro_after_init;
 438EXPORT_SYMBOL_GPL(system_freezable_wq);
 439struct workqueue_struct *system_power_efficient_wq __ro_after_init;
 440EXPORT_SYMBOL_GPL(system_power_efficient_wq);
 441struct workqueue_struct *system_freezable_power_efficient_wq __ro_after_init;
 442EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
 443
 444static int worker_thread(void *__worker);
 445static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
 446static void show_pwq(struct pool_workqueue *pwq);
 447static void show_one_worker_pool(struct worker_pool *pool);
 448
 449#define CREATE_TRACE_POINTS
 450#include <trace/events/workqueue.h>
 451
 452#define assert_rcu_or_pool_mutex()					\
 453	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
 454			 !lockdep_is_held(&wq_pool_mutex),		\
 455			 "RCU or wq_pool_mutex should be held")
 456
 457#define assert_rcu_or_wq_mutex_or_pool_mutex(wq)			\
 458	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
 459			 !lockdep_is_held(&wq->mutex) &&		\
 460			 !lockdep_is_held(&wq_pool_mutex),		\
 461			 "RCU, wq->mutex or wq_pool_mutex should be held")
 462
 463#define for_each_cpu_worker_pool(pool, cpu)				\
 464	for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];		\
 465	     (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
 466	     (pool)++)
 467
 468/**
 469 * for_each_pool - iterate through all worker_pools in the system
 470 * @pool: iteration cursor
 471 * @pi: integer used for iteration
 472 *
 473 * This must be called either with wq_pool_mutex held or RCU read
 474 * locked.  If the pool needs to be used beyond the locking in effect, the
 475 * caller is responsible for guaranteeing that the pool stays online.
 476 *
 477 * The if/else clause exists only for the lockdep assertion and can be
 478 * ignored.
 479 */
 480#define for_each_pool(pool, pi)						\
 481	idr_for_each_entry(&worker_pool_idr, pool, pi)			\
 482		if (({ assert_rcu_or_pool_mutex(); false; })) { }	\
 483		else
 484
 485/**
 486 * for_each_pool_worker - iterate through all workers of a worker_pool
 487 * @worker: iteration cursor
 488 * @pool: worker_pool to iterate workers of
 489 *
 490 * This must be called with wq_pool_attach_mutex.
 491 *
 492 * The if/else clause exists only for the lockdep assertion and can be
 493 * ignored.
 494 */
 495#define for_each_pool_worker(worker, pool)				\
 496	list_for_each_entry((worker), &(pool)->workers, node)		\
 497		if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
 498		else
 499
 500/**
 501 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
 502 * @pwq: iteration cursor
 503 * @wq: the target workqueue
 504 *
 505 * This must be called either with wq->mutex held or RCU read locked.
 506 * If the pwq needs to be used beyond the locking in effect, the caller is
 507 * responsible for guaranteeing that the pwq stays online.
 508 *
 509 * The if/else clause exists only for the lockdep assertion and can be
 510 * ignored.
 511 */
 512#define for_each_pwq(pwq, wq)						\
 513	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node,		\
 514				 lockdep_is_held(&(wq->mutex)))
 515
 516#ifdef CONFIG_DEBUG_OBJECTS_WORK
 517
 518static const struct debug_obj_descr work_debug_descr;
 519
 520static void *work_debug_hint(void *addr)
 521{
 522	return ((struct work_struct *) addr)->func;
 523}
 524
 525static bool work_is_static_object(void *addr)
 526{
 527	struct work_struct *work = addr;
 528
 529	return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
 530}
 531
 532/*
 533 * fixup_init is called when:
 534 * - an active object is initialized
 535 */
 536static bool work_fixup_init(void *addr, enum debug_obj_state state)
 537{
 538	struct work_struct *work = addr;
 539
 540	switch (state) {
 541	case ODEBUG_STATE_ACTIVE:
 542		cancel_work_sync(work);
 543		debug_object_init(work, &work_debug_descr);
 544		return true;
 545	default:
 546		return false;
 547	}
 548}
 549
 550/*
 551 * fixup_free is called when:
 552 * - an active object is freed
 553 */
 554static bool work_fixup_free(void *addr, enum debug_obj_state state)
 555{
 556	struct work_struct *work = addr;
 557
 558	switch (state) {
 559	case ODEBUG_STATE_ACTIVE:
 560		cancel_work_sync(work);
 561		debug_object_free(work, &work_debug_descr);
 562		return true;
 563	default:
 564		return false;
 565	}
 566}
 567
 568static const struct debug_obj_descr work_debug_descr = {
 569	.name		= "work_struct",
 570	.debug_hint	= work_debug_hint,
 571	.is_static_object = work_is_static_object,
 572	.fixup_init	= work_fixup_init,
 573	.fixup_free	= work_fixup_free,
 574};
 575
 576static inline void debug_work_activate(struct work_struct *work)
 577{
 578	debug_object_activate(work, &work_debug_descr);
 579}
 580
 581static inline void debug_work_deactivate(struct work_struct *work)
 582{
 583	debug_object_deactivate(work, &work_debug_descr);
 584}
 585
 586void __init_work(struct work_struct *work, int onstack)
 587{
 588	if (onstack)
 589		debug_object_init_on_stack(work, &work_debug_descr);
 590	else
 591		debug_object_init(work, &work_debug_descr);
 592}
 593EXPORT_SYMBOL_GPL(__init_work);
 594
 595void destroy_work_on_stack(struct work_struct *work)
 596{
 597	debug_object_free(work, &work_debug_descr);
 598}
 599EXPORT_SYMBOL_GPL(destroy_work_on_stack);
 600
 601void destroy_delayed_work_on_stack(struct delayed_work *work)
 602{
 603	destroy_timer_on_stack(&work->timer);
 604	debug_object_free(&work->work, &work_debug_descr);
 605}
 606EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
 607
 608#else
 609static inline void debug_work_activate(struct work_struct *work) { }
 610static inline void debug_work_deactivate(struct work_struct *work) { }
 611#endif
 612
 613/**
 614 * worker_pool_assign_id - allocate ID and assign it to @pool
 615 * @pool: the pool pointer of interest
 616 *
 617 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
 618 * successfully, -errno on failure.
 619 */
 620static int worker_pool_assign_id(struct worker_pool *pool)
 621{
 622	int ret;
 623
 624	lockdep_assert_held(&wq_pool_mutex);
 625
 626	ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
 627			GFP_KERNEL);
 628	if (ret >= 0) {
 629		pool->id = ret;
 630		return 0;
 631	}
 632	return ret;
 633}
 634
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 635static unsigned int work_color_to_flags(int color)
 636{
 637	return color << WORK_STRUCT_COLOR_SHIFT;
 638}
 639
 640static int get_work_color(unsigned long work_data)
 641{
 642	return (work_data >> WORK_STRUCT_COLOR_SHIFT) &
 643		((1 << WORK_STRUCT_COLOR_BITS) - 1);
 644}
 645
 646static int work_next_color(int color)
 647{
 648	return (color + 1) % WORK_NR_COLORS;
 649}
 650
 651/*
 652 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
 653 * contain the pointer to the queued pwq.  Once execution starts, the flag
 654 * is cleared and the high bits contain OFFQ flags and pool ID.
 655 *
 656 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
 657 * and clear_work_data() can be used to set the pwq, pool or clear
 658 * work->data.  These functions should only be called while the work is
 659 * owned - ie. while the PENDING bit is set.
 660 *
 661 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
 662 * corresponding to a work.  Pool is available once the work has been
 663 * queued anywhere after initialization until it is sync canceled.  pwq is
 664 * available only while the work item is queued.
 665 *
 666 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
 667 * canceled.  While being canceled, a work item may have its PENDING set
 668 * but stay off timer and worklist for arbitrarily long and nobody should
 669 * try to steal the PENDING bit.
 670 */
 671static inline void set_work_data(struct work_struct *work, unsigned long data,
 672				 unsigned long flags)
 673{
 674	WARN_ON_ONCE(!work_pending(work));
 675	atomic_long_set(&work->data, data | flags | work_static(work));
 676}
 677
 678static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
 679			 unsigned long extra_flags)
 680{
 681	set_work_data(work, (unsigned long)pwq,
 682		      WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
 683}
 684
 685static void set_work_pool_and_keep_pending(struct work_struct *work,
 686					   int pool_id)
 687{
 688	set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
 689		      WORK_STRUCT_PENDING);
 690}
 691
 692static void set_work_pool_and_clear_pending(struct work_struct *work,
 693					    int pool_id)
 694{
 695	/*
 696	 * The following wmb is paired with the implied mb in
 697	 * test_and_set_bit(PENDING) and ensures all updates to @work made
 698	 * here are visible to and precede any updates by the next PENDING
 699	 * owner.
 700	 */
 701	smp_wmb();
 702	set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
 703	/*
 704	 * The following mb guarantees that previous clear of a PENDING bit
 705	 * will not be reordered with any speculative LOADS or STORES from
 706	 * work->current_func, which is executed afterwards.  This possible
 707	 * reordering can lead to a missed execution on attempt to queue
 708	 * the same @work.  E.g. consider this case:
 709	 *
 710	 *   CPU#0                         CPU#1
 711	 *   ----------------------------  --------------------------------
 712	 *
 713	 * 1  STORE event_indicated
 714	 * 2  queue_work_on() {
 715	 * 3    test_and_set_bit(PENDING)
 716	 * 4 }                             set_..._and_clear_pending() {
 717	 * 5                                 set_work_data() # clear bit
 718	 * 6                                 smp_mb()
 719	 * 7                               work->current_func() {
 720	 * 8				      LOAD event_indicated
 721	 *				   }
 722	 *
 723	 * Without an explicit full barrier speculative LOAD on line 8 can
 724	 * be executed before CPU#0 does STORE on line 1.  If that happens,
 725	 * CPU#0 observes the PENDING bit is still set and new execution of
 726	 * a @work is not queued in a hope, that CPU#1 will eventually
 727	 * finish the queued @work.  Meanwhile CPU#1 does not see
 728	 * event_indicated is set, because speculative LOAD was executed
 729	 * before actual STORE.
 730	 */
 731	smp_mb();
 732}
 733
 734static void clear_work_data(struct work_struct *work)
 735{
 736	smp_wmb();	/* see set_work_pool_and_clear_pending() */
 737	set_work_data(work, WORK_STRUCT_NO_POOL, 0);
 738}
 739
 740static inline struct pool_workqueue *work_struct_pwq(unsigned long data)
 741{
 742	return (struct pool_workqueue *)(data & WORK_STRUCT_WQ_DATA_MASK);
 743}
 744
 745static struct pool_workqueue *get_work_pwq(struct work_struct *work)
 746{
 747	unsigned long data = atomic_long_read(&work->data);
 748
 749	if (data & WORK_STRUCT_PWQ)
 750		return work_struct_pwq(data);
 751	else
 752		return NULL;
 753}
 754
 755/**
 756 * get_work_pool - return the worker_pool a given work was associated with
 757 * @work: the work item of interest
 758 *
 759 * Pools are created and destroyed under wq_pool_mutex, and allows read
 760 * access under RCU read lock.  As such, this function should be
 761 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
 762 *
 763 * All fields of the returned pool are accessible as long as the above
 764 * mentioned locking is in effect.  If the returned pool needs to be used
 765 * beyond the critical section, the caller is responsible for ensuring the
 766 * returned pool is and stays online.
 767 *
 768 * Return: The worker_pool @work was last associated with.  %NULL if none.
 769 */
 770static struct worker_pool *get_work_pool(struct work_struct *work)
 771{
 772	unsigned long data = atomic_long_read(&work->data);
 773	int pool_id;
 774
 775	assert_rcu_or_pool_mutex();
 776
 777	if (data & WORK_STRUCT_PWQ)
 778		return work_struct_pwq(data)->pool;
 
 779
 780	pool_id = data >> WORK_OFFQ_POOL_SHIFT;
 781	if (pool_id == WORK_OFFQ_POOL_NONE)
 782		return NULL;
 783
 784	return idr_find(&worker_pool_idr, pool_id);
 785}
 786
 787/**
 788 * get_work_pool_id - return the worker pool ID a given work is associated with
 789 * @work: the work item of interest
 790 *
 791 * Return: The worker_pool ID @work was last associated with.
 792 * %WORK_OFFQ_POOL_NONE if none.
 793 */
 794static int get_work_pool_id(struct work_struct *work)
 795{
 796	unsigned long data = atomic_long_read(&work->data);
 797
 798	if (data & WORK_STRUCT_PWQ)
 799		return work_struct_pwq(data)->pool->id;
 
 800
 801	return data >> WORK_OFFQ_POOL_SHIFT;
 802}
 803
 804static void mark_work_canceling(struct work_struct *work)
 805{
 806	unsigned long pool_id = get_work_pool_id(work);
 807
 808	pool_id <<= WORK_OFFQ_POOL_SHIFT;
 809	set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
 810}
 811
 812static bool work_is_canceling(struct work_struct *work)
 813{
 814	unsigned long data = atomic_long_read(&work->data);
 815
 816	return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
 817}
 818
 819/*
 820 * Policy functions.  These define the policies on how the global worker
 821 * pools are managed.  Unless noted otherwise, these functions assume that
 822 * they're being called with pool->lock held.
 823 */
 824
 
 
 
 
 
 825/*
 826 * Need to wake up a worker?  Called from anything but currently
 827 * running workers.
 828 *
 829 * Note that, because unbound workers never contribute to nr_running, this
 830 * function will always return %true for unbound pools as long as the
 831 * worklist isn't empty.
 832 */
 833static bool need_more_worker(struct worker_pool *pool)
 834{
 835	return !list_empty(&pool->worklist) && !pool->nr_running;
 836}
 837
 838/* Can I start working?  Called from busy but !running workers. */
 839static bool may_start_working(struct worker_pool *pool)
 840{
 841	return pool->nr_idle;
 842}
 843
 844/* Do I need to keep working?  Called from currently running workers. */
 845static bool keep_working(struct worker_pool *pool)
 846{
 847	return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
 
 848}
 849
 850/* Do we need a new worker?  Called from manager. */
 851static bool need_to_create_worker(struct worker_pool *pool)
 852{
 853	return need_more_worker(pool) && !may_start_working(pool);
 854}
 855
 856/* Do we have too many workers and should some go away? */
 857static bool too_many_workers(struct worker_pool *pool)
 858{
 859	bool managing = pool->flags & POOL_MANAGER_ACTIVE;
 860	int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
 861	int nr_busy = pool->nr_workers - nr_idle;
 862
 863	return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
 864}
 865
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 866/**
 867 * worker_set_flags - set worker flags and adjust nr_running accordingly
 868 * @worker: self
 869 * @flags: flags to set
 870 *
 871 * Set @flags in @worker->flags and adjust nr_running accordingly.
 
 
 
 872 */
 873static inline void worker_set_flags(struct worker *worker, unsigned int flags)
 874{
 875	struct worker_pool *pool = worker->pool;
 876
 877	lockdep_assert_held(&pool->lock);
 878
 879	/* If transitioning into NOT_RUNNING, adjust nr_running. */
 880	if ((flags & WORKER_NOT_RUNNING) &&
 881	    !(worker->flags & WORKER_NOT_RUNNING)) {
 882		pool->nr_running--;
 883	}
 884
 885	worker->flags |= flags;
 886}
 887
 888/**
 889 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
 890 * @worker: self
 891 * @flags: flags to clear
 892 *
 893 * Clear @flags in @worker->flags and adjust nr_running accordingly.
 
 
 
 894 */
 895static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
 896{
 897	struct worker_pool *pool = worker->pool;
 898	unsigned int oflags = worker->flags;
 899
 900	lockdep_assert_held(&pool->lock);
 901
 902	worker->flags &= ~flags;
 903
 904	/*
 905	 * If transitioning out of NOT_RUNNING, increment nr_running.  Note
 906	 * that the nested NOT_RUNNING is not a noop.  NOT_RUNNING is mask
 907	 * of multiple flags, not a single flag.
 908	 */
 909	if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
 910		if (!(worker->flags & WORKER_NOT_RUNNING))
 911			pool->nr_running++;
 912}
 913
 914/* Return the first idle worker.  Called with pool->lock held. */
 915static struct worker *first_idle_worker(struct worker_pool *pool)
 916{
 917	if (unlikely(list_empty(&pool->idle_list)))
 918		return NULL;
 919
 920	return list_first_entry(&pool->idle_list, struct worker, entry);
 921}
 922
 923/**
 924 * worker_enter_idle - enter idle state
 925 * @worker: worker which is entering idle state
 926 *
 927 * @worker is entering idle state.  Update stats and idle timer if
 928 * necessary.
 929 *
 930 * LOCKING:
 931 * raw_spin_lock_irq(pool->lock).
 932 */
 933static void worker_enter_idle(struct worker *worker)
 934{
 935	struct worker_pool *pool = worker->pool;
 936
 937	if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
 938	    WARN_ON_ONCE(!list_empty(&worker->entry) &&
 939			 (worker->hentry.next || worker->hentry.pprev)))
 940		return;
 941
 942	/* can't use worker_set_flags(), also called from create_worker() */
 943	worker->flags |= WORKER_IDLE;
 944	pool->nr_idle++;
 945	worker->last_active = jiffies;
 946
 947	/* idle_list is LIFO */
 948	list_add(&worker->entry, &pool->idle_list);
 949
 950	if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
 951		mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
 952
 953	/* Sanity check nr_running. */
 954	WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
 955}
 956
 957/**
 958 * worker_leave_idle - leave idle state
 959 * @worker: worker which is leaving idle state
 960 *
 961 * @worker is leaving idle state.  Update stats.
 962 *
 963 * LOCKING:
 964 * raw_spin_lock_irq(pool->lock).
 965 */
 966static void worker_leave_idle(struct worker *worker)
 967{
 968	struct worker_pool *pool = worker->pool;
 969
 970	if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
 971		return;
 972	worker_clr_flags(worker, WORKER_IDLE);
 973	pool->nr_idle--;
 974	list_del_init(&worker->entry);
 975}
 976
 977/**
 978 * find_worker_executing_work - find worker which is executing a work
 979 * @pool: pool of interest
 980 * @work: work to find worker for
 981 *
 982 * Find a worker which is executing @work on @pool by searching
 983 * @pool->busy_hash which is keyed by the address of @work.  For a worker
 984 * to match, its current execution should match the address of @work and
 985 * its work function.  This is to avoid unwanted dependency between
 986 * unrelated work executions through a work item being recycled while still
 987 * being executed.
 988 *
 989 * This is a bit tricky.  A work item may be freed once its execution
 990 * starts and nothing prevents the freed area from being recycled for
 991 * another work item.  If the same work item address ends up being reused
 992 * before the original execution finishes, workqueue will identify the
 993 * recycled work item as currently executing and make it wait until the
 994 * current execution finishes, introducing an unwanted dependency.
 995 *
 996 * This function checks the work item address and work function to avoid
 997 * false positives.  Note that this isn't complete as one may construct a
 998 * work function which can introduce dependency onto itself through a
 999 * recycled work item.  Well, if somebody wants to shoot oneself in the
1000 * foot that badly, there's only so much we can do, and if such deadlock
1001 * actually occurs, it should be easy to locate the culprit work function.
1002 *
1003 * CONTEXT:
1004 * raw_spin_lock_irq(pool->lock).
1005 *
1006 * Return:
1007 * Pointer to worker which is executing @work if found, %NULL
1008 * otherwise.
1009 */
1010static struct worker *find_worker_executing_work(struct worker_pool *pool,
1011						 struct work_struct *work)
1012{
1013	struct worker *worker;
1014
1015	hash_for_each_possible(pool->busy_hash, worker, hentry,
1016			       (unsigned long)work)
1017		if (worker->current_work == work &&
1018		    worker->current_func == work->func)
1019			return worker;
1020
1021	return NULL;
1022}
1023
1024/**
1025 * move_linked_works - move linked works to a list
1026 * @work: start of series of works to be scheduled
1027 * @head: target list to append @work to
1028 * @nextp: out parameter for nested worklist walking
1029 *
1030 * Schedule linked works starting from @work to @head. Work series to be
1031 * scheduled starts at @work and includes any consecutive work with
1032 * WORK_STRUCT_LINKED set in its predecessor. See assign_work() for details on
1033 * @nextp.
 
 
 
1034 *
1035 * CONTEXT:
1036 * raw_spin_lock_irq(pool->lock).
1037 */
1038static void move_linked_works(struct work_struct *work, struct list_head *head,
1039			      struct work_struct **nextp)
1040{
1041	struct work_struct *n;
1042
1043	/*
1044	 * Linked worklist will always end before the end of the list,
1045	 * use NULL for list head.
1046	 */
1047	list_for_each_entry_safe_from(work, n, NULL, entry) {
1048		list_move_tail(&work->entry, head);
1049		if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1050			break;
1051	}
1052
1053	/*
1054	 * If we're already inside safe list traversal and have moved
1055	 * multiple works to the scheduled queue, the next position
1056	 * needs to be updated.
1057	 */
1058	if (nextp)
1059		*nextp = n;
1060}
1061
1062/**
1063 * assign_work - assign a work item and its linked work items to a worker
1064 * @work: work to assign
1065 * @worker: worker to assign to
1066 * @nextp: out parameter for nested worklist walking
1067 *
1068 * Assign @work and its linked work items to @worker. If @work is already being
1069 * executed by another worker in the same pool, it'll be punted there.
1070 *
1071 * If @nextp is not NULL, it's updated to point to the next work of the last
1072 * scheduled work. This allows assign_work() to be nested inside
1073 * list_for_each_entry_safe().
1074 *
1075 * Returns %true if @work was successfully assigned to @worker. %false if @work
1076 * was punted to another worker already executing it.
1077 */
1078static bool assign_work(struct work_struct *work, struct worker *worker,
1079			struct work_struct **nextp)
1080{
1081	struct worker_pool *pool = worker->pool;
1082	struct worker *collision;
1083
1084	lockdep_assert_held(&pool->lock);
1085
1086	/*
1087	 * A single work shouldn't be executed concurrently by multiple workers.
1088	 * __queue_work() ensures that @work doesn't jump to a different pool
1089	 * while still running in the previous pool. Here, we should ensure that
1090	 * @work is not executed concurrently by multiple workers from the same
1091	 * pool. Check whether anyone is already processing the work. If so,
1092	 * defer the work to the currently executing one.
1093	 */
1094	collision = find_worker_executing_work(pool, work);
1095	if (unlikely(collision)) {
1096		move_linked_works(work, &collision->scheduled, nextp);
1097		return false;
1098	}
1099
1100	move_linked_works(work, &worker->scheduled, nextp);
1101	return true;
1102}
1103
1104/**
1105 * kick_pool - wake up an idle worker if necessary
1106 * @pool: pool to kick
1107 *
1108 * @pool may have pending work items. Wake up worker if necessary. Returns
1109 * whether a worker was woken up.
1110 */
1111static bool kick_pool(struct worker_pool *pool)
1112{
1113	struct worker *worker = first_idle_worker(pool);
1114	struct task_struct *p;
1115
1116	lockdep_assert_held(&pool->lock);
1117
1118	if (!need_more_worker(pool) || !worker)
1119		return false;
1120
1121	p = worker->task;
1122
1123#ifdef CONFIG_SMP
1124	/*
1125	 * Idle @worker is about to execute @work and waking up provides an
1126	 * opportunity to migrate @worker at a lower cost by setting the task's
1127	 * wake_cpu field. Let's see if we want to move @worker to improve
1128	 * execution locality.
1129	 *
1130	 * We're waking the worker that went idle the latest and there's some
1131	 * chance that @worker is marked idle but hasn't gone off CPU yet. If
1132	 * so, setting the wake_cpu won't do anything. As this is a best-effort
1133	 * optimization and the race window is narrow, let's leave as-is for
1134	 * now. If this becomes pronounced, we can skip over workers which are
1135	 * still on cpu when picking an idle worker.
1136	 *
1137	 * If @pool has non-strict affinity, @worker might have ended up outside
1138	 * its affinity scope. Repatriate.
1139	 */
1140	if (!pool->attrs->affn_strict &&
1141	    !cpumask_test_cpu(p->wake_cpu, pool->attrs->__pod_cpumask)) {
1142		struct work_struct *work = list_first_entry(&pool->worklist,
1143						struct work_struct, entry);
1144		p->wake_cpu = cpumask_any_distribute(pool->attrs->__pod_cpumask);
1145		get_work_pwq(work)->stats[PWQ_STAT_REPATRIATED]++;
1146	}
1147#endif
1148	wake_up_process(p);
1149	return true;
1150}
1151
1152#ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
1153
1154/*
1155 * Concurrency-managed per-cpu work items that hog CPU for longer than
1156 * wq_cpu_intensive_thresh_us trigger the automatic CPU_INTENSIVE mechanism,
1157 * which prevents them from stalling other concurrency-managed work items. If a
1158 * work function keeps triggering this mechanism, it's likely that the work item
1159 * should be using an unbound workqueue instead.
1160 *
1161 * wq_cpu_intensive_report() tracks work functions which trigger such conditions
1162 * and report them so that they can be examined and converted to use unbound
1163 * workqueues as appropriate. To avoid flooding the console, each violating work
1164 * function is tracked and reported with exponential backoff.
1165 */
1166#define WCI_MAX_ENTS 128
1167
1168struct wci_ent {
1169	work_func_t		func;
1170	atomic64_t		cnt;
1171	struct hlist_node	hash_node;
1172};
1173
1174static struct wci_ent wci_ents[WCI_MAX_ENTS];
1175static int wci_nr_ents;
1176static DEFINE_RAW_SPINLOCK(wci_lock);
1177static DEFINE_HASHTABLE(wci_hash, ilog2(WCI_MAX_ENTS));
1178
1179static struct wci_ent *wci_find_ent(work_func_t func)
1180{
1181	struct wci_ent *ent;
1182
1183	hash_for_each_possible_rcu(wci_hash, ent, hash_node,
1184				   (unsigned long)func) {
1185		if (ent->func == func)
1186			return ent;
1187	}
1188	return NULL;
1189}
1190
1191static void wq_cpu_intensive_report(work_func_t func)
1192{
1193	struct wci_ent *ent;
1194
1195restart:
1196	ent = wci_find_ent(func);
1197	if (ent) {
1198		u64 cnt;
1199
1200		/*
1201		 * Start reporting from the fourth time and back off
1202		 * exponentially.
1203		 */
1204		cnt = atomic64_inc_return_relaxed(&ent->cnt);
1205		if (cnt >= 4 && is_power_of_2(cnt))
1206			printk_deferred(KERN_WARNING "workqueue: %ps hogged CPU for >%luus %llu times, consider switching to WQ_UNBOUND\n",
1207					ent->func, wq_cpu_intensive_thresh_us,
1208					atomic64_read(&ent->cnt));
1209		return;
1210	}
1211
1212	/*
1213	 * @func is a new violation. Allocate a new entry for it. If wcn_ents[]
1214	 * is exhausted, something went really wrong and we probably made enough
1215	 * noise already.
1216	 */
1217	if (wci_nr_ents >= WCI_MAX_ENTS)
1218		return;
1219
1220	raw_spin_lock(&wci_lock);
1221
1222	if (wci_nr_ents >= WCI_MAX_ENTS) {
1223		raw_spin_unlock(&wci_lock);
1224		return;
1225	}
1226
1227	if (wci_find_ent(func)) {
1228		raw_spin_unlock(&wci_lock);
1229		goto restart;
1230	}
1231
1232	ent = &wci_ents[wci_nr_ents++];
1233	ent->func = func;
1234	atomic64_set(&ent->cnt, 1);
1235	hash_add_rcu(wci_hash, &ent->hash_node, (unsigned long)func);
1236
1237	raw_spin_unlock(&wci_lock);
1238}
1239
1240#else	/* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1241static void wq_cpu_intensive_report(work_func_t func) {}
1242#endif	/* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1243
1244/**
1245 * wq_worker_running - a worker is running again
1246 * @task: task waking up
1247 *
1248 * This function is called when a worker returns from schedule()
1249 */
1250void wq_worker_running(struct task_struct *task)
1251{
1252	struct worker *worker = kthread_data(task);
1253
1254	if (!READ_ONCE(worker->sleeping))
1255		return;
1256
1257	/*
1258	 * If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
1259	 * and the nr_running increment below, we may ruin the nr_running reset
1260	 * and leave with an unexpected pool->nr_running == 1 on the newly unbound
1261	 * pool. Protect against such race.
1262	 */
1263	preempt_disable();
1264	if (!(worker->flags & WORKER_NOT_RUNNING))
1265		worker->pool->nr_running++;
1266	preempt_enable();
1267
1268	/*
1269	 * CPU intensive auto-detection cares about how long a work item hogged
1270	 * CPU without sleeping. Reset the starting timestamp on wakeup.
1271	 */
1272	worker->current_at = worker->task->se.sum_exec_runtime;
1273
1274	WRITE_ONCE(worker->sleeping, 0);
1275}
1276
1277/**
1278 * wq_worker_sleeping - a worker is going to sleep
1279 * @task: task going to sleep
1280 *
1281 * This function is called from schedule() when a busy worker is
1282 * going to sleep.
1283 */
1284void wq_worker_sleeping(struct task_struct *task)
1285{
1286	struct worker *worker = kthread_data(task);
1287	struct worker_pool *pool;
1288
1289	/*
1290	 * Rescuers, which may not have all the fields set up like normal
1291	 * workers, also reach here, let's not access anything before
1292	 * checking NOT_RUNNING.
1293	 */
1294	if (worker->flags & WORKER_NOT_RUNNING)
1295		return;
1296
1297	pool = worker->pool;
1298
1299	/* Return if preempted before wq_worker_running() was reached */
1300	if (READ_ONCE(worker->sleeping))
1301		return;
1302
1303	WRITE_ONCE(worker->sleeping, 1);
1304	raw_spin_lock_irq(&pool->lock);
1305
1306	/*
1307	 * Recheck in case unbind_workers() preempted us. We don't
1308	 * want to decrement nr_running after the worker is unbound
1309	 * and nr_running has been reset.
1310	 */
1311	if (worker->flags & WORKER_NOT_RUNNING) {
1312		raw_spin_unlock_irq(&pool->lock);
1313		return;
1314	}
1315
1316	pool->nr_running--;
1317	if (kick_pool(pool))
1318		worker->current_pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1319
1320	raw_spin_unlock_irq(&pool->lock);
1321}
1322
1323/**
1324 * wq_worker_tick - a scheduler tick occurred while a kworker is running
1325 * @task: task currently running
1326 *
1327 * Called from scheduler_tick(). We're in the IRQ context and the current
1328 * worker's fields which follow the 'K' locking rule can be accessed safely.
1329 */
1330void wq_worker_tick(struct task_struct *task)
1331{
1332	struct worker *worker = kthread_data(task);
1333	struct pool_workqueue *pwq = worker->current_pwq;
1334	struct worker_pool *pool = worker->pool;
1335
1336	if (!pwq)
1337		return;
1338
1339	pwq->stats[PWQ_STAT_CPU_TIME] += TICK_USEC;
1340
1341	if (!wq_cpu_intensive_thresh_us)
1342		return;
1343
1344	/*
1345	 * If the current worker is concurrency managed and hogged the CPU for
1346	 * longer than wq_cpu_intensive_thresh_us, it's automatically marked
1347	 * CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
1348	 *
1349	 * Set @worker->sleeping means that @worker is in the process of
1350	 * switching out voluntarily and won't be contributing to
1351	 * @pool->nr_running until it wakes up. As wq_worker_sleeping() also
1352	 * decrements ->nr_running, setting CPU_INTENSIVE here can lead to
1353	 * double decrements. The task is releasing the CPU anyway. Let's skip.
1354	 * We probably want to make this prettier in the future.
1355	 */
1356	if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) ||
1357	    worker->task->se.sum_exec_runtime - worker->current_at <
1358	    wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
1359		return;
1360
1361	raw_spin_lock(&pool->lock);
1362
1363	worker_set_flags(worker, WORKER_CPU_INTENSIVE);
1364	wq_cpu_intensive_report(worker->current_func);
1365	pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
1366
1367	if (kick_pool(pool))
1368		pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1369
1370	raw_spin_unlock(&pool->lock);
1371}
1372
1373/**
1374 * wq_worker_last_func - retrieve worker's last work function
1375 * @task: Task to retrieve last work function of.
1376 *
1377 * Determine the last function a worker executed. This is called from
1378 * the scheduler to get a worker's last known identity.
1379 *
1380 * CONTEXT:
1381 * raw_spin_lock_irq(rq->lock)
1382 *
1383 * This function is called during schedule() when a kworker is going
1384 * to sleep. It's used by psi to identify aggregation workers during
1385 * dequeuing, to allow periodic aggregation to shut-off when that
1386 * worker is the last task in the system or cgroup to go to sleep.
1387 *
1388 * As this function doesn't involve any workqueue-related locking, it
1389 * only returns stable values when called from inside the scheduler's
1390 * queuing and dequeuing paths, when @task, which must be a kworker,
1391 * is guaranteed to not be processing any works.
1392 *
1393 * Return:
1394 * The last work function %current executed as a worker, NULL if it
1395 * hasn't executed any work yet.
1396 */
1397work_func_t wq_worker_last_func(struct task_struct *task)
1398{
1399	struct worker *worker = kthread_data(task);
1400
1401	return worker->last_func;
1402}
1403
1404/**
1405 * get_pwq - get an extra reference on the specified pool_workqueue
1406 * @pwq: pool_workqueue to get
1407 *
1408 * Obtain an extra reference on @pwq.  The caller should guarantee that
1409 * @pwq has positive refcnt and be holding the matching pool->lock.
1410 */
1411static void get_pwq(struct pool_workqueue *pwq)
1412{
1413	lockdep_assert_held(&pwq->pool->lock);
1414	WARN_ON_ONCE(pwq->refcnt <= 0);
1415	pwq->refcnt++;
1416}
1417
1418/**
1419 * put_pwq - put a pool_workqueue reference
1420 * @pwq: pool_workqueue to put
1421 *
1422 * Drop a reference of @pwq.  If its refcnt reaches zero, schedule its
1423 * destruction.  The caller should be holding the matching pool->lock.
1424 */
1425static void put_pwq(struct pool_workqueue *pwq)
1426{
1427	lockdep_assert_held(&pwq->pool->lock);
1428	if (likely(--pwq->refcnt))
1429		return;
 
 
1430	/*
1431	 * @pwq can't be released under pool->lock, bounce to a dedicated
1432	 * kthread_worker to avoid A-A deadlocks.
 
 
 
 
1433	 */
1434	kthread_queue_work(pwq_release_worker, &pwq->release_work);
1435}
1436
1437/**
1438 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1439 * @pwq: pool_workqueue to put (can be %NULL)
1440 *
1441 * put_pwq() with locking.  This function also allows %NULL @pwq.
1442 */
1443static void put_pwq_unlocked(struct pool_workqueue *pwq)
1444{
1445	if (pwq) {
1446		/*
1447		 * As both pwqs and pools are RCU protected, the
1448		 * following lock operations are safe.
1449		 */
1450		raw_spin_lock_irq(&pwq->pool->lock);
1451		put_pwq(pwq);
1452		raw_spin_unlock_irq(&pwq->pool->lock);
1453	}
1454}
1455
1456static void pwq_activate_inactive_work(struct work_struct *work)
1457{
1458	struct pool_workqueue *pwq = get_work_pwq(work);
1459
1460	trace_workqueue_activate_work(work);
1461	if (list_empty(&pwq->pool->worklist))
1462		pwq->pool->watchdog_ts = jiffies;
1463	move_linked_works(work, &pwq->pool->worklist, NULL);
1464	__clear_bit(WORK_STRUCT_INACTIVE_BIT, work_data_bits(work));
1465	pwq->nr_active++;
1466}
1467
1468static void pwq_activate_first_inactive(struct pool_workqueue *pwq)
1469{
1470	struct work_struct *work = list_first_entry(&pwq->inactive_works,
1471						    struct work_struct, entry);
1472
1473	pwq_activate_inactive_work(work);
1474}
1475
1476/**
1477 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1478 * @pwq: pwq of interest
1479 * @work_data: work_data of work which left the queue
1480 *
1481 * A work either has completed or is removed from pending queue,
1482 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1483 *
1484 * CONTEXT:
1485 * raw_spin_lock_irq(pool->lock).
1486 */
1487static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_data)
1488{
1489	int color = get_work_color(work_data);
1490
1491	if (!(work_data & WORK_STRUCT_INACTIVE)) {
1492		pwq->nr_active--;
1493		if (!list_empty(&pwq->inactive_works)) {
1494			/* one down, submit an inactive one */
1495			if (pwq->nr_active < pwq->max_active)
1496				pwq_activate_first_inactive(pwq);
1497		}
1498	}
1499
1500	pwq->nr_in_flight[color]--;
1501
 
 
 
 
 
 
 
1502	/* is flush in progress and are we at the flushing tip? */
1503	if (likely(pwq->flush_color != color))
1504		goto out_put;
1505
1506	/* are there still in-flight works? */
1507	if (pwq->nr_in_flight[color])
1508		goto out_put;
1509
1510	/* this pwq is done, clear flush_color */
1511	pwq->flush_color = -1;
1512
1513	/*
1514	 * If this was the last pwq, wake up the first flusher.  It
1515	 * will handle the rest.
1516	 */
1517	if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1518		complete(&pwq->wq->first_flusher->done);
1519out_put:
1520	put_pwq(pwq);
1521}
1522
1523/**
1524 * try_to_grab_pending - steal work item from worklist and disable irq
1525 * @work: work item to steal
1526 * @is_dwork: @work is a delayed_work
1527 * @flags: place to store irq state
1528 *
1529 * Try to grab PENDING bit of @work.  This function can handle @work in any
1530 * stable state - idle, on timer or on worklist.
1531 *
1532 * Return:
1533 *
1534 *  ========	================================================================
1535 *  1		if @work was pending and we successfully stole PENDING
1536 *  0		if @work was idle and we claimed PENDING
1537 *  -EAGAIN	if PENDING couldn't be grabbed at the moment, safe to busy-retry
1538 *  -ENOENT	if someone else is canceling @work, this state may persist
1539 *		for arbitrarily long
1540 *  ========	================================================================
1541 *
1542 * Note:
1543 * On >= 0 return, the caller owns @work's PENDING bit.  To avoid getting
1544 * interrupted while holding PENDING and @work off queue, irq must be
1545 * disabled on entry.  This, combined with delayed_work->timer being
1546 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1547 *
1548 * On successful return, >= 0, irq is disabled and the caller is
1549 * responsible for releasing it using local_irq_restore(*@flags).
1550 *
1551 * This function is safe to call from any context including IRQ handler.
1552 */
1553static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1554			       unsigned long *flags)
1555{
1556	struct worker_pool *pool;
1557	struct pool_workqueue *pwq;
1558
1559	local_irq_save(*flags);
1560
1561	/* try to steal the timer if it exists */
1562	if (is_dwork) {
1563		struct delayed_work *dwork = to_delayed_work(work);
1564
1565		/*
1566		 * dwork->timer is irqsafe.  If del_timer() fails, it's
1567		 * guaranteed that the timer is not queued anywhere and not
1568		 * running on the local CPU.
1569		 */
1570		if (likely(del_timer(&dwork->timer)))
1571			return 1;
1572	}
1573
1574	/* try to claim PENDING the normal way */
1575	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1576		return 0;
1577
1578	rcu_read_lock();
1579	/*
1580	 * The queueing is in progress, or it is already queued. Try to
1581	 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1582	 */
1583	pool = get_work_pool(work);
1584	if (!pool)
1585		goto fail;
1586
1587	raw_spin_lock(&pool->lock);
1588	/*
1589	 * work->data is guaranteed to point to pwq only while the work
1590	 * item is queued on pwq->wq, and both updating work->data to point
1591	 * to pwq on queueing and to pool on dequeueing are done under
1592	 * pwq->pool->lock.  This in turn guarantees that, if work->data
1593	 * points to pwq which is associated with a locked pool, the work
1594	 * item is currently queued on that pool.
1595	 */
1596	pwq = get_work_pwq(work);
1597	if (pwq && pwq->pool == pool) {
1598		debug_work_deactivate(work);
1599
1600		/*
1601		 * A cancelable inactive work item must be in the
1602		 * pwq->inactive_works since a queued barrier can't be
1603		 * canceled (see the comments in insert_wq_barrier()).
1604		 *
1605		 * An inactive work item cannot be grabbed directly because
1606		 * it might have linked barrier work items which, if left
1607		 * on the inactive_works list, will confuse pwq->nr_active
1608		 * management later on and cause stall.  Make sure the work
1609		 * item is activated before grabbing.
1610		 */
1611		if (*work_data_bits(work) & WORK_STRUCT_INACTIVE)
1612			pwq_activate_inactive_work(work);
1613
1614		list_del_init(&work->entry);
1615		pwq_dec_nr_in_flight(pwq, *work_data_bits(work));
1616
1617		/* work->data points to pwq iff queued, point to pool */
1618		set_work_pool_and_keep_pending(work, pool->id);
1619
1620		raw_spin_unlock(&pool->lock);
1621		rcu_read_unlock();
1622		return 1;
1623	}
1624	raw_spin_unlock(&pool->lock);
1625fail:
1626	rcu_read_unlock();
1627	local_irq_restore(*flags);
1628	if (work_is_canceling(work))
1629		return -ENOENT;
1630	cpu_relax();
1631	return -EAGAIN;
1632}
1633
1634/**
1635 * insert_work - insert a work into a pool
1636 * @pwq: pwq @work belongs to
1637 * @work: work to insert
1638 * @head: insertion point
1639 * @extra_flags: extra WORK_STRUCT_* flags to set
1640 *
1641 * Insert @work which belongs to @pwq after @head.  @extra_flags is or'd to
1642 * work_struct flags.
1643 *
1644 * CONTEXT:
1645 * raw_spin_lock_irq(pool->lock).
1646 */
1647static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1648			struct list_head *head, unsigned int extra_flags)
1649{
1650	debug_work_activate(work);
1651
1652	/* record the work call stack in order to print it in KASAN reports */
1653	kasan_record_aux_stack_noalloc(work);
1654
1655	/* we own @work, set data and link */
1656	set_work_pwq(work, pwq, extra_flags);
1657	list_add_tail(&work->entry, head);
1658	get_pwq(pwq);
 
 
 
 
 
 
 
 
 
 
1659}
1660
1661/*
1662 * Test whether @work is being queued from another work executing on the
1663 * same workqueue.
1664 */
1665static bool is_chained_work(struct workqueue_struct *wq)
1666{
1667	struct worker *worker;
1668
1669	worker = current_wq_worker();
1670	/*
1671	 * Return %true iff I'm a worker executing a work item on @wq.  If
1672	 * I'm @worker, it's safe to dereference it without locking.
1673	 */
1674	return worker && worker->current_pwq->wq == wq;
1675}
1676
1677/*
1678 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1679 * by wq_unbound_cpumask.  Otherwise, round robin among the allowed ones to
1680 * avoid perturbing sensitive tasks.
1681 */
1682static int wq_select_unbound_cpu(int cpu)
1683{
 
1684	int new_cpu;
1685
1686	if (likely(!wq_debug_force_rr_cpu)) {
1687		if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1688			return cpu;
1689	} else {
1690		pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
 
1691	}
1692
 
 
 
1693	new_cpu = __this_cpu_read(wq_rr_cpu_last);
1694	new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1695	if (unlikely(new_cpu >= nr_cpu_ids)) {
1696		new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1697		if (unlikely(new_cpu >= nr_cpu_ids))
1698			return cpu;
1699	}
1700	__this_cpu_write(wq_rr_cpu_last, new_cpu);
1701
1702	return new_cpu;
1703}
1704
1705static void __queue_work(int cpu, struct workqueue_struct *wq,
1706			 struct work_struct *work)
1707{
1708	struct pool_workqueue *pwq;
1709	struct worker_pool *last_pool, *pool;
 
1710	unsigned int work_flags;
1711	unsigned int req_cpu = cpu;
1712
1713	/*
1714	 * While a work item is PENDING && off queue, a task trying to
1715	 * steal the PENDING will busy-loop waiting for it to either get
1716	 * queued or lose PENDING.  Grabbing PENDING and queueing should
1717	 * happen with IRQ disabled.
1718	 */
1719	lockdep_assert_irqs_disabled();
1720
 
1721
1722	/*
1723	 * For a draining wq, only works from the same workqueue are
1724	 * allowed. The __WQ_DESTROYING helps to spot the issue that
1725	 * queues a new work item to a wq after destroy_workqueue(wq).
1726	 */
1727	if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
1728		     WARN_ON_ONCE(!is_chained_work(wq))))
1729		return;
1730	rcu_read_lock();
1731retry:
1732	/* pwq which will be used unless @work is executing elsewhere */
1733	if (req_cpu == WORK_CPU_UNBOUND) {
1734		if (wq->flags & WQ_UNBOUND)
1735			cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1736		else
 
 
1737			cpu = raw_smp_processor_id();
 
1738	}
1739
1740	pwq = rcu_dereference(*per_cpu_ptr(wq->cpu_pwq, cpu));
1741	pool = pwq->pool;
1742
1743	/*
1744	 * If @work was previously on a different pool, it might still be
1745	 * running there, in which case the work needs to be queued on that
1746	 * pool to guarantee non-reentrancy.
1747	 */
1748	last_pool = get_work_pool(work);
1749	if (last_pool && last_pool != pool) {
1750		struct worker *worker;
1751
1752		raw_spin_lock(&last_pool->lock);
1753
1754		worker = find_worker_executing_work(last_pool, work);
1755
1756		if (worker && worker->current_pwq->wq == wq) {
1757			pwq = worker->current_pwq;
1758			pool = pwq->pool;
1759			WARN_ON_ONCE(pool != last_pool);
1760		} else {
1761			/* meh... not running there, queue here */
1762			raw_spin_unlock(&last_pool->lock);
1763			raw_spin_lock(&pool->lock);
1764		}
1765	} else {
1766		raw_spin_lock(&pool->lock);
1767	}
1768
1769	/*
1770	 * pwq is determined and locked. For unbound pools, we could have raced
1771	 * with pwq release and it could already be dead. If its refcnt is zero,
1772	 * repeat pwq selection. Note that unbound pwqs never die without
1773	 * another pwq replacing it in cpu_pwq or while work items are executing
1774	 * on it, so the retrying is guaranteed to make forward-progress.
 
1775	 */
1776	if (unlikely(!pwq->refcnt)) {
1777		if (wq->flags & WQ_UNBOUND) {
1778			raw_spin_unlock(&pool->lock);
1779			cpu_relax();
1780			goto retry;
1781		}
1782		/* oops */
1783		WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1784			  wq->name, cpu);
1785	}
1786
1787	/* pwq determined, queue */
1788	trace_workqueue_queue_work(req_cpu, pwq, work);
1789
1790	if (WARN_ON(!list_empty(&work->entry)))
1791		goto out;
1792
1793	pwq->nr_in_flight[pwq->work_color]++;
1794	work_flags = work_color_to_flags(pwq->work_color);
1795
1796	if (likely(pwq->nr_active < pwq->max_active)) {
1797		if (list_empty(&pool->worklist))
1798			pool->watchdog_ts = jiffies;
1799
1800		trace_workqueue_activate_work(work);
1801		pwq->nr_active++;
1802		insert_work(pwq, work, &pool->worklist, work_flags);
1803		kick_pool(pool);
 
1804	} else {
1805		work_flags |= WORK_STRUCT_INACTIVE;
1806		insert_work(pwq, work, &pwq->inactive_works, work_flags);
1807	}
1808
 
 
1809out:
1810	raw_spin_unlock(&pool->lock);
1811	rcu_read_unlock();
1812}
1813
1814/**
1815 * queue_work_on - queue work on specific cpu
1816 * @cpu: CPU number to execute work on
1817 * @wq: workqueue to use
1818 * @work: work to queue
1819 *
1820 * We queue the work to a specific CPU, the caller must ensure it
1821 * can't go away.  Callers that fail to ensure that the specified
1822 * CPU cannot go away will execute on a randomly chosen CPU.
1823 * But note well that callers specifying a CPU that never has been
1824 * online will get a splat.
1825 *
1826 * Return: %false if @work was already on a queue, %true otherwise.
1827 */
1828bool queue_work_on(int cpu, struct workqueue_struct *wq,
1829		   struct work_struct *work)
1830{
1831	bool ret = false;
1832	unsigned long flags;
1833
1834	local_irq_save(flags);
1835
1836	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1837		__queue_work(cpu, wq, work);
1838		ret = true;
1839	}
1840
1841	local_irq_restore(flags);
1842	return ret;
1843}
1844EXPORT_SYMBOL(queue_work_on);
1845
1846/**
1847 * select_numa_node_cpu - Select a CPU based on NUMA node
1848 * @node: NUMA node ID that we want to select a CPU from
1849 *
1850 * This function will attempt to find a "random" cpu available on a given
1851 * node. If there are no CPUs available on the given node it will return
1852 * WORK_CPU_UNBOUND indicating that we should just schedule to any
1853 * available CPU if we need to schedule this work.
1854 */
1855static int select_numa_node_cpu(int node)
1856{
1857	int cpu;
1858
 
 
 
 
1859	/* Delay binding to CPU if node is not valid or online */
1860	if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
1861		return WORK_CPU_UNBOUND;
1862
1863	/* Use local node/cpu if we are already there */
1864	cpu = raw_smp_processor_id();
1865	if (node == cpu_to_node(cpu))
1866		return cpu;
1867
1868	/* Use "random" otherwise know as "first" online CPU of node */
1869	cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
1870
1871	/* If CPU is valid return that, otherwise just defer */
1872	return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
1873}
1874
1875/**
1876 * queue_work_node - queue work on a "random" cpu for a given NUMA node
1877 * @node: NUMA node that we are targeting the work for
1878 * @wq: workqueue to use
1879 * @work: work to queue
1880 *
1881 * We queue the work to a "random" CPU within a given NUMA node. The basic
1882 * idea here is to provide a way to somehow associate work with a given
1883 * NUMA node.
1884 *
1885 * This function will only make a best effort attempt at getting this onto
1886 * the right NUMA node. If no node is requested or the requested node is
1887 * offline then we just fall back to standard queue_work behavior.
1888 *
1889 * Currently the "random" CPU ends up being the first available CPU in the
1890 * intersection of cpu_online_mask and the cpumask of the node, unless we
1891 * are running on the node. In that case we just use the current CPU.
1892 *
1893 * Return: %false if @work was already on a queue, %true otherwise.
1894 */
1895bool queue_work_node(int node, struct workqueue_struct *wq,
1896		     struct work_struct *work)
1897{
1898	unsigned long flags;
1899	bool ret = false;
1900
1901	/*
1902	 * This current implementation is specific to unbound workqueues.
1903	 * Specifically we only return the first available CPU for a given
1904	 * node instead of cycling through individual CPUs within the node.
1905	 *
1906	 * If this is used with a per-cpu workqueue then the logic in
1907	 * workqueue_select_cpu_near would need to be updated to allow for
1908	 * some round robin type logic.
1909	 */
1910	WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
1911
1912	local_irq_save(flags);
1913
1914	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1915		int cpu = select_numa_node_cpu(node);
1916
1917		__queue_work(cpu, wq, work);
1918		ret = true;
1919	}
1920
1921	local_irq_restore(flags);
1922	return ret;
1923}
1924EXPORT_SYMBOL_GPL(queue_work_node);
1925
1926void delayed_work_timer_fn(struct timer_list *t)
1927{
1928	struct delayed_work *dwork = from_timer(dwork, t, timer);
1929
1930	/* should have been called from irqsafe timer with irq already off */
1931	__queue_work(dwork->cpu, dwork->wq, &dwork->work);
1932}
1933EXPORT_SYMBOL(delayed_work_timer_fn);
1934
1935static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1936				struct delayed_work *dwork, unsigned long delay)
1937{
1938	struct timer_list *timer = &dwork->timer;
1939	struct work_struct *work = &dwork->work;
1940
1941	WARN_ON_ONCE(!wq);
1942	WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1943	WARN_ON_ONCE(timer_pending(timer));
1944	WARN_ON_ONCE(!list_empty(&work->entry));
1945
1946	/*
1947	 * If @delay is 0, queue @dwork->work immediately.  This is for
1948	 * both optimization and correctness.  The earliest @timer can
1949	 * expire is on the closest next tick and delayed_work users depend
1950	 * on that there's no such delay when @delay is 0.
1951	 */
1952	if (!delay) {
1953		__queue_work(cpu, wq, &dwork->work);
1954		return;
1955	}
1956
1957	dwork->wq = wq;
1958	dwork->cpu = cpu;
1959	timer->expires = jiffies + delay;
1960
1961	if (unlikely(cpu != WORK_CPU_UNBOUND))
1962		add_timer_on(timer, cpu);
1963	else
1964		add_timer(timer);
1965}
1966
1967/**
1968 * queue_delayed_work_on - queue work on specific CPU after delay
1969 * @cpu: CPU number to execute work on
1970 * @wq: workqueue to use
1971 * @dwork: work to queue
1972 * @delay: number of jiffies to wait before queueing
1973 *
1974 * Return: %false if @work was already on a queue, %true otherwise.  If
1975 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1976 * execution.
1977 */
1978bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1979			   struct delayed_work *dwork, unsigned long delay)
1980{
1981	struct work_struct *work = &dwork->work;
1982	bool ret = false;
1983	unsigned long flags;
1984
1985	/* read the comment in __queue_work() */
1986	local_irq_save(flags);
1987
1988	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1989		__queue_delayed_work(cpu, wq, dwork, delay);
1990		ret = true;
1991	}
1992
1993	local_irq_restore(flags);
1994	return ret;
1995}
1996EXPORT_SYMBOL(queue_delayed_work_on);
1997
1998/**
1999 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
2000 * @cpu: CPU number to execute work on
2001 * @wq: workqueue to use
2002 * @dwork: work to queue
2003 * @delay: number of jiffies to wait before queueing
2004 *
2005 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
2006 * modify @dwork's timer so that it expires after @delay.  If @delay is
2007 * zero, @work is guaranteed to be scheduled immediately regardless of its
2008 * current state.
2009 *
2010 * Return: %false if @dwork was idle and queued, %true if @dwork was
2011 * pending and its timer was modified.
2012 *
2013 * This function is safe to call from any context including IRQ handler.
2014 * See try_to_grab_pending() for details.
2015 */
2016bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
2017			 struct delayed_work *dwork, unsigned long delay)
2018{
2019	unsigned long flags;
2020	int ret;
2021
2022	do {
2023		ret = try_to_grab_pending(&dwork->work, true, &flags);
2024	} while (unlikely(ret == -EAGAIN));
2025
2026	if (likely(ret >= 0)) {
2027		__queue_delayed_work(cpu, wq, dwork, delay);
2028		local_irq_restore(flags);
2029	}
2030
2031	/* -ENOENT from try_to_grab_pending() becomes %true */
2032	return ret;
2033}
2034EXPORT_SYMBOL_GPL(mod_delayed_work_on);
2035
2036static void rcu_work_rcufn(struct rcu_head *rcu)
2037{
2038	struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
2039
2040	/* read the comment in __queue_work() */
2041	local_irq_disable();
2042	__queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
2043	local_irq_enable();
2044}
2045
2046/**
2047 * queue_rcu_work - queue work after a RCU grace period
2048 * @wq: workqueue to use
2049 * @rwork: work to queue
2050 *
2051 * Return: %false if @rwork was already pending, %true otherwise.  Note
2052 * that a full RCU grace period is guaranteed only after a %true return.
2053 * While @rwork is guaranteed to be executed after a %false return, the
2054 * execution may happen before a full RCU grace period has passed.
2055 */
2056bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
2057{
2058	struct work_struct *work = &rwork->work;
2059
2060	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
2061		rwork->wq = wq;
2062		call_rcu_hurry(&rwork->rcu, rcu_work_rcufn);
2063		return true;
2064	}
2065
2066	return false;
2067}
2068EXPORT_SYMBOL(queue_rcu_work);
2069
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2070static struct worker *alloc_worker(int node)
2071{
2072	struct worker *worker;
2073
2074	worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
2075	if (worker) {
2076		INIT_LIST_HEAD(&worker->entry);
2077		INIT_LIST_HEAD(&worker->scheduled);
2078		INIT_LIST_HEAD(&worker->node);
2079		/* on creation a worker is in !idle && prep state */
2080		worker->flags = WORKER_PREP;
2081	}
2082	return worker;
2083}
2084
2085static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
2086{
2087	if (pool->cpu < 0 && pool->attrs->affn_strict)
2088		return pool->attrs->__pod_cpumask;
2089	else
2090		return pool->attrs->cpumask;
2091}
2092
2093/**
2094 * worker_attach_to_pool() - attach a worker to a pool
2095 * @worker: worker to be attached
2096 * @pool: the target pool
2097 *
2098 * Attach @worker to @pool.  Once attached, the %WORKER_UNBOUND flag and
2099 * cpu-binding of @worker are kept coordinated with the pool across
2100 * cpu-[un]hotplugs.
2101 */
2102static void worker_attach_to_pool(struct worker *worker,
2103				   struct worker_pool *pool)
2104{
2105	mutex_lock(&wq_pool_attach_mutex);
2106
2107	/*
 
 
 
 
 
 
2108	 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
2109	 * stable across this function.  See the comments above the flag
2110	 * definition for details.
2111	 */
2112	if (pool->flags & POOL_DISASSOCIATED)
2113		worker->flags |= WORKER_UNBOUND;
2114	else
2115		kthread_set_per_cpu(worker->task, pool->cpu);
2116
2117	if (worker->rescue_wq)
2118		set_cpus_allowed_ptr(worker->task, pool_allowed_cpus(pool));
2119
2120	list_add_tail(&worker->node, &pool->workers);
2121	worker->pool = pool;
2122
2123	mutex_unlock(&wq_pool_attach_mutex);
2124}
2125
2126/**
2127 * worker_detach_from_pool() - detach a worker from its pool
2128 * @worker: worker which is attached to its pool
2129 *
2130 * Undo the attaching which had been done in worker_attach_to_pool().  The
2131 * caller worker shouldn't access to the pool after detached except it has
2132 * other reference to the pool.
2133 */
2134static void worker_detach_from_pool(struct worker *worker)
2135{
2136	struct worker_pool *pool = worker->pool;
2137	struct completion *detach_completion = NULL;
2138
2139	mutex_lock(&wq_pool_attach_mutex);
2140
2141	kthread_set_per_cpu(worker->task, -1);
2142	list_del(&worker->node);
2143	worker->pool = NULL;
2144
2145	if (list_empty(&pool->workers) && list_empty(&pool->dying_workers))
2146		detach_completion = pool->detach_completion;
2147	mutex_unlock(&wq_pool_attach_mutex);
2148
2149	/* clear leftover flags without pool->lock after it is detached */
2150	worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
2151
2152	if (detach_completion)
2153		complete(detach_completion);
2154}
2155
2156/**
2157 * create_worker - create a new workqueue worker
2158 * @pool: pool the new worker will belong to
2159 *
2160 * Create and start a new worker which is attached to @pool.
2161 *
2162 * CONTEXT:
2163 * Might sleep.  Does GFP_KERNEL allocations.
2164 *
2165 * Return:
2166 * Pointer to the newly created worker.
2167 */
2168static struct worker *create_worker(struct worker_pool *pool)
2169{
2170	struct worker *worker;
2171	int id;
2172	char id_buf[23];
2173
2174	/* ID is needed to determine kthread name */
2175	id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
2176	if (id < 0) {
2177		pr_err_once("workqueue: Failed to allocate a worker ID: %pe\n",
2178			    ERR_PTR(id));
2179		return NULL;
2180	}
2181
2182	worker = alloc_worker(pool->node);
2183	if (!worker) {
2184		pr_err_once("workqueue: Failed to allocate a worker\n");
2185		goto fail;
2186	}
2187
2188	worker->id = id;
2189
2190	if (pool->cpu >= 0)
2191		snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
2192			 pool->attrs->nice < 0  ? "H" : "");
2193	else
2194		snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
2195
2196	worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
2197					      "kworker/%s", id_buf);
2198	if (IS_ERR(worker->task)) {
2199		if (PTR_ERR(worker->task) == -EINTR) {
2200			pr_err("workqueue: Interrupted when creating a worker thread \"kworker/%s\"\n",
2201			       id_buf);
2202		} else {
2203			pr_err_once("workqueue: Failed to create a worker thread: %pe",
2204				    worker->task);
2205		}
2206		goto fail;
2207	}
2208
2209	set_user_nice(worker->task, pool->attrs->nice);
2210	kthread_bind_mask(worker->task, pool_allowed_cpus(pool));
2211
2212	/* successful, attach the worker to the pool */
2213	worker_attach_to_pool(worker, pool);
2214
2215	/* start the newly created worker */
2216	raw_spin_lock_irq(&pool->lock);
2217
2218	worker->pool->nr_workers++;
2219	worker_enter_idle(worker);
2220	kick_pool(pool);
2221
2222	/*
2223	 * @worker is waiting on a completion in kthread() and will trigger hung
2224	 * check if not woken up soon. As kick_pool() might not have waken it
2225	 * up, wake it up explicitly once more.
2226	 */
2227	wake_up_process(worker->task);
2228
2229	raw_spin_unlock_irq(&pool->lock);
2230
2231	return worker;
2232
2233fail:
2234	ida_free(&pool->worker_ida, id);
 
2235	kfree(worker);
2236	return NULL;
2237}
2238
2239static void unbind_worker(struct worker *worker)
2240{
2241	lockdep_assert_held(&wq_pool_attach_mutex);
2242
2243	kthread_set_per_cpu(worker->task, -1);
2244	if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
2245		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
2246	else
2247		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
2248}
2249
2250static void wake_dying_workers(struct list_head *cull_list)
2251{
2252	struct worker *worker, *tmp;
2253
2254	list_for_each_entry_safe(worker, tmp, cull_list, entry) {
2255		list_del_init(&worker->entry);
2256		unbind_worker(worker);
2257		/*
2258		 * If the worker was somehow already running, then it had to be
2259		 * in pool->idle_list when set_worker_dying() happened or we
2260		 * wouldn't have gotten here.
2261		 *
2262		 * Thus, the worker must either have observed the WORKER_DIE
2263		 * flag, or have set its state to TASK_IDLE. Either way, the
2264		 * below will be observed by the worker and is safe to do
2265		 * outside of pool->lock.
2266		 */
2267		wake_up_process(worker->task);
2268	}
2269}
2270
2271/**
2272 * set_worker_dying - Tag a worker for destruction
2273 * @worker: worker to be destroyed
2274 * @list: transfer worker away from its pool->idle_list and into list
2275 *
2276 * Tag @worker for destruction and adjust @pool stats accordingly.  The worker
2277 * should be idle.
2278 *
2279 * CONTEXT:
2280 * raw_spin_lock_irq(pool->lock).
2281 */
2282static void set_worker_dying(struct worker *worker, struct list_head *list)
2283{
2284	struct worker_pool *pool = worker->pool;
2285
2286	lockdep_assert_held(&pool->lock);
2287	lockdep_assert_held(&wq_pool_attach_mutex);
2288
2289	/* sanity check frenzy */
2290	if (WARN_ON(worker->current_work) ||
2291	    WARN_ON(!list_empty(&worker->scheduled)) ||
2292	    WARN_ON(!(worker->flags & WORKER_IDLE)))
2293		return;
2294
2295	pool->nr_workers--;
2296	pool->nr_idle--;
2297
 
2298	worker->flags |= WORKER_DIE;
2299
2300	list_move(&worker->entry, list);
2301	list_move(&worker->node, &pool->dying_workers);
2302}
2303
2304/**
2305 * idle_worker_timeout - check if some idle workers can now be deleted.
2306 * @t: The pool's idle_timer that just expired
2307 *
2308 * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in
2309 * worker_leave_idle(), as a worker flicking between idle and active while its
2310 * pool is at the too_many_workers() tipping point would cause too much timer
2311 * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let
2312 * it expire and re-evaluate things from there.
2313 */
2314static void idle_worker_timeout(struct timer_list *t)
2315{
2316	struct worker_pool *pool = from_timer(pool, t, idle_timer);
2317	bool do_cull = false;
2318
2319	if (work_pending(&pool->idle_cull_work))
2320		return;
2321
2322	raw_spin_lock_irq(&pool->lock);
2323
2324	if (too_many_workers(pool)) {
2325		struct worker *worker;
2326		unsigned long expires;
2327
2328		/* idle_list is kept in LIFO order, check the last one */
2329		worker = list_entry(pool->idle_list.prev, struct worker, entry);
2330		expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2331		do_cull = !time_before(jiffies, expires);
2332
2333		if (!do_cull)
2334			mod_timer(&pool->idle_timer, expires);
2335	}
2336	raw_spin_unlock_irq(&pool->lock);
2337
2338	if (do_cull)
2339		queue_work(system_unbound_wq, &pool->idle_cull_work);
2340}
2341
2342/**
2343 * idle_cull_fn - cull workers that have been idle for too long.
2344 * @work: the pool's work for handling these idle workers
2345 *
2346 * This goes through a pool's idle workers and gets rid of those that have been
2347 * idle for at least IDLE_WORKER_TIMEOUT seconds.
2348 *
2349 * We don't want to disturb isolated CPUs because of a pcpu kworker being
2350 * culled, so this also resets worker affinity. This requires a sleepable
2351 * context, hence the split between timer callback and work item.
2352 */
2353static void idle_cull_fn(struct work_struct *work)
2354{
2355	struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work);
2356	LIST_HEAD(cull_list);
2357
2358	/*
2359	 * Grabbing wq_pool_attach_mutex here ensures an already-running worker
2360	 * cannot proceed beyong worker_detach_from_pool() in its self-destruct
2361	 * path. This is required as a previously-preempted worker could run after
2362	 * set_worker_dying() has happened but before wake_dying_workers() did.
2363	 */
2364	mutex_lock(&wq_pool_attach_mutex);
2365	raw_spin_lock_irq(&pool->lock);
2366
2367	while (too_many_workers(pool)) {
2368		struct worker *worker;
2369		unsigned long expires;
2370
 
2371		worker = list_entry(pool->idle_list.prev, struct worker, entry);
2372		expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2373
2374		if (time_before(jiffies, expires)) {
2375			mod_timer(&pool->idle_timer, expires);
2376			break;
2377		}
2378
2379		set_worker_dying(worker, &cull_list);
2380	}
2381
2382	raw_spin_unlock_irq(&pool->lock);
2383	wake_dying_workers(&cull_list);
2384	mutex_unlock(&wq_pool_attach_mutex);
2385}
2386
2387static void send_mayday(struct work_struct *work)
2388{
2389	struct pool_workqueue *pwq = get_work_pwq(work);
2390	struct workqueue_struct *wq = pwq->wq;
2391
2392	lockdep_assert_held(&wq_mayday_lock);
2393
2394	if (!wq->rescuer)
2395		return;
2396
2397	/* mayday mayday mayday */
2398	if (list_empty(&pwq->mayday_node)) {
2399		/*
2400		 * If @pwq is for an unbound wq, its base ref may be put at
2401		 * any time due to an attribute change.  Pin @pwq until the
2402		 * rescuer is done with it.
2403		 */
2404		get_pwq(pwq);
2405		list_add_tail(&pwq->mayday_node, &wq->maydays);
2406		wake_up_process(wq->rescuer->task);
2407		pwq->stats[PWQ_STAT_MAYDAY]++;
2408	}
2409}
2410
2411static void pool_mayday_timeout(struct timer_list *t)
2412{
2413	struct worker_pool *pool = from_timer(pool, t, mayday_timer);
2414	struct work_struct *work;
2415
2416	raw_spin_lock_irq(&pool->lock);
2417	raw_spin_lock(&wq_mayday_lock);		/* for wq->maydays */
2418
2419	if (need_to_create_worker(pool)) {
2420		/*
2421		 * We've been trying to create a new worker but
2422		 * haven't been successful.  We might be hitting an
2423		 * allocation deadlock.  Send distress signals to
2424		 * rescuers.
2425		 */
2426		list_for_each_entry(work, &pool->worklist, entry)
2427			send_mayday(work);
2428	}
2429
2430	raw_spin_unlock(&wq_mayday_lock);
2431	raw_spin_unlock_irq(&pool->lock);
2432
2433	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
2434}
2435
2436/**
2437 * maybe_create_worker - create a new worker if necessary
2438 * @pool: pool to create a new worker for
2439 *
2440 * Create a new worker for @pool if necessary.  @pool is guaranteed to
2441 * have at least one idle worker on return from this function.  If
2442 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
2443 * sent to all rescuers with works scheduled on @pool to resolve
2444 * possible allocation deadlock.
2445 *
2446 * On return, need_to_create_worker() is guaranteed to be %false and
2447 * may_start_working() %true.
2448 *
2449 * LOCKING:
2450 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2451 * multiple times.  Does GFP_KERNEL allocations.  Called only from
2452 * manager.
2453 */
2454static void maybe_create_worker(struct worker_pool *pool)
2455__releases(&pool->lock)
2456__acquires(&pool->lock)
2457{
2458restart:
2459	raw_spin_unlock_irq(&pool->lock);
2460
2461	/* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
2462	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
2463
2464	while (true) {
2465		if (create_worker(pool) || !need_to_create_worker(pool))
2466			break;
2467
2468		schedule_timeout_interruptible(CREATE_COOLDOWN);
2469
2470		if (!need_to_create_worker(pool))
2471			break;
2472	}
2473
2474	del_timer_sync(&pool->mayday_timer);
2475	raw_spin_lock_irq(&pool->lock);
2476	/*
2477	 * This is necessary even after a new worker was just successfully
2478	 * created as @pool->lock was dropped and the new worker might have
2479	 * already become busy.
2480	 */
2481	if (need_to_create_worker(pool))
2482		goto restart;
2483}
2484
2485/**
2486 * manage_workers - manage worker pool
2487 * @worker: self
2488 *
2489 * Assume the manager role and manage the worker pool @worker belongs
2490 * to.  At any given time, there can be only zero or one manager per
2491 * pool.  The exclusion is handled automatically by this function.
2492 *
2493 * The caller can safely start processing works on false return.  On
2494 * true return, it's guaranteed that need_to_create_worker() is false
2495 * and may_start_working() is true.
2496 *
2497 * CONTEXT:
2498 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2499 * multiple times.  Does GFP_KERNEL allocations.
2500 *
2501 * Return:
2502 * %false if the pool doesn't need management and the caller can safely
2503 * start processing works, %true if management function was performed and
2504 * the conditions that the caller verified before calling the function may
2505 * no longer be true.
2506 */
2507static bool manage_workers(struct worker *worker)
2508{
2509	struct worker_pool *pool = worker->pool;
2510
2511	if (pool->flags & POOL_MANAGER_ACTIVE)
2512		return false;
2513
2514	pool->flags |= POOL_MANAGER_ACTIVE;
2515	pool->manager = worker;
2516
2517	maybe_create_worker(pool);
2518
2519	pool->manager = NULL;
2520	pool->flags &= ~POOL_MANAGER_ACTIVE;
2521	rcuwait_wake_up(&manager_wait);
2522	return true;
2523}
2524
2525/**
2526 * process_one_work - process single work
2527 * @worker: self
2528 * @work: work to process
2529 *
2530 * Process @work.  This function contains all the logics necessary to
2531 * process a single work including synchronization against and
2532 * interaction with other workers on the same cpu, queueing and
2533 * flushing.  As long as context requirement is met, any worker can
2534 * call this function to process a work.
2535 *
2536 * CONTEXT:
2537 * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
2538 */
2539static void process_one_work(struct worker *worker, struct work_struct *work)
2540__releases(&pool->lock)
2541__acquires(&pool->lock)
2542{
2543	struct pool_workqueue *pwq = get_work_pwq(work);
2544	struct worker_pool *pool = worker->pool;
2545	unsigned long work_data;
 
 
2546#ifdef CONFIG_LOCKDEP
2547	/*
2548	 * It is permissible to free the struct work_struct from
2549	 * inside the function that is called from it, this we need to
2550	 * take into account for lockdep too.  To avoid bogus "held
2551	 * lock freed" warnings as well as problems when looking into
2552	 * work->lockdep_map, make a copy and use that here.
2553	 */
2554	struct lockdep_map lockdep_map;
2555
2556	lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2557#endif
2558	/* ensure we're on the correct CPU */
2559	WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2560		     raw_smp_processor_id() != pool->cpu);
2561
 
 
 
 
 
 
 
 
 
 
 
 
2562	/* claim and dequeue */
2563	debug_work_deactivate(work);
2564	hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2565	worker->current_work = work;
2566	worker->current_func = work->func;
2567	worker->current_pwq = pwq;
2568	worker->current_at = worker->task->se.sum_exec_runtime;
2569	work_data = *work_data_bits(work);
2570	worker->current_color = get_work_color(work_data);
2571
2572	/*
2573	 * Record wq name for cmdline and debug reporting, may get
2574	 * overridden through set_worker_desc().
2575	 */
2576	strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2577
2578	list_del_init(&work->entry);
2579
2580	/*
2581	 * CPU intensive works don't participate in concurrency management.
2582	 * They're the scheduler's responsibility.  This takes @worker out
2583	 * of concurrency management and the next code block will chain
2584	 * execution of the pending work items.
2585	 */
2586	if (unlikely(pwq->wq->flags & WQ_CPU_INTENSIVE))
2587		worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2588
2589	/*
2590	 * Kick @pool if necessary. It's always noop for per-cpu worker pools
2591	 * since nr_running would always be >= 1 at this point. This is used to
2592	 * chain execution of the pending work items for WORKER_NOT_RUNNING
2593	 * workers such as the UNBOUND and CPU_INTENSIVE ones.
 
2594	 */
2595	kick_pool(pool);
 
2596
2597	/*
2598	 * Record the last pool and clear PENDING which should be the last
2599	 * update to @work.  Also, do this inside @pool->lock so that
2600	 * PENDING and queued state changes happen together while IRQ is
2601	 * disabled.
2602	 */
2603	set_work_pool_and_clear_pending(work, pool->id);
2604
2605	pwq->stats[PWQ_STAT_STARTED]++;
2606	raw_spin_unlock_irq(&pool->lock);
2607
2608	lock_map_acquire(&pwq->wq->lockdep_map);
2609	lock_map_acquire(&lockdep_map);
2610	/*
2611	 * Strictly speaking we should mark the invariant state without holding
2612	 * any locks, that is, before these two lock_map_acquire()'s.
2613	 *
2614	 * However, that would result in:
2615	 *
2616	 *   A(W1)
2617	 *   WFC(C)
2618	 *		A(W1)
2619	 *		C(C)
2620	 *
2621	 * Which would create W1->C->W1 dependencies, even though there is no
2622	 * actual deadlock possible. There are two solutions, using a
2623	 * read-recursive acquire on the work(queue) 'locks', but this will then
2624	 * hit the lockdep limitation on recursive locks, or simply discard
2625	 * these locks.
2626	 *
2627	 * AFAICT there is no possible deadlock scenario between the
2628	 * flush_work() and complete() primitives (except for single-threaded
2629	 * workqueues), so hiding them isn't a problem.
2630	 */
2631	lockdep_invariant_state(true);
2632	trace_workqueue_execute_start(work);
2633	worker->current_func(work);
2634	/*
2635	 * While we must be careful to not use "work" after this, the trace
2636	 * point will only record its address.
2637	 */
2638	trace_workqueue_execute_end(work, worker->current_func);
2639	pwq->stats[PWQ_STAT_COMPLETED]++;
2640	lock_map_release(&lockdep_map);
2641	lock_map_release(&pwq->wq->lockdep_map);
2642
2643	if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2644		pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2645		       "     last function: %ps\n",
2646		       current->comm, preempt_count(), task_pid_nr(current),
2647		       worker->current_func);
2648		debug_show_held_locks(current);
2649		dump_stack();
2650	}
2651
2652	/*
2653	 * The following prevents a kworker from hogging CPU on !PREEMPTION
2654	 * kernels, where a requeueing work item waiting for something to
2655	 * happen could deadlock with stop_machine as such work item could
2656	 * indefinitely requeue itself while all other CPUs are trapped in
2657	 * stop_machine. At the same time, report a quiescent RCU state so
2658	 * the same condition doesn't freeze RCU.
2659	 */
2660	cond_resched();
2661
2662	raw_spin_lock_irq(&pool->lock);
2663
2664	/*
2665	 * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
2666	 * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
2667	 * wq_cpu_intensive_thresh_us. Clear it.
2668	 */
2669	worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2670
2671	/* tag the worker for identification in schedule() */
2672	worker->last_func = worker->current_func;
2673
2674	/* we're done with it, release */
2675	hash_del(&worker->hentry);
2676	worker->current_work = NULL;
2677	worker->current_func = NULL;
2678	worker->current_pwq = NULL;
2679	worker->current_color = INT_MAX;
2680	pwq_dec_nr_in_flight(pwq, work_data);
2681}
2682
2683/**
2684 * process_scheduled_works - process scheduled works
2685 * @worker: self
2686 *
2687 * Process all scheduled works.  Please note that the scheduled list
2688 * may change while processing a work, so this function repeatedly
2689 * fetches a work from the top and executes it.
2690 *
2691 * CONTEXT:
2692 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2693 * multiple times.
2694 */
2695static void process_scheduled_works(struct worker *worker)
2696{
2697	struct work_struct *work;
2698	bool first = true;
2699
2700	while ((work = list_first_entry_or_null(&worker->scheduled,
2701						struct work_struct, entry))) {
2702		if (first) {
2703			worker->pool->watchdog_ts = jiffies;
2704			first = false;
2705		}
2706		process_one_work(worker, work);
2707	}
2708}
2709
2710static void set_pf_worker(bool val)
2711{
2712	mutex_lock(&wq_pool_attach_mutex);
2713	if (val)
2714		current->flags |= PF_WQ_WORKER;
2715	else
2716		current->flags &= ~PF_WQ_WORKER;
2717	mutex_unlock(&wq_pool_attach_mutex);
2718}
2719
2720/**
2721 * worker_thread - the worker thread function
2722 * @__worker: self
2723 *
2724 * The worker thread function.  All workers belong to a worker_pool -
2725 * either a per-cpu one or dynamic unbound one.  These workers process all
2726 * work items regardless of their specific target workqueue.  The only
2727 * exception is work items which belong to workqueues with a rescuer which
2728 * will be explained in rescuer_thread().
2729 *
2730 * Return: 0
2731 */
2732static int worker_thread(void *__worker)
2733{
2734	struct worker *worker = __worker;
2735	struct worker_pool *pool = worker->pool;
2736
2737	/* tell the scheduler that this is a workqueue worker */
2738	set_pf_worker(true);
2739woke_up:
2740	raw_spin_lock_irq(&pool->lock);
2741
2742	/* am I supposed to die? */
2743	if (unlikely(worker->flags & WORKER_DIE)) {
2744		raw_spin_unlock_irq(&pool->lock);
 
2745		set_pf_worker(false);
2746
2747		set_task_comm(worker->task, "kworker/dying");
2748		ida_free(&pool->worker_ida, worker->id);
2749		worker_detach_from_pool(worker);
2750		WARN_ON_ONCE(!list_empty(&worker->entry));
2751		kfree(worker);
2752		return 0;
2753	}
2754
2755	worker_leave_idle(worker);
2756recheck:
2757	/* no more worker necessary? */
2758	if (!need_more_worker(pool))
2759		goto sleep;
2760
2761	/* do we need to manage? */
2762	if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2763		goto recheck;
2764
2765	/*
2766	 * ->scheduled list can only be filled while a worker is
2767	 * preparing to process a work or actually processing it.
2768	 * Make sure nobody diddled with it while I was sleeping.
2769	 */
2770	WARN_ON_ONCE(!list_empty(&worker->scheduled));
2771
2772	/*
2773	 * Finish PREP stage.  We're guaranteed to have at least one idle
2774	 * worker or that someone else has already assumed the manager
2775	 * role.  This is where @worker starts participating in concurrency
2776	 * management if applicable and concurrency management is restored
2777	 * after being rebound.  See rebind_workers() for details.
2778	 */
2779	worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2780
2781	do {
2782		struct work_struct *work =
2783			list_first_entry(&pool->worklist,
2784					 struct work_struct, entry);
2785
2786		if (assign_work(work, worker, NULL))
 
 
 
 
 
 
 
 
2787			process_scheduled_works(worker);
 
2788	} while (keep_working(pool));
2789
2790	worker_set_flags(worker, WORKER_PREP);
2791sleep:
2792	/*
2793	 * pool->lock is held and there's no work to process and no need to
2794	 * manage, sleep.  Workers are woken up only while holding
2795	 * pool->lock or from local cpu, so setting the current state
2796	 * before releasing pool->lock is enough to prevent losing any
2797	 * event.
2798	 */
2799	worker_enter_idle(worker);
2800	__set_current_state(TASK_IDLE);
2801	raw_spin_unlock_irq(&pool->lock);
2802	schedule();
2803	goto woke_up;
2804}
2805
2806/**
2807 * rescuer_thread - the rescuer thread function
2808 * @__rescuer: self
2809 *
2810 * Workqueue rescuer thread function.  There's one rescuer for each
2811 * workqueue which has WQ_MEM_RECLAIM set.
2812 *
2813 * Regular work processing on a pool may block trying to create a new
2814 * worker which uses GFP_KERNEL allocation which has slight chance of
2815 * developing into deadlock if some works currently on the same queue
2816 * need to be processed to satisfy the GFP_KERNEL allocation.  This is
2817 * the problem rescuer solves.
2818 *
2819 * When such condition is possible, the pool summons rescuers of all
2820 * workqueues which have works queued on the pool and let them process
2821 * those works so that forward progress can be guaranteed.
2822 *
2823 * This should happen rarely.
2824 *
2825 * Return: 0
2826 */
2827static int rescuer_thread(void *__rescuer)
2828{
2829	struct worker *rescuer = __rescuer;
2830	struct workqueue_struct *wq = rescuer->rescue_wq;
 
2831	bool should_stop;
2832
2833	set_user_nice(current, RESCUER_NICE_LEVEL);
2834
2835	/*
2836	 * Mark rescuer as worker too.  As WORKER_PREP is never cleared, it
2837	 * doesn't participate in concurrency management.
2838	 */
2839	set_pf_worker(true);
2840repeat:
2841	set_current_state(TASK_IDLE);
2842
2843	/*
2844	 * By the time the rescuer is requested to stop, the workqueue
2845	 * shouldn't have any work pending, but @wq->maydays may still have
2846	 * pwq(s) queued.  This can happen by non-rescuer workers consuming
2847	 * all the work items before the rescuer got to them.  Go through
2848	 * @wq->maydays processing before acting on should_stop so that the
2849	 * list is always empty on exit.
2850	 */
2851	should_stop = kthread_should_stop();
2852
2853	/* see whether any pwq is asking for help */
2854	raw_spin_lock_irq(&wq_mayday_lock);
2855
2856	while (!list_empty(&wq->maydays)) {
2857		struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2858					struct pool_workqueue, mayday_node);
2859		struct worker_pool *pool = pwq->pool;
2860		struct work_struct *work, *n;
 
2861
2862		__set_current_state(TASK_RUNNING);
2863		list_del_init(&pwq->mayday_node);
2864
2865		raw_spin_unlock_irq(&wq_mayday_lock);
2866
2867		worker_attach_to_pool(rescuer, pool);
2868
2869		raw_spin_lock_irq(&pool->lock);
2870
2871		/*
2872		 * Slurp in all works issued via this workqueue and
2873		 * process'em.
2874		 */
2875		WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
2876		list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2877			if (get_work_pwq(work) == pwq &&
2878			    assign_work(work, rescuer, &n))
2879				pwq->stats[PWQ_STAT_RESCUED]++;
 
 
 
2880		}
2881
2882		if (!list_empty(&rescuer->scheduled)) {
2883			process_scheduled_works(rescuer);
2884
2885			/*
2886			 * The above execution of rescued work items could
2887			 * have created more to rescue through
2888			 * pwq_activate_first_inactive() or chained
2889			 * queueing.  Let's put @pwq back on mayday list so
2890			 * that such back-to-back work items, which may be
2891			 * being used to relieve memory pressure, don't
2892			 * incur MAYDAY_INTERVAL delay inbetween.
2893			 */
2894			if (pwq->nr_active && need_to_create_worker(pool)) {
2895				raw_spin_lock(&wq_mayday_lock);
2896				/*
2897				 * Queue iff we aren't racing destruction
2898				 * and somebody else hasn't queued it already.
2899				 */
2900				if (wq->rescuer && list_empty(&pwq->mayday_node)) {
2901					get_pwq(pwq);
2902					list_add_tail(&pwq->mayday_node, &wq->maydays);
2903				}
2904				raw_spin_unlock(&wq_mayday_lock);
2905			}
2906		}
2907
2908		/*
2909		 * Put the reference grabbed by send_mayday().  @pool won't
2910		 * go away while we're still attached to it.
2911		 */
2912		put_pwq(pwq);
2913
2914		/*
2915		 * Leave this pool. Notify regular workers; otherwise, we end up
2916		 * with 0 concurrency and stalling the execution.
 
2917		 */
2918		kick_pool(pool);
 
2919
2920		raw_spin_unlock_irq(&pool->lock);
2921
2922		worker_detach_from_pool(rescuer);
2923
2924		raw_spin_lock_irq(&wq_mayday_lock);
2925	}
2926
2927	raw_spin_unlock_irq(&wq_mayday_lock);
2928
2929	if (should_stop) {
2930		__set_current_state(TASK_RUNNING);
2931		set_pf_worker(false);
2932		return 0;
2933	}
2934
2935	/* rescuers should never participate in concurrency management */
2936	WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2937	schedule();
2938	goto repeat;
2939}
2940
2941/**
2942 * check_flush_dependency - check for flush dependency sanity
2943 * @target_wq: workqueue being flushed
2944 * @target_work: work item being flushed (NULL for workqueue flushes)
2945 *
2946 * %current is trying to flush the whole @target_wq or @target_work on it.
2947 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2948 * reclaiming memory or running on a workqueue which doesn't have
2949 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2950 * a deadlock.
2951 */
2952static void check_flush_dependency(struct workqueue_struct *target_wq,
2953				   struct work_struct *target_work)
2954{
2955	work_func_t target_func = target_work ? target_work->func : NULL;
2956	struct worker *worker;
2957
2958	if (target_wq->flags & WQ_MEM_RECLAIM)
2959		return;
2960
2961	worker = current_wq_worker();
2962
2963	WARN_ONCE(current->flags & PF_MEMALLOC,
2964		  "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
2965		  current->pid, current->comm, target_wq->name, target_func);
2966	WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2967			      (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2968		  "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
2969		  worker->current_pwq->wq->name, worker->current_func,
2970		  target_wq->name, target_func);
2971}
2972
2973struct wq_barrier {
2974	struct work_struct	work;
2975	struct completion	done;
2976	struct task_struct	*task;	/* purely informational */
2977};
2978
2979static void wq_barrier_func(struct work_struct *work)
2980{
2981	struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2982	complete(&barr->done);
2983}
2984
2985/**
2986 * insert_wq_barrier - insert a barrier work
2987 * @pwq: pwq to insert barrier into
2988 * @barr: wq_barrier to insert
2989 * @target: target work to attach @barr to
2990 * @worker: worker currently executing @target, NULL if @target is not executing
2991 *
2992 * @barr is linked to @target such that @barr is completed only after
2993 * @target finishes execution.  Please note that the ordering
2994 * guarantee is observed only with respect to @target and on the local
2995 * cpu.
2996 *
2997 * Currently, a queued barrier can't be canceled.  This is because
2998 * try_to_grab_pending() can't determine whether the work to be
2999 * grabbed is at the head of the queue and thus can't clear LINKED
3000 * flag of the previous work while there must be a valid next work
3001 * after a work with LINKED flag set.
3002 *
3003 * Note that when @worker is non-NULL, @target may be modified
3004 * underneath us, so we can't reliably determine pwq from @target.
3005 *
3006 * CONTEXT:
3007 * raw_spin_lock_irq(pool->lock).
3008 */
3009static void insert_wq_barrier(struct pool_workqueue *pwq,
3010			      struct wq_barrier *barr,
3011			      struct work_struct *target, struct worker *worker)
3012{
3013	unsigned int work_flags = 0;
3014	unsigned int work_color;
3015	struct list_head *head;
 
3016
3017	/*
3018	 * debugobject calls are safe here even with pool->lock locked
3019	 * as we know for sure that this will not trigger any of the
3020	 * checks and call back into the fixup functions where we
3021	 * might deadlock.
3022	 */
3023	INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
3024	__set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
3025
3026	init_completion_map(&barr->done, &target->lockdep_map);
3027
3028	barr->task = current;
3029
3030	/* The barrier work item does not participate in pwq->nr_active. */
3031	work_flags |= WORK_STRUCT_INACTIVE;
3032
3033	/*
3034	 * If @target is currently being executed, schedule the
3035	 * barrier to the worker; otherwise, put it after @target.
3036	 */
3037	if (worker) {
3038		head = worker->scheduled.next;
3039		work_color = worker->current_color;
3040	} else {
3041		unsigned long *bits = work_data_bits(target);
3042
3043		head = target->entry.next;
3044		/* there can already be other linked works, inherit and set */
3045		work_flags |= *bits & WORK_STRUCT_LINKED;
3046		work_color = get_work_color(*bits);
3047		__set_bit(WORK_STRUCT_LINKED_BIT, bits);
3048	}
3049
3050	pwq->nr_in_flight[work_color]++;
3051	work_flags |= work_color_to_flags(work_color);
3052
3053	insert_work(pwq, &barr->work, head, work_flags);
3054}
3055
3056/**
3057 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
3058 * @wq: workqueue being flushed
3059 * @flush_color: new flush color, < 0 for no-op
3060 * @work_color: new work color, < 0 for no-op
3061 *
3062 * Prepare pwqs for workqueue flushing.
3063 *
3064 * If @flush_color is non-negative, flush_color on all pwqs should be
3065 * -1.  If no pwq has in-flight commands at the specified color, all
3066 * pwq->flush_color's stay at -1 and %false is returned.  If any pwq
3067 * has in flight commands, its pwq->flush_color is set to
3068 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
3069 * wakeup logic is armed and %true is returned.
3070 *
3071 * The caller should have initialized @wq->first_flusher prior to
3072 * calling this function with non-negative @flush_color.  If
3073 * @flush_color is negative, no flush color update is done and %false
3074 * is returned.
3075 *
3076 * If @work_color is non-negative, all pwqs should have the same
3077 * work_color which is previous to @work_color and all will be
3078 * advanced to @work_color.
3079 *
3080 * CONTEXT:
3081 * mutex_lock(wq->mutex).
3082 *
3083 * Return:
3084 * %true if @flush_color >= 0 and there's something to flush.  %false
3085 * otherwise.
3086 */
3087static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
3088				      int flush_color, int work_color)
3089{
3090	bool wait = false;
3091	struct pool_workqueue *pwq;
3092
3093	if (flush_color >= 0) {
3094		WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
3095		atomic_set(&wq->nr_pwqs_to_flush, 1);
3096	}
3097
3098	for_each_pwq(pwq, wq) {
3099		struct worker_pool *pool = pwq->pool;
3100
3101		raw_spin_lock_irq(&pool->lock);
3102
3103		if (flush_color >= 0) {
3104			WARN_ON_ONCE(pwq->flush_color != -1);
3105
3106			if (pwq->nr_in_flight[flush_color]) {
3107				pwq->flush_color = flush_color;
3108				atomic_inc(&wq->nr_pwqs_to_flush);
3109				wait = true;
3110			}
3111		}
3112
3113		if (work_color >= 0) {
3114			WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
3115			pwq->work_color = work_color;
3116		}
3117
3118		raw_spin_unlock_irq(&pool->lock);
3119	}
3120
3121	if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
3122		complete(&wq->first_flusher->done);
3123
3124	return wait;
3125}
3126
3127/**
3128 * __flush_workqueue - ensure that any scheduled work has run to completion.
3129 * @wq: workqueue to flush
3130 *
3131 * This function sleeps until all work items which were queued on entry
3132 * have finished execution, but it is not livelocked by new incoming ones.
3133 */
3134void __flush_workqueue(struct workqueue_struct *wq)
3135{
3136	struct wq_flusher this_flusher = {
3137		.list = LIST_HEAD_INIT(this_flusher.list),
3138		.flush_color = -1,
3139		.done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
3140	};
3141	int next_color;
3142
3143	if (WARN_ON(!wq_online))
3144		return;
3145
3146	lock_map_acquire(&wq->lockdep_map);
3147	lock_map_release(&wq->lockdep_map);
3148
3149	mutex_lock(&wq->mutex);
3150
3151	/*
3152	 * Start-to-wait phase
3153	 */
3154	next_color = work_next_color(wq->work_color);
3155
3156	if (next_color != wq->flush_color) {
3157		/*
3158		 * Color space is not full.  The current work_color
3159		 * becomes our flush_color and work_color is advanced
3160		 * by one.
3161		 */
3162		WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
3163		this_flusher.flush_color = wq->work_color;
3164		wq->work_color = next_color;
3165
3166		if (!wq->first_flusher) {
3167			/* no flush in progress, become the first flusher */
3168			WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3169
3170			wq->first_flusher = &this_flusher;
3171
3172			if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
3173						       wq->work_color)) {
3174				/* nothing to flush, done */
3175				wq->flush_color = next_color;
3176				wq->first_flusher = NULL;
3177				goto out_unlock;
3178			}
3179		} else {
3180			/* wait in queue */
3181			WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
3182			list_add_tail(&this_flusher.list, &wq->flusher_queue);
3183			flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3184		}
3185	} else {
3186		/*
3187		 * Oops, color space is full, wait on overflow queue.
3188		 * The next flush completion will assign us
3189		 * flush_color and transfer to flusher_queue.
3190		 */
3191		list_add_tail(&this_flusher.list, &wq->flusher_overflow);
3192	}
3193
3194	check_flush_dependency(wq, NULL);
3195
3196	mutex_unlock(&wq->mutex);
3197
3198	wait_for_completion(&this_flusher.done);
3199
3200	/*
3201	 * Wake-up-and-cascade phase
3202	 *
3203	 * First flushers are responsible for cascading flushes and
3204	 * handling overflow.  Non-first flushers can simply return.
3205	 */
3206	if (READ_ONCE(wq->first_flusher) != &this_flusher)
3207		return;
3208
3209	mutex_lock(&wq->mutex);
3210
3211	/* we might have raced, check again with mutex held */
3212	if (wq->first_flusher != &this_flusher)
3213		goto out_unlock;
3214
3215	WRITE_ONCE(wq->first_flusher, NULL);
3216
3217	WARN_ON_ONCE(!list_empty(&this_flusher.list));
3218	WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3219
3220	while (true) {
3221		struct wq_flusher *next, *tmp;
3222
3223		/* complete all the flushers sharing the current flush color */
3224		list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
3225			if (next->flush_color != wq->flush_color)
3226				break;
3227			list_del_init(&next->list);
3228			complete(&next->done);
3229		}
3230
3231		WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
3232			     wq->flush_color != work_next_color(wq->work_color));
3233
3234		/* this flush_color is finished, advance by one */
3235		wq->flush_color = work_next_color(wq->flush_color);
3236
3237		/* one color has been freed, handle overflow queue */
3238		if (!list_empty(&wq->flusher_overflow)) {
3239			/*
3240			 * Assign the same color to all overflowed
3241			 * flushers, advance work_color and append to
3242			 * flusher_queue.  This is the start-to-wait
3243			 * phase for these overflowed flushers.
3244			 */
3245			list_for_each_entry(tmp, &wq->flusher_overflow, list)
3246				tmp->flush_color = wq->work_color;
3247
3248			wq->work_color = work_next_color(wq->work_color);
3249
3250			list_splice_tail_init(&wq->flusher_overflow,
3251					      &wq->flusher_queue);
3252			flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3253		}
3254
3255		if (list_empty(&wq->flusher_queue)) {
3256			WARN_ON_ONCE(wq->flush_color != wq->work_color);
3257			break;
3258		}
3259
3260		/*
3261		 * Need to flush more colors.  Make the next flusher
3262		 * the new first flusher and arm pwqs.
3263		 */
3264		WARN_ON_ONCE(wq->flush_color == wq->work_color);
3265		WARN_ON_ONCE(wq->flush_color != next->flush_color);
3266
3267		list_del_init(&next->list);
3268		wq->first_flusher = next;
3269
3270		if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
3271			break;
3272
3273		/*
3274		 * Meh... this color is already done, clear first
3275		 * flusher and repeat cascading.
3276		 */
3277		wq->first_flusher = NULL;
3278	}
3279
3280out_unlock:
3281	mutex_unlock(&wq->mutex);
3282}
3283EXPORT_SYMBOL(__flush_workqueue);
3284
3285/**
3286 * drain_workqueue - drain a workqueue
3287 * @wq: workqueue to drain
3288 *
3289 * Wait until the workqueue becomes empty.  While draining is in progress,
3290 * only chain queueing is allowed.  IOW, only currently pending or running
3291 * work items on @wq can queue further work items on it.  @wq is flushed
3292 * repeatedly until it becomes empty.  The number of flushing is determined
3293 * by the depth of chaining and should be relatively short.  Whine if it
3294 * takes too long.
3295 */
3296void drain_workqueue(struct workqueue_struct *wq)
3297{
3298	unsigned int flush_cnt = 0;
3299	struct pool_workqueue *pwq;
3300
3301	/*
3302	 * __queue_work() needs to test whether there are drainers, is much
3303	 * hotter than drain_workqueue() and already looks at @wq->flags.
3304	 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
3305	 */
3306	mutex_lock(&wq->mutex);
3307	if (!wq->nr_drainers++)
3308		wq->flags |= __WQ_DRAINING;
3309	mutex_unlock(&wq->mutex);
3310reflush:
3311	__flush_workqueue(wq);
3312
3313	mutex_lock(&wq->mutex);
3314
3315	for_each_pwq(pwq, wq) {
3316		bool drained;
3317
3318		raw_spin_lock_irq(&pwq->pool->lock);
3319		drained = !pwq->nr_active && list_empty(&pwq->inactive_works);
3320		raw_spin_unlock_irq(&pwq->pool->lock);
3321
3322		if (drained)
3323			continue;
3324
3325		if (++flush_cnt == 10 ||
3326		    (flush_cnt % 100 == 0 && flush_cnt <= 1000))
3327			pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
3328				wq->name, __func__, flush_cnt);
3329
3330		mutex_unlock(&wq->mutex);
3331		goto reflush;
3332	}
3333
3334	if (!--wq->nr_drainers)
3335		wq->flags &= ~__WQ_DRAINING;
3336	mutex_unlock(&wq->mutex);
3337}
3338EXPORT_SYMBOL_GPL(drain_workqueue);
3339
3340static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
3341			     bool from_cancel)
3342{
3343	struct worker *worker = NULL;
3344	struct worker_pool *pool;
3345	struct pool_workqueue *pwq;
3346
3347	might_sleep();
3348
3349	rcu_read_lock();
3350	pool = get_work_pool(work);
3351	if (!pool) {
3352		rcu_read_unlock();
3353		return false;
3354	}
3355
3356	raw_spin_lock_irq(&pool->lock);
3357	/* see the comment in try_to_grab_pending() with the same code */
3358	pwq = get_work_pwq(work);
3359	if (pwq) {
3360		if (unlikely(pwq->pool != pool))
3361			goto already_gone;
3362	} else {
3363		worker = find_worker_executing_work(pool, work);
3364		if (!worker)
3365			goto already_gone;
3366		pwq = worker->current_pwq;
3367	}
3368
3369	check_flush_dependency(pwq->wq, work);
3370
3371	insert_wq_barrier(pwq, barr, work, worker);
3372	raw_spin_unlock_irq(&pool->lock);
3373
3374	/*
3375	 * Force a lock recursion deadlock when using flush_work() inside a
3376	 * single-threaded or rescuer equipped workqueue.
3377	 *
3378	 * For single threaded workqueues the deadlock happens when the work
3379	 * is after the work issuing the flush_work(). For rescuer equipped
3380	 * workqueues the deadlock happens when the rescuer stalls, blocking
3381	 * forward progress.
3382	 */
3383	if (!from_cancel &&
3384	    (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
3385		lock_map_acquire(&pwq->wq->lockdep_map);
3386		lock_map_release(&pwq->wq->lockdep_map);
3387	}
3388	rcu_read_unlock();
3389	return true;
3390already_gone:
3391	raw_spin_unlock_irq(&pool->lock);
3392	rcu_read_unlock();
3393	return false;
3394}
3395
3396static bool __flush_work(struct work_struct *work, bool from_cancel)
3397{
3398	struct wq_barrier barr;
3399
3400	if (WARN_ON(!wq_online))
3401		return false;
3402
3403	if (WARN_ON(!work->func))
3404		return false;
3405
3406	lock_map_acquire(&work->lockdep_map);
3407	lock_map_release(&work->lockdep_map);
 
 
3408
3409	if (start_flush_work(work, &barr, from_cancel)) {
3410		wait_for_completion(&barr.done);
3411		destroy_work_on_stack(&barr.work);
3412		return true;
3413	} else {
3414		return false;
3415	}
3416}
3417
3418/**
3419 * flush_work - wait for a work to finish executing the last queueing instance
3420 * @work: the work to flush
3421 *
3422 * Wait until @work has finished execution.  @work is guaranteed to be idle
3423 * on return if it hasn't been requeued since flush started.
3424 *
3425 * Return:
3426 * %true if flush_work() waited for the work to finish execution,
3427 * %false if it was already idle.
3428 */
3429bool flush_work(struct work_struct *work)
3430{
3431	return __flush_work(work, false);
3432}
3433EXPORT_SYMBOL_GPL(flush_work);
3434
3435struct cwt_wait {
3436	wait_queue_entry_t		wait;
3437	struct work_struct	*work;
3438};
3439
3440static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
3441{
3442	struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
3443
3444	if (cwait->work != key)
3445		return 0;
3446	return autoremove_wake_function(wait, mode, sync, key);
3447}
3448
3449static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
3450{
3451	static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
3452	unsigned long flags;
3453	int ret;
3454
3455	do {
3456		ret = try_to_grab_pending(work, is_dwork, &flags);
3457		/*
3458		 * If someone else is already canceling, wait for it to
3459		 * finish.  flush_work() doesn't work for PREEMPT_NONE
3460		 * because we may get scheduled between @work's completion
3461		 * and the other canceling task resuming and clearing
3462		 * CANCELING - flush_work() will return false immediately
3463		 * as @work is no longer busy, try_to_grab_pending() will
3464		 * return -ENOENT as @work is still being canceled and the
3465		 * other canceling task won't be able to clear CANCELING as
3466		 * we're hogging the CPU.
3467		 *
3468		 * Let's wait for completion using a waitqueue.  As this
3469		 * may lead to the thundering herd problem, use a custom
3470		 * wake function which matches @work along with exclusive
3471		 * wait and wakeup.
3472		 */
3473		if (unlikely(ret == -ENOENT)) {
3474			struct cwt_wait cwait;
3475
3476			init_wait(&cwait.wait);
3477			cwait.wait.func = cwt_wakefn;
3478			cwait.work = work;
3479
3480			prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
3481						  TASK_UNINTERRUPTIBLE);
3482			if (work_is_canceling(work))
3483				schedule();
3484			finish_wait(&cancel_waitq, &cwait.wait);
3485		}
3486	} while (unlikely(ret < 0));
3487
3488	/* tell other tasks trying to grab @work to back off */
3489	mark_work_canceling(work);
3490	local_irq_restore(flags);
3491
3492	/*
3493	 * This allows canceling during early boot.  We know that @work
3494	 * isn't executing.
3495	 */
3496	if (wq_online)
3497		__flush_work(work, true);
3498
3499	clear_work_data(work);
3500
3501	/*
3502	 * Paired with prepare_to_wait() above so that either
3503	 * waitqueue_active() is visible here or !work_is_canceling() is
3504	 * visible there.
3505	 */
3506	smp_mb();
3507	if (waitqueue_active(&cancel_waitq))
3508		__wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3509
3510	return ret;
3511}
3512
3513/**
3514 * cancel_work_sync - cancel a work and wait for it to finish
3515 * @work: the work to cancel
3516 *
3517 * Cancel @work and wait for its execution to finish.  This function
3518 * can be used even if the work re-queues itself or migrates to
3519 * another workqueue.  On return from this function, @work is
3520 * guaranteed to be not pending or executing on any CPU.
3521 *
3522 * cancel_work_sync(&delayed_work->work) must not be used for
3523 * delayed_work's.  Use cancel_delayed_work_sync() instead.
3524 *
3525 * The caller must ensure that the workqueue on which @work was last
3526 * queued can't be destroyed before this function returns.
3527 *
3528 * Return:
3529 * %true if @work was pending, %false otherwise.
3530 */
3531bool cancel_work_sync(struct work_struct *work)
3532{
3533	return __cancel_work_timer(work, false);
3534}
3535EXPORT_SYMBOL_GPL(cancel_work_sync);
3536
3537/**
3538 * flush_delayed_work - wait for a dwork to finish executing the last queueing
3539 * @dwork: the delayed work to flush
3540 *
3541 * Delayed timer is cancelled and the pending work is queued for
3542 * immediate execution.  Like flush_work(), this function only
3543 * considers the last queueing instance of @dwork.
3544 *
3545 * Return:
3546 * %true if flush_work() waited for the work to finish execution,
3547 * %false if it was already idle.
3548 */
3549bool flush_delayed_work(struct delayed_work *dwork)
3550{
3551	local_irq_disable();
3552	if (del_timer_sync(&dwork->timer))
3553		__queue_work(dwork->cpu, dwork->wq, &dwork->work);
3554	local_irq_enable();
3555	return flush_work(&dwork->work);
3556}
3557EXPORT_SYMBOL(flush_delayed_work);
3558
3559/**
3560 * flush_rcu_work - wait for a rwork to finish executing the last queueing
3561 * @rwork: the rcu work to flush
3562 *
3563 * Return:
3564 * %true if flush_rcu_work() waited for the work to finish execution,
3565 * %false if it was already idle.
3566 */
3567bool flush_rcu_work(struct rcu_work *rwork)
3568{
3569	if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3570		rcu_barrier();
3571		flush_work(&rwork->work);
3572		return true;
3573	} else {
3574		return flush_work(&rwork->work);
3575	}
3576}
3577EXPORT_SYMBOL(flush_rcu_work);
3578
3579static bool __cancel_work(struct work_struct *work, bool is_dwork)
3580{
3581	unsigned long flags;
3582	int ret;
3583
3584	do {
3585		ret = try_to_grab_pending(work, is_dwork, &flags);
3586	} while (unlikely(ret == -EAGAIN));
3587
3588	if (unlikely(ret < 0))
3589		return false;
3590
3591	set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3592	local_irq_restore(flags);
3593	return ret;
3594}
3595
3596/*
3597 * See cancel_delayed_work()
3598 */
3599bool cancel_work(struct work_struct *work)
3600{
3601	return __cancel_work(work, false);
3602}
3603EXPORT_SYMBOL(cancel_work);
3604
3605/**
3606 * cancel_delayed_work - cancel a delayed work
3607 * @dwork: delayed_work to cancel
3608 *
3609 * Kill off a pending delayed_work.
3610 *
3611 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3612 * pending.
3613 *
3614 * Note:
3615 * The work callback function may still be running on return, unless
3616 * it returns %true and the work doesn't re-arm itself.  Explicitly flush or
3617 * use cancel_delayed_work_sync() to wait on it.
3618 *
3619 * This function is safe to call from any context including IRQ handler.
3620 */
3621bool cancel_delayed_work(struct delayed_work *dwork)
3622{
3623	return __cancel_work(&dwork->work, true);
3624}
3625EXPORT_SYMBOL(cancel_delayed_work);
3626
3627/**
3628 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3629 * @dwork: the delayed work cancel
3630 *
3631 * This is cancel_work_sync() for delayed works.
3632 *
3633 * Return:
3634 * %true if @dwork was pending, %false otherwise.
3635 */
3636bool cancel_delayed_work_sync(struct delayed_work *dwork)
3637{
3638	return __cancel_work_timer(&dwork->work, true);
3639}
3640EXPORT_SYMBOL(cancel_delayed_work_sync);
3641
3642/**
3643 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3644 * @func: the function to call
3645 *
3646 * schedule_on_each_cpu() executes @func on each online CPU using the
3647 * system workqueue and blocks until all CPUs have completed.
3648 * schedule_on_each_cpu() is very slow.
3649 *
3650 * Return:
3651 * 0 on success, -errno on failure.
3652 */
3653int schedule_on_each_cpu(work_func_t func)
3654{
3655	int cpu;
3656	struct work_struct __percpu *works;
3657
3658	works = alloc_percpu(struct work_struct);
3659	if (!works)
3660		return -ENOMEM;
3661
3662	cpus_read_lock();
3663
3664	for_each_online_cpu(cpu) {
3665		struct work_struct *work = per_cpu_ptr(works, cpu);
3666
3667		INIT_WORK(work, func);
3668		schedule_work_on(cpu, work);
3669	}
3670
3671	for_each_online_cpu(cpu)
3672		flush_work(per_cpu_ptr(works, cpu));
3673
3674	cpus_read_unlock();
3675	free_percpu(works);
3676	return 0;
3677}
3678
3679/**
3680 * execute_in_process_context - reliably execute the routine with user context
3681 * @fn:		the function to execute
3682 * @ew:		guaranteed storage for the execute work structure (must
3683 *		be available when the work executes)
3684 *
3685 * Executes the function immediately if process context is available,
3686 * otherwise schedules the function for delayed execution.
3687 *
3688 * Return:	0 - function was executed
3689 *		1 - function was scheduled for execution
3690 */
3691int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3692{
3693	if (!in_interrupt()) {
3694		fn(&ew->work);
3695		return 0;
3696	}
3697
3698	INIT_WORK(&ew->work, fn);
3699	schedule_work(&ew->work);
3700
3701	return 1;
3702}
3703EXPORT_SYMBOL_GPL(execute_in_process_context);
3704
3705/**
3706 * free_workqueue_attrs - free a workqueue_attrs
3707 * @attrs: workqueue_attrs to free
3708 *
3709 * Undo alloc_workqueue_attrs().
3710 */
3711void free_workqueue_attrs(struct workqueue_attrs *attrs)
3712{
3713	if (attrs) {
3714		free_cpumask_var(attrs->cpumask);
3715		free_cpumask_var(attrs->__pod_cpumask);
3716		kfree(attrs);
3717	}
3718}
3719
3720/**
3721 * alloc_workqueue_attrs - allocate a workqueue_attrs
3722 *
3723 * Allocate a new workqueue_attrs, initialize with default settings and
3724 * return it.
3725 *
3726 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3727 */
3728struct workqueue_attrs *alloc_workqueue_attrs(void)
3729{
3730	struct workqueue_attrs *attrs;
3731
3732	attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
3733	if (!attrs)
3734		goto fail;
3735	if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
3736		goto fail;
3737	if (!alloc_cpumask_var(&attrs->__pod_cpumask, GFP_KERNEL))
3738		goto fail;
3739
3740	cpumask_copy(attrs->cpumask, cpu_possible_mask);
3741	attrs->affn_scope = WQ_AFFN_DFL;
3742	return attrs;
3743fail:
3744	free_workqueue_attrs(attrs);
3745	return NULL;
3746}
3747
3748static void copy_workqueue_attrs(struct workqueue_attrs *to,
3749				 const struct workqueue_attrs *from)
3750{
3751	to->nice = from->nice;
3752	cpumask_copy(to->cpumask, from->cpumask);
3753	cpumask_copy(to->__pod_cpumask, from->__pod_cpumask);
3754	to->affn_strict = from->affn_strict;
3755
3756	/*
3757	 * Unlike hash and equality test, copying shouldn't ignore wq-only
3758	 * fields as copying is used for both pool and wq attrs. Instead,
3759	 * get_unbound_pool() explicitly clears the fields.
3760	 */
3761	to->affn_scope = from->affn_scope;
3762	to->ordered = from->ordered;
3763}
3764
3765/*
3766 * Some attrs fields are workqueue-only. Clear them for worker_pool's. See the
3767 * comments in 'struct workqueue_attrs' definition.
3768 */
3769static void wqattrs_clear_for_pool(struct workqueue_attrs *attrs)
3770{
3771	attrs->affn_scope = WQ_AFFN_NR_TYPES;
3772	attrs->ordered = false;
3773}
3774
3775/* hash value of the content of @attr */
3776static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3777{
3778	u32 hash = 0;
3779
3780	hash = jhash_1word(attrs->nice, hash);
3781	hash = jhash(cpumask_bits(attrs->cpumask),
3782		     BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3783	hash = jhash(cpumask_bits(attrs->__pod_cpumask),
3784		     BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3785	hash = jhash_1word(attrs->affn_strict, hash);
3786	return hash;
3787}
3788
3789/* content equality test */
3790static bool wqattrs_equal(const struct workqueue_attrs *a,
3791			  const struct workqueue_attrs *b)
3792{
3793	if (a->nice != b->nice)
3794		return false;
3795	if (!cpumask_equal(a->cpumask, b->cpumask))
3796		return false;
3797	if (!cpumask_equal(a->__pod_cpumask, b->__pod_cpumask))
3798		return false;
3799	if (a->affn_strict != b->affn_strict)
3800		return false;
3801	return true;
3802}
3803
3804/* Update @attrs with actually available CPUs */
3805static void wqattrs_actualize_cpumask(struct workqueue_attrs *attrs,
3806				      const cpumask_t *unbound_cpumask)
3807{
3808	/*
3809	 * Calculate the effective CPU mask of @attrs given @unbound_cpumask. If
3810	 * @attrs->cpumask doesn't overlap with @unbound_cpumask, we fallback to
3811	 * @unbound_cpumask.
3812	 */
3813	cpumask_and(attrs->cpumask, attrs->cpumask, unbound_cpumask);
3814	if (unlikely(cpumask_empty(attrs->cpumask)))
3815		cpumask_copy(attrs->cpumask, unbound_cpumask);
3816}
3817
3818/* find wq_pod_type to use for @attrs */
3819static const struct wq_pod_type *
3820wqattrs_pod_type(const struct workqueue_attrs *attrs)
3821{
3822	enum wq_affn_scope scope;
3823	struct wq_pod_type *pt;
3824
3825	/* to synchronize access to wq_affn_dfl */
3826	lockdep_assert_held(&wq_pool_mutex);
3827
3828	if (attrs->affn_scope == WQ_AFFN_DFL)
3829		scope = wq_affn_dfl;
3830	else
3831		scope = attrs->affn_scope;
3832
3833	pt = &wq_pod_types[scope];
3834
3835	if (!WARN_ON_ONCE(attrs->affn_scope == WQ_AFFN_NR_TYPES) &&
3836	    likely(pt->nr_pods))
3837		return pt;
3838
3839	/*
3840	 * Before workqueue_init_topology(), only SYSTEM is available which is
3841	 * initialized in workqueue_init_early().
3842	 */
3843	pt = &wq_pod_types[WQ_AFFN_SYSTEM];
3844	BUG_ON(!pt->nr_pods);
3845	return pt;
3846}
3847
3848/**
3849 * init_worker_pool - initialize a newly zalloc'd worker_pool
3850 * @pool: worker_pool to initialize
3851 *
3852 * Initialize a newly zalloc'd @pool.  It also allocates @pool->attrs.
3853 *
3854 * Return: 0 on success, -errno on failure.  Even on failure, all fields
3855 * inside @pool proper are initialized and put_unbound_pool() can be called
3856 * on @pool safely to release it.
3857 */
3858static int init_worker_pool(struct worker_pool *pool)
3859{
3860	raw_spin_lock_init(&pool->lock);
3861	pool->id = -1;
3862	pool->cpu = -1;
3863	pool->node = NUMA_NO_NODE;
3864	pool->flags |= POOL_DISASSOCIATED;
3865	pool->watchdog_ts = jiffies;
3866	INIT_LIST_HEAD(&pool->worklist);
3867	INIT_LIST_HEAD(&pool->idle_list);
3868	hash_init(pool->busy_hash);
3869
3870	timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3871	INIT_WORK(&pool->idle_cull_work, idle_cull_fn);
3872
3873	timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3874
3875	INIT_LIST_HEAD(&pool->workers);
3876	INIT_LIST_HEAD(&pool->dying_workers);
3877
3878	ida_init(&pool->worker_ida);
3879	INIT_HLIST_NODE(&pool->hash_node);
3880	pool->refcnt = 1;
3881
3882	/* shouldn't fail above this point */
3883	pool->attrs = alloc_workqueue_attrs();
3884	if (!pool->attrs)
3885		return -ENOMEM;
3886
3887	wqattrs_clear_for_pool(pool->attrs);
3888
3889	return 0;
3890}
3891
3892#ifdef CONFIG_LOCKDEP
3893static void wq_init_lockdep(struct workqueue_struct *wq)
3894{
3895	char *lock_name;
3896
3897	lockdep_register_key(&wq->key);
3898	lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
3899	if (!lock_name)
3900		lock_name = wq->name;
3901
3902	wq->lock_name = lock_name;
3903	lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
3904}
3905
3906static void wq_unregister_lockdep(struct workqueue_struct *wq)
3907{
3908	lockdep_unregister_key(&wq->key);
3909}
3910
3911static void wq_free_lockdep(struct workqueue_struct *wq)
3912{
3913	if (wq->lock_name != wq->name)
3914		kfree(wq->lock_name);
3915}
3916#else
3917static void wq_init_lockdep(struct workqueue_struct *wq)
3918{
3919}
3920
3921static void wq_unregister_lockdep(struct workqueue_struct *wq)
3922{
3923}
3924
3925static void wq_free_lockdep(struct workqueue_struct *wq)
3926{
3927}
3928#endif
3929
3930static void rcu_free_wq(struct rcu_head *rcu)
3931{
3932	struct workqueue_struct *wq =
3933		container_of(rcu, struct workqueue_struct, rcu);
3934
3935	wq_free_lockdep(wq);
3936	free_percpu(wq->cpu_pwq);
3937	free_workqueue_attrs(wq->unbound_attrs);
 
 
 
 
3938	kfree(wq);
3939}
3940
3941static void rcu_free_pool(struct rcu_head *rcu)
3942{
3943	struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3944
3945	ida_destroy(&pool->worker_ida);
3946	free_workqueue_attrs(pool->attrs);
3947	kfree(pool);
3948}
3949
 
 
 
 
 
 
 
 
 
 
 
 
3950/**
3951 * put_unbound_pool - put a worker_pool
3952 * @pool: worker_pool to put
3953 *
3954 * Put @pool.  If its refcnt reaches zero, it gets destroyed in RCU
3955 * safe manner.  get_unbound_pool() calls this function on its failure path
3956 * and this function should be able to release pools which went through,
3957 * successfully or not, init_worker_pool().
3958 *
3959 * Should be called with wq_pool_mutex held.
3960 */
3961static void put_unbound_pool(struct worker_pool *pool)
3962{
3963	DECLARE_COMPLETION_ONSTACK(detach_completion);
3964	struct worker *worker;
3965	LIST_HEAD(cull_list);
3966
3967	lockdep_assert_held(&wq_pool_mutex);
3968
3969	if (--pool->refcnt)
3970		return;
3971
3972	/* sanity checks */
3973	if (WARN_ON(!(pool->cpu < 0)) ||
3974	    WARN_ON(!list_empty(&pool->worklist)))
3975		return;
3976
3977	/* release id and unhash */
3978	if (pool->id >= 0)
3979		idr_remove(&worker_pool_idr, pool->id);
3980	hash_del(&pool->hash_node);
3981
3982	/*
3983	 * Become the manager and destroy all workers.  This prevents
3984	 * @pool's workers from blocking on attach_mutex.  We're the last
3985	 * manager and @pool gets freed with the flag set.
3986	 *
3987	 * Having a concurrent manager is quite unlikely to happen as we can
3988	 * only get here with
3989	 *   pwq->refcnt == pool->refcnt == 0
3990	 * which implies no work queued to the pool, which implies no worker can
3991	 * become the manager. However a worker could have taken the role of
3992	 * manager before the refcnts dropped to 0, since maybe_create_worker()
3993	 * drops pool->lock
3994	 */
3995	while (true) {
3996		rcuwait_wait_event(&manager_wait,
3997				   !(pool->flags & POOL_MANAGER_ACTIVE),
3998				   TASK_UNINTERRUPTIBLE);
3999
4000		mutex_lock(&wq_pool_attach_mutex);
4001		raw_spin_lock_irq(&pool->lock);
4002		if (!(pool->flags & POOL_MANAGER_ACTIVE)) {
4003			pool->flags |= POOL_MANAGER_ACTIVE;
4004			break;
4005		}
4006		raw_spin_unlock_irq(&pool->lock);
4007		mutex_unlock(&wq_pool_attach_mutex);
4008	}
4009
4010	while ((worker = first_idle_worker(pool)))
4011		set_worker_dying(worker, &cull_list);
4012	WARN_ON(pool->nr_workers || pool->nr_idle);
4013	raw_spin_unlock_irq(&pool->lock);
4014
4015	wake_dying_workers(&cull_list);
4016
4017	if (!list_empty(&pool->workers) || !list_empty(&pool->dying_workers))
4018		pool->detach_completion = &detach_completion;
4019	mutex_unlock(&wq_pool_attach_mutex);
4020
4021	if (pool->detach_completion)
4022		wait_for_completion(pool->detach_completion);
4023
4024	/* shut down the timers */
4025	del_timer_sync(&pool->idle_timer);
4026	cancel_work_sync(&pool->idle_cull_work);
4027	del_timer_sync(&pool->mayday_timer);
4028
4029	/* RCU protected to allow dereferences from get_work_pool() */
4030	call_rcu(&pool->rcu, rcu_free_pool);
4031}
4032
4033/**
4034 * get_unbound_pool - get a worker_pool with the specified attributes
4035 * @attrs: the attributes of the worker_pool to get
4036 *
4037 * Obtain a worker_pool which has the same attributes as @attrs, bump the
4038 * reference count and return it.  If there already is a matching
4039 * worker_pool, it will be used; otherwise, this function attempts to
4040 * create a new one.
4041 *
4042 * Should be called with wq_pool_mutex held.
4043 *
4044 * Return: On success, a worker_pool with the same attributes as @attrs.
4045 * On failure, %NULL.
4046 */
4047static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
4048{
4049	struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_NUMA];
4050	u32 hash = wqattrs_hash(attrs);
4051	struct worker_pool *pool;
4052	int pod, node = NUMA_NO_NODE;
 
4053
4054	lockdep_assert_held(&wq_pool_mutex);
4055
4056	/* do we already have a matching pool? */
4057	hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
4058		if (wqattrs_equal(pool->attrs, attrs)) {
4059			pool->refcnt++;
4060			return pool;
4061		}
4062	}
4063
4064	/* If __pod_cpumask is contained inside a NUMA pod, that's our node */
4065	for (pod = 0; pod < pt->nr_pods; pod++) {
4066		if (cpumask_subset(attrs->__pod_cpumask, pt->pod_cpus[pod])) {
4067			node = pt->pod_node[pod];
4068			break;
 
 
 
4069		}
4070	}
4071
4072	/* nope, create a new one */
4073	pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);
4074	if (!pool || init_worker_pool(pool) < 0)
4075		goto fail;
4076
4077	pool->node = node;
4078	copy_workqueue_attrs(pool->attrs, attrs);
4079	wqattrs_clear_for_pool(pool->attrs);
 
 
 
 
 
 
4080
4081	if (worker_pool_assign_id(pool) < 0)
4082		goto fail;
4083
4084	/* create and start the initial worker */
4085	if (wq_online && !create_worker(pool))
4086		goto fail;
4087
4088	/* install */
4089	hash_add(unbound_pool_hash, &pool->hash_node, hash);
4090
4091	return pool;
4092fail:
4093	if (pool)
4094		put_unbound_pool(pool);
4095	return NULL;
4096}
4097
4098static void rcu_free_pwq(struct rcu_head *rcu)
4099{
4100	kmem_cache_free(pwq_cache,
4101			container_of(rcu, struct pool_workqueue, rcu));
4102}
4103
4104/*
4105 * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero
4106 * refcnt and needs to be destroyed.
4107 */
4108static void pwq_release_workfn(struct kthread_work *work)
4109{
4110	struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
4111						  release_work);
4112	struct workqueue_struct *wq = pwq->wq;
4113	struct worker_pool *pool = pwq->pool;
4114	bool is_last = false;
4115
4116	/*
4117	 * When @pwq is not linked, it doesn't hold any reference to the
4118	 * @wq, and @wq is invalid to access.
4119	 */
4120	if (!list_empty(&pwq->pwqs_node)) {
4121		mutex_lock(&wq->mutex);
4122		list_del_rcu(&pwq->pwqs_node);
4123		is_last = list_empty(&wq->pwqs);
4124		mutex_unlock(&wq->mutex);
4125	}
4126
4127	if (wq->flags & WQ_UNBOUND) {
4128		mutex_lock(&wq_pool_mutex);
4129		put_unbound_pool(pool);
4130		mutex_unlock(&wq_pool_mutex);
4131	}
 
 
 
4132
4133	call_rcu(&pwq->rcu, rcu_free_pwq);
4134
4135	/*
4136	 * If we're the last pwq going away, @wq is already dead and no one
4137	 * is gonna access it anymore.  Schedule RCU free.
4138	 */
4139	if (is_last) {
4140		wq_unregister_lockdep(wq);
4141		call_rcu(&wq->rcu, rcu_free_wq);
4142	}
4143}
4144
4145/**
4146 * pwq_adjust_max_active - update a pwq's max_active to the current setting
4147 * @pwq: target pool_workqueue
4148 *
4149 * If @pwq isn't freezing, set @pwq->max_active to the associated
4150 * workqueue's saved_max_active and activate inactive work items
4151 * accordingly.  If @pwq is freezing, clear @pwq->max_active to zero.
4152 */
4153static void pwq_adjust_max_active(struct pool_workqueue *pwq)
4154{
4155	struct workqueue_struct *wq = pwq->wq;
4156	bool freezable = wq->flags & WQ_FREEZABLE;
4157	unsigned long flags;
4158
4159	/* for @wq->saved_max_active */
4160	lockdep_assert_held(&wq->mutex);
4161
4162	/* fast exit for non-freezable wqs */
4163	if (!freezable && pwq->max_active == wq->saved_max_active)
4164		return;
4165
4166	/* this function can be called during early boot w/ irq disabled */
4167	raw_spin_lock_irqsave(&pwq->pool->lock, flags);
4168
4169	/*
4170	 * During [un]freezing, the caller is responsible for ensuring that
4171	 * this function is called at least once after @workqueue_freezing
4172	 * is updated and visible.
4173	 */
4174	if (!freezable || !workqueue_freezing) {
4175		pwq->max_active = wq->saved_max_active;
4176
4177		while (!list_empty(&pwq->inactive_works) &&
4178		       pwq->nr_active < pwq->max_active)
4179			pwq_activate_first_inactive(pwq);
4180
4181		kick_pool(pwq->pool);
 
 
 
 
4182	} else {
4183		pwq->max_active = 0;
4184	}
4185
4186	raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
4187}
4188
4189/* initialize newly allocated @pwq which is associated with @wq and @pool */
4190static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
4191		     struct worker_pool *pool)
4192{
4193	BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
4194
4195	memset(pwq, 0, sizeof(*pwq));
4196
4197	pwq->pool = pool;
4198	pwq->wq = wq;
4199	pwq->flush_color = -1;
4200	pwq->refcnt = 1;
4201	INIT_LIST_HEAD(&pwq->inactive_works);
4202	INIT_LIST_HEAD(&pwq->pwqs_node);
4203	INIT_LIST_HEAD(&pwq->mayday_node);
4204	kthread_init_work(&pwq->release_work, pwq_release_workfn);
4205}
4206
4207/* sync @pwq with the current state of its associated wq and link it */
4208static void link_pwq(struct pool_workqueue *pwq)
4209{
4210	struct workqueue_struct *wq = pwq->wq;
4211
4212	lockdep_assert_held(&wq->mutex);
4213
4214	/* may be called multiple times, ignore if already linked */
4215	if (!list_empty(&pwq->pwqs_node))
4216		return;
4217
4218	/* set the matching work_color */
4219	pwq->work_color = wq->work_color;
4220
4221	/* sync max_active to the current setting */
4222	pwq_adjust_max_active(pwq);
4223
4224	/* link in @pwq */
4225	list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
4226}
4227
4228/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
4229static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
4230					const struct workqueue_attrs *attrs)
4231{
4232	struct worker_pool *pool;
4233	struct pool_workqueue *pwq;
4234
4235	lockdep_assert_held(&wq_pool_mutex);
4236
4237	pool = get_unbound_pool(attrs);
4238	if (!pool)
4239		return NULL;
4240
4241	pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
4242	if (!pwq) {
4243		put_unbound_pool(pool);
4244		return NULL;
4245	}
4246
4247	init_pwq(pwq, wq, pool);
4248	return pwq;
4249}
4250
4251/**
4252 * wq_calc_pod_cpumask - calculate a wq_attrs' cpumask for a pod
4253 * @attrs: the wq_attrs of the default pwq of the target workqueue
4254 * @cpu: the target CPU
4255 * @cpu_going_down: if >= 0, the CPU to consider as offline
 
 
 
 
 
4256 *
4257 * Calculate the cpumask a workqueue with @attrs should use on @pod. If
4258 * @cpu_going_down is >= 0, that cpu is considered offline during calculation.
4259 * The result is stored in @attrs->__pod_cpumask.
 
4260 *
4261 * If pod affinity is not enabled, @attrs->cpumask is always used. If enabled
4262 * and @pod has online CPUs requested by @attrs, the returned cpumask is the
4263 * intersection of the possible CPUs of @pod and @attrs->cpumask.
4264 *
4265 * The caller is responsible for ensuring that the cpumask of @pod stays stable.
 
4266 */
4267static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu,
4268				int cpu_going_down)
4269{
4270	const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
4271	int pod = pt->cpu_pod[cpu];
4272
4273	/* does @pod have any online CPUs @attrs wants? */
4274	cpumask_and(attrs->__pod_cpumask, pt->pod_cpus[pod], attrs->cpumask);
4275	cpumask_and(attrs->__pod_cpumask, attrs->__pod_cpumask, cpu_online_mask);
4276	if (cpu_going_down >= 0)
4277		cpumask_clear_cpu(cpu_going_down, attrs->__pod_cpumask);
4278
4279	if (cpumask_empty(attrs->__pod_cpumask)) {
4280		cpumask_copy(attrs->__pod_cpumask, attrs->cpumask);
4281		return;
4282	}
4283
4284	/* yeap, return possible CPUs in @pod that @attrs wants */
4285	cpumask_and(attrs->__pod_cpumask, attrs->cpumask, pt->pod_cpus[pod]);
4286
4287	if (cpumask_empty(attrs->__pod_cpumask))
4288		pr_warn_once("WARNING: workqueue cpumask: online intersect > "
4289				"possible intersect\n");
 
 
 
 
 
 
 
 
4290}
4291
4292/* install @pwq into @wq's cpu_pwq and return the old pwq */
4293static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
4294					int cpu, struct pool_workqueue *pwq)
 
4295{
4296	struct pool_workqueue *old_pwq;
4297
4298	lockdep_assert_held(&wq_pool_mutex);
4299	lockdep_assert_held(&wq->mutex);
4300
4301	/* link_pwq() can handle duplicate calls */
4302	link_pwq(pwq);
4303
4304	old_pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4305	rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq);
4306	return old_pwq;
4307}
4308
4309/* context to store the prepared attrs & pwqs before applying */
4310struct apply_wqattrs_ctx {
4311	struct workqueue_struct	*wq;		/* target workqueue */
4312	struct workqueue_attrs	*attrs;		/* attrs to apply */
4313	struct list_head	list;		/* queued for batching commit */
4314	struct pool_workqueue	*dfl_pwq;
4315	struct pool_workqueue	*pwq_tbl[];
4316};
4317
4318/* free the resources after success or abort */
4319static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
4320{
4321	if (ctx) {
4322		int cpu;
4323
4324		for_each_possible_cpu(cpu)
4325			put_pwq_unlocked(ctx->pwq_tbl[cpu]);
4326		put_pwq_unlocked(ctx->dfl_pwq);
4327
4328		free_workqueue_attrs(ctx->attrs);
4329
4330		kfree(ctx);
4331	}
4332}
4333
4334/* allocate the attrs and pwqs for later installation */
4335static struct apply_wqattrs_ctx *
4336apply_wqattrs_prepare(struct workqueue_struct *wq,
4337		      const struct workqueue_attrs *attrs,
4338		      const cpumask_var_t unbound_cpumask)
4339{
4340	struct apply_wqattrs_ctx *ctx;
4341	struct workqueue_attrs *new_attrs;
4342	int cpu;
4343
4344	lockdep_assert_held(&wq_pool_mutex);
4345
4346	if (WARN_ON(attrs->affn_scope < 0 ||
4347		    attrs->affn_scope >= WQ_AFFN_NR_TYPES))
4348		return ERR_PTR(-EINVAL);
4349
4350	ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_cpu_ids), GFP_KERNEL);
4351
4352	new_attrs = alloc_workqueue_attrs();
4353	if (!ctx || !new_attrs)
 
4354		goto out_free;
4355
4356	/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4357	 * If something goes wrong during CPU up/down, we'll fall back to
4358	 * the default pwq covering whole @attrs->cpumask.  Always create
4359	 * it even if we don't use it immediately.
4360	 */
4361	copy_workqueue_attrs(new_attrs, attrs);
4362	wqattrs_actualize_cpumask(new_attrs, unbound_cpumask);
4363	cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4364	ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
4365	if (!ctx->dfl_pwq)
4366		goto out_free;
4367
4368	for_each_possible_cpu(cpu) {
4369		if (new_attrs->ordered) {
4370			ctx->dfl_pwq->refcnt++;
4371			ctx->pwq_tbl[cpu] = ctx->dfl_pwq;
4372		} else {
4373			wq_calc_pod_cpumask(new_attrs, cpu, -1);
4374			ctx->pwq_tbl[cpu] = alloc_unbound_pwq(wq, new_attrs);
4375			if (!ctx->pwq_tbl[cpu])
4376				goto out_free;
 
 
 
4377		}
4378	}
4379
4380	/* save the user configured attrs and sanitize it. */
4381	copy_workqueue_attrs(new_attrs, attrs);
4382	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
4383	cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4384	ctx->attrs = new_attrs;
4385
4386	ctx->wq = wq;
 
4387	return ctx;
4388
4389out_free:
 
4390	free_workqueue_attrs(new_attrs);
4391	apply_wqattrs_cleanup(ctx);
4392	return ERR_PTR(-ENOMEM);
4393}
4394
4395/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
4396static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
4397{
4398	int cpu;
4399
4400	/* all pwqs have been created successfully, let's install'em */
4401	mutex_lock(&ctx->wq->mutex);
4402
4403	copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
4404
4405	/* save the previous pwq and install the new one */
4406	for_each_possible_cpu(cpu)
4407		ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
4408							ctx->pwq_tbl[cpu]);
4409
4410	/* @dfl_pwq might not have been used, ensure it's linked */
4411	link_pwq(ctx->dfl_pwq);
4412	swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
4413
4414	mutex_unlock(&ctx->wq->mutex);
4415}
4416
 
 
 
 
 
 
 
 
 
 
 
 
 
4417static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
4418					const struct workqueue_attrs *attrs)
4419{
4420	struct apply_wqattrs_ctx *ctx;
4421
4422	/* only unbound workqueues can change attributes */
4423	if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
4424		return -EINVAL;
4425
4426	/* creating multiple pwqs breaks ordering guarantee */
4427	if (!list_empty(&wq->pwqs)) {
4428		if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4429			return -EINVAL;
4430
4431		wq->flags &= ~__WQ_ORDERED;
4432	}
4433
4434	ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
4435	if (IS_ERR(ctx))
4436		return PTR_ERR(ctx);
4437
4438	/* the ctx has been prepared successfully, let's commit it */
4439	apply_wqattrs_commit(ctx);
4440	apply_wqattrs_cleanup(ctx);
4441
4442	return 0;
4443}
4444
4445/**
4446 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
4447 * @wq: the target workqueue
4448 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
4449 *
4450 * Apply @attrs to an unbound workqueue @wq. Unless disabled, this function maps
4451 * a separate pwq to each CPU pod with possibles CPUs in @attrs->cpumask so that
4452 * work items are affine to the pod it was issued on. Older pwqs are released as
4453 * in-flight work items finish. Note that a work item which repeatedly requeues
4454 * itself back-to-back will stay on its current pwq.
 
4455 *
4456 * Performs GFP_KERNEL allocations.
4457 *
4458 * Assumes caller has CPU hotplug read exclusion, i.e. cpus_read_lock().
4459 *
4460 * Return: 0 on success and -errno on failure.
4461 */
4462int apply_workqueue_attrs(struct workqueue_struct *wq,
4463			  const struct workqueue_attrs *attrs)
4464{
4465	int ret;
4466
4467	lockdep_assert_cpus_held();
4468
4469	mutex_lock(&wq_pool_mutex);
4470	ret = apply_workqueue_attrs_locked(wq, attrs);
4471	mutex_unlock(&wq_pool_mutex);
4472
4473	return ret;
4474}
4475
4476/**
4477 * wq_update_pod - update pod affinity of a wq for CPU hot[un]plug
4478 * @wq: the target workqueue
4479 * @cpu: the CPU to update pool association for
4480 * @hotplug_cpu: the CPU coming up or going down
4481 * @online: whether @cpu is coming up or going down
4482 *
4483 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4484 * %CPU_DOWN_FAILED.  @cpu is being hot[un]plugged, update pod affinity of
4485 * @wq accordingly.
4486 *
4487 *
4488 * If pod affinity can't be adjusted due to memory allocation failure, it falls
4489 * back to @wq->dfl_pwq which may not be optimal but is always correct.
4490 *
4491 * Note that when the last allowed CPU of a pod goes offline for a workqueue
4492 * with a cpumask spanning multiple pods, the workers which were already
4493 * executing the work items for the workqueue will lose their CPU affinity and
4494 * may execute on any CPU. This is similar to how per-cpu workqueues behave on
4495 * CPU_DOWN. If a workqueue user wants strict affinity, it's the user's
4496 * responsibility to flush the work item from CPU_DOWN_PREPARE.
 
4497 */
4498static void wq_update_pod(struct workqueue_struct *wq, int cpu,
4499			  int hotplug_cpu, bool online)
4500{
4501	int off_cpu = online ? -1 : hotplug_cpu;
 
4502	struct pool_workqueue *old_pwq = NULL, *pwq;
4503	struct workqueue_attrs *target_attrs;
 
4504
4505	lockdep_assert_held(&wq_pool_mutex);
4506
4507	if (!(wq->flags & WQ_UNBOUND) || wq->unbound_attrs->ordered)
 
4508		return;
4509
4510	/*
4511	 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4512	 * Let's use a preallocated one.  The following buf is protected by
4513	 * CPU hotplug exclusion.
4514	 */
4515	target_attrs = wq_update_pod_attrs_buf;
 
4516
4517	copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4518	wqattrs_actualize_cpumask(target_attrs, wq_unbound_cpumask);
4519
4520	/* nothing to do if the target cpumask matches the current pwq */
4521	wq_calc_pod_cpumask(target_attrs, cpu, off_cpu);
4522	pwq = rcu_dereference_protected(*per_cpu_ptr(wq->cpu_pwq, cpu),
4523					lockdep_is_held(&wq_pool_mutex));
4524	if (wqattrs_equal(target_attrs, pwq->pool->attrs))
4525		return;
 
 
 
 
 
 
4526
4527	/* create a new pwq */
4528	pwq = alloc_unbound_pwq(wq, target_attrs);
4529	if (!pwq) {
4530		pr_warn("workqueue: allocation failed while updating CPU pod affinity of \"%s\"\n",
4531			wq->name);
4532		goto use_dfl_pwq;
4533	}
4534
4535	/* Install the new pwq. */
4536	mutex_lock(&wq->mutex);
4537	old_pwq = install_unbound_pwq(wq, cpu, pwq);
4538	goto out_unlock;
4539
4540use_dfl_pwq:
4541	mutex_lock(&wq->mutex);
4542	raw_spin_lock_irq(&wq->dfl_pwq->pool->lock);
4543	get_pwq(wq->dfl_pwq);
4544	raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4545	old_pwq = install_unbound_pwq(wq, cpu, wq->dfl_pwq);
4546out_unlock:
4547	mutex_unlock(&wq->mutex);
4548	put_pwq_unlocked(old_pwq);
4549}
4550
4551static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4552{
4553	bool highpri = wq->flags & WQ_HIGHPRI;
4554	int cpu, ret;
4555
4556	wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
4557	if (!wq->cpu_pwq)
4558		goto enomem;
4559
4560	if (!(wq->flags & WQ_UNBOUND)) {
 
 
 
 
4561		for_each_possible_cpu(cpu) {
4562			struct pool_workqueue **pwq_p =
4563				per_cpu_ptr(wq->cpu_pwq, cpu);
4564			struct worker_pool *pool =
4565				&(per_cpu_ptr(cpu_worker_pools, cpu)[highpri]);
4566
4567			*pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL,
4568						       pool->node);
4569			if (!*pwq_p)
4570				goto enomem;
4571
4572			init_pwq(*pwq_p, wq, pool);
4573
4574			mutex_lock(&wq->mutex);
4575			link_pwq(*pwq_p);
4576			mutex_unlock(&wq->mutex);
4577		}
4578		return 0;
4579	}
4580
4581	cpus_read_lock();
4582	if (wq->flags & __WQ_ORDERED) {
4583		ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4584		/* there should only be single pwq for ordering guarantee */
4585		WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4586			      wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4587		     "ordering guarantee broken for workqueue %s\n", wq->name);
4588	} else {
4589		ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4590	}
4591	cpus_read_unlock();
4592
4593	/* for unbound pwq, flush the pwq_release_worker ensures that the
4594	 * pwq_release_workfn() completes before calling kfree(wq).
4595	 */
4596	if (ret)
4597		kthread_flush_worker(pwq_release_worker);
4598
4599	return ret;
4600
4601enomem:
4602	if (wq->cpu_pwq) {
4603		for_each_possible_cpu(cpu) {
4604			struct pool_workqueue *pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4605
4606			if (pwq)
4607				kmem_cache_free(pwq_cache, pwq);
4608		}
4609		free_percpu(wq->cpu_pwq);
4610		wq->cpu_pwq = NULL;
4611	}
4612	return -ENOMEM;
4613}
4614
4615static int wq_clamp_max_active(int max_active, unsigned int flags,
4616			       const char *name)
4617{
4618	if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
 
 
4619		pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4620			max_active, name, 1, WQ_MAX_ACTIVE);
4621
4622	return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
4623}
4624
4625/*
4626 * Workqueues which may be used during memory reclaim should have a rescuer
4627 * to guarantee forward progress.
4628 */
4629static int init_rescuer(struct workqueue_struct *wq)
4630{
4631	struct worker *rescuer;
4632	int ret;
4633
4634	if (!(wq->flags & WQ_MEM_RECLAIM))
4635		return 0;
4636
4637	rescuer = alloc_worker(NUMA_NO_NODE);
4638	if (!rescuer) {
4639		pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
4640		       wq->name);
4641		return -ENOMEM;
4642	}
4643
4644	rescuer->rescue_wq = wq;
4645	rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name);
4646	if (IS_ERR(rescuer->task)) {
4647		ret = PTR_ERR(rescuer->task);
4648		pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
4649		       wq->name, ERR_PTR(ret));
4650		kfree(rescuer);
4651		return ret;
4652	}
4653
4654	wq->rescuer = rescuer;
4655	kthread_bind_mask(rescuer->task, cpu_possible_mask);
4656	wake_up_process(rescuer->task);
4657
4658	return 0;
4659}
4660
4661__printf(1, 4)
4662struct workqueue_struct *alloc_workqueue(const char *fmt,
4663					 unsigned int flags,
4664					 int max_active, ...)
4665{
 
4666	va_list args;
4667	struct workqueue_struct *wq;
4668	struct pool_workqueue *pwq;
4669
4670	/*
4671	 * Unbound && max_active == 1 used to imply ordered, which is no longer
4672	 * the case on many machines due to per-pod pools. While
4673	 * alloc_ordered_workqueue() is the right way to create an ordered
4674	 * workqueue, keep the previous behavior to avoid subtle breakages.
 
4675	 */
4676	if ((flags & WQ_UNBOUND) && max_active == 1)
4677		flags |= __WQ_ORDERED;
4678
4679	/* see the comment above the definition of WQ_POWER_EFFICIENT */
4680	if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4681		flags |= WQ_UNBOUND;
4682
4683	/* allocate wq and format name */
4684	wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 
 
 
4685	if (!wq)
4686		return NULL;
4687
4688	if (flags & WQ_UNBOUND) {
4689		wq->unbound_attrs = alloc_workqueue_attrs();
4690		if (!wq->unbound_attrs)
4691			goto err_free_wq;
4692	}
4693
4694	va_start(args, max_active);
4695	vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4696	va_end(args);
4697
4698	max_active = max_active ?: WQ_DFL_ACTIVE;
4699	max_active = wq_clamp_max_active(max_active, flags, wq->name);
4700
4701	/* init wq */
4702	wq->flags = flags;
4703	wq->saved_max_active = max_active;
4704	mutex_init(&wq->mutex);
4705	atomic_set(&wq->nr_pwqs_to_flush, 0);
4706	INIT_LIST_HEAD(&wq->pwqs);
4707	INIT_LIST_HEAD(&wq->flusher_queue);
4708	INIT_LIST_HEAD(&wq->flusher_overflow);
4709	INIT_LIST_HEAD(&wq->maydays);
4710
4711	wq_init_lockdep(wq);
4712	INIT_LIST_HEAD(&wq->list);
4713
4714	if (alloc_and_link_pwqs(wq) < 0)
4715		goto err_unreg_lockdep;
4716
4717	if (wq_online && init_rescuer(wq) < 0)
4718		goto err_destroy;
4719
4720	if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4721		goto err_destroy;
4722
4723	/*
4724	 * wq_pool_mutex protects global freeze state and workqueues list.
4725	 * Grab it, adjust max_active and add the new @wq to workqueues
4726	 * list.
4727	 */
4728	mutex_lock(&wq_pool_mutex);
4729
4730	mutex_lock(&wq->mutex);
4731	for_each_pwq(pwq, wq)
4732		pwq_adjust_max_active(pwq);
4733	mutex_unlock(&wq->mutex);
4734
4735	list_add_tail_rcu(&wq->list, &workqueues);
4736
4737	mutex_unlock(&wq_pool_mutex);
4738
4739	return wq;
4740
4741err_unreg_lockdep:
4742	wq_unregister_lockdep(wq);
4743	wq_free_lockdep(wq);
4744err_free_wq:
4745	free_workqueue_attrs(wq->unbound_attrs);
4746	kfree(wq);
4747	return NULL;
4748err_destroy:
4749	destroy_workqueue(wq);
4750	return NULL;
4751}
4752EXPORT_SYMBOL_GPL(alloc_workqueue);
4753
4754static bool pwq_busy(struct pool_workqueue *pwq)
4755{
4756	int i;
4757
4758	for (i = 0; i < WORK_NR_COLORS; i++)
4759		if (pwq->nr_in_flight[i])
4760			return true;
4761
4762	if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1))
4763		return true;
4764	if (pwq->nr_active || !list_empty(&pwq->inactive_works))
4765		return true;
4766
4767	return false;
4768}
4769
4770/**
4771 * destroy_workqueue - safely terminate a workqueue
4772 * @wq: target workqueue
4773 *
4774 * Safely destroy a workqueue. All work currently pending will be done first.
4775 */
4776void destroy_workqueue(struct workqueue_struct *wq)
4777{
4778	struct pool_workqueue *pwq;
4779	int cpu;
4780
4781	/*
4782	 * Remove it from sysfs first so that sanity check failure doesn't
4783	 * lead to sysfs name conflicts.
4784	 */
4785	workqueue_sysfs_unregister(wq);
4786
4787	/* mark the workqueue destruction is in progress */
4788	mutex_lock(&wq->mutex);
4789	wq->flags |= __WQ_DESTROYING;
4790	mutex_unlock(&wq->mutex);
4791
4792	/* drain it before proceeding with destruction */
4793	drain_workqueue(wq);
4794
4795	/* kill rescuer, if sanity checks fail, leave it w/o rescuer */
4796	if (wq->rescuer) {
4797		struct worker *rescuer = wq->rescuer;
4798
4799		/* this prevents new queueing */
4800		raw_spin_lock_irq(&wq_mayday_lock);
4801		wq->rescuer = NULL;
4802		raw_spin_unlock_irq(&wq_mayday_lock);
4803
4804		/* rescuer will empty maydays list before exiting */
4805		kthread_stop(rescuer->task);
4806		kfree(rescuer);
4807	}
4808
4809	/*
4810	 * Sanity checks - grab all the locks so that we wait for all
4811	 * in-flight operations which may do put_pwq().
4812	 */
4813	mutex_lock(&wq_pool_mutex);
4814	mutex_lock(&wq->mutex);
4815	for_each_pwq(pwq, wq) {
4816		raw_spin_lock_irq(&pwq->pool->lock);
4817		if (WARN_ON(pwq_busy(pwq))) {
4818			pr_warn("%s: %s has the following busy pwq\n",
4819				__func__, wq->name);
4820			show_pwq(pwq);
4821			raw_spin_unlock_irq(&pwq->pool->lock);
4822			mutex_unlock(&wq->mutex);
4823			mutex_unlock(&wq_pool_mutex);
4824			show_one_workqueue(wq);
4825			return;
4826		}
4827		raw_spin_unlock_irq(&pwq->pool->lock);
4828	}
4829	mutex_unlock(&wq->mutex);
4830
4831	/*
4832	 * wq list is used to freeze wq, remove from list after
4833	 * flushing is complete in case freeze races us.
4834	 */
4835	list_del_rcu(&wq->list);
4836	mutex_unlock(&wq_pool_mutex);
4837
4838	/*
4839	 * We're the sole accessor of @wq. Directly access cpu_pwq and dfl_pwq
4840	 * to put the base refs. @wq will be auto-destroyed from the last
4841	 * pwq_put. RCU read lock prevents @wq from going away from under us.
4842	 */
4843	rcu_read_lock();
 
 
 
 
 
 
 
 
 
 
 
 
4844
4845	for_each_possible_cpu(cpu) {
4846		pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4847		RCU_INIT_POINTER(*per_cpu_ptr(wq->cpu_pwq, cpu), NULL);
 
 
 
4848		put_pwq_unlocked(pwq);
4849	}
4850
4851	put_pwq_unlocked(wq->dfl_pwq);
4852	wq->dfl_pwq = NULL;
4853
4854	rcu_read_unlock();
4855}
4856EXPORT_SYMBOL_GPL(destroy_workqueue);
4857
4858/**
4859 * workqueue_set_max_active - adjust max_active of a workqueue
4860 * @wq: target workqueue
4861 * @max_active: new max_active value.
4862 *
4863 * Set max_active of @wq to @max_active.
4864 *
4865 * CONTEXT:
4866 * Don't call from IRQ context.
4867 */
4868void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4869{
4870	struct pool_workqueue *pwq;
4871
4872	/* disallow meddling with max_active for ordered workqueues */
4873	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4874		return;
4875
4876	max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4877
4878	mutex_lock(&wq->mutex);
4879
4880	wq->flags &= ~__WQ_ORDERED;
4881	wq->saved_max_active = max_active;
4882
4883	for_each_pwq(pwq, wq)
4884		pwq_adjust_max_active(pwq);
4885
4886	mutex_unlock(&wq->mutex);
4887}
4888EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4889
4890/**
4891 * current_work - retrieve %current task's work struct
4892 *
4893 * Determine if %current task is a workqueue worker and what it's working on.
4894 * Useful to find out the context that the %current task is running in.
4895 *
4896 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4897 */
4898struct work_struct *current_work(void)
4899{
4900	struct worker *worker = current_wq_worker();
4901
4902	return worker ? worker->current_work : NULL;
4903}
4904EXPORT_SYMBOL(current_work);
4905
4906/**
4907 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4908 *
4909 * Determine whether %current is a workqueue rescuer.  Can be used from
4910 * work functions to determine whether it's being run off the rescuer task.
4911 *
4912 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4913 */
4914bool current_is_workqueue_rescuer(void)
4915{
4916	struct worker *worker = current_wq_worker();
4917
4918	return worker && worker->rescue_wq;
4919}
4920
4921/**
4922 * workqueue_congested - test whether a workqueue is congested
4923 * @cpu: CPU in question
4924 * @wq: target workqueue
4925 *
4926 * Test whether @wq's cpu workqueue for @cpu is congested.  There is
4927 * no synchronization around this function and the test result is
4928 * unreliable and only useful as advisory hints or for debugging.
4929 *
4930 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4931 *
4932 * With the exception of ordered workqueues, all workqueues have per-cpu
4933 * pool_workqueues, each with its own congested state. A workqueue being
4934 * congested on one CPU doesn't mean that the workqueue is contested on any
4935 * other CPUs.
4936 *
4937 * Return:
4938 * %true if congested, %false otherwise.
4939 */
4940bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4941{
4942	struct pool_workqueue *pwq;
4943	bool ret;
4944
4945	rcu_read_lock();
4946	preempt_disable();
4947
4948	if (cpu == WORK_CPU_UNBOUND)
4949		cpu = smp_processor_id();
4950
4951	pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4952	ret = !list_empty(&pwq->inactive_works);
 
 
4953
 
4954	preempt_enable();
4955	rcu_read_unlock();
4956
4957	return ret;
4958}
4959EXPORT_SYMBOL_GPL(workqueue_congested);
4960
4961/**
4962 * work_busy - test whether a work is currently pending or running
4963 * @work: the work to be tested
4964 *
4965 * Test whether @work is currently pending or running.  There is no
4966 * synchronization around this function and the test result is
4967 * unreliable and only useful as advisory hints or for debugging.
4968 *
4969 * Return:
4970 * OR'd bitmask of WORK_BUSY_* bits.
4971 */
4972unsigned int work_busy(struct work_struct *work)
4973{
4974	struct worker_pool *pool;
4975	unsigned long flags;
4976	unsigned int ret = 0;
4977
4978	if (work_pending(work))
4979		ret |= WORK_BUSY_PENDING;
4980
4981	rcu_read_lock();
4982	pool = get_work_pool(work);
4983	if (pool) {
4984		raw_spin_lock_irqsave(&pool->lock, flags);
4985		if (find_worker_executing_work(pool, work))
4986			ret |= WORK_BUSY_RUNNING;
4987		raw_spin_unlock_irqrestore(&pool->lock, flags);
4988	}
4989	rcu_read_unlock();
4990
4991	return ret;
4992}
4993EXPORT_SYMBOL_GPL(work_busy);
4994
4995/**
4996 * set_worker_desc - set description for the current work item
4997 * @fmt: printf-style format string
4998 * @...: arguments for the format string
4999 *
5000 * This function can be called by a running work function to describe what
5001 * the work item is about.  If the worker task gets dumped, this
5002 * information will be printed out together to help debugging.  The
5003 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
5004 */
5005void set_worker_desc(const char *fmt, ...)
5006{
5007	struct worker *worker = current_wq_worker();
5008	va_list args;
5009
5010	if (worker) {
5011		va_start(args, fmt);
5012		vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
5013		va_end(args);
5014	}
5015}
5016EXPORT_SYMBOL_GPL(set_worker_desc);
5017
5018/**
5019 * print_worker_info - print out worker information and description
5020 * @log_lvl: the log level to use when printing
5021 * @task: target task
5022 *
5023 * If @task is a worker and currently executing a work item, print out the
5024 * name of the workqueue being serviced and worker description set with
5025 * set_worker_desc() by the currently executing work item.
5026 *
5027 * This function can be safely called on any task as long as the
5028 * task_struct itself is accessible.  While safe, this function isn't
5029 * synchronized and may print out mixups or garbages of limited length.
5030 */
5031void print_worker_info(const char *log_lvl, struct task_struct *task)
5032{
5033	work_func_t *fn = NULL;
5034	char name[WQ_NAME_LEN] = { };
5035	char desc[WORKER_DESC_LEN] = { };
5036	struct pool_workqueue *pwq = NULL;
5037	struct workqueue_struct *wq = NULL;
5038	struct worker *worker;
5039
5040	if (!(task->flags & PF_WQ_WORKER))
5041		return;
5042
5043	/*
5044	 * This function is called without any synchronization and @task
5045	 * could be in any state.  Be careful with dereferences.
5046	 */
5047	worker = kthread_probe_data(task);
5048
5049	/*
5050	 * Carefully copy the associated workqueue's workfn, name and desc.
5051	 * Keep the original last '\0' in case the original is garbage.
5052	 */
5053	copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
5054	copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
5055	copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
5056	copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
5057	copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
5058
5059	if (fn || name[0] || desc[0]) {
5060		printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
5061		if (strcmp(name, desc))
5062			pr_cont(" (%s)", desc);
5063		pr_cont("\n");
5064	}
5065}
5066
5067static void pr_cont_pool_info(struct worker_pool *pool)
5068{
5069	pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
5070	if (pool->node != NUMA_NO_NODE)
5071		pr_cont(" node=%d", pool->node);
5072	pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
5073}
5074
5075struct pr_cont_work_struct {
5076	bool comma;
5077	work_func_t func;
5078	long ctr;
5079};
5080
5081static void pr_cont_work_flush(bool comma, work_func_t func, struct pr_cont_work_struct *pcwsp)
5082{
5083	if (!pcwsp->ctr)
5084		goto out_record;
5085	if (func == pcwsp->func) {
5086		pcwsp->ctr++;
5087		return;
5088	}
5089	if (pcwsp->ctr == 1)
5090		pr_cont("%s %ps", pcwsp->comma ? "," : "", pcwsp->func);
5091	else
5092		pr_cont("%s %ld*%ps", pcwsp->comma ? "," : "", pcwsp->ctr, pcwsp->func);
5093	pcwsp->ctr = 0;
5094out_record:
5095	if ((long)func == -1L)
5096		return;
5097	pcwsp->comma = comma;
5098	pcwsp->func = func;
5099	pcwsp->ctr = 1;
5100}
5101
5102static void pr_cont_work(bool comma, struct work_struct *work, struct pr_cont_work_struct *pcwsp)
5103{
5104	if (work->func == wq_barrier_func) {
5105		struct wq_barrier *barr;
5106
5107		barr = container_of(work, struct wq_barrier, work);
5108
5109		pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5110		pr_cont("%s BAR(%d)", comma ? "," : "",
5111			task_pid_nr(barr->task));
5112	} else {
5113		if (!comma)
5114			pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5115		pr_cont_work_flush(comma, work->func, pcwsp);
5116	}
5117}
5118
5119static void show_pwq(struct pool_workqueue *pwq)
5120{
5121	struct pr_cont_work_struct pcws = { .ctr = 0, };
5122	struct worker_pool *pool = pwq->pool;
5123	struct work_struct *work;
5124	struct worker *worker;
5125	bool has_in_flight = false, has_pending = false;
5126	int bkt;
5127
5128	pr_info("  pwq %d:", pool->id);
5129	pr_cont_pool_info(pool);
5130
5131	pr_cont(" active=%d/%d refcnt=%d%s\n",
5132		pwq->nr_active, pwq->max_active, pwq->refcnt,
5133		!list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
5134
5135	hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5136		if (worker->current_pwq == pwq) {
5137			has_in_flight = true;
5138			break;
5139		}
5140	}
5141	if (has_in_flight) {
5142		bool comma = false;
5143
5144		pr_info("    in-flight:");
5145		hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5146			if (worker->current_pwq != pwq)
5147				continue;
5148
5149			pr_cont("%s %d%s:%ps", comma ? "," : "",
5150				task_pid_nr(worker->task),
5151				worker->rescue_wq ? "(RESCUER)" : "",
5152				worker->current_func);
5153			list_for_each_entry(work, &worker->scheduled, entry)
5154				pr_cont_work(false, work, &pcws);
5155			pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5156			comma = true;
5157		}
5158		pr_cont("\n");
5159	}
5160
5161	list_for_each_entry(work, &pool->worklist, entry) {
5162		if (get_work_pwq(work) == pwq) {
5163			has_pending = true;
5164			break;
5165		}
5166	}
5167	if (has_pending) {
5168		bool comma = false;
5169
5170		pr_info("    pending:");
5171		list_for_each_entry(work, &pool->worklist, entry) {
5172			if (get_work_pwq(work) != pwq)
5173				continue;
5174
5175			pr_cont_work(comma, work, &pcws);
5176			comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5177		}
5178		pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5179		pr_cont("\n");
5180	}
5181
5182	if (!list_empty(&pwq->inactive_works)) {
5183		bool comma = false;
5184
5185		pr_info("    inactive:");
5186		list_for_each_entry(work, &pwq->inactive_works, entry) {
5187			pr_cont_work(comma, work, &pcws);
5188			comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5189		}
5190		pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5191		pr_cont("\n");
5192	}
5193}
5194
5195/**
5196 * show_one_workqueue - dump state of specified workqueue
5197 * @wq: workqueue whose state will be printed
5198 */
5199void show_one_workqueue(struct workqueue_struct *wq)
5200{
5201	struct pool_workqueue *pwq;
5202	bool idle = true;
5203	unsigned long flags;
5204
5205	for_each_pwq(pwq, wq) {
5206		if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5207			idle = false;
5208			break;
5209		}
5210	}
5211	if (idle) /* Nothing to print for idle workqueue */
5212		return;
5213
5214	pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
5215
5216	for_each_pwq(pwq, wq) {
5217		raw_spin_lock_irqsave(&pwq->pool->lock, flags);
5218		if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5219			/*
5220			 * Defer printing to avoid deadlocks in console
5221			 * drivers that queue work while holding locks
5222			 * also taken in their write paths.
5223			 */
5224			printk_deferred_enter();
5225			show_pwq(pwq);
5226			printk_deferred_exit();
5227		}
5228		raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
5229		/*
5230		 * We could be printing a lot from atomic context, e.g.
5231		 * sysrq-t -> show_all_workqueues(). Avoid triggering
5232		 * hard lockup.
5233		 */
5234		touch_nmi_watchdog();
5235	}
5236
5237}
5238
5239/**
5240 * show_one_worker_pool - dump state of specified worker pool
5241 * @pool: worker pool whose state will be printed
5242 */
5243static void show_one_worker_pool(struct worker_pool *pool)
5244{
5245	struct worker *worker;
5246	bool first = true;
5247	unsigned long flags;
5248	unsigned long hung = 0;
5249
5250	raw_spin_lock_irqsave(&pool->lock, flags);
5251	if (pool->nr_workers == pool->nr_idle)
5252		goto next_pool;
5253
5254	/* How long the first pending work is waiting for a worker. */
5255	if (!list_empty(&pool->worklist))
5256		hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000;
5257
5258	/*
5259	 * Defer printing to avoid deadlocks in console drivers that
5260	 * queue work while holding locks also taken in their write
5261	 * paths.
5262	 */
5263	printk_deferred_enter();
5264	pr_info("pool %d:", pool->id);
5265	pr_cont_pool_info(pool);
5266	pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers);
5267	if (pool->manager)
5268		pr_cont(" manager: %d",
5269			task_pid_nr(pool->manager->task));
5270	list_for_each_entry(worker, &pool->idle_list, entry) {
5271		pr_cont(" %s%d", first ? "idle: " : "",
5272			task_pid_nr(worker->task));
5273		first = false;
5274	}
5275	pr_cont("\n");
5276	printk_deferred_exit();
5277next_pool:
5278	raw_spin_unlock_irqrestore(&pool->lock, flags);
5279	/*
5280	 * We could be printing a lot from atomic context, e.g.
5281	 * sysrq-t -> show_all_workqueues(). Avoid triggering
5282	 * hard lockup.
5283	 */
5284	touch_nmi_watchdog();
5285
5286}
5287
5288/**
5289 * show_all_workqueues - dump workqueue state
5290 *
5291 * Called from a sysrq handler and prints out all busy workqueues and pools.
 
5292 */
5293void show_all_workqueues(void)
5294{
5295	struct workqueue_struct *wq;
5296	struct worker_pool *pool;
 
5297	int pi;
5298
5299	rcu_read_lock();
5300
5301	pr_info("Showing busy workqueues and worker pools:\n");
5302
5303	list_for_each_entry_rcu(wq, &workqueues, list)
5304		show_one_workqueue(wq);
 
5305
5306	for_each_pool(pool, pi)
5307		show_one_worker_pool(pool);
 
 
 
 
 
 
5308
5309	rcu_read_unlock();
5310}
5311
5312/**
5313 * show_freezable_workqueues - dump freezable workqueue state
5314 *
5315 * Called from try_to_freeze_tasks() and prints out all freezable workqueues
5316 * still busy.
5317 */
5318void show_freezable_workqueues(void)
5319{
5320	struct workqueue_struct *wq;
 
 
 
 
5321
5322	rcu_read_lock();
 
 
5323
5324	pr_info("Showing freezable workqueues that are still busy:\n");
 
 
5325
5326	list_for_each_entry_rcu(wq, &workqueues, list) {
5327		if (!(wq->flags & WQ_FREEZABLE))
5328			continue;
5329		show_one_workqueue(wq);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5330	}
5331
5332	rcu_read_unlock();
5333}
5334
5335/* used to show worker information through /proc/PID/{comm,stat,status} */
5336void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
5337{
5338	int off;
5339
5340	/* always show the actual comm */
5341	off = strscpy(buf, task->comm, size);
5342	if (off < 0)
5343		return;
5344
5345	/* stabilize PF_WQ_WORKER and worker pool association */
5346	mutex_lock(&wq_pool_attach_mutex);
5347
5348	if (task->flags & PF_WQ_WORKER) {
5349		struct worker *worker = kthread_data(task);
5350		struct worker_pool *pool = worker->pool;
5351
5352		if (pool) {
5353			raw_spin_lock_irq(&pool->lock);
5354			/*
5355			 * ->desc tracks information (wq name or
5356			 * set_worker_desc()) for the latest execution.  If
5357			 * current, prepend '+', otherwise '-'.
5358			 */
5359			if (worker->desc[0] != '\0') {
5360				if (worker->current_work)
5361					scnprintf(buf + off, size - off, "+%s",
5362						  worker->desc);
5363				else
5364					scnprintf(buf + off, size - off, "-%s",
5365						  worker->desc);
5366			}
5367			raw_spin_unlock_irq(&pool->lock);
5368		}
5369	}
5370
5371	mutex_unlock(&wq_pool_attach_mutex);
5372}
5373
5374#ifdef CONFIG_SMP
5375
5376/*
5377 * CPU hotplug.
5378 *
5379 * There are two challenges in supporting CPU hotplug.  Firstly, there
5380 * are a lot of assumptions on strong associations among work, pwq and
5381 * pool which make migrating pending and scheduled works very
5382 * difficult to implement without impacting hot paths.  Secondly,
5383 * worker pools serve mix of short, long and very long running works making
5384 * blocked draining impractical.
5385 *
5386 * This is solved by allowing the pools to be disassociated from the CPU
5387 * running as an unbound one and allowing it to be reattached later if the
5388 * cpu comes back online.
5389 */
5390
5391static void unbind_workers(int cpu)
5392{
5393	struct worker_pool *pool;
5394	struct worker *worker;
5395
5396	for_each_cpu_worker_pool(pool, cpu) {
5397		mutex_lock(&wq_pool_attach_mutex);
5398		raw_spin_lock_irq(&pool->lock);
5399
5400		/*
5401		 * We've blocked all attach/detach operations. Make all workers
5402		 * unbound and set DISASSOCIATED.  Before this, all workers
5403		 * must be on the cpu.  After this, they may become diasporas.
5404		 * And the preemption disabled section in their sched callbacks
5405		 * are guaranteed to see WORKER_UNBOUND since the code here
5406		 * is on the same cpu.
5407		 */
5408		for_each_pool_worker(worker, pool)
5409			worker->flags |= WORKER_UNBOUND;
5410
5411		pool->flags |= POOL_DISASSOCIATED;
5412
 
 
 
5413		/*
5414		 * The handling of nr_running in sched callbacks are disabled
5415		 * now.  Zap nr_running.  After this, nr_running stays zero and
5416		 * need_more_worker() and keep_working() are always true as
5417		 * long as the worklist is not empty.  This pool now behaves as
5418		 * an unbound (in terms of concurrency management) pool which
 
 
 
 
 
 
 
 
5419		 * are served by workers tied to the pool.
5420		 */
5421		pool->nr_running = 0;
5422
5423		/*
5424		 * With concurrency management just turned off, a busy
5425		 * worker blocking could lead to lengthy stalls.  Kick off
5426		 * unbound chain execution of currently pending work items.
5427		 */
5428		kick_pool(pool);
5429
5430		raw_spin_unlock_irq(&pool->lock);
5431
5432		for_each_pool_worker(worker, pool)
5433			unbind_worker(worker);
5434
5435		mutex_unlock(&wq_pool_attach_mutex);
5436	}
5437}
5438
5439/**
5440 * rebind_workers - rebind all workers of a pool to the associated CPU
5441 * @pool: pool of interest
5442 *
5443 * @pool->cpu is coming online.  Rebind all workers to the CPU.
5444 */
5445static void rebind_workers(struct worker_pool *pool)
5446{
5447	struct worker *worker;
5448
5449	lockdep_assert_held(&wq_pool_attach_mutex);
5450
5451	/*
5452	 * Restore CPU affinity of all workers.  As all idle workers should
5453	 * be on the run-queue of the associated CPU before any local
5454	 * wake-ups for concurrency management happen, restore CPU affinity
5455	 * of all workers first and then clear UNBOUND.  As we're called
5456	 * from CPU_ONLINE, the following shouldn't fail.
5457	 */
5458	for_each_pool_worker(worker, pool) {
5459		kthread_set_per_cpu(worker->task, pool->cpu);
5460		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
5461						  pool_allowed_cpus(pool)) < 0);
5462	}
5463
5464	raw_spin_lock_irq(&pool->lock);
5465
5466	pool->flags &= ~POOL_DISASSOCIATED;
5467
5468	for_each_pool_worker(worker, pool) {
5469		unsigned int worker_flags = worker->flags;
5470
5471		/*
 
 
 
 
 
 
 
 
 
 
 
5472		 * We want to clear UNBOUND but can't directly call
5473		 * worker_clr_flags() or adjust nr_running.  Atomically
5474		 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
5475		 * @worker will clear REBOUND using worker_clr_flags() when
5476		 * it initiates the next execution cycle thus restoring
5477		 * concurrency management.  Note that when or whether
5478		 * @worker clears REBOUND doesn't affect correctness.
5479		 *
5480		 * WRITE_ONCE() is necessary because @worker->flags may be
5481		 * tested without holding any lock in
5482		 * wq_worker_running().  Without it, NOT_RUNNING test may
5483		 * fail incorrectly leading to premature concurrency
5484		 * management operations.
5485		 */
5486		WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
5487		worker_flags |= WORKER_REBOUND;
5488		worker_flags &= ~WORKER_UNBOUND;
5489		WRITE_ONCE(worker->flags, worker_flags);
5490	}
5491
5492	raw_spin_unlock_irq(&pool->lock);
5493}
5494
5495/**
5496 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
5497 * @pool: unbound pool of interest
5498 * @cpu: the CPU which is coming up
5499 *
5500 * An unbound pool may end up with a cpumask which doesn't have any online
5501 * CPUs.  When a worker of such pool get scheduled, the scheduler resets
5502 * its cpus_allowed.  If @cpu is in @pool's cpumask which didn't have any
5503 * online CPU before, cpus_allowed of all its workers should be restored.
5504 */
5505static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
5506{
5507	static cpumask_t cpumask;
5508	struct worker *worker;
5509
5510	lockdep_assert_held(&wq_pool_attach_mutex);
5511
5512	/* is @cpu allowed for @pool? */
5513	if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
5514		return;
5515
5516	cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
5517
5518	/* as we're called from CPU_ONLINE, the following shouldn't fail */
5519	for_each_pool_worker(worker, pool)
5520		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
5521}
5522
5523int workqueue_prepare_cpu(unsigned int cpu)
5524{
5525	struct worker_pool *pool;
5526
5527	for_each_cpu_worker_pool(pool, cpu) {
5528		if (pool->nr_workers)
5529			continue;
5530		if (!create_worker(pool))
5531			return -ENOMEM;
5532	}
5533	return 0;
5534}
5535
5536int workqueue_online_cpu(unsigned int cpu)
5537{
5538	struct worker_pool *pool;
5539	struct workqueue_struct *wq;
5540	int pi;
5541
5542	mutex_lock(&wq_pool_mutex);
5543
5544	for_each_pool(pool, pi) {
5545		mutex_lock(&wq_pool_attach_mutex);
5546
5547		if (pool->cpu == cpu)
5548			rebind_workers(pool);
5549		else if (pool->cpu < 0)
5550			restore_unbound_workers_cpumask(pool, cpu);
5551
5552		mutex_unlock(&wq_pool_attach_mutex);
5553	}
5554
5555	/* update pod affinity of unbound workqueues */
5556	list_for_each_entry(wq, &workqueues, list) {
5557		struct workqueue_attrs *attrs = wq->unbound_attrs;
5558
5559		if (attrs) {
5560			const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5561			int tcpu;
5562
5563			for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5564				wq_update_pod(wq, tcpu, cpu, true);
5565		}
5566	}
5567
5568	mutex_unlock(&wq_pool_mutex);
5569	return 0;
5570}
5571
5572int workqueue_offline_cpu(unsigned int cpu)
5573{
5574	struct workqueue_struct *wq;
5575
5576	/* unbinding per-cpu workers should happen on the local CPU */
5577	if (WARN_ON(cpu != smp_processor_id()))
5578		return -1;
5579
5580	unbind_workers(cpu);
5581
5582	/* update pod affinity of unbound workqueues */
5583	mutex_lock(&wq_pool_mutex);
5584	list_for_each_entry(wq, &workqueues, list) {
5585		struct workqueue_attrs *attrs = wq->unbound_attrs;
5586
5587		if (attrs) {
5588			const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5589			int tcpu;
5590
5591			for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5592				wq_update_pod(wq, tcpu, cpu, false);
5593		}
5594	}
5595	mutex_unlock(&wq_pool_mutex);
5596
5597	return 0;
5598}
5599
5600struct work_for_cpu {
5601	struct work_struct work;
5602	long (*fn)(void *);
5603	void *arg;
5604	long ret;
5605};
5606
5607static void work_for_cpu_fn(struct work_struct *work)
5608{
5609	struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
5610
5611	wfc->ret = wfc->fn(wfc->arg);
5612}
5613
5614/**
5615 * work_on_cpu_key - run a function in thread context on a particular cpu
5616 * @cpu: the cpu to run on
5617 * @fn: the function to run
5618 * @arg: the function arg
5619 * @key: The lock class key for lock debugging purposes
5620 *
5621 * It is up to the caller to ensure that the cpu doesn't go offline.
5622 * The caller must not hold any locks which would prevent @fn from completing.
5623 *
5624 * Return: The value @fn returns.
5625 */
5626long work_on_cpu_key(int cpu, long (*fn)(void *),
5627		     void *arg, struct lock_class_key *key)
5628{
5629	struct work_for_cpu wfc = { .fn = fn, .arg = arg };
5630
5631	INIT_WORK_ONSTACK_KEY(&wfc.work, work_for_cpu_fn, key);
5632	schedule_work_on(cpu, &wfc.work);
5633	flush_work(&wfc.work);
5634	destroy_work_on_stack(&wfc.work);
5635	return wfc.ret;
5636}
5637EXPORT_SYMBOL_GPL(work_on_cpu_key);
5638
5639/**
5640 * work_on_cpu_safe_key - run a function in thread context on a particular cpu
5641 * @cpu: the cpu to run on
5642 * @fn:  the function to run
5643 * @arg: the function argument
5644 * @key: The lock class key for lock debugging purposes
5645 *
5646 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
5647 * any locks which would prevent @fn from completing.
5648 *
5649 * Return: The value @fn returns.
5650 */
5651long work_on_cpu_safe_key(int cpu, long (*fn)(void *),
5652			  void *arg, struct lock_class_key *key)
5653{
5654	long ret = -ENODEV;
5655
5656	cpus_read_lock();
5657	if (cpu_online(cpu))
5658		ret = work_on_cpu_key(cpu, fn, arg, key);
5659	cpus_read_unlock();
5660	return ret;
5661}
5662EXPORT_SYMBOL_GPL(work_on_cpu_safe_key);
5663#endif /* CONFIG_SMP */
5664
5665#ifdef CONFIG_FREEZER
5666
5667/**
5668 * freeze_workqueues_begin - begin freezing workqueues
5669 *
5670 * Start freezing workqueues.  After this function returns, all freezable
5671 * workqueues will queue new works to their inactive_works list instead of
5672 * pool->worklist.
5673 *
5674 * CONTEXT:
5675 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5676 */
5677void freeze_workqueues_begin(void)
5678{
5679	struct workqueue_struct *wq;
5680	struct pool_workqueue *pwq;
5681
5682	mutex_lock(&wq_pool_mutex);
5683
5684	WARN_ON_ONCE(workqueue_freezing);
5685	workqueue_freezing = true;
5686
5687	list_for_each_entry(wq, &workqueues, list) {
5688		mutex_lock(&wq->mutex);
5689		for_each_pwq(pwq, wq)
5690			pwq_adjust_max_active(pwq);
5691		mutex_unlock(&wq->mutex);
5692	}
5693
5694	mutex_unlock(&wq_pool_mutex);
5695}
5696
5697/**
5698 * freeze_workqueues_busy - are freezable workqueues still busy?
5699 *
5700 * Check whether freezing is complete.  This function must be called
5701 * between freeze_workqueues_begin() and thaw_workqueues().
5702 *
5703 * CONTEXT:
5704 * Grabs and releases wq_pool_mutex.
5705 *
5706 * Return:
5707 * %true if some freezable workqueues are still busy.  %false if freezing
5708 * is complete.
5709 */
5710bool freeze_workqueues_busy(void)
5711{
5712	bool busy = false;
5713	struct workqueue_struct *wq;
5714	struct pool_workqueue *pwq;
5715
5716	mutex_lock(&wq_pool_mutex);
5717
5718	WARN_ON_ONCE(!workqueue_freezing);
5719
5720	list_for_each_entry(wq, &workqueues, list) {
5721		if (!(wq->flags & WQ_FREEZABLE))
5722			continue;
5723		/*
5724		 * nr_active is monotonically decreasing.  It's safe
5725		 * to peek without lock.
5726		 */
5727		rcu_read_lock();
5728		for_each_pwq(pwq, wq) {
5729			WARN_ON_ONCE(pwq->nr_active < 0);
5730			if (pwq->nr_active) {
5731				busy = true;
5732				rcu_read_unlock();
5733				goto out_unlock;
5734			}
5735		}
5736		rcu_read_unlock();
5737	}
5738out_unlock:
5739	mutex_unlock(&wq_pool_mutex);
5740	return busy;
5741}
5742
5743/**
5744 * thaw_workqueues - thaw workqueues
5745 *
5746 * Thaw workqueues.  Normal queueing is restored and all collected
5747 * frozen works are transferred to their respective pool worklists.
5748 *
5749 * CONTEXT:
5750 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5751 */
5752void thaw_workqueues(void)
5753{
5754	struct workqueue_struct *wq;
5755	struct pool_workqueue *pwq;
5756
5757	mutex_lock(&wq_pool_mutex);
5758
5759	if (!workqueue_freezing)
5760		goto out_unlock;
5761
5762	workqueue_freezing = false;
5763
5764	/* restore max_active and repopulate worklist */
5765	list_for_each_entry(wq, &workqueues, list) {
5766		mutex_lock(&wq->mutex);
5767		for_each_pwq(pwq, wq)
5768			pwq_adjust_max_active(pwq);
5769		mutex_unlock(&wq->mutex);
5770	}
5771
5772out_unlock:
5773	mutex_unlock(&wq_pool_mutex);
5774}
5775#endif /* CONFIG_FREEZER */
5776
5777static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
5778{
5779	LIST_HEAD(ctxs);
5780	int ret = 0;
5781	struct workqueue_struct *wq;
5782	struct apply_wqattrs_ctx *ctx, *n;
5783
5784	lockdep_assert_held(&wq_pool_mutex);
5785
5786	list_for_each_entry(wq, &workqueues, list) {
5787		if (!(wq->flags & WQ_UNBOUND))
5788			continue;
5789		/* creating multiple pwqs breaks ordering guarantee */
5790		if (wq->flags & __WQ_ORDERED)
5791			continue;
5792
5793		ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
5794		if (IS_ERR(ctx)) {
5795			ret = PTR_ERR(ctx);
5796			break;
5797		}
5798
5799		list_add_tail(&ctx->list, &ctxs);
5800	}
5801
5802	list_for_each_entry_safe(ctx, n, &ctxs, list) {
5803		if (!ret)
5804			apply_wqattrs_commit(ctx);
5805		apply_wqattrs_cleanup(ctx);
5806	}
5807
5808	if (!ret) {
5809		mutex_lock(&wq_pool_attach_mutex);
5810		cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
5811		mutex_unlock(&wq_pool_attach_mutex);
5812	}
5813	return ret;
5814}
5815
5816/**
5817 * workqueue_unbound_exclude_cpumask - Exclude given CPUs from unbound cpumask
5818 * @exclude_cpumask: the cpumask to be excluded from wq_unbound_cpumask
5819 *
5820 * This function can be called from cpuset code to provide a set of isolated
5821 * CPUs that should be excluded from wq_unbound_cpumask. The caller must hold
5822 * either cpus_read_lock or cpus_write_lock.
 
 
 
 
5823 */
5824int workqueue_unbound_exclude_cpumask(cpumask_var_t exclude_cpumask)
5825{
5826	cpumask_var_t cpumask;
5827	int ret = 0;
5828
5829	if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5830		return -ENOMEM;
5831
5832	lockdep_assert_cpus_held();
5833	mutex_lock(&wq_pool_mutex);
5834
5835	/* Save the current isolated cpumask & export it via sysfs */
5836	cpumask_copy(wq_isolated_cpumask, exclude_cpumask);
5837
5838	/*
5839	 * If the operation fails, it will fall back to
5840	 * wq_requested_unbound_cpumask which is initially set to
5841	 * (HK_TYPE_WQ ∩ HK_TYPE_DOMAIN) house keeping mask and rewritten
5842	 * by any subsequent write to workqueue/cpumask sysfs file.
5843	 */
5844	if (!cpumask_andnot(cpumask, wq_requested_unbound_cpumask, exclude_cpumask))
5845		cpumask_copy(cpumask, wq_requested_unbound_cpumask);
5846	if (!cpumask_equal(cpumask, wq_unbound_cpumask))
5847		ret = workqueue_apply_unbound_cpumask(cpumask);
5848
5849	mutex_unlock(&wq_pool_mutex);
5850	free_cpumask_var(cpumask);
5851	return ret;
5852}
5853
5854static int parse_affn_scope(const char *val)
5855{
5856	int i;
5857
5858	for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
5859		if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
5860			return i;
5861	}
5862	return -EINVAL;
5863}
5864
5865static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)
5866{
5867	struct workqueue_struct *wq;
5868	int affn, cpu;
5869
5870	affn = parse_affn_scope(val);
5871	if (affn < 0)
5872		return affn;
5873	if (affn == WQ_AFFN_DFL)
5874		return -EINVAL;
5875
5876	cpus_read_lock();
5877	mutex_lock(&wq_pool_mutex);
5878
5879	wq_affn_dfl = affn;
 
 
 
 
 
 
5880
5881	list_for_each_entry(wq, &workqueues, list) {
5882		for_each_online_cpu(cpu) {
5883			wq_update_pod(wq, cpu, cpu, true);
5884		}
5885	}
5886
5887	mutex_unlock(&wq_pool_mutex);
5888	cpus_read_unlock();
5889
5890	return 0;
5891}
5892
5893static int wq_affn_dfl_get(char *buffer, const struct kernel_param *kp)
5894{
5895	return scnprintf(buffer, PAGE_SIZE, "%s\n", wq_affn_names[wq_affn_dfl]);
5896}
5897
5898static const struct kernel_param_ops wq_affn_dfl_ops = {
5899	.set	= wq_affn_dfl_set,
5900	.get	= wq_affn_dfl_get,
5901};
5902
5903module_param_cb(default_affinity_scope, &wq_affn_dfl_ops, NULL, 0644);
5904
5905#ifdef CONFIG_SYSFS
5906/*
5907 * Workqueues with WQ_SYSFS flag set is visible to userland via
5908 * /sys/bus/workqueue/devices/WQ_NAME.  All visible workqueues have the
5909 * following attributes.
5910 *
5911 *  per_cpu		RO bool	: whether the workqueue is per-cpu or unbound
5912 *  max_active		RW int	: maximum number of in-flight work items
5913 *
5914 * Unbound workqueues have the following extra attributes.
5915 *
5916 *  nice		RW int	: nice value of the workers
5917 *  cpumask		RW mask	: bitmask of allowed CPUs for the workers
5918 *  affinity_scope	RW str  : worker CPU affinity scope (cache, numa, none)
5919 *  affinity_strict	RW bool : worker CPU affinity is strict
5920 */
5921struct wq_device {
5922	struct workqueue_struct		*wq;
5923	struct device			dev;
5924};
5925
5926static struct workqueue_struct *dev_to_wq(struct device *dev)
5927{
5928	struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5929
5930	return wq_dev->wq;
5931}
5932
5933static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5934			    char *buf)
5935{
5936	struct workqueue_struct *wq = dev_to_wq(dev);
5937
5938	return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5939}
5940static DEVICE_ATTR_RO(per_cpu);
5941
5942static ssize_t max_active_show(struct device *dev,
5943			       struct device_attribute *attr, char *buf)
5944{
5945	struct workqueue_struct *wq = dev_to_wq(dev);
5946
5947	return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5948}
5949
5950static ssize_t max_active_store(struct device *dev,
5951				struct device_attribute *attr, const char *buf,
5952				size_t count)
5953{
5954	struct workqueue_struct *wq = dev_to_wq(dev);
5955	int val;
5956
5957	if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5958		return -EINVAL;
5959
5960	workqueue_set_max_active(wq, val);
5961	return count;
5962}
5963static DEVICE_ATTR_RW(max_active);
5964
5965static struct attribute *wq_sysfs_attrs[] = {
5966	&dev_attr_per_cpu.attr,
5967	&dev_attr_max_active.attr,
5968	NULL,
5969};
5970ATTRIBUTE_GROUPS(wq_sysfs);
5971
5972static void apply_wqattrs_lock(void)
 
5973{
5974	/* CPUs should stay stable across pwq creations and installations */
5975	cpus_read_lock();
5976	mutex_lock(&wq_pool_mutex);
5977}
5978
5979static void apply_wqattrs_unlock(void)
5980{
5981	mutex_unlock(&wq_pool_mutex);
5982	cpus_read_unlock();
 
 
 
 
 
 
 
 
 
5983}
5984
5985static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5986			    char *buf)
5987{
5988	struct workqueue_struct *wq = dev_to_wq(dev);
5989	int written;
5990
5991	mutex_lock(&wq->mutex);
5992	written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5993	mutex_unlock(&wq->mutex);
5994
5995	return written;
5996}
5997
5998/* prepare workqueue_attrs for sysfs store operations */
5999static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
6000{
6001	struct workqueue_attrs *attrs;
6002
6003	lockdep_assert_held(&wq_pool_mutex);
6004
6005	attrs = alloc_workqueue_attrs();
6006	if (!attrs)
6007		return NULL;
6008
6009	copy_workqueue_attrs(attrs, wq->unbound_attrs);
6010	return attrs;
6011}
6012
6013static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
6014			     const char *buf, size_t count)
6015{
6016	struct workqueue_struct *wq = dev_to_wq(dev);
6017	struct workqueue_attrs *attrs;
6018	int ret = -ENOMEM;
6019
6020	apply_wqattrs_lock();
6021
6022	attrs = wq_sysfs_prep_attrs(wq);
6023	if (!attrs)
6024		goto out_unlock;
6025
6026	if (sscanf(buf, "%d", &attrs->nice) == 1 &&
6027	    attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
6028		ret = apply_workqueue_attrs_locked(wq, attrs);
6029	else
6030		ret = -EINVAL;
6031
6032out_unlock:
6033	apply_wqattrs_unlock();
6034	free_workqueue_attrs(attrs);
6035	return ret ?: count;
6036}
6037
6038static ssize_t wq_cpumask_show(struct device *dev,
6039			       struct device_attribute *attr, char *buf)
6040{
6041	struct workqueue_struct *wq = dev_to_wq(dev);
6042	int written;
6043
6044	mutex_lock(&wq->mutex);
6045	written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
6046			    cpumask_pr_args(wq->unbound_attrs->cpumask));
6047	mutex_unlock(&wq->mutex);
6048	return written;
6049}
6050
6051static ssize_t wq_cpumask_store(struct device *dev,
6052				struct device_attribute *attr,
6053				const char *buf, size_t count)
6054{
6055	struct workqueue_struct *wq = dev_to_wq(dev);
6056	struct workqueue_attrs *attrs;
6057	int ret = -ENOMEM;
6058
6059	apply_wqattrs_lock();
6060
6061	attrs = wq_sysfs_prep_attrs(wq);
6062	if (!attrs)
6063		goto out_unlock;
6064
6065	ret = cpumask_parse(buf, attrs->cpumask);
6066	if (!ret)
6067		ret = apply_workqueue_attrs_locked(wq, attrs);
6068
6069out_unlock:
6070	apply_wqattrs_unlock();
6071	free_workqueue_attrs(attrs);
6072	return ret ?: count;
6073}
6074
6075static ssize_t wq_affn_scope_show(struct device *dev,
6076				  struct device_attribute *attr, char *buf)
6077{
6078	struct workqueue_struct *wq = dev_to_wq(dev);
6079	int written;
6080
6081	mutex_lock(&wq->mutex);
6082	if (wq->unbound_attrs->affn_scope == WQ_AFFN_DFL)
6083		written = scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
6084				    wq_affn_names[WQ_AFFN_DFL],
6085				    wq_affn_names[wq_affn_dfl]);
6086	else
6087		written = scnprintf(buf, PAGE_SIZE, "%s\n",
6088				    wq_affn_names[wq->unbound_attrs->affn_scope]);
6089	mutex_unlock(&wq->mutex);
6090
6091	return written;
6092}
6093
6094static ssize_t wq_affn_scope_store(struct device *dev,
6095				   struct device_attribute *attr,
6096				   const char *buf, size_t count)
6097{
6098	struct workqueue_struct *wq = dev_to_wq(dev);
6099	struct workqueue_attrs *attrs;
6100	int affn, ret = -ENOMEM;
6101
6102	affn = parse_affn_scope(buf);
6103	if (affn < 0)
6104		return affn;
6105
6106	apply_wqattrs_lock();
6107	attrs = wq_sysfs_prep_attrs(wq);
6108	if (attrs) {
6109		attrs->affn_scope = affn;
6110		ret = apply_workqueue_attrs_locked(wq, attrs);
6111	}
6112	apply_wqattrs_unlock();
6113	free_workqueue_attrs(attrs);
6114	return ret ?: count;
6115}
6116
6117static ssize_t wq_affinity_strict_show(struct device *dev,
6118				       struct device_attribute *attr, char *buf)
6119{
6120	struct workqueue_struct *wq = dev_to_wq(dev);
6121
6122	return scnprintf(buf, PAGE_SIZE, "%d\n",
6123			 wq->unbound_attrs->affn_strict);
6124}
6125
6126static ssize_t wq_affinity_strict_store(struct device *dev,
6127					struct device_attribute *attr,
6128					const char *buf, size_t count)
6129{
6130	struct workqueue_struct *wq = dev_to_wq(dev);
6131	struct workqueue_attrs *attrs;
6132	int v, ret = -ENOMEM;
6133
6134	if (sscanf(buf, "%d", &v) != 1)
6135		return -EINVAL;
6136
6137	apply_wqattrs_lock();
 
6138	attrs = wq_sysfs_prep_attrs(wq);
6139	if (attrs) {
6140		attrs->affn_strict = (bool)v;
 
 
 
 
6141		ret = apply_workqueue_attrs_locked(wq, attrs);
6142	}
 
 
6143	apply_wqattrs_unlock();
6144	free_workqueue_attrs(attrs);
6145	return ret ?: count;
6146}
6147
6148static struct device_attribute wq_sysfs_unbound_attrs[] = {
 
6149	__ATTR(nice, 0644, wq_nice_show, wq_nice_store),
6150	__ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
6151	__ATTR(affinity_scope, 0644, wq_affn_scope_show, wq_affn_scope_store),
6152	__ATTR(affinity_strict, 0644, wq_affinity_strict_show, wq_affinity_strict_store),
6153	__ATTR_NULL,
6154};
6155
6156static struct bus_type wq_subsys = {
6157	.name				= "workqueue",
6158	.dev_groups			= wq_sysfs_groups,
6159};
6160
6161/**
6162 *  workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
6163 *  @cpumask: the cpumask to set
6164 *
6165 *  The low-level workqueues cpumask is a global cpumask that limits
6166 *  the affinity of all unbound workqueues.  This function check the @cpumask
6167 *  and apply it to all unbound workqueues and updates all pwqs of them.
6168 *
6169 *  Return:	0	- Success
6170 *		-EINVAL	- Invalid @cpumask
6171 *		-ENOMEM	- Failed to allocate memory for attrs or pwqs.
6172 */
6173static int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
6174{
6175	int ret = -EINVAL;
6176
6177	/*
6178	 * Not excluding isolated cpus on purpose.
6179	 * If the user wishes to include them, we allow that.
6180	 */
6181	cpumask_and(cpumask, cpumask, cpu_possible_mask);
6182	if (!cpumask_empty(cpumask)) {
6183		apply_wqattrs_lock();
6184		cpumask_copy(wq_requested_unbound_cpumask, cpumask);
6185		if (cpumask_equal(cpumask, wq_unbound_cpumask)) {
6186			ret = 0;
6187			goto out_unlock;
6188		}
6189
6190		ret = workqueue_apply_unbound_cpumask(cpumask);
6191
6192out_unlock:
6193		apply_wqattrs_unlock();
6194	}
6195
6196	return ret;
6197}
6198
6199static ssize_t __wq_cpumask_show(struct device *dev,
6200		struct device_attribute *attr, char *buf, cpumask_var_t mask)
6201{
6202	int written;
6203
6204	mutex_lock(&wq_pool_mutex);
6205	written = scnprintf(buf, PAGE_SIZE, "%*pb\n", cpumask_pr_args(mask));
 
6206	mutex_unlock(&wq_pool_mutex);
6207
6208	return written;
6209}
6210
6211static ssize_t wq_unbound_cpumask_show(struct device *dev,
6212		struct device_attribute *attr, char *buf)
6213{
6214	return __wq_cpumask_show(dev, attr, buf, wq_unbound_cpumask);
6215}
6216
6217static ssize_t wq_requested_cpumask_show(struct device *dev,
6218		struct device_attribute *attr, char *buf)
6219{
6220	return __wq_cpumask_show(dev, attr, buf, wq_requested_unbound_cpumask);
6221}
6222
6223static ssize_t wq_isolated_cpumask_show(struct device *dev,
6224		struct device_attribute *attr, char *buf)
6225{
6226	return __wq_cpumask_show(dev, attr, buf, wq_isolated_cpumask);
6227}
6228
6229static ssize_t wq_unbound_cpumask_store(struct device *dev,
6230		struct device_attribute *attr, const char *buf, size_t count)
6231{
6232	cpumask_var_t cpumask;
6233	int ret;
6234
6235	if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
6236		return -ENOMEM;
6237
6238	ret = cpumask_parse(buf, cpumask);
6239	if (!ret)
6240		ret = workqueue_set_unbound_cpumask(cpumask);
6241
6242	free_cpumask_var(cpumask);
6243	return ret ? ret : count;
6244}
6245
6246static struct device_attribute wq_sysfs_cpumask_attrs[] = {
6247	__ATTR(cpumask, 0644, wq_unbound_cpumask_show,
6248	       wq_unbound_cpumask_store),
6249	__ATTR(cpumask_requested, 0444, wq_requested_cpumask_show, NULL),
6250	__ATTR(cpumask_isolated, 0444, wq_isolated_cpumask_show, NULL),
6251	__ATTR_NULL,
6252};
6253
6254static int __init wq_sysfs_init(void)
6255{
6256	struct device *dev_root;
6257	int err;
6258
6259	err = subsys_virtual_register(&wq_subsys, NULL);
6260	if (err)
6261		return err;
6262
6263	dev_root = bus_get_dev_root(&wq_subsys);
6264	if (dev_root) {
6265		struct device_attribute *attr;
6266
6267		for (attr = wq_sysfs_cpumask_attrs; attr->attr.name; attr++) {
6268			err = device_create_file(dev_root, attr);
6269			if (err)
6270				break;
6271		}
6272		put_device(dev_root);
6273	}
6274	return err;
6275}
6276core_initcall(wq_sysfs_init);
6277
6278static void wq_device_release(struct device *dev)
6279{
6280	struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
6281
6282	kfree(wq_dev);
6283}
6284
6285/**
6286 * workqueue_sysfs_register - make a workqueue visible in sysfs
6287 * @wq: the workqueue to register
6288 *
6289 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
6290 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
6291 * which is the preferred method.
6292 *
6293 * Workqueue user should use this function directly iff it wants to apply
6294 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
6295 * apply_workqueue_attrs() may race against userland updating the
6296 * attributes.
6297 *
6298 * Return: 0 on success, -errno on failure.
6299 */
6300int workqueue_sysfs_register(struct workqueue_struct *wq)
6301{
6302	struct wq_device *wq_dev;
6303	int ret;
6304
6305	/*
6306	 * Adjusting max_active or creating new pwqs by applying
6307	 * attributes breaks ordering guarantee.  Disallow exposing ordered
6308	 * workqueues.
6309	 */
6310	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
6311		return -EINVAL;
6312
6313	wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
6314	if (!wq_dev)
6315		return -ENOMEM;
6316
6317	wq_dev->wq = wq;
6318	wq_dev->dev.bus = &wq_subsys;
6319	wq_dev->dev.release = wq_device_release;
6320	dev_set_name(&wq_dev->dev, "%s", wq->name);
6321
6322	/*
6323	 * unbound_attrs are created separately.  Suppress uevent until
6324	 * everything is ready.
6325	 */
6326	dev_set_uevent_suppress(&wq_dev->dev, true);
6327
6328	ret = device_register(&wq_dev->dev);
6329	if (ret) {
6330		put_device(&wq_dev->dev);
6331		wq->wq_dev = NULL;
6332		return ret;
6333	}
6334
6335	if (wq->flags & WQ_UNBOUND) {
6336		struct device_attribute *attr;
6337
6338		for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
6339			ret = device_create_file(&wq_dev->dev, attr);
6340			if (ret) {
6341				device_unregister(&wq_dev->dev);
6342				wq->wq_dev = NULL;
6343				return ret;
6344			}
6345		}
6346	}
6347
6348	dev_set_uevent_suppress(&wq_dev->dev, false);
6349	kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
6350	return 0;
6351}
6352
6353/**
6354 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
6355 * @wq: the workqueue to unregister
6356 *
6357 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
6358 */
6359static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
6360{
6361	struct wq_device *wq_dev = wq->wq_dev;
6362
6363	if (!wq->wq_dev)
6364		return;
6365
6366	wq->wq_dev = NULL;
6367	device_unregister(&wq_dev->dev);
6368}
6369#else	/* CONFIG_SYSFS */
6370static void workqueue_sysfs_unregister(struct workqueue_struct *wq)	{ }
6371#endif	/* CONFIG_SYSFS */
6372
6373/*
6374 * Workqueue watchdog.
6375 *
6376 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
6377 * flush dependency, a concurrency managed work item which stays RUNNING
6378 * indefinitely.  Workqueue stalls can be very difficult to debug as the
6379 * usual warning mechanisms don't trigger and internal workqueue state is
6380 * largely opaque.
6381 *
6382 * Workqueue watchdog monitors all worker pools periodically and dumps
6383 * state if some pools failed to make forward progress for a while where
6384 * forward progress is defined as the first item on ->worklist changing.
6385 *
6386 * This mechanism is controlled through the kernel parameter
6387 * "workqueue.watchdog_thresh" which can be updated at runtime through the
6388 * corresponding sysfs parameter file.
6389 */
6390#ifdef CONFIG_WQ_WATCHDOG
6391
6392static unsigned long wq_watchdog_thresh = 30;
6393static struct timer_list wq_watchdog_timer;
6394
6395static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
6396static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
6397
6398/*
6399 * Show workers that might prevent the processing of pending work items.
6400 * The only candidates are CPU-bound workers in the running state.
6401 * Pending work items should be handled by another idle worker
6402 * in all other situations.
6403 */
6404static void show_cpu_pool_hog(struct worker_pool *pool)
6405{
6406	struct worker *worker;
6407	unsigned long flags;
6408	int bkt;
6409
6410	raw_spin_lock_irqsave(&pool->lock, flags);
6411
6412	hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6413		if (task_is_running(worker->task)) {
6414			/*
6415			 * Defer printing to avoid deadlocks in console
6416			 * drivers that queue work while holding locks
6417			 * also taken in their write paths.
6418			 */
6419			printk_deferred_enter();
6420
6421			pr_info("pool %d:\n", pool->id);
6422			sched_show_task(worker->task);
6423
6424			printk_deferred_exit();
6425		}
6426	}
6427
6428	raw_spin_unlock_irqrestore(&pool->lock, flags);
6429}
6430
6431static void show_cpu_pools_hogs(void)
6432{
6433	struct worker_pool *pool;
6434	int pi;
6435
6436	pr_info("Showing backtraces of running workers in stalled CPU-bound worker pools:\n");
6437
6438	rcu_read_lock();
6439
6440	for_each_pool(pool, pi) {
6441		if (pool->cpu_stall)
6442			show_cpu_pool_hog(pool);
6443
6444	}
6445
6446	rcu_read_unlock();
6447}
6448
6449static void wq_watchdog_reset_touched(void)
6450{
6451	int cpu;
6452
6453	wq_watchdog_touched = jiffies;
6454	for_each_possible_cpu(cpu)
6455		per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
6456}
6457
6458static void wq_watchdog_timer_fn(struct timer_list *unused)
6459{
6460	unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
6461	bool lockup_detected = false;
6462	bool cpu_pool_stall = false;
6463	unsigned long now = jiffies;
6464	struct worker_pool *pool;
6465	int pi;
6466
6467	if (!thresh)
6468		return;
6469
6470	rcu_read_lock();
6471
6472	for_each_pool(pool, pi) {
6473		unsigned long pool_ts, touched, ts;
6474
6475		pool->cpu_stall = false;
6476		if (list_empty(&pool->worklist))
6477			continue;
6478
6479		/*
6480		 * If a virtual machine is stopped by the host it can look to
6481		 * the watchdog like a stall.
6482		 */
6483		kvm_check_and_clear_guest_paused();
6484
6485		/* get the latest of pool and touched timestamps */
6486		if (pool->cpu >= 0)
6487			touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
6488		else
6489			touched = READ_ONCE(wq_watchdog_touched);
6490		pool_ts = READ_ONCE(pool->watchdog_ts);
 
6491
6492		if (time_after(pool_ts, touched))
6493			ts = pool_ts;
6494		else
6495			ts = touched;
6496
 
 
 
 
 
 
 
 
6497		/* did we stall? */
6498		if (time_after(now, ts + thresh)) {
6499			lockup_detected = true;
6500			if (pool->cpu >= 0) {
6501				pool->cpu_stall = true;
6502				cpu_pool_stall = true;
6503			}
6504			pr_emerg("BUG: workqueue lockup - pool");
6505			pr_cont_pool_info(pool);
6506			pr_cont(" stuck for %us!\n",
6507				jiffies_to_msecs(now - pool_ts) / 1000);
6508		}
6509
6510
6511	}
6512
6513	rcu_read_unlock();
6514
6515	if (lockup_detected)
6516		show_all_workqueues();
6517
6518	if (cpu_pool_stall)
6519		show_cpu_pools_hogs();
6520
6521	wq_watchdog_reset_touched();
6522	mod_timer(&wq_watchdog_timer, jiffies + thresh);
6523}
6524
6525notrace void wq_watchdog_touch(int cpu)
6526{
6527	if (cpu >= 0)
6528		per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
6529
6530	wq_watchdog_touched = jiffies;
6531}
6532
6533static void wq_watchdog_set_thresh(unsigned long thresh)
6534{
6535	wq_watchdog_thresh = 0;
6536	del_timer_sync(&wq_watchdog_timer);
6537
6538	if (thresh) {
6539		wq_watchdog_thresh = thresh;
6540		wq_watchdog_reset_touched();
6541		mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
6542	}
6543}
6544
6545static int wq_watchdog_param_set_thresh(const char *val,
6546					const struct kernel_param *kp)
6547{
6548	unsigned long thresh;
6549	int ret;
6550
6551	ret = kstrtoul(val, 0, &thresh);
6552	if (ret)
6553		return ret;
6554
6555	if (system_wq)
6556		wq_watchdog_set_thresh(thresh);
6557	else
6558		wq_watchdog_thresh = thresh;
6559
6560	return 0;
6561}
6562
6563static const struct kernel_param_ops wq_watchdog_thresh_ops = {
6564	.set	= wq_watchdog_param_set_thresh,
6565	.get	= param_get_ulong,
6566};
6567
6568module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
6569		0644);
6570
6571static void wq_watchdog_init(void)
6572{
6573	timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
6574	wq_watchdog_set_thresh(wq_watchdog_thresh);
6575}
6576
6577#else	/* CONFIG_WQ_WATCHDOG */
6578
6579static inline void wq_watchdog_init(void) { }
6580
6581#endif	/* CONFIG_WQ_WATCHDOG */
6582
6583static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask)
6584{
6585	if (!cpumask_intersects(wq_unbound_cpumask, mask)) {
6586		pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n",
6587			cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask));
 
 
 
 
 
6588		return;
6589	}
6590
6591	cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6592}
6593
6594/**
6595 * workqueue_init_early - early init for workqueue subsystem
6596 *
6597 * This is the first step of three-staged workqueue subsystem initialization and
6598 * invoked as soon as the bare basics - memory allocation, cpumasks and idr are
6599 * up. It sets up all the data structures and system workqueues and allows early
6600 * boot code to create workqueues and queue/cancel work items. Actual work item
6601 * execution starts only after kthreads can be created and scheduled right
6602 * before early initcalls.
6603 */
6604void __init workqueue_init_early(void)
6605{
6606	struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_SYSTEM];
6607	int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
 
6608	int i, cpu;
6609
6610	BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
6611
6612	BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
6613	BUG_ON(!alloc_cpumask_var(&wq_requested_unbound_cpumask, GFP_KERNEL));
6614	BUG_ON(!zalloc_cpumask_var(&wq_isolated_cpumask, GFP_KERNEL));
6615
6616	cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
6617	restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ));
6618	restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN));
6619	if (!cpumask_empty(&wq_cmdline_cpumask))
6620		restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask);
6621
6622	cpumask_copy(wq_requested_unbound_cpumask, wq_unbound_cpumask);
6623
6624	pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
6625
6626	wq_update_pod_attrs_buf = alloc_workqueue_attrs();
6627	BUG_ON(!wq_update_pod_attrs_buf);
6628
6629	/* initialize WQ_AFFN_SYSTEM pods */
6630	pt->pod_cpus = kcalloc(1, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6631	pt->pod_node = kcalloc(1, sizeof(pt->pod_node[0]), GFP_KERNEL);
6632	pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6633	BUG_ON(!pt->pod_cpus || !pt->pod_node || !pt->cpu_pod);
6634
6635	BUG_ON(!zalloc_cpumask_var_node(&pt->pod_cpus[0], GFP_KERNEL, NUMA_NO_NODE));
6636
6637	pt->nr_pods = 1;
6638	cpumask_copy(pt->pod_cpus[0], cpu_possible_mask);
6639	pt->pod_node[0] = NUMA_NO_NODE;
6640	pt->cpu_pod[0] = 0;
6641
6642	/* initialize CPU pools */
6643	for_each_possible_cpu(cpu) {
6644		struct worker_pool *pool;
6645
6646		i = 0;
6647		for_each_cpu_worker_pool(pool, cpu) {
6648			BUG_ON(init_worker_pool(pool));
6649			pool->cpu = cpu;
6650			cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
6651			cpumask_copy(pool->attrs->__pod_cpumask, cpumask_of(cpu));
6652			pool->attrs->nice = std_nice[i++];
6653			pool->attrs->affn_strict = true;
6654			pool->node = cpu_to_node(cpu);
6655
6656			/* alloc pool ID */
6657			mutex_lock(&wq_pool_mutex);
6658			BUG_ON(worker_pool_assign_id(pool));
6659			mutex_unlock(&wq_pool_mutex);
6660		}
6661	}
6662
6663	/* create default unbound and ordered wq attrs */
6664	for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
6665		struct workqueue_attrs *attrs;
6666
6667		BUG_ON(!(attrs = alloc_workqueue_attrs()));
6668		attrs->nice = std_nice[i];
6669		unbound_std_wq_attrs[i] = attrs;
6670
6671		/*
6672		 * An ordered wq should have only one pwq as ordering is
6673		 * guaranteed by max_active which is enforced by pwqs.
 
6674		 */
6675		BUG_ON(!(attrs = alloc_workqueue_attrs()));
6676		attrs->nice = std_nice[i];
6677		attrs->ordered = true;
6678		ordered_wq_attrs[i] = attrs;
6679	}
6680
6681	system_wq = alloc_workqueue("events", 0, 0);
6682	system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
6683	system_long_wq = alloc_workqueue("events_long", 0, 0);
6684	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
6685					    WQ_MAX_ACTIVE);
6686	system_freezable_wq = alloc_workqueue("events_freezable",
6687					      WQ_FREEZABLE, 0);
6688	system_power_efficient_wq = alloc_workqueue("events_power_efficient",
6689					      WQ_POWER_EFFICIENT, 0);
6690	system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
6691					      WQ_FREEZABLE | WQ_POWER_EFFICIENT,
6692					      0);
6693	BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
6694	       !system_unbound_wq || !system_freezable_wq ||
6695	       !system_power_efficient_wq ||
6696	       !system_freezable_power_efficient_wq);
6697}
6698
6699static void __init wq_cpu_intensive_thresh_init(void)
6700{
6701	unsigned long thresh;
6702	unsigned long bogo;
6703
6704	pwq_release_worker = kthread_create_worker(0, "pool_workqueue_release");
6705	BUG_ON(IS_ERR(pwq_release_worker));
6706
6707	/* if the user set it to a specific value, keep it */
6708	if (wq_cpu_intensive_thresh_us != ULONG_MAX)
6709		return;
6710
6711	/*
6712	 * The default of 10ms is derived from the fact that most modern (as of
6713	 * 2023) processors can do a lot in 10ms and that it's just below what
6714	 * most consider human-perceivable. However, the kernel also runs on a
6715	 * lot slower CPUs including microcontrollers where the threshold is way
6716	 * too low.
6717	 *
6718	 * Let's scale up the threshold upto 1 second if BogoMips is below 4000.
6719	 * This is by no means accurate but it doesn't have to be. The mechanism
6720	 * is still useful even when the threshold is fully scaled up. Also, as
6721	 * the reports would usually be applicable to everyone, some machines
6722	 * operating on longer thresholds won't significantly diminish their
6723	 * usefulness.
6724	 */
6725	thresh = 10 * USEC_PER_MSEC;
6726
6727	/* see init/calibrate.c for lpj -> BogoMIPS calculation */
6728	bogo = max_t(unsigned long, loops_per_jiffy / 500000 * HZ, 1);
6729	if (bogo < 4000)
6730		thresh = min_t(unsigned long, thresh * 4000 / bogo, USEC_PER_SEC);
6731
6732	pr_debug("wq_cpu_intensive_thresh: lpj=%lu BogoMIPS=%lu thresh_us=%lu\n",
6733		 loops_per_jiffy, bogo, thresh);
6734
6735	wq_cpu_intensive_thresh_us = thresh;
6736}
6737
6738/**
6739 * workqueue_init - bring workqueue subsystem fully online
6740 *
6741 * This is the second step of three-staged workqueue subsystem initialization
6742 * and invoked as soon as kthreads can be created and scheduled. Workqueues have
6743 * been created and work items queued on them, but there are no kworkers
6744 * executing the work items yet. Populate the worker pools with the initial
6745 * workers and enable future kworker creations.
6746 */
6747void __init workqueue_init(void)
6748{
6749	struct workqueue_struct *wq;
6750	struct worker_pool *pool;
6751	int cpu, bkt;
6752
6753	wq_cpu_intensive_thresh_init();
 
 
 
 
 
 
 
 
 
6754
6755	mutex_lock(&wq_pool_mutex);
6756
6757	/*
6758	 * Per-cpu pools created earlier could be missing node hint. Fix them
6759	 * up. Also, create a rescuer for workqueues that requested it.
6760	 */
6761	for_each_possible_cpu(cpu) {
6762		for_each_cpu_worker_pool(pool, cpu) {
6763			pool->node = cpu_to_node(cpu);
6764		}
6765	}
6766
6767	list_for_each_entry(wq, &workqueues, list) {
 
6768		WARN(init_rescuer(wq),
6769		     "workqueue: failed to create early rescuer for %s",
6770		     wq->name);
6771	}
6772
6773	mutex_unlock(&wq_pool_mutex);
6774
6775	/* create the initial workers */
6776	for_each_online_cpu(cpu) {
6777		for_each_cpu_worker_pool(pool, cpu) {
6778			pool->flags &= ~POOL_DISASSOCIATED;
6779			BUG_ON(!create_worker(pool));
6780		}
6781	}
6782
6783	hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
6784		BUG_ON(!create_worker(pool));
6785
6786	wq_online = true;
6787	wq_watchdog_init();
6788}
6789
6790/*
6791 * Initialize @pt by first initializing @pt->cpu_pod[] with pod IDs according to
6792 * @cpu_shares_pod(). Each subset of CPUs that share a pod is assigned a unique
6793 * and consecutive pod ID. The rest of @pt is initialized accordingly.
6794 */
6795static void __init init_pod_type(struct wq_pod_type *pt,
6796				 bool (*cpus_share_pod)(int, int))
6797{
6798	int cur, pre, cpu, pod;
6799
6800	pt->nr_pods = 0;
6801
6802	/* init @pt->cpu_pod[] according to @cpus_share_pod() */
6803	pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6804	BUG_ON(!pt->cpu_pod);
6805
6806	for_each_possible_cpu(cur) {
6807		for_each_possible_cpu(pre) {
6808			if (pre >= cur) {
6809				pt->cpu_pod[cur] = pt->nr_pods++;
6810				break;
6811			}
6812			if (cpus_share_pod(cur, pre)) {
6813				pt->cpu_pod[cur] = pt->cpu_pod[pre];
6814				break;
6815			}
6816		}
6817	}
6818
6819	/* init the rest to match @pt->cpu_pod[] */
6820	pt->pod_cpus = kcalloc(pt->nr_pods, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6821	pt->pod_node = kcalloc(pt->nr_pods, sizeof(pt->pod_node[0]), GFP_KERNEL);
6822	BUG_ON(!pt->pod_cpus || !pt->pod_node);
6823
6824	for (pod = 0; pod < pt->nr_pods; pod++)
6825		BUG_ON(!zalloc_cpumask_var(&pt->pod_cpus[pod], GFP_KERNEL));
6826
6827	for_each_possible_cpu(cpu) {
6828		cpumask_set_cpu(cpu, pt->pod_cpus[pt->cpu_pod[cpu]]);
6829		pt->pod_node[pt->cpu_pod[cpu]] = cpu_to_node(cpu);
6830	}
6831}
6832
6833static bool __init cpus_dont_share(int cpu0, int cpu1)
6834{
6835	return false;
6836}
6837
6838static bool __init cpus_share_smt(int cpu0, int cpu1)
6839{
6840#ifdef CONFIG_SCHED_SMT
6841	return cpumask_test_cpu(cpu0, cpu_smt_mask(cpu1));
6842#else
6843	return false;
6844#endif
6845}
6846
6847static bool __init cpus_share_numa(int cpu0, int cpu1)
6848{
6849	return cpu_to_node(cpu0) == cpu_to_node(cpu1);
6850}
6851
6852/**
6853 * workqueue_init_topology - initialize CPU pods for unbound workqueues
6854 *
6855 * This is the third step of there-staged workqueue subsystem initialization and
6856 * invoked after SMP and topology information are fully initialized. It
6857 * initializes the unbound CPU pods accordingly.
6858 */
6859void __init workqueue_init_topology(void)
6860{
6861	struct workqueue_struct *wq;
6862	int cpu;
6863
6864	init_pod_type(&wq_pod_types[WQ_AFFN_CPU], cpus_dont_share);
6865	init_pod_type(&wq_pod_types[WQ_AFFN_SMT], cpus_share_smt);
6866	init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
6867	init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
6868
6869	mutex_lock(&wq_pool_mutex);
6870
6871	/*
6872	 * Workqueues allocated earlier would have all CPUs sharing the default
6873	 * worker pool. Explicitly call wq_update_pod() on all workqueue and CPU
6874	 * combinations to apply per-pod sharing.
6875	 */
6876	list_for_each_entry(wq, &workqueues, list) {
6877		for_each_online_cpu(cpu) {
6878			wq_update_pod(wq, cpu, cpu, true);
6879		}
6880	}
6881
6882	mutex_unlock(&wq_pool_mutex);
6883}
6884
6885void __warn_flushing_systemwide_wq(void)
6886{
6887	pr_warn("WARNING: Flushing system-wide workqueues will be prohibited in near future.\n");
6888	dump_stack();
6889}
6890EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
6891
6892static int __init workqueue_unbound_cpus_setup(char *str)
6893{
6894	if (cpulist_parse(str, &wq_cmdline_cpumask) < 0) {
6895		cpumask_clear(&wq_cmdline_cpumask);
6896		pr_warn("workqueue.unbound_cpus: incorrect CPU range, using default\n");
6897	}
6898
6899	return 1;
6900}
6901__setup("workqueue.unbound_cpus=", workqueue_unbound_cpus_setup);