1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  Kernel internal timers
   4 *
   5 *  Copyright (C) 1991, 1992  Linus Torvalds
   6 *
   7 *  1997-01-28  Modified by Finn Arne Gangstad to make timers scale better.
   8 *
   9 *  1997-09-10  Updated NTP code according to technical memorandum Jan '96
  10 *              "A Kernel Model for Precision Timekeeping" by Dave Mills
  11 *  1998-12-24  Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
  12 *              serialize accesses to xtime/lost_ticks).
  13 *                              Copyright (C) 1998  Andrea Arcangeli
  14 *  1999-03-10  Improved NTP compatibility by Ulrich Windl
  15 *  2002-05-31	Move sys_sysinfo here and make its locking sane, Robert Love
  16 *  2000-10-05  Implemented scalable SMP per-CPU timer handling.
  17 *                              Copyright (C) 2000, 2001, 2002  Ingo Molnar
  18 *              Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
  19 */
  20
  21#include <linux/kernel_stat.h>
  22#include <linux/export.h>
  23#include <linux/interrupt.h>
  24#include <linux/percpu.h>
  25#include <linux/init.h>
  26#include <linux/mm.h>
  27#include <linux/swap.h>
  28#include <linux/pid_namespace.h>
  29#include <linux/notifier.h>
  30#include <linux/thread_info.h>
  31#include <linux/time.h>
  32#include <linux/jiffies.h>
  33#include <linux/posix-timers.h>
  34#include <linux/cpu.h>
  35#include <linux/syscalls.h>
  36#include <linux/delay.h>
  37#include <linux/tick.h>
  38#include <linux/kallsyms.h>
  39#include <linux/irq_work.h>
  40#include <linux/sched/signal.h>
  41#include <linux/sched/sysctl.h>
  42#include <linux/sched/nohz.h>
  43#include <linux/sched/debug.h>
  44#include <linux/slab.h>
  45#include <linux/compat.h>
  46#include <linux/random.h>
 
  47
  48#include <linux/uaccess.h>
  49#include <asm/unistd.h>
  50#include <asm/div64.h>
  51#include <asm/timex.h>
  52#include <asm/io.h>
  53
  54#include "tick-internal.h"
 
  55
  56#define CREATE_TRACE_POINTS
  57#include <trace/events/timer.h>
  58
  59__visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
  60
  61EXPORT_SYMBOL(jiffies_64);
  62
  63/*
  64 * The timer wheel has LVL_DEPTH array levels. Each level provides an array of
  65 * LVL_SIZE buckets. Each level is driven by its own clock and therefor each
  66 * level has a different granularity.
  67 *
  68 * The level granularity is:		LVL_CLK_DIV ^ lvl
  69 * The level clock frequency is:	HZ / (LVL_CLK_DIV ^ level)
  70 *
  71 * The array level of a newly armed timer depends on the relative expiry
  72 * time. The farther the expiry time is away the higher the array level and
  73 * therefor the granularity becomes.
  74 *
  75 * Contrary to the original timer wheel implementation, which aims for 'exact'
  76 * expiry of the timers, this implementation removes the need for recascading
  77 * the timers into the lower array levels. The previous 'classic' timer wheel
  78 * implementation of the kernel already violated the 'exact' expiry by adding
  79 * slack to the expiry time to provide batched expiration. The granularity
  80 * levels provide implicit batching.
  81 *
  82 * This is an optimization of the original timer wheel implementation for the
  83 * majority of the timer wheel use cases: timeouts. The vast majority of
  84 * timeout timers (networking, disk I/O ...) are canceled before expiry. If
  85 * the timeout expires it indicates that normal operation is disturbed, so it
  86 * does not matter much whether the timeout comes with a slight delay.
  87 *
  88 * The only exception to this are networking timers with a small expiry
  89 * time. They rely on the granularity. Those fit into the first wheel level,
  90 * which has HZ granularity.
  91 *
  92 * We don't have cascading anymore. timers with a expiry time above the
  93 * capacity of the last wheel level are force expired at the maximum timeout
  94 * value of the last wheel level. From data sampling we know that the maximum
  95 * value observed is 5 days (network connection tracking), so this should not
  96 * be an issue.
  97 *
  98 * The currently chosen array constants values are a good compromise between
  99 * array size and granularity.
 100 *
 101 * This results in the following granularity and range levels:
 102 *
 103 * HZ 1000 steps
 104 * Level Offset  Granularity            Range
 105 *  0      0         1 ms                0 ms -         63 ms
 106 *  1     64         8 ms               64 ms -        511 ms
 107 *  2    128        64 ms              512 ms -       4095 ms (512ms - ~4s)
 108 *  3    192       512 ms             4096 ms -      32767 ms (~4s - ~32s)
 109 *  4    256      4096 ms (~4s)      32768 ms -     262143 ms (~32s - ~4m)
 110 *  5    320     32768 ms (~32s)    262144 ms -    2097151 ms (~4m - ~34m)
 111 *  6    384    262144 ms (~4m)    2097152 ms -   16777215 ms (~34m - ~4h)
 112 *  7    448   2097152 ms (~34m)  16777216 ms -  134217727 ms (~4h - ~1d)
 113 *  8    512  16777216 ms (~4h)  134217728 ms - 1073741822 ms (~1d - ~12d)
 114 *
 115 * HZ  300
 116 * Level Offset  Granularity            Range
 117 *  0	   0         3 ms                0 ms -        210 ms
 118 *  1	  64        26 ms              213 ms -       1703 ms (213ms - ~1s)
 119 *  2	 128       213 ms             1706 ms -      13650 ms (~1s - ~13s)
 120 *  3	 192      1706 ms (~1s)      13653 ms -     109223 ms (~13s - ~1m)
 121 *  4	 256     13653 ms (~13s)    109226 ms -     873810 ms (~1m - ~14m)
 122 *  5	 320    109226 ms (~1m)     873813 ms -    6990503 ms (~14m - ~1h)
 123 *  6	 384    873813 ms (~14m)   6990506 ms -   55924050 ms (~1h - ~15h)
 124 *  7	 448   6990506 ms (~1h)   55924053 ms -  447392423 ms (~15h - ~5d)
 125 *  8    512  55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
 126 *
 127 * HZ  250
 128 * Level Offset  Granularity            Range
 129 *  0	   0         4 ms                0 ms -        255 ms
 130 *  1	  64        32 ms              256 ms -       2047 ms (256ms - ~2s)
 131 *  2	 128       256 ms             2048 ms -      16383 ms (~2s - ~16s)
 132 *  3	 192      2048 ms (~2s)      16384 ms -     131071 ms (~16s - ~2m)
 133 *  4	 256     16384 ms (~16s)    131072 ms -    1048575 ms (~2m - ~17m)
 134 *  5	 320    131072 ms (~2m)    1048576 ms -    8388607 ms (~17m - ~2h)
 135 *  6	 384   1048576 ms (~17m)   8388608 ms -   67108863 ms (~2h - ~18h)
 136 *  7	 448   8388608 ms (~2h)   67108864 ms -  536870911 ms (~18h - ~6d)
 137 *  8    512  67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
 138 *
 139 * HZ  100
 140 * Level Offset  Granularity            Range
 141 *  0	   0         10 ms               0 ms -        630 ms
 142 *  1	  64         80 ms             640 ms -       5110 ms (640ms - ~5s)
 143 *  2	 128        640 ms            5120 ms -      40950 ms (~5s - ~40s)
 144 *  3	 192       5120 ms (~5s)     40960 ms -     327670 ms (~40s - ~5m)
 145 *  4	 256      40960 ms (~40s)   327680 ms -    2621430 ms (~5m - ~43m)
 146 *  5	 320     327680 ms (~5m)   2621440 ms -   20971510 ms (~43m - ~5h)
 147 *  6	 384    2621440 ms (~43m) 20971520 ms -  167772150 ms (~5h - ~1d)
 148 *  7	 448   20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
 149 */
 150
 151/* Clock divisor for the next level */
 152#define LVL_CLK_SHIFT	3
 153#define LVL_CLK_DIV	(1UL << LVL_CLK_SHIFT)
 154#define LVL_CLK_MASK	(LVL_CLK_DIV - 1)
 155#define LVL_SHIFT(n)	((n) * LVL_CLK_SHIFT)
 156#define LVL_GRAN(n)	(1UL << LVL_SHIFT(n))
 157
 158/*
 159 * The time start value for each level to select the bucket at enqueue
 160 * time. We start from the last possible delta of the previous level
 161 * so that we can later add an extra LVL_GRAN(n) to n (see calc_index()).
 162 */
 163#define LVL_START(n)	((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
 164
 165/* Size of each clock level */
 166#define LVL_BITS	6
 167#define LVL_SIZE	(1UL << LVL_BITS)
 168#define LVL_MASK	(LVL_SIZE - 1)
 169#define LVL_OFFS(n)	((n) * LVL_SIZE)
 170
 171/* Level depth */
 172#if HZ > 100
 173# define LVL_DEPTH	9
 174# else
 175# define LVL_DEPTH	8
 176#endif
 177
 178/* The cutoff (max. capacity of the wheel) */
 179#define WHEEL_TIMEOUT_CUTOFF	(LVL_START(LVL_DEPTH))
 180#define WHEEL_TIMEOUT_MAX	(WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
 181
 182/*
 183 * The resulting wheel size. If NOHZ is configured we allocate two
 184 * wheels so we have a separate storage for the deferrable timers.
 185 */
 186#define WHEEL_SIZE	(LVL_SIZE * LVL_DEPTH)
 187
 188#ifdef CONFIG_NO_HZ_COMMON
 189# define NR_BASES	2
 190# define BASE_STD	0
 191# define BASE_DEF	1
 
 
 
 
 
 192#else
 193# define NR_BASES	1
 194# define BASE_STD	0
 
 195# define BASE_DEF	0
 196#endif
 197
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 198struct timer_base {
 199	raw_spinlock_t		lock;
 200	struct timer_list	*running_timer;
 201#ifdef CONFIG_PREEMPT_RT
 202	spinlock_t		expiry_lock;
 203	atomic_t		timer_waiters;
 204#endif
 205	unsigned long		clk;
 206	unsigned long		next_expiry;
 207	unsigned int		cpu;
 208	bool			next_expiry_recalc;
 209	bool			is_idle;
 210	bool			timers_pending;
 211	DECLARE_BITMAP(pending_map, WHEEL_SIZE);
 212	struct hlist_head	vectors[WHEEL_SIZE];
 213} ____cacheline_aligned;
 214
 215static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
 216
 217#ifdef CONFIG_NO_HZ_COMMON
 218
 219static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
 220static DEFINE_MUTEX(timer_keys_mutex);
 221
 222static void timer_update_keys(struct work_struct *work);
 223static DECLARE_WORK(timer_update_work, timer_update_keys);
 224
 225#ifdef CONFIG_SMP
 226unsigned int sysctl_timer_migration = 1;
 227
 228DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
 229
 230static void timers_update_migration(void)
 231{
 232	if (sysctl_timer_migration && tick_nohz_active)
 233		static_branch_enable(&timers_migration_enabled);
 234	else
 235		static_branch_disable(&timers_migration_enabled);
 236}
 237#else
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 238static inline void timers_update_migration(void) { }
 239#endif /* !CONFIG_SMP */
 240
 241static void timer_update_keys(struct work_struct *work)
 242{
 243	mutex_lock(&timer_keys_mutex);
 244	timers_update_migration();
 245	static_branch_enable(&timers_nohz_active);
 246	mutex_unlock(&timer_keys_mutex);
 247}
 248
 249void timers_update_nohz(void)
 250{
 251	schedule_work(&timer_update_work);
 252}
 253
 254int timer_migration_handler(struct ctl_table *table, int write,
 255			    void *buffer, size_t *lenp, loff_t *ppos)
 256{
 257	int ret;
 258
 259	mutex_lock(&timer_keys_mutex);
 260	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 261	if (!ret && write)
 262		timers_update_migration();
 263	mutex_unlock(&timer_keys_mutex);
 264	return ret;
 265}
 266
 267static inline bool is_timers_nohz_active(void)
 268{
 269	return static_branch_unlikely(&timers_nohz_active);
 270}
 271#else
 272static inline bool is_timers_nohz_active(void) { return false; }
 273#endif /* NO_HZ_COMMON */
 274
 275static unsigned long round_jiffies_common(unsigned long j, int cpu,
 276		bool force_up)
 277{
 278	int rem;
 279	unsigned long original = j;
 280
 281	/*
 282	 * We don't want all cpus firing their timers at once hitting the
 283	 * same lock or cachelines, so we skew each extra cpu with an extra
 284	 * 3 jiffies. This 3 jiffies came originally from the mm/ code which
 285	 * already did this.
 286	 * The skew is done by adding 3*cpunr, then round, then subtract this
 287	 * extra offset again.
 288	 */
 289	j += cpu * 3;
 290
 291	rem = j % HZ;
 292
 293	/*
 294	 * If the target jiffie is just after a whole second (which can happen
 295	 * due to delays of the timer irq, long irq off times etc etc) then
 296	 * we should round down to the whole second, not up. Use 1/4th second
 297	 * as cutoff for this rounding as an extreme upper bound for this.
 298	 * But never round down if @force_up is set.
 299	 */
 300	if (rem < HZ/4 && !force_up) /* round down */
 301		j = j - rem;
 302	else /* round up */
 303		j = j - rem + HZ;
 304
 305	/* now that we have rounded, subtract the extra skew again */
 306	j -= cpu * 3;
 307
 308	/*
 309	 * Make sure j is still in the future. Otherwise return the
 310	 * unmodified value.
 311	 */
 312	return time_is_after_jiffies(j) ? j : original;
 313}
 314
 315/**
 316 * __round_jiffies - function to round jiffies to a full second
 317 * @j: the time in (absolute) jiffies that should be rounded
 318 * @cpu: the processor number on which the timeout will happen
 319 *
 320 * __round_jiffies() rounds an absolute time in the future (in jiffies)
 321 * up or down to (approximately) full seconds. This is useful for timers
 322 * for which the exact time they fire does not matter too much, as long as
 323 * they fire approximately every X seconds.
 324 *
 325 * By rounding these timers to whole seconds, all such timers will fire
 326 * at the same time, rather than at various times spread out. The goal
 327 * of this is to have the CPU wake up less, which saves power.
 328 *
 329 * The exact rounding is skewed for each processor to avoid all
 330 * processors firing at the exact same time, which could lead
 331 * to lock contention or spurious cache line bouncing.
 332 *
 333 * The return value is the rounded version of the @j parameter.
 334 */
 335unsigned long __round_jiffies(unsigned long j, int cpu)
 336{
 337	return round_jiffies_common(j, cpu, false);
 338}
 339EXPORT_SYMBOL_GPL(__round_jiffies);
 340
 341/**
 342 * __round_jiffies_relative - function to round jiffies to a full second
 343 * @j: the time in (relative) jiffies that should be rounded
 344 * @cpu: the processor number on which the timeout will happen
 345 *
 346 * __round_jiffies_relative() rounds a time delta  in the future (in jiffies)
 347 * up or down to (approximately) full seconds. This is useful for timers
 348 * for which the exact time they fire does not matter too much, as long as
 349 * they fire approximately every X seconds.
 350 *
 351 * By rounding these timers to whole seconds, all such timers will fire
 352 * at the same time, rather than at various times spread out. The goal
 353 * of this is to have the CPU wake up less, which saves power.
 354 *
 355 * The exact rounding is skewed for each processor to avoid all
 356 * processors firing at the exact same time, which could lead
 357 * to lock contention or spurious cache line bouncing.
 358 *
 359 * The return value is the rounded version of the @j parameter.
 360 */
 361unsigned long __round_jiffies_relative(unsigned long j, int cpu)
 362{
 363	unsigned long j0 = jiffies;
 364
 365	/* Use j0 because jiffies might change while we run */
 366	return round_jiffies_common(j + j0, cpu, false) - j0;
 367}
 368EXPORT_SYMBOL_GPL(__round_jiffies_relative);
 369
 370/**
 371 * round_jiffies - function to round jiffies to a full second
 372 * @j: the time in (absolute) jiffies that should be rounded
 373 *
 374 * round_jiffies() rounds an absolute time in the future (in jiffies)
 375 * up or down to (approximately) full seconds. This is useful for timers
 376 * for which the exact time they fire does not matter too much, as long as
 377 * they fire approximately every X seconds.
 378 *
 379 * By rounding these timers to whole seconds, all such timers will fire
 380 * at the same time, rather than at various times spread out. The goal
 381 * of this is to have the CPU wake up less, which saves power.
 382 *
 383 * The return value is the rounded version of the @j parameter.
 384 */
 385unsigned long round_jiffies(unsigned long j)
 386{
 387	return round_jiffies_common(j, raw_smp_processor_id(), false);
 388}
 389EXPORT_SYMBOL_GPL(round_jiffies);
 390
 391/**
 392 * round_jiffies_relative - function to round jiffies to a full second
 393 * @j: the time in (relative) jiffies that should be rounded
 394 *
 395 * round_jiffies_relative() rounds a time delta  in the future (in jiffies)
 396 * up or down to (approximately) full seconds. This is useful for timers
 397 * for which the exact time they fire does not matter too much, as long as
 398 * they fire approximately every X seconds.
 399 *
 400 * By rounding these timers to whole seconds, all such timers will fire
 401 * at the same time, rather than at various times spread out. The goal
 402 * of this is to have the CPU wake up less, which saves power.
 403 *
 404 * The return value is the rounded version of the @j parameter.
 405 */
 406unsigned long round_jiffies_relative(unsigned long j)
 407{
 408	return __round_jiffies_relative(j, raw_smp_processor_id());
 409}
 410EXPORT_SYMBOL_GPL(round_jiffies_relative);
 411
 412/**
 413 * __round_jiffies_up - function to round jiffies up to a full second
 414 * @j: the time in (absolute) jiffies that should be rounded
 415 * @cpu: the processor number on which the timeout will happen
 416 *
 417 * This is the same as __round_jiffies() except that it will never
 418 * round down.  This is useful for timeouts for which the exact time
 419 * of firing does not matter too much, as long as they don't fire too
 420 * early.
 421 */
 422unsigned long __round_jiffies_up(unsigned long j, int cpu)
 423{
 424	return round_jiffies_common(j, cpu, true);
 425}
 426EXPORT_SYMBOL_GPL(__round_jiffies_up);
 427
 428/**
 429 * __round_jiffies_up_relative - function to round jiffies up to a full second
 430 * @j: the time in (relative) jiffies that should be rounded
 431 * @cpu: the processor number on which the timeout will happen
 432 *
 433 * This is the same as __round_jiffies_relative() except that it will never
 434 * round down.  This is useful for timeouts for which the exact time
 435 * of firing does not matter too much, as long as they don't fire too
 436 * early.
 437 */
 438unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
 439{
 440	unsigned long j0 = jiffies;
 441
 442	/* Use j0 because jiffies might change while we run */
 443	return round_jiffies_common(j + j0, cpu, true) - j0;
 444}
 445EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
 446
 447/**
 448 * round_jiffies_up - function to round jiffies up to a full second
 449 * @j: the time in (absolute) jiffies that should be rounded
 450 *
 451 * This is the same as round_jiffies() except that it will never
 452 * round down.  This is useful for timeouts for which the exact time
 453 * of firing does not matter too much, as long as they don't fire too
 454 * early.
 455 */
 456unsigned long round_jiffies_up(unsigned long j)
 457{
 458	return round_jiffies_common(j, raw_smp_processor_id(), true);
 459}
 460EXPORT_SYMBOL_GPL(round_jiffies_up);
 461
 462/**
 463 * round_jiffies_up_relative - function to round jiffies up to a full second
 464 * @j: the time in (relative) jiffies that should be rounded
 465 *
 466 * This is the same as round_jiffies_relative() except that it will never
 467 * round down.  This is useful for timeouts for which the exact time
 468 * of firing does not matter too much, as long as they don't fire too
 469 * early.
 470 */
 471unsigned long round_jiffies_up_relative(unsigned long j)
 472{
 473	return __round_jiffies_up_relative(j, raw_smp_processor_id());
 474}
 475EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
 476
 477
 478static inline unsigned int timer_get_idx(struct timer_list *timer)
 479{
 480	return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
 481}
 482
 483static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
 484{
 485	timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
 486			idx << TIMER_ARRAYSHIFT;
 487}
 488
 489/*
 490 * Helper function to calculate the array index for a given expiry
 491 * time.
 492 */
 493static inline unsigned calc_index(unsigned long expires, unsigned lvl,
 494				  unsigned long *bucket_expiry)
 495{
 496
 497	/*
 498	 * The timer wheel has to guarantee that a timer does not fire
 499	 * early. Early expiry can happen due to:
 500	 * - Timer is armed at the edge of a tick
 501	 * - Truncation of the expiry time in the outer wheel levels
 502	 *
 503	 * Round up with level granularity to prevent this.
 504	 */
 505	expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
 506	*bucket_expiry = expires << LVL_SHIFT(lvl);
 507	return LVL_OFFS(lvl) + (expires & LVL_MASK);
 508}
 509
 510static int calc_wheel_index(unsigned long expires, unsigned long clk,
 511			    unsigned long *bucket_expiry)
 512{
 513	unsigned long delta = expires - clk;
 514	unsigned int idx;
 515
 516	if (delta < LVL_START(1)) {
 517		idx = calc_index(expires, 0, bucket_expiry);
 518	} else if (delta < LVL_START(2)) {
 519		idx = calc_index(expires, 1, bucket_expiry);
 520	} else if (delta < LVL_START(3)) {
 521		idx = calc_index(expires, 2, bucket_expiry);
 522	} else if (delta < LVL_START(4)) {
 523		idx = calc_index(expires, 3, bucket_expiry);
 524	} else if (delta < LVL_START(5)) {
 525		idx = calc_index(expires, 4, bucket_expiry);
 526	} else if (delta < LVL_START(6)) {
 527		idx = calc_index(expires, 5, bucket_expiry);
 528	} else if (delta < LVL_START(7)) {
 529		idx = calc_index(expires, 6, bucket_expiry);
 530	} else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
 531		idx = calc_index(expires, 7, bucket_expiry);
 532	} else if ((long) delta < 0) {
 533		idx = clk & LVL_MASK;
 534		*bucket_expiry = clk;
 535	} else {
 536		/*
 537		 * Force expire obscene large timeouts to expire at the
 538		 * capacity limit of the wheel.
 539		 */
 540		if (delta >= WHEEL_TIMEOUT_CUTOFF)
 541			expires = clk + WHEEL_TIMEOUT_MAX;
 542
 543		idx = calc_index(expires, LVL_DEPTH - 1, bucket_expiry);
 544	}
 545	return idx;
 546}
 547
 548static void
 549trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
 550{
 551	if (!is_timers_nohz_active())
 552		return;
 553
 554	/*
 555	 * TODO: This wants some optimizing similar to the code below, but we
 556	 * will do that when we switch from push to pull for deferrable timers.
 
 
 
 557	 */
 558	if (timer->flags & TIMER_DEFERRABLE) {
 559		if (tick_nohz_full_cpu(base->cpu))
 560			wake_up_nohz_cpu(base->cpu);
 561		return;
 562	}
 563
 564	/*
 565	 * We might have to IPI the remote CPU if the base is idle and the
 566	 * timer is not deferrable. If the other CPU is on the way to idle
 567	 * then it can't set base->is_idle as we hold the base lock:
 568	 */
 569	if (base->is_idle)
 
 
 
 
 
 570		wake_up_nohz_cpu(base->cpu);
 
 571}
 572
 573/*
 574 * Enqueue the timer into the hash bucket, mark it pending in
 575 * the bitmap, store the index in the timer flags then wake up
 576 * the target CPU if needed.
 577 */
 578static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
 579			  unsigned int idx, unsigned long bucket_expiry)
 580{
 581
 582	hlist_add_head(&timer->entry, base->vectors + idx);
 583	__set_bit(idx, base->pending_map);
 584	timer_set_idx(timer, idx);
 585
 586	trace_timer_start(timer, timer->expires, timer->flags);
 587
 588	/*
 589	 * Check whether this is the new first expiring timer. The
 590	 * effective expiry time of the timer is required here
 591	 * (bucket_expiry) instead of timer->expires.
 592	 */
 593	if (time_before(bucket_expiry, base->next_expiry)) {
 594		/*
 595		 * Set the next expiry time and kick the CPU so it
 596		 * can reevaluate the wheel:
 597		 */
 598		base->next_expiry = bucket_expiry;
 599		base->timers_pending = true;
 600		base->next_expiry_recalc = false;
 601		trigger_dyntick_cpu(base, timer);
 602	}
 603}
 604
 605static void internal_add_timer(struct timer_base *base, struct timer_list *timer)
 606{
 607	unsigned long bucket_expiry;
 608	unsigned int idx;
 609
 610	idx = calc_wheel_index(timer->expires, base->clk, &bucket_expiry);
 611	enqueue_timer(base, timer, idx, bucket_expiry);
 612}
 613
 614#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
 615
 616static const struct debug_obj_descr timer_debug_descr;
 617
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 618static void *timer_debug_hint(void *addr)
 619{
 620	return ((struct timer_list *) addr)->function;
 
 
 
 
 
 
 
 
 
 
 
 621}
 622
 623static bool timer_is_static_object(void *addr)
 624{
 625	struct timer_list *timer = addr;
 626
 627	return (timer->entry.pprev == NULL &&
 628		timer->entry.next == TIMER_ENTRY_STATIC);
 629}
 630
 631/*
 632 * fixup_init is called when:
 633 * - an active object is initialized
 634 */
 635static bool timer_fixup_init(void *addr, enum debug_obj_state state)
 636{
 637	struct timer_list *timer = addr;
 638
 639	switch (state) {
 640	case ODEBUG_STATE_ACTIVE:
 641		del_timer_sync(timer);
 642		debug_object_init(timer, &timer_debug_descr);
 643		return true;
 644	default:
 645		return false;
 646	}
 647}
 648
 649/* Stub timer callback for improperly used timers. */
 650static void stub_timer(struct timer_list *unused)
 651{
 652	WARN_ON(1);
 653}
 654
 655/*
 656 * fixup_activate is called when:
 657 * - an active object is activated
 658 * - an unknown non-static object is activated
 659 */
 660static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
 661{
 662	struct timer_list *timer = addr;
 663
 664	switch (state) {
 665	case ODEBUG_STATE_NOTAVAILABLE:
 666		timer_setup(timer, stub_timer, 0);
 667		return true;
 668
 669	case ODEBUG_STATE_ACTIVE:
 670		WARN_ON(1);
 671		fallthrough;
 672	default:
 673		return false;
 674	}
 675}
 676
 677/*
 678 * fixup_free is called when:
 679 * - an active object is freed
 680 */
 681static bool timer_fixup_free(void *addr, enum debug_obj_state state)
 682{
 683	struct timer_list *timer = addr;
 684
 685	switch (state) {
 686	case ODEBUG_STATE_ACTIVE:
 687		del_timer_sync(timer);
 688		debug_object_free(timer, &timer_debug_descr);
 689		return true;
 690	default:
 691		return false;
 692	}
 693}
 694
 695/*
 696 * fixup_assert_init is called when:
 697 * - an untracked/uninit-ed object is found
 698 */
 699static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
 700{
 701	struct timer_list *timer = addr;
 702
 703	switch (state) {
 704	case ODEBUG_STATE_NOTAVAILABLE:
 705		timer_setup(timer, stub_timer, 0);
 706		return true;
 707	default:
 708		return false;
 709	}
 710}
 711
 712static const struct debug_obj_descr timer_debug_descr = {
 713	.name			= "timer_list",
 714	.debug_hint		= timer_debug_hint,
 715	.is_static_object	= timer_is_static_object,
 716	.fixup_init		= timer_fixup_init,
 717	.fixup_activate		= timer_fixup_activate,
 718	.fixup_free		= timer_fixup_free,
 719	.fixup_assert_init	= timer_fixup_assert_init,
 720};
 721
 722static inline void debug_timer_init(struct timer_list *timer)
 723{
 724	debug_object_init(timer, &timer_debug_descr);
 725}
 726
 727static inline void debug_timer_activate(struct timer_list *timer)
 728{
 729	debug_object_activate(timer, &timer_debug_descr);
 730}
 731
 732static inline void debug_timer_deactivate(struct timer_list *timer)
 733{
 734	debug_object_deactivate(timer, &timer_debug_descr);
 735}
 736
 737static inline void debug_timer_assert_init(struct timer_list *timer)
 738{
 739	debug_object_assert_init(timer, &timer_debug_descr);
 740}
 741
 742static void do_init_timer(struct timer_list *timer,
 743			  void (*func)(struct timer_list *),
 744			  unsigned int flags,
 745			  const char *name, struct lock_class_key *key);
 746
 747void init_timer_on_stack_key(struct timer_list *timer,
 748			     void (*func)(struct timer_list *),
 749			     unsigned int flags,
 750			     const char *name, struct lock_class_key *key)
 751{
 752	debug_object_init_on_stack(timer, &timer_debug_descr);
 753	do_init_timer(timer, func, flags, name, key);
 754}
 755EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
 756
 757void destroy_timer_on_stack(struct timer_list *timer)
 758{
 759	debug_object_free(timer, &timer_debug_descr);
 760}
 761EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
 762
 763#else
 764static inline void debug_timer_init(struct timer_list *timer) { }
 765static inline void debug_timer_activate(struct timer_list *timer) { }
 766static inline void debug_timer_deactivate(struct timer_list *timer) { }
 767static inline void debug_timer_assert_init(struct timer_list *timer) { }
 768#endif
 769
 770static inline void debug_init(struct timer_list *timer)
 771{
 772	debug_timer_init(timer);
 773	trace_timer_init(timer);
 774}
 775
 776static inline void debug_deactivate(struct timer_list *timer)
 777{
 778	debug_timer_deactivate(timer);
 779	trace_timer_cancel(timer);
 780}
 781
 782static inline void debug_assert_init(struct timer_list *timer)
 783{
 784	debug_timer_assert_init(timer);
 785}
 786
 787static void do_init_timer(struct timer_list *timer,
 788			  void (*func)(struct timer_list *),
 789			  unsigned int flags,
 790			  const char *name, struct lock_class_key *key)
 791{
 792	timer->entry.pprev = NULL;
 793	timer->function = func;
 794	if (WARN_ON_ONCE(flags & ~TIMER_INIT_FLAGS))
 795		flags &= TIMER_INIT_FLAGS;
 796	timer->flags = flags | raw_smp_processor_id();
 797	lockdep_init_map(&timer->lockdep_map, name, key, 0);
 798}
 799
 800/**
 801 * init_timer_key - initialize a timer
 802 * @timer: the timer to be initialized
 803 * @func: timer callback function
 804 * @flags: timer flags
 805 * @name: name of the timer
 806 * @key: lockdep class key of the fake lock used for tracking timer
 807 *       sync lock dependencies
 808 *
 809 * init_timer_key() must be done to a timer prior calling *any* of the
 810 * other timer functions.
 811 */
 812void init_timer_key(struct timer_list *timer,
 813		    void (*func)(struct timer_list *), unsigned int flags,
 814		    const char *name, struct lock_class_key *key)
 815{
 816	debug_init(timer);
 817	do_init_timer(timer, func, flags, name, key);
 818}
 819EXPORT_SYMBOL(init_timer_key);
 820
 821static inline void detach_timer(struct timer_list *timer, bool clear_pending)
 822{
 823	struct hlist_node *entry = &timer->entry;
 824
 825	debug_deactivate(timer);
 826
 827	__hlist_del(entry);
 828	if (clear_pending)
 829		entry->pprev = NULL;
 830	entry->next = LIST_POISON2;
 831}
 832
 833static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
 834			     bool clear_pending)
 835{
 836	unsigned idx = timer_get_idx(timer);
 837
 838	if (!timer_pending(timer))
 839		return 0;
 840
 841	if (hlist_is_singular_node(&timer->entry, base->vectors + idx)) {
 842		__clear_bit(idx, base->pending_map);
 843		base->next_expiry_recalc = true;
 844	}
 845
 846	detach_timer(timer, clear_pending);
 847	return 1;
 848}
 849
 850static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
 851{
 852	struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
 
 
 
 853
 854	/*
 855	 * If the timer is deferrable and NO_HZ_COMMON is set then we need
 856	 * to use the deferrable base.
 857	 */
 858	if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
 859		base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
 860	return base;
 861}
 862
 863static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
 864{
 865	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
 
 
 
 866
 867	/*
 868	 * If the timer is deferrable and NO_HZ_COMMON is set then we need
 869	 * to use the deferrable base.
 870	 */
 871	if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
 872		base = this_cpu_ptr(&timer_bases[BASE_DEF]);
 873	return base;
 874}
 875
 876static inline struct timer_base *get_timer_base(u32 tflags)
 877{
 878	return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
 879}
 880
 881static inline struct timer_base *
 882get_target_base(struct timer_base *base, unsigned tflags)
 883{
 884#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
 885	if (static_branch_likely(&timers_migration_enabled) &&
 886	    !(tflags & TIMER_PINNED))
 887		return get_timer_cpu_base(tflags, get_nohz_timer_target());
 888#endif
 889	return get_timer_this_cpu_base(tflags);
 890}
 891
 892static inline void forward_timer_base(struct timer_base *base)
 893{
 894	unsigned long jnow = READ_ONCE(jiffies);
 895
 896	/*
 897	 * No need to forward if we are close enough below jiffies.
 898	 * Also while executing timers, base->clk is 1 offset ahead
 899	 * of jiffies to avoid endless requeuing to current jiffies.
 900	 */
 901	if ((long)(jnow - base->clk) < 1)
 902		return;
 903
 904	/*
 905	 * If the next expiry value is > jiffies, then we fast forward to
 906	 * jiffies otherwise we forward to the next expiry value.
 907	 */
 908	if (time_after(base->next_expiry, jnow)) {
 909		base->clk = jnow;
 910	} else {
 911		if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk)))
 912			return;
 913		base->clk = base->next_expiry;
 914	}
 
 915}
 916
 
 
 
 
 917
 918/*
 919 * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
 920 * that all timers which are tied to this base are locked, and the base itself
 921 * is locked too.
 922 *
 923 * So __run_timers/migrate_timers can safely modify all timers which could
 924 * be found in the base->vectors array.
 925 *
 926 * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
 927 * to wait until the migration is done.
 928 */
 929static struct timer_base *lock_timer_base(struct timer_list *timer,
 930					  unsigned long *flags)
 931	__acquires(timer->base->lock)
 932{
 933	for (;;) {
 934		struct timer_base *base;
 935		u32 tf;
 936
 937		/*
 938		 * We need to use READ_ONCE() here, otherwise the compiler
 939		 * might re-read @tf between the check for TIMER_MIGRATING
 940		 * and spin_lock().
 941		 */
 942		tf = READ_ONCE(timer->flags);
 943
 944		if (!(tf & TIMER_MIGRATING)) {
 945			base = get_timer_base(tf);
 946			raw_spin_lock_irqsave(&base->lock, *flags);
 947			if (timer->flags == tf)
 948				return base;
 949			raw_spin_unlock_irqrestore(&base->lock, *flags);
 950		}
 951		cpu_relax();
 952	}
 953}
 954
 955#define MOD_TIMER_PENDING_ONLY		0x01
 956#define MOD_TIMER_REDUCE		0x02
 957#define MOD_TIMER_NOTPENDING		0x04
 958
 959static inline int
 960__mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
 961{
 962	unsigned long clk = 0, flags, bucket_expiry;
 963	struct timer_base *base, *new_base;
 964	unsigned int idx = UINT_MAX;
 965	int ret = 0;
 966
 967	BUG_ON(!timer->function);
 968
 969	/*
 970	 * This is a common optimization triggered by the networking code - if
 971	 * the timer is re-modified to have the same timeout or ends up in the
 972	 * same array bucket then just return:
 973	 */
 974	if (!(options & MOD_TIMER_NOTPENDING) && timer_pending(timer)) {
 975		/*
 976		 * The downside of this optimization is that it can result in
 977		 * larger granularity than you would get from adding a new
 978		 * timer with this expiry.
 979		 */
 980		long diff = timer->expires - expires;
 981
 982		if (!diff)
 983			return 1;
 984		if (options & MOD_TIMER_REDUCE && diff <= 0)
 985			return 1;
 986
 987		/*
 988		 * We lock timer base and calculate the bucket index right
 989		 * here. If the timer ends up in the same bucket, then we
 990		 * just update the expiry time and avoid the whole
 991		 * dequeue/enqueue dance.
 992		 */
 993		base = lock_timer_base(timer, &flags);
 
 
 
 
 
 
 
 
 994		forward_timer_base(base);
 995
 996		if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
 997		    time_before_eq(timer->expires, expires)) {
 998			ret = 1;
 999			goto out_unlock;
1000		}
1001
1002		clk = base->clk;
1003		idx = calc_wheel_index(expires, clk, &bucket_expiry);
1004
1005		/*
1006		 * Retrieve and compare the array index of the pending
1007		 * timer. If it matches set the expiry to the new value so a
1008		 * subsequent call will exit in the expires check above.
1009		 */
1010		if (idx == timer_get_idx(timer)) {
1011			if (!(options & MOD_TIMER_REDUCE))
1012				timer->expires = expires;
1013			else if (time_after(timer->expires, expires))
1014				timer->expires = expires;
1015			ret = 1;
1016			goto out_unlock;
1017		}
1018	} else {
1019		base = lock_timer_base(timer, &flags);
 
 
 
 
 
 
 
 
1020		forward_timer_base(base);
1021	}
1022
1023	ret = detach_if_pending(timer, base, false);
1024	if (!ret && (options & MOD_TIMER_PENDING_ONLY))
1025		goto out_unlock;
1026
1027	new_base = get_target_base(base, timer->flags);
1028
1029	if (base != new_base) {
1030		/*
1031		 * We are trying to schedule the timer on the new base.
1032		 * However we can't change timer's base while it is running,
1033		 * otherwise del_timer_sync() can't detect that the timer's
1034		 * handler yet has not finished. This also guarantees that the
1035		 * timer is serialized wrt itself.
1036		 */
1037		if (likely(base->running_timer != timer)) {
1038			/* See the comment in lock_timer_base() */
1039			timer->flags |= TIMER_MIGRATING;
1040
1041			raw_spin_unlock(&base->lock);
1042			base = new_base;
1043			raw_spin_lock(&base->lock);
1044			WRITE_ONCE(timer->flags,
1045				   (timer->flags & ~TIMER_BASEMASK) | base->cpu);
1046			forward_timer_base(base);
1047		}
1048	}
1049
1050	debug_timer_activate(timer);
1051
1052	timer->expires = expires;
1053	/*
1054	 * If 'idx' was calculated above and the base time did not advance
1055	 * between calculating 'idx' and possibly switching the base, only
1056	 * enqueue_timer() is required. Otherwise we need to (re)calculate
1057	 * the wheel index via internal_add_timer().
1058	 */
1059	if (idx != UINT_MAX && clk == base->clk)
1060		enqueue_timer(base, timer, idx, bucket_expiry);
1061	else
1062		internal_add_timer(base, timer);
1063
1064out_unlock:
1065	raw_spin_unlock_irqrestore(&base->lock, flags);
1066
1067	return ret;
1068}
1069
1070/**
1071 * mod_timer_pending - modify a pending timer's timeout
1072 * @timer: the pending timer to be modified
1073 * @expires: new timeout in jiffies
1074 *
1075 * mod_timer_pending() is the same for pending timers as mod_timer(),
1076 * but will not re-activate and modify already deleted timers.
1077 *
1078 * It is useful for unserialized use of timers.
 
 
 
 
 
 
1079 */
1080int mod_timer_pending(struct timer_list *timer, unsigned long expires)
1081{
1082	return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
1083}
1084EXPORT_SYMBOL(mod_timer_pending);
1085
1086/**
1087 * mod_timer - modify a timer's timeout
1088 * @timer: the timer to be modified
1089 * @expires: new timeout in jiffies
1090 *
1091 * mod_timer() is a more efficient way to update the expire field of an
1092 * active timer (if the timer is inactive it will be activated)
1093 *
1094 * mod_timer(timer, expires) is equivalent to:
1095 *
1096 *     del_timer(timer); timer->expires = expires; add_timer(timer);
1097 *
 
 
 
 
1098 * Note that if there are multiple unserialized concurrent users of the
1099 * same timer, then mod_timer() is the only safe way to modify the timeout,
1100 * since add_timer() cannot modify an already running timer.
1101 *
1102 * The function returns whether it has modified a pending timer or not.
1103 * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
1104 * active timer returns 1.)
 
 
 
 
 
 
1105 */
1106int mod_timer(struct timer_list *timer, unsigned long expires)
1107{
1108	return __mod_timer(timer, expires, 0);
1109}
1110EXPORT_SYMBOL(mod_timer);
1111
1112/**
1113 * timer_reduce - Modify a timer's timeout if it would reduce the timeout
1114 * @timer:	The timer to be modified
1115 * @expires:	New timeout in jiffies
1116 *
1117 * timer_reduce() is very similar to mod_timer(), except that it will only
1118 * modify a running timer if that would reduce the expiration time (it will
1119 * start a timer that isn't running).
 
 
 
 
 
 
 
 
 
 
 
1120 */
1121int timer_reduce(struct timer_list *timer, unsigned long expires)
1122{
1123	return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
1124}
1125EXPORT_SYMBOL(timer_reduce);
1126
1127/**
1128 * add_timer - start a timer
1129 * @timer: the timer to be added
1130 *
1131 * The kernel will do a ->function(@timer) callback from the
1132 * timer interrupt at the ->expires point in the future. The
1133 * current time is 'jiffies'.
1134 *
1135 * The timer's ->expires, ->function fields must be set prior calling this
1136 * function.
 
 
 
 
 
 
1137 *
1138 * Timers with an ->expires field in the past will be executed in the next
1139 * timer tick.
1140 */
1141void add_timer(struct timer_list *timer)
1142{
1143	BUG_ON(timer_pending(timer));
 
1144	__mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
1145}
1146EXPORT_SYMBOL(add_timer);
1147
1148/**
1149 * add_timer_on - start a timer on a particular CPU
1150 * @timer: the timer to be added
1151 * @cpu: the CPU to start it on
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1152 *
1153 * This is not very scalable on SMP. Double adds are not possible.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1154 */
1155void add_timer_on(struct timer_list *timer, int cpu)
1156{
1157	struct timer_base *new_base, *base;
1158	unsigned long flags;
1159
1160	BUG_ON(timer_pending(timer) || !timer->function);
 
 
 
 
 
 
1161
1162	new_base = get_timer_cpu_base(timer->flags, cpu);
1163
1164	/*
1165	 * If @timer was on a different CPU, it should be migrated with the
1166	 * old base locked to prevent other operations proceeding with the
1167	 * wrong base locked.  See lock_timer_base().
1168	 */
1169	base = lock_timer_base(timer, &flags);
 
 
 
 
 
 
 
1170	if (base != new_base) {
1171		timer->flags |= TIMER_MIGRATING;
1172
1173		raw_spin_unlock(&base->lock);
1174		base = new_base;
1175		raw_spin_lock(&base->lock);
1176		WRITE_ONCE(timer->flags,
1177			   (timer->flags & ~TIMER_BASEMASK) | cpu);
1178	}
1179	forward_timer_base(base);
1180
1181	debug_timer_activate(timer);
1182	internal_add_timer(base, timer);
 
1183	raw_spin_unlock_irqrestore(&base->lock, flags);
1184}
1185EXPORT_SYMBOL_GPL(add_timer_on);
1186
1187/**
1188 * del_timer - deactivate a timer.
1189 * @timer: the timer to be deactivated
1190 *
1191 * del_timer() deactivates a timer - this works on both active and inactive
1192 * timers.
1193 *
1194 * The function returns whether it has deactivated a pending timer or not.
1195 * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
1196 * active timer returns 1.)
 
 
 
 
1197 */
1198int del_timer(struct timer_list *timer)
1199{
1200	struct timer_base *base;
1201	unsigned long flags;
1202	int ret = 0;
1203
1204	debug_assert_init(timer);
1205
1206	if (timer_pending(timer)) {
 
 
 
 
 
 
 
 
 
 
 
1207		base = lock_timer_base(timer, &flags);
1208		ret = detach_if_pending(timer, base, true);
 
 
1209		raw_spin_unlock_irqrestore(&base->lock, flags);
1210	}
1211
1212	return ret;
1213}
1214EXPORT_SYMBOL(del_timer);
1215
1216/**
1217 * try_to_del_timer_sync - Try to deactivate a timer
1218 * @timer: timer to delete
1219 *
1220 * This function tries to deactivate a timer. Upon successful (ret >= 0)
1221 * exit the timer is not queued and the handler is not running on any CPU.
 
 
 
 
 
 
 
1222 */
1223int try_to_del_timer_sync(struct timer_list *timer)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1224{
1225	struct timer_base *base;
1226	unsigned long flags;
1227	int ret = -1;
1228
1229	debug_assert_init(timer);
1230
1231	base = lock_timer_base(timer, &flags);
1232
1233	if (base->running_timer != timer)
1234		ret = detach_if_pending(timer, base, true);
 
 
1235
1236	raw_spin_unlock_irqrestore(&base->lock, flags);
1237
1238	return ret;
1239}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1240EXPORT_SYMBOL(try_to_del_timer_sync);
1241
1242#ifdef CONFIG_PREEMPT_RT
1243static __init void timer_base_init_expiry_lock(struct timer_base *base)
1244{
1245	spin_lock_init(&base->expiry_lock);
1246}
1247
1248static inline void timer_base_lock_expiry(struct timer_base *base)
1249{
1250	spin_lock(&base->expiry_lock);
1251}
1252
1253static inline void timer_base_unlock_expiry(struct timer_base *base)
1254{
1255	spin_unlock(&base->expiry_lock);
1256}
1257
1258/*
1259 * The counterpart to del_timer_wait_running().
1260 *
1261 * If there is a waiter for base->expiry_lock, then it was waiting for the
1262 * timer callback to finish. Drop expiry_lock and reacquire it. That allows
1263 * the waiter to acquire the lock and make progress.
1264 */
1265static void timer_sync_wait_running(struct timer_base *base)
 
 
1266{
1267	if (atomic_read(&base->timer_waiters)) {
1268		raw_spin_unlock_irq(&base->lock);
1269		spin_unlock(&base->expiry_lock);
1270		spin_lock(&base->expiry_lock);
1271		raw_spin_lock_irq(&base->lock);
1272	}
1273}
1274
1275/*
1276 * This function is called on PREEMPT_RT kernels when the fast path
1277 * deletion of a timer failed because the timer callback function was
1278 * running.
1279 *
1280 * This prevents priority inversion, if the softirq thread on a remote CPU
1281 * got preempted, and it prevents a life lock when the task which tries to
1282 * delete a timer preempted the softirq thread running the timer callback
1283 * function.
1284 */
1285static void del_timer_wait_running(struct timer_list *timer)
1286{
1287	u32 tf;
1288
1289	tf = READ_ONCE(timer->flags);
1290	if (!(tf & (TIMER_MIGRATING | TIMER_IRQSAFE))) {
1291		struct timer_base *base = get_timer_base(tf);
1292
1293		/*
1294		 * Mark the base as contended and grab the expiry lock,
1295		 * which is held by the softirq across the timer
1296		 * callback. Drop the lock immediately so the softirq can
1297		 * expire the next timer. In theory the timer could already
1298		 * be running again, but that's more than unlikely and just
1299		 * causes another wait loop.
1300		 */
1301		atomic_inc(&base->timer_waiters);
1302		spin_lock_bh(&base->expiry_lock);
1303		atomic_dec(&base->timer_waiters);
1304		spin_unlock_bh(&base->expiry_lock);
1305	}
1306}
1307#else
1308static inline void timer_base_init_expiry_lock(struct timer_base *base) { }
1309static inline void timer_base_lock_expiry(struct timer_base *base) { }
1310static inline void timer_base_unlock_expiry(struct timer_base *base) { }
1311static inline void timer_sync_wait_running(struct timer_base *base) { }
1312static inline void del_timer_wait_running(struct timer_list *timer) { }
1313#endif
1314
1315#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
1316/**
1317 * del_timer_sync - deactivate a timer and wait for the handler to finish.
1318 * @timer: the timer to be deactivated
1319 *
1320 * This function only differs from del_timer() on SMP: besides deactivating
1321 * the timer it also makes sure the handler has finished executing on other
1322 * CPUs.
1323 *
1324 * Synchronization rules: Callers must prevent restarting of the timer,
1325 * otherwise this function is meaningless. It must not be called from
1326 * interrupt contexts unless the timer is an irqsafe one. The caller must
1327 * not hold locks which would prevent completion of the timer's
1328 * handler. The timer's handler must not call add_timer_on(). Upon exit the
1329 * timer is not queued and the handler is not running on any CPU.
1330 *
1331 * Note: For !irqsafe timers, you must not hold locks that are held in
1332 *   interrupt context while calling this function. Even if the lock has
1333 *   nothing to do with the timer in question.  Here's why::
1334 *
1335 *    CPU0                             CPU1
1336 *    ----                             ----
1337 *                                     <SOFTIRQ>
1338 *                                       call_timer_fn();
1339 *                                       base->running_timer = mytimer;
1340 *    spin_lock_irq(somelock);
1341 *                                     <IRQ>
1342 *                                        spin_lock(somelock);
1343 *    del_timer_sync(mytimer);
1344 *    while (base->running_timer == mytimer);
1345 *
1346 * Now del_timer_sync() will never return and never release somelock.
1347 * The interrupt on the other CPU is waiting to grab somelock but
1348 * it has interrupted the softirq that CPU0 is waiting to finish.
1349 *
1350 * The function returns whether it has deactivated a pending timer or not.
1351 */
1352int del_timer_sync(struct timer_list *timer)
1353{
1354	int ret;
1355
1356#ifdef CONFIG_LOCKDEP
1357	unsigned long flags;
1358
1359	/*
1360	 * If lockdep gives a backtrace here, please reference
1361	 * the synchronization rules above.
1362	 */
1363	local_irq_save(flags);
1364	lock_map_acquire(&timer->lockdep_map);
1365	lock_map_release(&timer->lockdep_map);
1366	local_irq_restore(flags);
1367#endif
1368	/*
1369	 * don't use it in hardirq context, because it
1370	 * could lead to deadlock.
1371	 */
1372	WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
1373
1374	/*
1375	 * Must be able to sleep on PREEMPT_RT because of the slowpath in
1376	 * del_timer_wait_running().
1377	 */
1378	if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(timer->flags & TIMER_IRQSAFE))
1379		lockdep_assert_preemption_enabled();
1380
1381	do {
1382		ret = try_to_del_timer_sync(timer);
1383
1384		if (unlikely(ret < 0)) {
1385			del_timer_wait_running(timer);
1386			cpu_relax();
1387		}
1388	} while (ret < 0);
1389
1390	return ret;
1391}
1392EXPORT_SYMBOL(del_timer_sync);
1393#endif
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1394
1395static void call_timer_fn(struct timer_list *timer,
1396			  void (*fn)(struct timer_list *),
1397			  unsigned long baseclk)
1398{
1399	int count = preempt_count();
1400
1401#ifdef CONFIG_LOCKDEP
1402	/*
1403	 * It is permissible to free the timer from inside the
1404	 * function that is called from it, this we need to take into
1405	 * account for lockdep too. To avoid bogus "held lock freed"
1406	 * warnings as well as problems when looking into
1407	 * timer->lockdep_map, make a copy and use that here.
1408	 */
1409	struct lockdep_map lockdep_map;
1410
1411	lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1412#endif
1413	/*
1414	 * Couple the lock chain with the lock chain at
1415	 * del_timer_sync() by acquiring the lock_map around the fn()
1416	 * call here and in del_timer_sync().
1417	 */
1418	lock_map_acquire(&lockdep_map);
1419
1420	trace_timer_expire_entry(timer, baseclk);
1421	fn(timer);
1422	trace_timer_expire_exit(timer);
1423
1424	lock_map_release(&lockdep_map);
1425
1426	if (count != preempt_count()) {
1427		WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
1428			  fn, count, preempt_count());
1429		/*
1430		 * Restore the preempt count. That gives us a decent
1431		 * chance to survive and extract information. If the
1432		 * callback kept a lock held, bad luck, but not worse
1433		 * than the BUG() we had.
1434		 */
1435		preempt_count_set(count);
1436	}
1437}
1438
1439static void expire_timers(struct timer_base *base, struct hlist_head *head)
1440{
1441	/*
1442	 * This value is required only for tracing. base->clk was
1443	 * incremented directly before expire_timers was called. But expiry
1444	 * is related to the old base->clk value.
1445	 */
1446	unsigned long baseclk = base->clk - 1;
1447
1448	while (!hlist_empty(head)) {
1449		struct timer_list *timer;
1450		void (*fn)(struct timer_list *);
1451
1452		timer = hlist_entry(head->first, struct timer_list, entry);
1453
1454		base->running_timer = timer;
1455		detach_timer(timer, true);
1456
1457		fn = timer->function;
1458
 
 
 
 
 
 
1459		if (timer->flags & TIMER_IRQSAFE) {
1460			raw_spin_unlock(&base->lock);
1461			call_timer_fn(timer, fn, baseclk);
1462			raw_spin_lock(&base->lock);
1463			base->running_timer = NULL;
1464		} else {
1465			raw_spin_unlock_irq(&base->lock);
1466			call_timer_fn(timer, fn, baseclk);
1467			raw_spin_lock_irq(&base->lock);
1468			base->running_timer = NULL;
1469			timer_sync_wait_running(base);
1470		}
1471	}
1472}
1473
1474static int collect_expired_timers(struct timer_base *base,
1475				  struct hlist_head *heads)
1476{
1477	unsigned long clk = base->clk = base->next_expiry;
1478	struct hlist_head *vec;
1479	int i, levels = 0;
1480	unsigned int idx;
1481
1482	for (i = 0; i < LVL_DEPTH; i++) {
1483		idx = (clk & LVL_MASK) + i * LVL_SIZE;
1484
1485		if (__test_and_clear_bit(idx, base->pending_map)) {
1486			vec = base->vectors + idx;
1487			hlist_move_list(vec, heads++);
1488			levels++;
1489		}
1490		/* Is it time to look at the next level? */
1491		if (clk & LVL_CLK_MASK)
1492			break;
1493		/* Shift clock for the next level granularity */
1494		clk >>= LVL_CLK_SHIFT;
1495	}
1496	return levels;
1497}
1498
1499/*
1500 * Find the next pending bucket of a level. Search from level start (@offset)
1501 * + @clk upwards and if nothing there, search from start of the level
1502 * (@offset) up to @offset + clk.
1503 */
1504static int next_pending_bucket(struct timer_base *base, unsigned offset,
1505			       unsigned clk)
1506{
1507	unsigned pos, start = offset + clk;
1508	unsigned end = offset + LVL_SIZE;
1509
1510	pos = find_next_bit(base->pending_map, end, start);
1511	if (pos < end)
1512		return pos - start;
1513
1514	pos = find_next_bit(base->pending_map, start, offset);
1515	return pos < start ? pos + LVL_SIZE - start : -1;
1516}
1517
1518/*
1519 * Search the first expiring timer in the various clock levels. Caller must
1520 * hold base->lock.
 
 
1521 */
1522static unsigned long __next_timer_interrupt(struct timer_base *base)
1523{
1524	unsigned long clk, next, adj;
1525	unsigned lvl, offset = 0;
1526
1527	next = base->clk + NEXT_TIMER_MAX_DELTA;
1528	clk = base->clk;
1529	for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
1530		int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
1531		unsigned long lvl_clk = clk & LVL_CLK_MASK;
1532
1533		if (pos >= 0) {
1534			unsigned long tmp = clk + (unsigned long) pos;
1535
1536			tmp <<= LVL_SHIFT(lvl);
1537			if (time_before(tmp, next))
1538				next = tmp;
1539
1540			/*
1541			 * If the next expiration happens before we reach
1542			 * the next level, no need to check further.
1543			 */
1544			if (pos <= ((LVL_CLK_DIV - lvl_clk) & LVL_CLK_MASK))
1545				break;
1546		}
1547		/*
1548		 * Clock for the next level. If the current level clock lower
1549		 * bits are zero, we look at the next level as is. If not we
1550		 * need to advance it by one because that's going to be the
1551		 * next expiring bucket in that level. base->clk is the next
1552		 * expiring jiffie. So in case of:
1553		 *
1554		 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1555		 *  0    0    0    0    0    0
1556		 *
1557		 * we have to look at all levels @index 0. With
1558		 *
1559		 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1560		 *  0    0    0    0    0    2
1561		 *
1562		 * LVL0 has the next expiring bucket @index 2. The upper
1563		 * levels have the next expiring bucket @index 1.
1564		 *
1565		 * In case that the propagation wraps the next level the same
1566		 * rules apply:
1567		 *
1568		 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1569		 *  0    0    0    0    F    2
1570		 *
1571		 * So after looking at LVL0 we get:
1572		 *
1573		 * LVL5 LVL4 LVL3 LVL2 LVL1
1574		 *  0    0    0    1    0
1575		 *
1576		 * So no propagation from LVL1 to LVL2 because that happened
1577		 * with the add already, but then we need to propagate further
1578		 * from LVL2 to LVL3.
1579		 *
1580		 * So the simple check whether the lower bits of the current
1581		 * level are 0 or not is sufficient for all cases.
1582		 */
1583		adj = lvl_clk ? 1 : 0;
1584		clk >>= LVL_CLK_SHIFT;
1585		clk += adj;
1586	}
1587
 
1588	base->next_expiry_recalc = false;
1589	base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA);
1590
1591	return next;
1592}
1593
1594#ifdef CONFIG_NO_HZ_COMMON
1595/*
1596 * Check, if the next hrtimer event is before the next timer wheel
1597 * event:
1598 */
1599static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
1600{
1601	u64 nextevt = hrtimer_get_next_event();
1602
1603	/*
1604	 * If high resolution timers are enabled
1605	 * hrtimer_get_next_event() returns KTIME_MAX.
1606	 */
1607	if (expires <= nextevt)
1608		return expires;
1609
1610	/*
1611	 * If the next timer is already expired, return the tick base
1612	 * time so the tick is fired immediately.
1613	 */
1614	if (nextevt <= basem)
1615		return basem;
1616
1617	/*
1618	 * Round up to the next jiffie. High resolution timers are
1619	 * off, so the hrtimers are expired in the tick and we need to
1620	 * make sure that this tick really expires the timer to avoid
1621	 * a ping pong of the nohz stop code.
1622	 *
1623	 * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1624	 */
1625	return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
1626}
1627
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1628/**
1629 * get_next_timer_interrupt - return the time (clock mono) of the next timer
1630 * @basej:	base time jiffies
1631 * @basem:	base time clock monotonic
 
 
1632 *
1633 * Returns the tick aligned clock monotonic time of the next pending
1634 * timer or KTIME_MAX if no timer is pending.
 
 
 
 
 
1635 */
1636u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1637{
1638	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1639	u64 expires = KTIME_MAX;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1640	unsigned long nextevt;
 
1641
1642	/*
1643	 * Pretend that there is no timer pending if the cpu is offline.
1644	 * Possible pending timers will be migrated later to an active cpu.
1645	 */
1646	if (cpu_is_offline(smp_processor_id()))
1647		return expires;
 
 
 
1648
1649	raw_spin_lock(&base->lock);
1650	if (base->next_expiry_recalc)
1651		base->next_expiry = __next_timer_interrupt(base);
1652	nextevt = base->next_expiry;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1653
1654	/*
1655	 * We have a fresh next event. Check whether we can forward the
1656	 * base. We can only do that when @basej is past base->clk
1657	 * otherwise we might rewind base->clk.
1658	 */
1659	if (time_after(basej, base->clk)) {
1660		if (time_after(nextevt, basej))
1661			base->clk = basej;
1662		else if (time_after(nextevt, base->clk))
1663			base->clk = nextevt;
1664	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1665
1666	if (time_before_eq(nextevt, basej)) {
1667		expires = basem;
1668		base->is_idle = false;
1669	} else {
1670		if (base->timers_pending)
1671			expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
1672		/*
1673		 * If we expect to sleep more than a tick, mark the base idle.
1674		 * Also the tick is stopped so any added timer must forward
1675		 * the base clk itself to keep granularity small. This idle
1676		 * logic is only maintained for the BASE_STD base, deferrable
1677		 * timers may still see large granularity skew (by design).
 
1678		 */
1679		if ((expires - basem) > TICK_NSEC)
1680			base->is_idle = true;
1681	}
1682	raw_spin_unlock(&base->lock);
1683
1684	return cmp_next_hrtimer_event(basem, expires);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1685}
1686
1687/**
1688 * timer_clear_idle - Clear the idle state of the timer base
1689 *
1690 * Called with interrupts disabled
1691 */
1692void timer_clear_idle(void)
1693{
1694	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1695
1696	/*
1697	 * We do this unlocked. The worst outcome is a remote enqueue sending
1698	 * a pointless IPI, but taking the lock would just make the window for
1699	 * sending the IPI a few instructions smaller for the cost of taking
1700	 * the lock in the exit from idle path.
1701	 */
1702	base->is_idle = false;
 
 
 
 
 
 
 
1703}
1704#endif
1705
1706/**
1707 * __run_timers - run all expired timers (if any) on this CPU.
1708 * @base: the timer vector to be processed.
1709 */
1710static inline void __run_timers(struct timer_base *base)
1711{
1712	struct hlist_head heads[LVL_DEPTH];
1713	int levels;
1714
1715	if (time_before(jiffies, base->next_expiry))
1716		return;
1717
1718	timer_base_lock_expiry(base);
1719	raw_spin_lock_irq(&base->lock);
1720
1721	while (time_after_eq(jiffies, base->clk) &&
1722	       time_after_eq(jiffies, base->next_expiry)) {
1723		levels = collect_expired_timers(base, heads);
1724		/*
1725		 * The only possible reason for not finding any expired
1726		 * timer at this clk is that all matching timers have been
1727		 * dequeued.
 
 
 
 
 
 
 
 
1728		 */
1729		WARN_ON_ONCE(!levels && !base->next_expiry_recalc);
1730		base->clk++;
1731		base->next_expiry = __next_timer_interrupt(base);
1732
1733		while (levels--)
1734			expire_timers(base, heads + levels);
1735	}
 
 
 
 
 
 
 
 
 
 
 
1736	raw_spin_unlock_irq(&base->lock);
1737	timer_base_unlock_expiry(base);
1738}
1739
 
 
 
 
 
 
 
1740/*
1741 * This function runs timers and the timer-tq in bottom half context.
1742 */
1743static __latent_entropy void run_timer_softirq(struct softirq_action *h)
1744{
1745	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
 
 
 
1746
1747	__run_timers(base);
1748	if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
1749		__run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
1750}
1751
1752/*
1753 * Called by the local, per-CPU timer interrupt on SMP.
1754 */
1755static void run_local_timers(void)
1756{
1757	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1758
1759	hrtimer_run_queues();
1760	/* Raise the softirq only if required. */
1761	if (time_before(jiffies, base->next_expiry)) {
1762		if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
1763			return;
1764		/* CPU is awake, so check the deferrable base. */
1765		base++;
1766		if (time_before(jiffies, base->next_expiry))
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1767			return;
 
1768	}
1769	raise_softirq(TIMER_SOFTIRQ);
1770}
1771
1772/*
1773 * Called from the timer interrupt handler to charge one tick to the current
1774 * process.  user_tick is 1 if the tick is user time, 0 for system.
1775 */
1776void update_process_times(int user_tick)
1777{
1778	struct task_struct *p = current;
1779
1780	PRANDOM_ADD_NOISE(jiffies, user_tick, p, 0);
1781
1782	/* Note: this timer irq context must be accounted for as well. */
1783	account_process_tick(p, user_tick);
1784	run_local_timers();
1785	rcu_sched_clock_irq(user_tick);
1786#ifdef CONFIG_IRQ_WORK
1787	if (in_irq())
1788		irq_work_tick();
1789#endif
1790	scheduler_tick();
1791	if (IS_ENABLED(CONFIG_POSIX_TIMERS))
1792		run_posix_cpu_timers();
1793}
1794
1795/*
1796 * Since schedule_timeout()'s timer is defined on the stack, it must store
1797 * the target task on the stack as well.
1798 */
1799struct process_timer {
1800	struct timer_list timer;
1801	struct task_struct *task;
1802};
1803
1804static void process_timeout(struct timer_list *t)
1805{
1806	struct process_timer *timeout = from_timer(timeout, t, timer);
1807
1808	wake_up_process(timeout->task);
1809}
1810
1811/**
1812 * schedule_timeout - sleep until timeout
1813 * @timeout: timeout value in jiffies
1814 *
1815 * Make the current task sleep until @timeout jiffies have elapsed.
1816 * The function behavior depends on the current task state
1817 * (see also set_current_state() description):
1818 *
1819 * %TASK_RUNNING - the scheduler is called, but the task does not sleep
1820 * at all. That happens because sched_submit_work() does nothing for
1821 * tasks in %TASK_RUNNING state.
1822 *
1823 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1824 * pass before the routine returns unless the current task is explicitly
1825 * woken up, (e.g. by wake_up_process()).
1826 *
1827 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1828 * delivered to the current task or the current task is explicitly woken
1829 * up.
1830 *
1831 * The current task state is guaranteed to be %TASK_RUNNING when this
1832 * routine returns.
1833 *
1834 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1835 * the CPU away without a bound on the timeout. In this case the return
1836 * value will be %MAX_SCHEDULE_TIMEOUT.
1837 *
1838 * Returns 0 when the timer has expired otherwise the remaining time in
1839 * jiffies will be returned. In all cases the return value is guaranteed
1840 * to be non-negative.
1841 */
1842signed long __sched schedule_timeout(signed long timeout)
1843{
1844	struct process_timer timer;
1845	unsigned long expire;
1846
1847	switch (timeout)
1848	{
1849	case MAX_SCHEDULE_TIMEOUT:
1850		/*
1851		 * These two special cases are useful to be comfortable
1852		 * in the caller. Nothing more. We could take
1853		 * MAX_SCHEDULE_TIMEOUT from one of the negative value
1854		 * but I' d like to return a valid offset (>=0) to allow
1855		 * the caller to do everything it want with the retval.
1856		 */
1857		schedule();
1858		goto out;
1859	default:
1860		/*
1861		 * Another bit of PARANOID. Note that the retval will be
1862		 * 0 since no piece of kernel is supposed to do a check
1863		 * for a negative retval of schedule_timeout() (since it
1864		 * should never happens anyway). You just have the printk()
1865		 * that will tell you if something is gone wrong and where.
1866		 */
1867		if (timeout < 0) {
1868			printk(KERN_ERR "schedule_timeout: wrong timeout "
1869				"value %lx\n", timeout);
1870			dump_stack();
1871			__set_current_state(TASK_RUNNING);
1872			goto out;
1873		}
1874	}
1875
1876	expire = timeout + jiffies;
1877
1878	timer.task = current;
1879	timer_setup_on_stack(&timer.timer, process_timeout, 0);
1880	__mod_timer(&timer.timer, expire, MOD_TIMER_NOTPENDING);
1881	schedule();
1882	del_singleshot_timer_sync(&timer.timer);
1883
1884	/* Remove the timer from the object tracker */
1885	destroy_timer_on_stack(&timer.timer);
1886
1887	timeout = expire - jiffies;
1888
1889 out:
1890	return timeout < 0 ? 0 : timeout;
1891}
1892EXPORT_SYMBOL(schedule_timeout);
1893
1894/*
1895 * We can use __set_current_state() here because schedule_timeout() calls
1896 * schedule() unconditionally.
1897 */
1898signed long __sched schedule_timeout_interruptible(signed long timeout)
1899{
1900	__set_current_state(TASK_INTERRUPTIBLE);
1901	return schedule_timeout(timeout);
1902}
1903EXPORT_SYMBOL(schedule_timeout_interruptible);
1904
1905signed long __sched schedule_timeout_killable(signed long timeout)
1906{
1907	__set_current_state(TASK_KILLABLE);
1908	return schedule_timeout(timeout);
1909}
1910EXPORT_SYMBOL(schedule_timeout_killable);
1911
1912signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1913{
1914	__set_current_state(TASK_UNINTERRUPTIBLE);
1915	return schedule_timeout(timeout);
1916}
1917EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1918
1919/*
1920 * Like schedule_timeout_uninterruptible(), except this task will not contribute
1921 * to load average.
1922 */
1923signed long __sched schedule_timeout_idle(signed long timeout)
1924{
1925	__set_current_state(TASK_IDLE);
1926	return schedule_timeout(timeout);
1927}
1928EXPORT_SYMBOL(schedule_timeout_idle);
1929
1930#ifdef CONFIG_HOTPLUG_CPU
1931static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
1932{
1933	struct timer_list *timer;
1934	int cpu = new_base->cpu;
1935
1936	while (!hlist_empty(head)) {
1937		timer = hlist_entry(head->first, struct timer_list, entry);
1938		detach_timer(timer, false);
1939		timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
1940		internal_add_timer(new_base, timer);
1941	}
1942}
1943
1944int timers_prepare_cpu(unsigned int cpu)
1945{
1946	struct timer_base *base;
1947	int b;
1948
1949	for (b = 0; b < NR_BASES; b++) {
1950		base = per_cpu_ptr(&timer_bases[b], cpu);
1951		base->clk = jiffies;
1952		base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
 
1953		base->timers_pending = false;
1954		base->is_idle = false;
1955	}
1956	return 0;
1957}
1958
1959int timers_dead_cpu(unsigned int cpu)
1960{
1961	struct timer_base *old_base;
1962	struct timer_base *new_base;
1963	int b, i;
1964
1965	BUG_ON(cpu_online(cpu));
1966
1967	for (b = 0; b < NR_BASES; b++) {
1968		old_base = per_cpu_ptr(&timer_bases[b], cpu);
1969		new_base = get_cpu_ptr(&timer_bases[b]);
1970		/*
1971		 * The caller is globally serialized and nobody else
1972		 * takes two locks at once, deadlock is not possible.
1973		 */
1974		raw_spin_lock_irq(&new_base->lock);
1975		raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1976
1977		/*
1978		 * The current CPUs base clock might be stale. Update it
1979		 * before moving the timers over.
1980		 */
1981		forward_timer_base(new_base);
1982
1983		BUG_ON(old_base->running_timer);
 
1984
1985		for (i = 0; i < WHEEL_SIZE; i++)
1986			migrate_timer_list(new_base, old_base->vectors + i);
1987
1988		raw_spin_unlock(&old_base->lock);
1989		raw_spin_unlock_irq(&new_base->lock);
1990		put_cpu_ptr(&timer_bases);
1991	}
1992	return 0;
1993}
1994
1995#endif /* CONFIG_HOTPLUG_CPU */
1996
1997static void __init init_timer_cpu(int cpu)
1998{
1999	struct timer_base *base;
2000	int i;
2001
2002	for (i = 0; i < NR_BASES; i++) {
2003		base = per_cpu_ptr(&timer_bases[i], cpu);
2004		base->cpu = cpu;
2005		raw_spin_lock_init(&base->lock);
2006		base->clk = jiffies;
2007		base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
2008		timer_base_init_expiry_lock(base);
2009	}
2010}
2011
2012static void __init init_timer_cpus(void)
2013{
2014	int cpu;
2015
2016	for_each_possible_cpu(cpu)
2017		init_timer_cpu(cpu);
2018}
2019
2020void __init init_timers(void)
2021{
2022	init_timer_cpus();
2023	posix_cputimers_init_work();
2024	open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
2025}
2026
2027/**
2028 * msleep - sleep safely even with waitqueue interruptions
2029 * @msecs: Time in milliseconds to sleep for
2030 */
2031void msleep(unsigned int msecs)
2032{
2033	unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2034
2035	while (timeout)
2036		timeout = schedule_timeout_uninterruptible(timeout);
2037}
2038
2039EXPORT_SYMBOL(msleep);
2040
2041/**
2042 * msleep_interruptible - sleep waiting for signals
2043 * @msecs: Time in milliseconds to sleep for
2044 */
2045unsigned long msleep_interruptible(unsigned int msecs)
2046{
2047	unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2048
2049	while (timeout && !signal_pending(current))
2050		timeout = schedule_timeout_interruptible(timeout);
2051	return jiffies_to_msecs(timeout);
2052}
2053
2054EXPORT_SYMBOL(msleep_interruptible);
2055
2056/**
2057 * usleep_range - Sleep for an approximate time
2058 * @min: Minimum time in usecs to sleep
2059 * @max: Maximum time in usecs to sleep
2060 *
2061 * In non-atomic context where the exact wakeup time is flexible, use
2062 * usleep_range() instead of udelay().  The sleep improves responsiveness
2063 * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
2064 * power usage by allowing hrtimers to take advantage of an already-
2065 * scheduled interrupt instead of scheduling a new one just for this sleep.
2066 */
2067void __sched usleep_range(unsigned long min, unsigned long max)
2068{
2069	ktime_t exp = ktime_add_us(ktime_get(), min);
2070	u64 delta = (u64)(max - min) * NSEC_PER_USEC;
2071
2072	for (;;) {
2073		__set_current_state(TASK_UNINTERRUPTIBLE);
2074		/* Do not return before the requested sleep time has elapsed */
2075		if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
2076			break;
2077	}
2078}
2079EXPORT_SYMBOL(usleep_range);