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1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
4 * Internal non-public definitions.
5 *
6 * Copyright IBM Corporation, 2008
7 *
8 * Author: Ingo Molnar <mingo@elte.hu>
9 * Paul E. McKenney <paulmck@linux.ibm.com>
10 */
11
12#include <linux/cache.h>
13#include <linux/kthread.h>
14#include <linux/spinlock.h>
15#include <linux/rtmutex.h>
16#include <linux/threads.h>
17#include <linux/cpumask.h>
18#include <linux/seqlock.h>
19#include <linux/swait.h>
20#include <linux/rcu_node_tree.h>
21
22#include "rcu_segcblist.h"
23
24/* Communicate arguments to a workqueue handler. */
25struct rcu_exp_work {
26 unsigned long rew_s;
27#ifdef CONFIG_RCU_EXP_KTHREAD
28 struct kthread_work rew_work;
29#else
30 struct work_struct rew_work;
31#endif /* CONFIG_RCU_EXP_KTHREAD */
32};
33
34/* RCU's kthread states for tracing. */
35#define RCU_KTHREAD_STOPPED 0
36#define RCU_KTHREAD_RUNNING 1
37#define RCU_KTHREAD_WAITING 2
38#define RCU_KTHREAD_OFFCPU 3
39#define RCU_KTHREAD_YIELDING 4
40#define RCU_KTHREAD_MAX 4
41
42/*
43 * Definition for node within the RCU grace-period-detection hierarchy.
44 */
45struct rcu_node {
46 raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
47 /* some rcu_state fields as well as */
48 /* following. */
49 unsigned long gp_seq; /* Track rsp->gp_seq. */
50 unsigned long gp_seq_needed; /* Track furthest future GP request. */
51 unsigned long completedqs; /* All QSes done for this node. */
52 unsigned long qsmask; /* CPUs or groups that need to switch in */
53 /* order for current grace period to proceed.*/
54 /* In leaf rcu_node, each bit corresponds to */
55 /* an rcu_data structure, otherwise, each */
56 /* bit corresponds to a child rcu_node */
57 /* structure. */
58 unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */
59 unsigned long qsmaskinit;
60 /* Per-GP initial value for qsmask. */
61 /* Initialized from ->qsmaskinitnext at the */
62 /* beginning of each grace period. */
63 unsigned long qsmaskinitnext;
64 unsigned long expmask; /* CPUs or groups that need to check in */
65 /* to allow the current expedited GP */
66 /* to complete. */
67 unsigned long expmaskinit;
68 /* Per-GP initial values for expmask. */
69 /* Initialized from ->expmaskinitnext at the */
70 /* beginning of each expedited GP. */
71 unsigned long expmaskinitnext;
72 /* Online CPUs for next expedited GP. */
73 /* Any CPU that has ever been online will */
74 /* have its bit set. */
75 unsigned long cbovldmask;
76 /* CPUs experiencing callback overload. */
77 unsigned long ffmask; /* Fully functional CPUs. */
78 unsigned long grpmask; /* Mask to apply to parent qsmask. */
79 /* Only one bit will be set in this mask. */
80 int grplo; /* lowest-numbered CPU here. */
81 int grphi; /* highest-numbered CPU here. */
82 u8 grpnum; /* group number for next level up. */
83 u8 level; /* root is at level 0. */
84 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
85 /* exit RCU read-side critical sections */
86 /* before propagating offline up the */
87 /* rcu_node tree? */
88 struct rcu_node *parent;
89 struct list_head blkd_tasks;
90 /* Tasks blocked in RCU read-side critical */
91 /* section. Tasks are placed at the head */
92 /* of this list and age towards the tail. */
93 struct list_head *gp_tasks;
94 /* Pointer to the first task blocking the */
95 /* current grace period, or NULL if there */
96 /* is no such task. */
97 struct list_head *exp_tasks;
98 /* Pointer to the first task blocking the */
99 /* current expedited grace period, or NULL */
100 /* if there is no such task. If there */
101 /* is no current expedited grace period, */
102 /* then there can cannot be any such task. */
103 struct list_head *boost_tasks;
104 /* Pointer to first task that needs to be */
105 /* priority boosted, or NULL if no priority */
106 /* boosting is needed for this rcu_node */
107 /* structure. If there are no tasks */
108 /* queued on this rcu_node structure that */
109 /* are blocking the current grace period, */
110 /* there can be no such task. */
111 struct rt_mutex boost_mtx;
112 /* Used only for the priority-boosting */
113 /* side effect, not as a lock. */
114 unsigned long boost_time;
115 /* When to start boosting (jiffies). */
116 struct mutex boost_kthread_mutex;
117 /* Exclusion for thread spawning and affinity */
118 /* manipulation. */
119 struct task_struct *boost_kthread_task;
120 /* kthread that takes care of priority */
121 /* boosting for this rcu_node structure. */
122 unsigned int boost_kthread_status;
123 /* State of boost_kthread_task for tracing. */
124 unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */
125#ifdef CONFIG_RCU_NOCB_CPU
126 struct swait_queue_head nocb_gp_wq[2];
127 /* Place for rcu_nocb_kthread() to wait GP. */
128#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
129 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
130
131 spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
132 unsigned long exp_seq_rq;
133 wait_queue_head_t exp_wq[4];
134 struct rcu_exp_work rew;
135 bool exp_need_flush; /* Need to flush workitem? */
136 raw_spinlock_t exp_poll_lock;
137 /* Lock and data for polled expedited grace periods. */
138 unsigned long exp_seq_poll_rq;
139 struct work_struct exp_poll_wq;
140} ____cacheline_internodealigned_in_smp;
141
142/*
143 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
144 * are indexed relative to this interval rather than the global CPU ID space.
145 * This generates the bit for a CPU in node-local masks.
146 */
147#define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))
148
149/*
150 * Union to allow "aggregate OR" operation on the need for a quiescent
151 * state by the normal and expedited grace periods.
152 */
153union rcu_noqs {
154 struct {
155 u8 norm;
156 u8 exp;
157 } b; /* Bits. */
158 u16 s; /* Set of bits, aggregate OR here. */
159};
160
161/*
162 * Record the snapshot of the core stats at half of the first RCU stall timeout.
163 * The member gp_seq is used to ensure that all members are updated only once
164 * during the sampling period. The snapshot is taken only if this gp_seq is not
165 * equal to rdp->gp_seq.
166 */
167struct rcu_snap_record {
168 unsigned long gp_seq; /* Track rdp->gp_seq counter */
169 u64 cputime_irq; /* Accumulated cputime of hard irqs */
170 u64 cputime_softirq;/* Accumulated cputime of soft irqs */
171 u64 cputime_system; /* Accumulated cputime of kernel tasks */
172 unsigned long nr_hardirqs; /* Accumulated number of hard irqs */
173 unsigned int nr_softirqs; /* Accumulated number of soft irqs */
174 unsigned long long nr_csw; /* Accumulated number of task switches */
175 unsigned long jiffies; /* Track jiffies value */
176};
177
178/* Per-CPU data for read-copy update. */
179struct rcu_data {
180 /* 1) quiescent-state and grace-period handling : */
181 unsigned long gp_seq; /* Track rsp->gp_seq counter. */
182 unsigned long gp_seq_needed; /* Track furthest future GP request. */
183 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
184 bool core_needs_qs; /* Core waits for quiescent state. */
185 bool beenonline; /* CPU online at least once. */
186 bool gpwrap; /* Possible ->gp_seq wrap. */
187 bool cpu_started; /* RCU watching this onlining CPU. */
188 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
189 unsigned long grpmask; /* Mask to apply to leaf qsmask. */
190 unsigned long ticks_this_gp; /* The number of scheduling-clock */
191 /* ticks this CPU has handled */
192 /* during and after the last grace */
193 /* period it is aware of. */
194 struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */
195 bool defer_qs_iw_pending; /* Scheduler attention pending? */
196 struct work_struct strict_work; /* Schedule readers for strict GPs. */
197
198 /* 2) batch handling */
199 struct rcu_segcblist cblist; /* Segmented callback list, with */
200 /* different callbacks waiting for */
201 /* different grace periods. */
202 long qlen_last_fqs_check;
203 /* qlen at last check for QS forcing */
204 unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */
205 unsigned long n_force_qs_snap;
206 /* did other CPU force QS recently? */
207 long blimit; /* Upper limit on a processed batch */
208
209 /* 3) dynticks interface. */
210 int dynticks_snap; /* Per-GP tracking for dynticks. */
211 bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */
212 bool rcu_urgent_qs; /* GP old need light quiescent state. */
213 bool rcu_forced_tick; /* Forced tick to provide QS. */
214 bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */
215
216 /* 4) rcu_barrier(), OOM callbacks, and expediting. */
217 unsigned long barrier_seq_snap; /* Snap of rcu_state.barrier_sequence. */
218 struct rcu_head barrier_head;
219 int exp_dynticks_snap; /* Double-check need for IPI. */
220
221 /* 5) Callback offloading. */
222#ifdef CONFIG_RCU_NOCB_CPU
223 struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
224 struct swait_queue_head nocb_state_wq; /* For offloading state changes */
225 struct task_struct *nocb_gp_kthread;
226 raw_spinlock_t nocb_lock; /* Guard following pair of fields. */
227 atomic_t nocb_lock_contended; /* Contention experienced. */
228 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
229 struct timer_list nocb_timer; /* Enforce finite deferral. */
230 unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */
231 struct mutex nocb_gp_kthread_mutex; /* Exclusion for nocb gp kthread */
232 /* spawning */
233
234 /* The following fields are used by call_rcu, hence own cacheline. */
235 raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
236 struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */
237 unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */
238 unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */
239 int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */
240
241 /* The following fields are used by GP kthread, hence own cacheline. */
242 raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;
243 u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */
244 u8 nocb_gp_bypass; /* Found a bypass on last scan? */
245 u8 nocb_gp_gp; /* GP to wait for on last scan? */
246 unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */
247 unsigned long nocb_gp_loops; /* # passes through wait code. */
248 struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */
249 bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */
250 struct task_struct *nocb_cb_kthread;
251 struct list_head nocb_head_rdp; /*
252 * Head of rcu_data list in wakeup chain,
253 * if rdp_gp.
254 */
255 struct list_head nocb_entry_rdp; /* rcu_data node in wakeup chain. */
256 struct rcu_data *nocb_toggling_rdp; /* rdp queued for (de-)offloading */
257
258 /* The following fields are used by CB kthread, hence new cacheline. */
259 struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;
260 /* GP rdp takes GP-end wakeups. */
261#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
262
263 /* 6) RCU priority boosting. */
264 struct task_struct *rcu_cpu_kthread_task;
265 /* rcuc per-CPU kthread or NULL. */
266 unsigned int rcu_cpu_kthread_status;
267 char rcu_cpu_has_work;
268 unsigned long rcuc_activity;
269
270 /* 7) Diagnostic data, including RCU CPU stall warnings. */
271 unsigned int softirq_snap; /* Snapshot of softirq activity. */
272 /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
273 struct irq_work rcu_iw; /* Check for non-irq activity. */
274 bool rcu_iw_pending; /* Is ->rcu_iw pending? */
275 unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */
276 unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */
277 short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */
278 unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */
279 short rcu_onl_gp_flags; /* ->gp_flags at last online. */
280 unsigned long last_fqs_resched; /* Time of last rcu_resched(). */
281 unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */
282 struct rcu_snap_record snap_record; /* Snapshot of core stats at half of */
283 /* the first RCU stall timeout */
284
285 long lazy_len; /* Length of buffered lazy callbacks. */
286 int cpu;
287};
288
289/* Values for nocb_defer_wakeup field in struct rcu_data. */
290#define RCU_NOCB_WAKE_NOT 0
291#define RCU_NOCB_WAKE_BYPASS 1
292#define RCU_NOCB_WAKE_LAZY 2
293#define RCU_NOCB_WAKE 3
294#define RCU_NOCB_WAKE_FORCE 4
295
296#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
297 /* For jiffies_till_first_fqs and */
298 /* and jiffies_till_next_fqs. */
299
300#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
301 /* delay between bouts of */
302 /* quiescent-state forcing. */
303
304#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
305 /* at least one scheduling clock */
306 /* irq before ratting on them. */
307
308#define rcu_wait(cond) \
309do { \
310 for (;;) { \
311 set_current_state(TASK_INTERRUPTIBLE); \
312 if (cond) \
313 break; \
314 schedule(); \
315 } \
316 __set_current_state(TASK_RUNNING); \
317} while (0)
318
319/*
320 * RCU global state, including node hierarchy. This hierarchy is
321 * represented in "heap" form in a dense array. The root (first level)
322 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
323 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
324 * and the third level in ->node[m+1] and following (->node[m+1] referenced
325 * by ->level[2]). The number of levels is determined by the number of
326 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
327 * consisting of a single rcu_node.
328 */
329struct rcu_state {
330 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
331 struct rcu_node *level[RCU_NUM_LVLS + 1];
332 /* Hierarchy levels (+1 to */
333 /* shut bogus gcc warning) */
334 int ncpus; /* # CPUs seen so far. */
335 int n_online_cpus; /* # CPUs online for RCU. */
336
337 /* The following fields are guarded by the root rcu_node's lock. */
338
339 unsigned long gp_seq ____cacheline_internodealigned_in_smp;
340 /* Grace-period sequence #. */
341 unsigned long gp_max; /* Maximum GP duration in */
342 /* jiffies. */
343 struct task_struct *gp_kthread; /* Task for grace periods. */
344 struct swait_queue_head gp_wq; /* Where GP task waits. */
345 short gp_flags; /* Commands for GP task. */
346 short gp_state; /* GP kthread sleep state. */
347 unsigned long gp_wake_time; /* Last GP kthread wake. */
348 unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */
349 unsigned long gp_seq_polled; /* GP seq for polled API. */
350 unsigned long gp_seq_polled_snap; /* ->gp_seq_polled at normal GP start. */
351 unsigned long gp_seq_polled_exp_snap; /* ->gp_seq_polled at expedited GP start. */
352
353 /* End of fields guarded by root rcu_node's lock. */
354
355 struct mutex barrier_mutex; /* Guards barrier fields. */
356 atomic_t barrier_cpu_count; /* # CPUs waiting on. */
357 struct completion barrier_completion; /* Wake at barrier end. */
358 unsigned long barrier_sequence; /* ++ at start and end of */
359 /* rcu_barrier(). */
360 /* End of fields guarded by barrier_mutex. */
361
362 raw_spinlock_t barrier_lock; /* Protects ->barrier_seq_snap. */
363
364 struct mutex exp_mutex; /* Serialize expedited GP. */
365 struct mutex exp_wake_mutex; /* Serialize wakeup. */
366 unsigned long expedited_sequence; /* Take a ticket. */
367 atomic_t expedited_need_qs; /* # CPUs left to check in. */
368 struct swait_queue_head expedited_wq; /* Wait for check-ins. */
369 int ncpus_snap; /* # CPUs seen last time. */
370 u8 cbovld; /* Callback overload now? */
371 u8 cbovldnext; /* ^ ^ next time? */
372
373 unsigned long jiffies_force_qs; /* Time at which to invoke */
374 /* force_quiescent_state(). */
375 unsigned long jiffies_kick_kthreads; /* Time at which to kick */
376 /* kthreads, if configured. */
377 unsigned long n_force_qs; /* Number of calls to */
378 /* force_quiescent_state(). */
379 unsigned long gp_start; /* Time at which GP started, */
380 /* but in jiffies. */
381 unsigned long gp_end; /* Time last GP ended, again */
382 /* in jiffies. */
383 unsigned long gp_activity; /* Time of last GP kthread */
384 /* activity in jiffies. */
385 unsigned long gp_req_activity; /* Time of last GP request */
386 /* in jiffies. */
387 unsigned long jiffies_stall; /* Time at which to check */
388 /* for CPU stalls. */
389 int nr_fqs_jiffies_stall; /* Number of fqs loops after
390 * which read jiffies and set
391 * jiffies_stall. Stall
392 * warnings disabled if !0. */
393 unsigned long jiffies_resched; /* Time at which to resched */
394 /* a reluctant CPU. */
395 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
396 /* GP start. */
397 const char *name; /* Name of structure. */
398 char abbr; /* Abbreviated name. */
399
400 arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
401 /* Synchronize offline with */
402 /* GP pre-initialization. */
403 int nocb_is_setup; /* nocb is setup from boot */
404};
405
406/* Values for rcu_state structure's gp_flags field. */
407#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
408#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
409#define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */
410
411/* Values for rcu_state structure's gp_state field. */
412#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
413#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
414#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */
415#define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */
416#define RCU_GP_INIT 4 /* Grace-period initialization. */
417#define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */
418#define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */
419#define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */
420#define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */
421
422/*
423 * In order to export the rcu_state name to the tracing tools, it
424 * needs to be added in the __tracepoint_string section.
425 * This requires defining a separate variable tp_<sname>_varname
426 * that points to the string being used, and this will allow
427 * the tracing userspace tools to be able to decipher the string
428 * address to the matching string.
429 */
430#ifdef CONFIG_PREEMPT_RCU
431#define RCU_ABBR 'p'
432#define RCU_NAME_RAW "rcu_preempt"
433#else /* #ifdef CONFIG_PREEMPT_RCU */
434#define RCU_ABBR 's'
435#define RCU_NAME_RAW "rcu_sched"
436#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
437#ifndef CONFIG_TRACING
438#define RCU_NAME RCU_NAME_RAW
439#else /* #ifdef CONFIG_TRACING */
440static char rcu_name[] = RCU_NAME_RAW;
441static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
442#define RCU_NAME rcu_name
443#endif /* #else #ifdef CONFIG_TRACING */
444
445/* Forward declarations for tree_plugin.h */
446static void rcu_bootup_announce(void);
447static void rcu_qs(void);
448static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
449#ifdef CONFIG_HOTPLUG_CPU
450static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
451#endif /* #ifdef CONFIG_HOTPLUG_CPU */
452static int rcu_print_task_exp_stall(struct rcu_node *rnp);
453static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
454static void rcu_flavor_sched_clock_irq(int user);
455static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
456static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
457static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
458static bool rcu_is_callbacks_kthread(struct rcu_data *rdp);
459static void rcu_cpu_kthread_setup(unsigned int cpu);
460static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
461static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
462static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
463static void zero_cpu_stall_ticks(struct rcu_data *rdp);
464static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
465static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
466static void rcu_init_one_nocb(struct rcu_node *rnp);
467static bool wake_nocb_gp(struct rcu_data *rdp, bool force);
468static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
469 unsigned long j, bool lazy);
470static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
471 bool *was_alldone, unsigned long flags,
472 bool lazy);
473static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
474 unsigned long flags);
475static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level);
476static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
477static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
478static void rcu_spawn_cpu_nocb_kthread(int cpu);
479static void show_rcu_nocb_state(struct rcu_data *rdp);
480static void rcu_nocb_lock(struct rcu_data *rdp);
481static void rcu_nocb_unlock(struct rcu_data *rdp);
482static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
483 unsigned long flags);
484static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
485#ifdef CONFIG_RCU_NOCB_CPU
486static void __init rcu_organize_nocb_kthreads(void);
487
488/*
489 * Disable IRQs before checking offloaded state so that local
490 * locking is safe against concurrent de-offloading.
491 */
492#define rcu_nocb_lock_irqsave(rdp, flags) \
493do { \
494 local_irq_save(flags); \
495 if (rcu_segcblist_is_offloaded(&(rdp)->cblist)) \
496 raw_spin_lock(&(rdp)->nocb_lock); \
497} while (0)
498#else /* #ifdef CONFIG_RCU_NOCB_CPU */
499#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
500#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
501
502static void rcu_bind_gp_kthread(void);
503static bool rcu_nohz_full_cpu(void);
504
505/* Forward declarations for tree_stall.h */
506static void record_gp_stall_check_time(void);
507static void rcu_iw_handler(struct irq_work *iwp);
508static void check_cpu_stall(struct rcu_data *rdp);
509static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
510 const unsigned long gpssdelay);
511
512/* Forward declarations for tree_exp.h. */
513static void sync_rcu_do_polled_gp(struct work_struct *wp);
1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
4 * Internal non-public definitions.
5 *
6 * Copyright IBM Corporation, 2008
7 *
8 * Author: Ingo Molnar <mingo@elte.hu>
9 * Paul E. McKenney <paulmck@linux.ibm.com>
10 */
11
12#include <linux/cache.h>
13#include <linux/spinlock.h>
14#include <linux/rtmutex.h>
15#include <linux/threads.h>
16#include <linux/cpumask.h>
17#include <linux/seqlock.h>
18#include <linux/swait.h>
19#include <linux/rcu_node_tree.h>
20
21#include "rcu_segcblist.h"
22
23/* Communicate arguments to a workqueue handler. */
24struct rcu_exp_work {
25 unsigned long rew_s;
26 struct work_struct rew_work;
27};
28
29/* RCU's kthread states for tracing. */
30#define RCU_KTHREAD_STOPPED 0
31#define RCU_KTHREAD_RUNNING 1
32#define RCU_KTHREAD_WAITING 2
33#define RCU_KTHREAD_OFFCPU 3
34#define RCU_KTHREAD_YIELDING 4
35#define RCU_KTHREAD_MAX 4
36
37/*
38 * Definition for node within the RCU grace-period-detection hierarchy.
39 */
40struct rcu_node {
41 raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
42 /* some rcu_state fields as well as */
43 /* following. */
44 unsigned long gp_seq; /* Track rsp->gp_seq. */
45 unsigned long gp_seq_needed; /* Track furthest future GP request. */
46 unsigned long completedqs; /* All QSes done for this node. */
47 unsigned long qsmask; /* CPUs or groups that need to switch in */
48 /* order for current grace period to proceed.*/
49 /* In leaf rcu_node, each bit corresponds to */
50 /* an rcu_data structure, otherwise, each */
51 /* bit corresponds to a child rcu_node */
52 /* structure. */
53 unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */
54 unsigned long qsmaskinit;
55 /* Per-GP initial value for qsmask. */
56 /* Initialized from ->qsmaskinitnext at the */
57 /* beginning of each grace period. */
58 unsigned long qsmaskinitnext;
59 unsigned long ofl_seq; /* CPU-hotplug operation sequence count. */
60 /* Online CPUs for next grace period. */
61 unsigned long expmask; /* CPUs or groups that need to check in */
62 /* to allow the current expedited GP */
63 /* to complete. */
64 unsigned long expmaskinit;
65 /* Per-GP initial values for expmask. */
66 /* Initialized from ->expmaskinitnext at the */
67 /* beginning of each expedited GP. */
68 unsigned long expmaskinitnext;
69 /* Online CPUs for next expedited GP. */
70 /* Any CPU that has ever been online will */
71 /* have its bit set. */
72 unsigned long cbovldmask;
73 /* CPUs experiencing callback overload. */
74 unsigned long ffmask; /* Fully functional CPUs. */
75 unsigned long grpmask; /* Mask to apply to parent qsmask. */
76 /* Only one bit will be set in this mask. */
77 int grplo; /* lowest-numbered CPU here. */
78 int grphi; /* highest-numbered CPU here. */
79 u8 grpnum; /* group number for next level up. */
80 u8 level; /* root is at level 0. */
81 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
82 /* exit RCU read-side critical sections */
83 /* before propagating offline up the */
84 /* rcu_node tree? */
85 struct rcu_node *parent;
86 struct list_head blkd_tasks;
87 /* Tasks blocked in RCU read-side critical */
88 /* section. Tasks are placed at the head */
89 /* of this list and age towards the tail. */
90 struct list_head *gp_tasks;
91 /* Pointer to the first task blocking the */
92 /* current grace period, or NULL if there */
93 /* is no such task. */
94 struct list_head *exp_tasks;
95 /* Pointer to the first task blocking the */
96 /* current expedited grace period, or NULL */
97 /* if there is no such task. If there */
98 /* is no current expedited grace period, */
99 /* then there can cannot be any such task. */
100 struct list_head *boost_tasks;
101 /* Pointer to first task that needs to be */
102 /* priority boosted, or NULL if no priority */
103 /* boosting is needed for this rcu_node */
104 /* structure. If there are no tasks */
105 /* queued on this rcu_node structure that */
106 /* are blocking the current grace period, */
107 /* there can be no such task. */
108 struct rt_mutex boost_mtx;
109 /* Used only for the priority-boosting */
110 /* side effect, not as a lock. */
111 unsigned long boost_time;
112 /* When to start boosting (jiffies). */
113 struct task_struct *boost_kthread_task;
114 /* kthread that takes care of priority */
115 /* boosting for this rcu_node structure. */
116 unsigned int boost_kthread_status;
117 /* State of boost_kthread_task for tracing. */
118 unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */
119#ifdef CONFIG_RCU_NOCB_CPU
120 struct swait_queue_head nocb_gp_wq[2];
121 /* Place for rcu_nocb_kthread() to wait GP. */
122#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
123 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
124
125 spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
126 unsigned long exp_seq_rq;
127 wait_queue_head_t exp_wq[4];
128 struct rcu_exp_work rew;
129 bool exp_need_flush; /* Need to flush workitem? */
130} ____cacheline_internodealigned_in_smp;
131
132/*
133 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
134 * are indexed relative to this interval rather than the global CPU ID space.
135 * This generates the bit for a CPU in node-local masks.
136 */
137#define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))
138
139/*
140 * Union to allow "aggregate OR" operation on the need for a quiescent
141 * state by the normal and expedited grace periods.
142 */
143union rcu_noqs {
144 struct {
145 u8 norm;
146 u8 exp;
147 } b; /* Bits. */
148 u16 s; /* Set of bits, aggregate OR here. */
149};
150
151/* Per-CPU data for read-copy update. */
152struct rcu_data {
153 /* 1) quiescent-state and grace-period handling : */
154 unsigned long gp_seq; /* Track rsp->gp_seq counter. */
155 unsigned long gp_seq_needed; /* Track furthest future GP request. */
156 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
157 bool core_needs_qs; /* Core waits for quiescent state. */
158 bool beenonline; /* CPU online at least once. */
159 bool gpwrap; /* Possible ->gp_seq wrap. */
160 bool exp_deferred_qs; /* This CPU awaiting a deferred QS? */
161 bool cpu_started; /* RCU watching this onlining CPU. */
162 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
163 unsigned long grpmask; /* Mask to apply to leaf qsmask. */
164 unsigned long ticks_this_gp; /* The number of scheduling-clock */
165 /* ticks this CPU has handled */
166 /* during and after the last grace */
167 /* period it is aware of. */
168 struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */
169 bool defer_qs_iw_pending; /* Scheduler attention pending? */
170 struct work_struct strict_work; /* Schedule readers for strict GPs. */
171
172 /* 2) batch handling */
173 struct rcu_segcblist cblist; /* Segmented callback list, with */
174 /* different callbacks waiting for */
175 /* different grace periods. */
176 long qlen_last_fqs_check;
177 /* qlen at last check for QS forcing */
178 unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */
179 unsigned long n_force_qs_snap;
180 /* did other CPU force QS recently? */
181 long blimit; /* Upper limit on a processed batch */
182
183 /* 3) dynticks interface. */
184 int dynticks_snap; /* Per-GP tracking for dynticks. */
185 long dynticks_nesting; /* Track process nesting level. */
186 long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */
187 atomic_t dynticks; /* Even value for idle, else odd. */
188 bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */
189 bool rcu_urgent_qs; /* GP old need light quiescent state. */
190 bool rcu_forced_tick; /* Forced tick to provide QS. */
191 bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */
192#ifdef CONFIG_RCU_FAST_NO_HZ
193 unsigned long last_accelerate; /* Last jiffy CBs were accelerated. */
194 unsigned long last_advance_all; /* Last jiffy CBs were all advanced. */
195 int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
196#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
197
198 /* 4) rcu_barrier(), OOM callbacks, and expediting. */
199 struct rcu_head barrier_head;
200 int exp_dynticks_snap; /* Double-check need for IPI. */
201
202 /* 5) Callback offloading. */
203#ifdef CONFIG_RCU_NOCB_CPU
204 struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
205 struct swait_queue_head nocb_state_wq; /* For offloading state changes */
206 struct task_struct *nocb_gp_kthread;
207 raw_spinlock_t nocb_lock; /* Guard following pair of fields. */
208 atomic_t nocb_lock_contended; /* Contention experienced. */
209 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
210 struct timer_list nocb_timer; /* Enforce finite deferral. */
211 unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */
212
213 /* The following fields are used by call_rcu, hence own cacheline. */
214 raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
215 struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */
216 unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */
217 unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */
218 int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */
219
220 /* The following fields are used by GP kthread, hence own cacheline. */
221 raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;
222 u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */
223 u8 nocb_gp_bypass; /* Found a bypass on last scan? */
224 u8 nocb_gp_gp; /* GP to wait for on last scan? */
225 unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */
226 unsigned long nocb_gp_loops; /* # passes through wait code. */
227 struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */
228 bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */
229 struct task_struct *nocb_cb_kthread;
230 struct rcu_data *nocb_next_cb_rdp;
231 /* Next rcu_data in wakeup chain. */
232
233 /* The following fields are used by CB kthread, hence new cacheline. */
234 struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;
235 /* GP rdp takes GP-end wakeups. */
236#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
237
238 /* 6) RCU priority boosting. */
239 struct task_struct *rcu_cpu_kthread_task;
240 /* rcuc per-CPU kthread or NULL. */
241 unsigned int rcu_cpu_kthread_status;
242 char rcu_cpu_has_work;
243
244 /* 7) Diagnostic data, including RCU CPU stall warnings. */
245 unsigned int softirq_snap; /* Snapshot of softirq activity. */
246 /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
247 struct irq_work rcu_iw; /* Check for non-irq activity. */
248 bool rcu_iw_pending; /* Is ->rcu_iw pending? */
249 unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */
250 unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */
251 short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */
252 unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */
253 short rcu_onl_gp_flags; /* ->gp_flags at last online. */
254 unsigned long last_fqs_resched; /* Time of last rcu_resched(). */
255
256 int cpu;
257};
258
259/* Values for nocb_defer_wakeup field in struct rcu_data. */
260#define RCU_NOCB_WAKE_NOT 0
261#define RCU_NOCB_WAKE_BYPASS 1
262#define RCU_NOCB_WAKE 2
263#define RCU_NOCB_WAKE_FORCE 3
264
265#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
266 /* For jiffies_till_first_fqs and */
267 /* and jiffies_till_next_fqs. */
268
269#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
270 /* delay between bouts of */
271 /* quiescent-state forcing. */
272
273#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
274 /* at least one scheduling clock */
275 /* irq before ratting on them. */
276
277#define rcu_wait(cond) \
278do { \
279 for (;;) { \
280 set_current_state(TASK_INTERRUPTIBLE); \
281 if (cond) \
282 break; \
283 schedule(); \
284 } \
285 __set_current_state(TASK_RUNNING); \
286} while (0)
287
288/*
289 * RCU global state, including node hierarchy. This hierarchy is
290 * represented in "heap" form in a dense array. The root (first level)
291 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
292 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
293 * and the third level in ->node[m+1] and following (->node[m+1] referenced
294 * by ->level[2]). The number of levels is determined by the number of
295 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
296 * consisting of a single rcu_node.
297 */
298struct rcu_state {
299 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
300 struct rcu_node *level[RCU_NUM_LVLS + 1];
301 /* Hierarchy levels (+1 to */
302 /* shut bogus gcc warning) */
303 int ncpus; /* # CPUs seen so far. */
304 int n_online_cpus; /* # CPUs online for RCU. */
305
306 /* The following fields are guarded by the root rcu_node's lock. */
307
308 u8 boost ____cacheline_internodealigned_in_smp;
309 /* Subject to priority boost. */
310 unsigned long gp_seq; /* Grace-period sequence #. */
311 unsigned long gp_max; /* Maximum GP duration in */
312 /* jiffies. */
313 struct task_struct *gp_kthread; /* Task for grace periods. */
314 struct swait_queue_head gp_wq; /* Where GP task waits. */
315 short gp_flags; /* Commands for GP task. */
316 short gp_state; /* GP kthread sleep state. */
317 unsigned long gp_wake_time; /* Last GP kthread wake. */
318 unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */
319
320 /* End of fields guarded by root rcu_node's lock. */
321
322 struct mutex barrier_mutex; /* Guards barrier fields. */
323 atomic_t barrier_cpu_count; /* # CPUs waiting on. */
324 struct completion barrier_completion; /* Wake at barrier end. */
325 unsigned long barrier_sequence; /* ++ at start and end of */
326 /* rcu_barrier(). */
327 /* End of fields guarded by barrier_mutex. */
328
329 struct mutex exp_mutex; /* Serialize expedited GP. */
330 struct mutex exp_wake_mutex; /* Serialize wakeup. */
331 unsigned long expedited_sequence; /* Take a ticket. */
332 atomic_t expedited_need_qs; /* # CPUs left to check in. */
333 struct swait_queue_head expedited_wq; /* Wait for check-ins. */
334 int ncpus_snap; /* # CPUs seen last time. */
335 u8 cbovld; /* Callback overload now? */
336 u8 cbovldnext; /* ^ ^ next time? */
337
338 unsigned long jiffies_force_qs; /* Time at which to invoke */
339 /* force_quiescent_state(). */
340 unsigned long jiffies_kick_kthreads; /* Time at which to kick */
341 /* kthreads, if configured. */
342 unsigned long n_force_qs; /* Number of calls to */
343 /* force_quiescent_state(). */
344 unsigned long gp_start; /* Time at which GP started, */
345 /* but in jiffies. */
346 unsigned long gp_end; /* Time last GP ended, again */
347 /* in jiffies. */
348 unsigned long gp_activity; /* Time of last GP kthread */
349 /* activity in jiffies. */
350 unsigned long gp_req_activity; /* Time of last GP request */
351 /* in jiffies. */
352 unsigned long jiffies_stall; /* Time at which to check */
353 /* for CPU stalls. */
354 unsigned long jiffies_resched; /* Time at which to resched */
355 /* a reluctant CPU. */
356 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
357 /* GP start. */
358 const char *name; /* Name of structure. */
359 char abbr; /* Abbreviated name. */
360
361 raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
362 /* Synchronize offline with */
363 /* GP pre-initialization. */
364};
365
366/* Values for rcu_state structure's gp_flags field. */
367#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
368#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
369#define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */
370
371/* Values for rcu_state structure's gp_state field. */
372#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
373#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
374#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */
375#define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */
376#define RCU_GP_INIT 4 /* Grace-period initialization. */
377#define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */
378#define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */
379#define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */
380#define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */
381
382/*
383 * In order to export the rcu_state name to the tracing tools, it
384 * needs to be added in the __tracepoint_string section.
385 * This requires defining a separate variable tp_<sname>_varname
386 * that points to the string being used, and this will allow
387 * the tracing userspace tools to be able to decipher the string
388 * address to the matching string.
389 */
390#ifdef CONFIG_PREEMPT_RCU
391#define RCU_ABBR 'p'
392#define RCU_NAME_RAW "rcu_preempt"
393#else /* #ifdef CONFIG_PREEMPT_RCU */
394#define RCU_ABBR 's'
395#define RCU_NAME_RAW "rcu_sched"
396#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
397#ifndef CONFIG_TRACING
398#define RCU_NAME RCU_NAME_RAW
399#else /* #ifdef CONFIG_TRACING */
400static char rcu_name[] = RCU_NAME_RAW;
401static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
402#define RCU_NAME rcu_name
403#endif /* #else #ifdef CONFIG_TRACING */
404
405/* Forward declarations for tree_plugin.h */
406static void rcu_bootup_announce(void);
407static void rcu_qs(void);
408static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
409#ifdef CONFIG_HOTPLUG_CPU
410static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
411#endif /* #ifdef CONFIG_HOTPLUG_CPU */
412static int rcu_print_task_exp_stall(struct rcu_node *rnp);
413static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
414static void rcu_flavor_sched_clock_irq(int user);
415static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
416static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
417static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
418static bool rcu_is_callbacks_kthread(void);
419static void rcu_cpu_kthread_setup(unsigned int cpu);
420static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
421static void __init rcu_spawn_boost_kthreads(void);
422static void rcu_cleanup_after_idle(void);
423static void rcu_prepare_for_idle(void);
424static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
425static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
426static void rcu_preempt_deferred_qs(struct task_struct *t);
427static void zero_cpu_stall_ticks(struct rcu_data *rdp);
428static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
429static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
430static void rcu_init_one_nocb(struct rcu_node *rnp);
431static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
432 unsigned long j);
433static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
434 bool *was_alldone, unsigned long flags);
435static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
436 unsigned long flags);
437static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level);
438static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
439static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
440static void rcu_spawn_cpu_nocb_kthread(int cpu);
441static void __init rcu_spawn_nocb_kthreads(void);
442static void show_rcu_nocb_state(struct rcu_data *rdp);
443static void rcu_nocb_lock(struct rcu_data *rdp);
444static void rcu_nocb_unlock(struct rcu_data *rdp);
445static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
446 unsigned long flags);
447static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
448#ifdef CONFIG_RCU_NOCB_CPU
449static void __init rcu_organize_nocb_kthreads(void);
450#define rcu_nocb_lock_irqsave(rdp, flags) \
451do { \
452 if (!rcu_segcblist_is_offloaded(&(rdp)->cblist)) \
453 local_irq_save(flags); \
454 else \
455 raw_spin_lock_irqsave(&(rdp)->nocb_lock, (flags)); \
456} while (0)
457#else /* #ifdef CONFIG_RCU_NOCB_CPU */
458#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
459#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
460
461static void rcu_bind_gp_kthread(void);
462static bool rcu_nohz_full_cpu(void);
463static void rcu_dynticks_task_enter(void);
464static void rcu_dynticks_task_exit(void);
465static void rcu_dynticks_task_trace_enter(void);
466static void rcu_dynticks_task_trace_exit(void);
467
468/* Forward declarations for tree_stall.h */
469static void record_gp_stall_check_time(void);
470static void rcu_iw_handler(struct irq_work *iwp);
471static void check_cpu_stall(struct rcu_data *rdp);
472static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
473 const unsigned long gpssdelay);