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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 <[email protected]>
9 * Paul E. McKenney <[email protected]>
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 kthread worker handler. */
25struct rcu_exp_work {
26 unsigned long rew_s;
27 struct kthread_work rew_work;
28};
29
30/* RCU's kthread states for tracing. */
31#define RCU_KTHREAD_STOPPED 0
32#define RCU_KTHREAD_RUNNING 1
33#define RCU_KTHREAD_WAITING 2
34#define RCU_KTHREAD_OFFCPU 3
35#define RCU_KTHREAD_YIELDING 4
36#define RCU_KTHREAD_MAX 4
37
38/*
39 * Definition for node within the RCU grace-period-detection hierarchy.
40 */
41struct rcu_node {
42 raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
43 /* some rcu_state fields as well as */
44 /* following. */
45 unsigned long gp_seq; /* Track rsp->gp_seq. */
46 unsigned long gp_seq_needed; /* Track furthest future GP request. */
47 unsigned long completedqs; /* All QSes done for this node. */
48 unsigned long qsmask; /* CPUs or groups that need to switch in */
49 /* order for current grace period to proceed.*/
50 /* In leaf rcu_node, each bit corresponds to */
51 /* an rcu_data structure, otherwise, each */
52 /* bit corresponds to a child rcu_node */
53 /* structure. */
54 unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */
55 unsigned long qsmaskinit;
56 /* Per-GP initial value for qsmask. */
57 /* Initialized from ->qsmaskinitnext at the */
58 /* beginning of each grace period. */
59 unsigned long qsmaskinitnext;
60 unsigned long expmask; /* CPUs or groups that need to check in */
61 /* to allow the current expedited GP */
62 /* to complete. */
63 unsigned long expmaskinit;
64 /* Per-GP initial values for expmask. */
65 /* Initialized from ->expmaskinitnext at the */
66 /* beginning of each expedited GP. */
67 unsigned long expmaskinitnext;
68 /* Online CPUs for next expedited GP. */
69 /* Any CPU that has ever been online will */
70 /* have its bit set. */
71 struct kthread_worker *exp_kworker;
72 /* Workers performing per node expedited GP */
73 /* initialization. */
74 unsigned long cbovldmask;
75 /* CPUs experiencing callback overload. */
76 unsigned long ffmask; /* Fully functional CPUs. */
77 unsigned long grpmask; /* Mask to apply to parent qsmask. */
78 /* Only one bit will be set in this mask. */
79 int grplo; /* lowest-numbered CPU here. */
80 int grphi; /* highest-numbered CPU here. */
81 u8 grpnum; /* group number for next level up. */
82 u8 level; /* root is at level 0. */
83 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
84 /* exit RCU read-side critical sections */
85 /* before propagating offline up the */
86 /* rcu_node tree? */
87 struct rcu_node *parent;
88 struct list_head blkd_tasks;
89 /* Tasks blocked in RCU read-side critical */
90 /* section. Tasks are placed at the head */
91 /* of this list and age towards the tail. */
92 struct list_head *gp_tasks;
93 /* Pointer to the first task blocking the */
94 /* current grace period, or NULL if there */
95 /* is no such task. */
96 struct list_head *exp_tasks;
97 /* Pointer to the first task blocking the */
98 /* current expedited grace period, or NULL */
99 /* if there is no such task. If there */
100 /* is no current expedited grace period, */
101 /* then there can cannot be any such task. */
102 struct list_head *boost_tasks;
103 /* Pointer to first task that needs to be */
104 /* priority boosted, or NULL if no priority */
105 /* boosting is needed for this rcu_node */
106 /* structure. If there are no tasks */
107 /* queued on this rcu_node structure that */
108 /* are blocking the current grace period, */
109 /* there can be no such task. */
110 struct rt_mutex boost_mtx;
111 /* Used only for the priority-boosting */
112 /* side effect, not as a lock. */
113 unsigned long boost_time;
114 /* When to start boosting (jiffies). */
115 struct mutex kthread_mutex;
116 /* Exclusion for thread spawning and affinity */
117 /* manipulation. */
118 struct task_struct *boost_kthread_task;
119 /* kthread that takes care of priority */
120 /* boosting for this rcu_node structure. */
121 unsigned int boost_kthread_status;
122 /* State of boost_kthread_task for tracing. */
123 unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */
124#ifdef CONFIG_RCU_NOCB_CPU
125 struct swait_queue_head nocb_gp_wq[2];
126 /* Place for rcu_nocb_kthread() to wait GP. */
127#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
128 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
129
130 spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
131 unsigned long exp_seq_rq;
132 wait_queue_head_t exp_wq[4];
133 struct rcu_exp_work rew;
134 bool exp_need_flush; /* Need to flush workitem? */
135 raw_spinlock_t exp_poll_lock;
136 /* Lock and data for polled expedited grace periods. */
137 unsigned long exp_seq_poll_rq;
138 struct work_struct exp_poll_wq;
139} ____cacheline_internodealigned_in_smp;
140
141/*
142 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
143 * are indexed relative to this interval rather than the global CPU ID space.
144 * This generates the bit for a CPU in node-local masks.
145 */
146#define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))
147
148/*
149 * Union to allow "aggregate OR" operation on the need for a quiescent
150 * state by the normal and expedited grace periods.
151 */
152union rcu_noqs {
153 struct {
154 u8 norm;
155 u8 exp;
156 } b; /* Bits. */
157 u16 s; /* Set of bits, aggregate OR here. */
158};
159
160/*
161 * Record the snapshot of the core stats at half of the first RCU stall timeout.
162 * The member gp_seq is used to ensure that all members are updated only once
163 * during the sampling period. The snapshot is taken only if this gp_seq is not
164 * equal to rdp->gp_seq.
165 */
166struct rcu_snap_record {
167 unsigned long gp_seq; /* Track rdp->gp_seq counter */
168 u64 cputime_irq; /* Accumulated cputime of hard irqs */
169 u64 cputime_softirq;/* Accumulated cputime of soft irqs */
170 u64 cputime_system; /* Accumulated cputime of kernel tasks */
171 u64 nr_hardirqs; /* Accumulated number of hard irqs */
172 unsigned int nr_softirqs; /* Accumulated number of soft irqs */
173 unsigned long long nr_csw; /* Accumulated number of task switches */
174 unsigned long jiffies; /* Track jiffies value */
175};
176
177/*
178 * An IRQ work (deferred_qs_iw) is used by RCU to get the scheduler's attention.
179 * to report quiescent states at the soonest possible time.
180 * The request can be in one of the following states:
181 * - DEFER_QS_IDLE: An IRQ work is yet to be scheduled.
182 * - DEFER_QS_PENDING: An IRQ work was scheduled but either not yet run, or it
183 * ran and we still haven't reported a quiescent state.
184 */
185#define DEFER_QS_IDLE 0
186#define DEFER_QS_PENDING 1
187
188/* Per-CPU data for read-copy update. */
189struct rcu_data {
190 /* 1) quiescent-state and grace-period handling : */
191 unsigned long gp_seq; /* Track rsp->gp_seq counter. */
192 unsigned long gp_seq_needed; /* Track furthest future GP request. */
193 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
194 bool core_needs_qs; /* Core waits for quiescent state. */
195 bool beenonline; /* CPU online at least once. */
196 bool gpwrap; /* Possible ->gp_seq wrap. */
197 unsigned int gpwrap_count; /* Count of GP sequence wrap. */
198 bool cpu_started; /* RCU watching this onlining CPU. */
199 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
200 unsigned long grpmask; /* Mask to apply to leaf qsmask. */
201 unsigned long ticks_this_gp; /* The number of scheduling-clock */
202 /* ticks this CPU has handled */
203 /* during and after the last grace */
204 /* period it is aware of. */
205 struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */
206 int defer_qs_pending; /* irqwork or softirq pending? */
207 struct work_struct strict_work; /* Schedule readers for strict GPs. */
208
209 /* 2) batch handling */
210 struct rcu_segcblist cblist; /* Segmented callback list, with */
211 /* different callbacks waiting for */
212 /* different grace periods. */
213 long qlen_last_fqs_check;
214 /* qlen at last check for QS forcing */
215 unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */
216 unsigned long n_force_qs_snap;
217 /* did other CPU force QS recently? */
218 long blimit; /* Upper limit on a processed batch */
219
220 /* 3) dynticks interface. */
221 int watching_snap; /* Per-GP tracking for dynticks. */
222 bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */
223 bool rcu_urgent_qs; /* GP old need light quiescent state. */
224 bool rcu_forced_tick; /* Forced tick to provide QS. */
225 bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */
226
227 /* 4) rcu_barrier(), OOM callbacks, and expediting. */
228 unsigned long barrier_seq_snap; /* Snap of rcu_state.barrier_sequence. */
229 struct rcu_head barrier_head;
230 int exp_watching_snap; /* Double-check need for IPI. */
231
232 /* 5) Callback offloading. */
233#ifdef CONFIG_RCU_NOCB_CPU
234 struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
235 struct swait_queue_head nocb_state_wq; /* For offloading state changes */
236 struct task_struct *nocb_gp_kthread;
237 raw_spinlock_t nocb_lock; /* Guard following pair of fields. */
238 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
239 struct timer_list nocb_timer; /* Enforce finite deferral. */
240 unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */
241 struct mutex nocb_gp_kthread_mutex; /* Exclusion for nocb gp kthread */
242 /* spawning */
243
244 /* The following fields are used by call_rcu, hence own cacheline. */
245 raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
246 struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */
247 unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */
248 unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */
249 int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */
250
251 /* The following fields are used by GP kthread, hence own cacheline. */
252 raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;
253 u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */
254 u8 nocb_gp_bypass; /* Found a bypass on last scan? */
255 u8 nocb_gp_gp; /* GP to wait for on last scan? */
256 struct rcu_gp_seq nocb_gp_seq; /* If so, GP state to wait for. */
257 unsigned long nocb_gp_loops; /* # passes through wait code. */
258 struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */
259 bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */
260 struct task_struct *nocb_cb_kthread;
261 struct list_head nocb_head_rdp; /*
262 * Head of rcu_data list in wakeup chain,
263 * if rdp_gp.
264 */
265 struct list_head nocb_entry_rdp; /* rcu_data node in wakeup chain. */
266 struct rcu_data *nocb_toggling_rdp; /* rdp queued for (de-)offloading */
267
268 /* The following fields are used by CB kthread, hence new cacheline. */
269 struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;
270 /* GP rdp takes GP-end wakeups. */
271#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
272
273 /* 6) RCU priority boosting. */
274 struct task_struct *rcu_cpu_kthread_task;
275 /* rcuc per-CPU kthread or NULL. */
276 unsigned int rcu_cpu_kthread_status;
277 char rcu_cpu_has_work;
278 unsigned long rcuc_activity;
279
280 /* 7) Diagnostic data, including RCU CPU stall warnings. */
281 unsigned int softirq_snap; /* Snapshot of softirq activity. */
282 /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
283 struct irq_work rcu_iw; /* Check for non-irq activity. */
284 bool rcu_iw_pending; /* Is ->rcu_iw pending? */
285 unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */
286 unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */
287 short rcu_ofl_gp_state; /* ->gp_state at last offline. */
288 unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */
289 short rcu_onl_gp_state; /* ->gp_state at last online. */
290 unsigned long last_fqs_resched; /* Time of last rcu_resched(). */
291 unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */
292 struct rcu_snap_record snap_record; /* Snapshot of core stats at half of */
293 /* the first RCU stall timeout */
294
295 long lazy_len; /* Length of buffered lazy callbacks. */
296 int cpu;
297};
298
299static inline void rcu_defer_qs_clear(struct rcu_data *rdp)
300{
301 WRITE_ONCE(rdp->defer_qs_pending, DEFER_QS_IDLE);
302}
303
304/* Values for nocb_defer_wakeup field in struct rcu_data. */
305#define RCU_NOCB_WAKE_NOT 0
306#define RCU_NOCB_WAKE_BYPASS 1
307#define RCU_NOCB_WAKE_LAZY 2
308#define RCU_NOCB_WAKE 3
309
310#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
311 /* For jiffies_till_first_fqs and */
312 /* and jiffies_till_next_fqs. */
313
314#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
315 /* delay between bouts of */
316 /* quiescent-state forcing. */
317
318#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
319 /* at least one scheduling clock */
320 /* irq before ratting on them. */
321
322#define rcu_wait(cond) \
323do { \
324 for (;;) { \
325 set_current_state(TASK_INTERRUPTIBLE); \
326 if (cond) \
327 break; \
328 schedule(); \
329 } \
330 __set_current_state(TASK_RUNNING); \
331} while (0)
332
333/*
334 * A max threshold for synchronize_rcu() users which are
335 * awaken directly by the rcu_gp_kthread(). Left part is
336 * deferred to the main worker.
337 */
338#define SR_MAX_USERS_WAKE_FROM_GP 5
339#define SR_NORMAL_GP_WAIT_HEAD_MAX 5
340
341struct sr_wait_node {
342 atomic_t inuse;
343 struct llist_node node;
344};
345
346/*
347 * RCU global state, including node hierarchy. This hierarchy is
348 * represented in "heap" form in a dense array. The root (first level)
349 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
350 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
351 * and the third level in ->node[m+1] and following (->node[m+1] referenced
352 * by ->level[2]). The number of levels is determined by the number of
353 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
354 * consisting of a single rcu_node.
355 */
356struct rcu_state {
357 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
358 struct rcu_node *level[RCU_NUM_LVLS + 1];
359 /* Hierarchy levels (+1 to */
360 /* shut bogus gcc warning) */
361 int ncpus; /* # CPUs seen so far. */
362 int n_online_cpus; /* # CPUs online for RCU. */
363
364 /* The following fields are guarded by the root rcu_node's lock. */
365
366 unsigned long gp_seq ____cacheline_internodealigned_in_smp;
367 /* Grace-period sequence #. */
368 unsigned long gp_max; /* Maximum GP duration in */
369 /* jiffies. */
370 struct task_struct *gp_kthread; /* Task for grace periods. */
371 struct swait_queue_head gp_wq; /* Where GP task waits. */
372 short gp_flags; /* Commands for GP task. */
373 short gp_state; /* GP kthread sleep state. */
374 unsigned long gp_wake_time; /* Last GP kthread wake. */
375 unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */
376 unsigned long gp_seq_polled; /* GP seq for polled API. */
377 unsigned long gp_seq_polled_snap; /* ->gp_seq_polled at normal GP start. */
378 unsigned long gp_seq_polled_exp_snap; /* ->gp_seq_polled at expedited GP start. */
379
380 /* End of fields guarded by root rcu_node's lock. */
381
382 struct mutex barrier_mutex; /* Guards barrier fields. */
383 atomic_t barrier_cpu_count; /* # CPUs waiting on. */
384 struct completion barrier_completion; /* Wake at barrier end. */
385 unsigned long barrier_sequence; /* ++ at start and end of */
386 /* rcu_barrier(). */
387 /* End of fields guarded by barrier_mutex. */
388
389 raw_spinlock_t barrier_lock; /* Protects ->barrier_seq_snap. */
390
391 struct mutex exp_mutex; /* Serialize expedited GP. */
392 struct mutex exp_wake_mutex; /* Serialize wakeup. */
393 unsigned long expedited_sequence; /* Take a ticket. */
394 struct swait_queue_head expedited_wq; /* Wait for check-ins. */
395 int ncpus_snap; /* # CPUs seen last time. */
396 u8 cbovld; /* Callback overload now? */
397 u8 cbovldnext; /* ^ ^ next time? */
398
399 unsigned long jiffies_force_qs; /* Time at which to invoke */
400 /* force_quiescent_state(). */
401 unsigned long jiffies_kick_kthreads; /* Time at which to kick */
402 /* kthreads, if configured. */
403 unsigned long n_force_qs; /* Number of calls to */
404 /* force_quiescent_state(). */
405 unsigned long gp_start; /* Time at which GP started, */
406 /* but in jiffies. */
407 unsigned long gp_end; /* Time last GP ended, again */
408 /* in jiffies. */
409 unsigned long gp_activity; /* Time of last GP kthread */
410 /* activity in jiffies. */
411 unsigned long gp_req_activity; /* Time of last GP request */
412 /* in jiffies. */
413 unsigned long jiffies_stall; /* Time at which to check */
414 /* for CPU stalls. */
415 int nr_fqs_jiffies_stall; /* Number of fqs loops after
416 * which read jiffies and set
417 * jiffies_stall. Stall
418 * warnings disabled if !0. */
419 unsigned long jiffies_resched; /* Time at which to resched */
420 /* a reluctant CPU. */
421 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
422 /* GP start. */
423 const char *name; /* Name of structure. */
424 char abbr; /* Abbreviated name. */
425
426 arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
427 /* Synchronize offline with */
428 /* GP pre-initialization. */
429
430 /* synchronize_rcu() part. */
431 struct llist_head srs_next; /* request a GP users. */
432 struct llist_node *srs_wait_tail; /* wait for GP users. */
433 struct llist_node *srs_done_tail; /* ready for GP users. */
434 struct sr_wait_node srs_wait_nodes[SR_NORMAL_GP_WAIT_HEAD_MAX];
435 struct work_struct srs_cleanup_work;
436 atomic_t srs_cleanups_pending; /* srs inflight worker cleanups. */
437
438#ifdef CONFIG_RCU_NOCB_CPU
439 struct mutex nocb_mutex; /* Guards (de-)offloading */
440 int nocb_is_setup; /* nocb is setup from boot */
441#endif
442};
443
444/* Values for rcu_state structure's gp_flags field. */
445#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
446#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
447#define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */
448
449/* Values for rcu_state structure's gp_state field. */
450#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
451#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
452#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */
453#define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */
454#define RCU_GP_INIT 4 /* Grace-period initialization. */
455#define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */
456#define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */
457#define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */
458#define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */
459
460/*
461 * In order to export the rcu_state name to the tracing tools, it
462 * needs to be added in the __tracepoint_string section.
463 * This requires defining a separate variable tp_<sname>_varname
464 * that points to the string being used, and this will allow
465 * the tracing userspace tools to be able to decipher the string
466 * address to the matching string.
467 */
468#ifdef CONFIG_PREEMPT_RCU
469#define RCU_ABBR 'p'
470#define RCU_NAME_RAW "rcu_preempt"
471#else /* #ifdef CONFIG_PREEMPT_RCU */
472#define RCU_ABBR 's'
473#define RCU_NAME_RAW "rcu_sched"
474#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
475#ifndef CONFIG_TRACING
476#define RCU_NAME RCU_NAME_RAW
477#else /* #ifdef CONFIG_TRACING */
478static char rcu_name[] = RCU_NAME_RAW;
479static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
480#define RCU_NAME rcu_name
481#endif /* #else #ifdef CONFIG_TRACING */
482
483/* Forward declarations for tree_plugin.h */
484static void rcu_bootup_announce(void);
485static void rcu_qs(void);
486static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
487#ifdef CONFIG_HOTPLUG_CPU
488static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
489#endif /* #ifdef CONFIG_HOTPLUG_CPU */
490static int rcu_print_task_exp_stall(struct rcu_node *rnp);
491static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
492static void rcu_flavor_sched_clock_irq(int user);
493static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
494static void rcu_preempt_deferred_qs_init(struct rcu_data *rdp);
495static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
496static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
497static bool rcu_is_callbacks_kthread(struct rcu_data *rdp);
498static void rcu_cpu_kthread_setup(unsigned int cpu);
499static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
500static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
501static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
502static void zero_cpu_stall_ticks(struct rcu_data *rdp);
503static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
504static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
505static void rcu_nocb_exp_cleanup(struct rcu_node *rnp);
506static void rcu_init_one_nocb(struct rcu_node *rnp);
507static bool wake_nocb_gp(struct rcu_data *rdp);
508static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
509 unsigned long j, bool lazy);
510static void call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *head,
511 unsigned long flags, bool lazy);
512static void __maybe_unused __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
513 unsigned long flags);
514static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level);
515static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
516static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
517static void rcu_spawn_cpu_nocb_kthread(int cpu);
518static void show_rcu_nocb_state(struct rcu_data *rdp);
519static void rcu_nocb_lock(struct rcu_data *rdp);
520static void rcu_nocb_unlock(struct rcu_data *rdp);
521static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
522 unsigned long flags);
523static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
524#ifdef CONFIG_RCU_NOCB_CPU
525static void __init rcu_organize_nocb_kthreads(void);
526
527/*
528 * Disable IRQs before checking offloaded state so that local
529 * locking is safe against concurrent de-offloading.
530 */
531#define rcu_nocb_lock_irqsave(rdp, flags) \
532do { \
533 local_irq_save(flags); \
534 if (rcu_segcblist_is_offloaded(&(rdp)->cblist)) \
535 raw_spin_lock(&(rdp)->nocb_lock); \
536} while (0)
537#else /* #ifdef CONFIG_RCU_NOCB_CPU */
538#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
539#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
540
541static void rcu_bind_gp_kthread(void);
542static bool rcu_nohz_full_cpu(void);
543
544/* Forward declarations for tree_stall.h */
545static void record_gp_stall_check_time(void);
546static void rcu_iw_handler(struct irq_work *iwp);
547static void check_cpu_stall(struct rcu_data *rdp);
548static void rcu_check_gp_start_stall(struct rcu_node *rnp, const unsigned long gpssdelay);
549
550/* Forward declarations for tree_exp.h. */
551static void sync_rcu_do_polled_gp(struct work_struct *wp);