tree.h

  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 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	unsigned long nocb_gp_seq;	/*  If so, ->gp_seq 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
299/* Values for nocb_defer_wakeup field in struct rcu_data. */
300#define RCU_NOCB_WAKE_NOT	0
301#define RCU_NOCB_WAKE_BYPASS	1
302#define RCU_NOCB_WAKE_LAZY	2
303#define RCU_NOCB_WAKE		3
304#define RCU_NOCB_WAKE_FORCE	4
305
306#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
307					/* For jiffies_till_first_fqs and */
308					/*  and jiffies_till_next_fqs. */
309
310#define RCU_JIFFIES_FQS_DIV	256	/* Very large systems need more */
311					/*  delay between bouts of */
312					/*  quiescent-state forcing. */
313
314#define RCU_STALL_RAT_DELAY	2	/* Allow other CPUs time to take */
315					/*  at least one scheduling clock */
316					/*  irq before ratting on them. */
317
318#define rcu_wait(cond)							\
319do {									\
320	for (;;) {							\
321		set_current_state(TASK_INTERRUPTIBLE);			\
322		if (cond)						\
323			break;						\
324		schedule();						\
325	}								\
326	__set_current_state(TASK_RUNNING);				\
327} while (0)
328
329/*
330 * A max threshold for synchronize_rcu() users which are
331 * awaken directly by the rcu_gp_kthread(). Left part is
332 * deferred to the main worker.
333 */
334#define SR_MAX_USERS_WAKE_FROM_GP 5
335#define SR_NORMAL_GP_WAIT_HEAD_MAX 5
336
337struct sr_wait_node {
338	atomic_t inuse;
339	struct llist_node node;
340};
341
342/*
343 * RCU global state, including node hierarchy.  This hierarchy is
344 * represented in "heap" form in a dense array.  The root (first level)
345 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
346 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
347 * and the third level in ->node[m+1] and following (->node[m+1] referenced
348 * by ->level[2]).  The number of levels is determined by the number of
349 * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
350 * consisting of a single rcu_node.
351 */
352struct rcu_state {
353	struct rcu_node node[NUM_RCU_NODES];	/* Hierarchy. */
354	struct rcu_node *level[RCU_NUM_LVLS + 1];
355						/* Hierarchy levels (+1 to */
356						/*  shut bogus gcc warning) */
357	int ncpus;				/* # CPUs seen so far. */
358	int n_online_cpus;			/* # CPUs online for RCU. */
359
360	/* The following fields are guarded by the root rcu_node's lock. */
361
362	unsigned long gp_seq ____cacheline_internodealigned_in_smp;
363						/* Grace-period sequence #. */
364	unsigned long gp_max;			/* Maximum GP duration in */
365						/*  jiffies. */
366	struct task_struct *gp_kthread;		/* Task for grace periods. */
367	struct swait_queue_head gp_wq;		/* Where GP task waits. */
368	short gp_flags;				/* Commands for GP task. */
369	short gp_state;				/* GP kthread sleep state. */
370	unsigned long gp_wake_time;		/* Last GP kthread wake. */
371	unsigned long gp_wake_seq;		/* ->gp_seq at ^^^. */
372	unsigned long gp_seq_polled;		/* GP seq for polled API. */
373	unsigned long gp_seq_polled_snap;	/* ->gp_seq_polled at normal GP start. */
374	unsigned long gp_seq_polled_exp_snap;	/* ->gp_seq_polled at expedited GP start. */
375
376	/* End of fields guarded by root rcu_node's lock. */
377
378	struct mutex barrier_mutex;		/* Guards barrier fields. */
379	atomic_t barrier_cpu_count;		/* # CPUs waiting on. */
380	struct completion barrier_completion;	/* Wake at barrier end. */
381	unsigned long barrier_sequence;		/* ++ at start and end of */
382						/*  rcu_barrier(). */
383	/* End of fields guarded by barrier_mutex. */
384
385	raw_spinlock_t barrier_lock;		/* Protects ->barrier_seq_snap. */
386
387	struct mutex exp_mutex;			/* Serialize expedited GP. */
388	struct mutex exp_wake_mutex;		/* Serialize wakeup. */
389	unsigned long expedited_sequence;	/* Take a ticket. */
390	atomic_t expedited_need_qs;		/* # CPUs left to check in. */
391	struct swait_queue_head expedited_wq;	/* Wait for check-ins. */
392	int ncpus_snap;				/* # CPUs seen last time. */
393	u8 cbovld;				/* Callback overload now? */
394	u8 cbovldnext;				/* ^        ^  next time? */
395
396	unsigned long jiffies_force_qs;		/* Time at which to invoke */
397						/*  force_quiescent_state(). */
398	unsigned long jiffies_kick_kthreads;	/* Time at which to kick */
399						/*  kthreads, if configured. */
400	unsigned long n_force_qs;		/* Number of calls to */
401						/*  force_quiescent_state(). */
402	unsigned long gp_start;			/* Time at which GP started, */
403						/*  but in jiffies. */
404	unsigned long gp_end;			/* Time last GP ended, again */
405						/*  in jiffies. */
406	unsigned long gp_activity;		/* Time of last GP kthread */
407						/*  activity in jiffies. */
408	unsigned long gp_req_activity;		/* Time of last GP request */
409						/*  in jiffies. */
410	unsigned long jiffies_stall;		/* Time at which to check */
411						/*  for CPU stalls. */
412	int nr_fqs_jiffies_stall;		/* Number of fqs loops after
413						 * which read jiffies and set
414						 * jiffies_stall. Stall
415						 * warnings disabled if !0. */
416	unsigned long jiffies_resched;		/* Time at which to resched */
417						/*  a reluctant CPU. */
418	unsigned long n_force_qs_gpstart;	/* Snapshot of n_force_qs at */
419						/*  GP start. */
420	const char *name;			/* Name of structure. */
421	char abbr;				/* Abbreviated name. */
422
423	arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
424						/* Synchronize offline with */
425						/*  GP pre-initialization. */
426
427	/* synchronize_rcu() part. */
428	struct llist_head srs_next;	/* request a GP users. */
429	struct llist_node *srs_wait_tail; /* wait for GP users. */
430	struct llist_node *srs_done_tail; /* ready for GP users. */
431	struct sr_wait_node srs_wait_nodes[SR_NORMAL_GP_WAIT_HEAD_MAX];
432	struct work_struct srs_cleanup_work;
433	atomic_t srs_cleanups_pending; /* srs inflight worker cleanups. */
434
435#ifdef CONFIG_RCU_NOCB_CPU
436	struct mutex nocb_mutex;		/* Guards (de-)offloading */
437	int nocb_is_setup;			/* nocb is setup from boot */
438#endif
439};
440
441/* Values for rcu_state structure's gp_flags field. */
442#define RCU_GP_FLAG_INIT 0x1	/* Need grace-period initialization. */
443#define RCU_GP_FLAG_FQS  0x2	/* Need grace-period quiescent-state forcing. */
444#define RCU_GP_FLAG_OVLD 0x4	/* Experiencing callback overload. */
445
446/* Values for rcu_state structure's gp_state field. */
447#define RCU_GP_IDLE	 0	/* Initial state and no GP in progress. */
448#define RCU_GP_WAIT_GPS  1	/* Wait for grace-period start. */
449#define RCU_GP_DONE_GPS  2	/* Wait done for grace-period start. */
450#define RCU_GP_ONOFF     3	/* Grace-period initialization hotplug. */
451#define RCU_GP_INIT      4	/* Grace-period initialization. */
452#define RCU_GP_WAIT_FQS  5	/* Wait for force-quiescent-state time. */
453#define RCU_GP_DOING_FQS 6	/* Wait done for force-quiescent-state time. */
454#define RCU_GP_CLEANUP   7	/* Grace-period cleanup started. */
455#define RCU_GP_CLEANED   8	/* Grace-period cleanup complete. */
456
457/*
458 * In order to export the rcu_state name to the tracing tools, it
459 * needs to be added in the __tracepoint_string section.
460 * This requires defining a separate variable tp_<sname>_varname
461 * that points to the string being used, and this will allow
462 * the tracing userspace tools to be able to decipher the string
463 * address to the matching string.
464 */
465#ifdef CONFIG_PREEMPT_RCU
466#define RCU_ABBR 'p'
467#define RCU_NAME_RAW "rcu_preempt"
468#else /* #ifdef CONFIG_PREEMPT_RCU */
469#define RCU_ABBR 's'
470#define RCU_NAME_RAW "rcu_sched"
471#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
472#ifndef CONFIG_TRACING
473#define RCU_NAME RCU_NAME_RAW
474#else /* #ifdef CONFIG_TRACING */
475static char rcu_name[] = RCU_NAME_RAW;
476static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
477#define RCU_NAME rcu_name
478#endif /* #else #ifdef CONFIG_TRACING */
479
480/* Forward declarations for tree_plugin.h */
481static void rcu_bootup_announce(void);
482static void rcu_qs(void);
483static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
484#ifdef CONFIG_HOTPLUG_CPU
485static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
486#endif /* #ifdef CONFIG_HOTPLUG_CPU */
487static int rcu_print_task_exp_stall(struct rcu_node *rnp);
488static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
489static void rcu_flavor_sched_clock_irq(int user);
490static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
491static void rcu_preempt_deferred_qs_init(struct rcu_data *rdp);
492static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
493static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
494static bool rcu_is_callbacks_kthread(struct rcu_data *rdp);
495static void rcu_cpu_kthread_setup(unsigned int cpu);
496static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
497static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
498static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
499static void zero_cpu_stall_ticks(struct rcu_data *rdp);
500static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
501static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
502static void rcu_init_one_nocb(struct rcu_node *rnp);
503static bool wake_nocb_gp(struct rcu_data *rdp, bool force);
504static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
505				  unsigned long j, bool lazy);
506static void call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *head,
507			  rcu_callback_t func, unsigned long flags, bool lazy);
508static void __maybe_unused __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
509						unsigned long flags);
510static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level);
511static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
512static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
513static void rcu_spawn_cpu_nocb_kthread(int cpu);
514static void show_rcu_nocb_state(struct rcu_data *rdp);
515static void rcu_nocb_lock(struct rcu_data *rdp);
516static void rcu_nocb_unlock(struct rcu_data *rdp);
517static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
518				       unsigned long flags);
519static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
520#ifdef CONFIG_RCU_NOCB_CPU
521static void __init rcu_organize_nocb_kthreads(void);
522
523/*
524 * Disable IRQs before checking offloaded state so that local
525 * locking is safe against concurrent de-offloading.
526 */
527#define rcu_nocb_lock_irqsave(rdp, flags)			\
528do {								\
529	local_irq_save(flags);					\
530	if (rcu_segcblist_is_offloaded(&(rdp)->cblist))	\
531		raw_spin_lock(&(rdp)->nocb_lock);		\
532} while (0)
533#else /* #ifdef CONFIG_RCU_NOCB_CPU */
534#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
535#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
536
537static void rcu_bind_gp_kthread(void);
538static bool rcu_nohz_full_cpu(void);
539
540/* Forward declarations for tree_stall.h */
541static void record_gp_stall_check_time(void);
542static void rcu_iw_handler(struct irq_work *iwp);
543static void check_cpu_stall(struct rcu_data *rdp);
544static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
545				     const unsigned long gpssdelay);
546
547/* Forward declarations for tree_exp.h. */
548static void sync_rcu_do_polled_gp(struct work_struct *wp);