2 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
3 * Internal non-public definitions.
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, you can access it online at
17 * http://www.gnu.org/licenses/gpl-2.0.html.
19 * Copyright IBM Corporation, 2008
21 * Author: Ingo Molnar <mingo@elte.hu>
22 * Paul E. McKenney <paulmck@linux.vnet.ibm.com>
25 #include <linux/cache.h>
26 #include <linux/spinlock.h>
27 #include <linux/threads.h>
28 #include <linux/cpumask.h>
29 #include <linux/seqlock.h>
30 #include <linux/wait-simple.h>
33 * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and
34 * CONFIG_RCU_FANOUT_LEAF.
35 * In theory, it should be possible to add more levels straightforwardly.
36 * In practice, this did work well going from three levels to four.
37 * Of course, your mileage may vary.
39 #define MAX_RCU_LVLS 4
40 #define RCU_FANOUT_1 (CONFIG_RCU_FANOUT_LEAF)
41 #define RCU_FANOUT_2 (RCU_FANOUT_1 * CONFIG_RCU_FANOUT)
42 #define RCU_FANOUT_3 (RCU_FANOUT_2 * CONFIG_RCU_FANOUT)
43 #define RCU_FANOUT_4 (RCU_FANOUT_3 * CONFIG_RCU_FANOUT)
45 #if NR_CPUS <= RCU_FANOUT_1
46 # define RCU_NUM_LVLS 1
47 # define NUM_RCU_LVL_0 1
48 # define NUM_RCU_LVL_1 (NR_CPUS)
49 # define NUM_RCU_LVL_2 0
50 # define NUM_RCU_LVL_3 0
51 # define NUM_RCU_LVL_4 0
52 #elif NR_CPUS <= RCU_FANOUT_2
53 # define RCU_NUM_LVLS 2
54 # define NUM_RCU_LVL_0 1
55 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
56 # define NUM_RCU_LVL_2 (NR_CPUS)
57 # define NUM_RCU_LVL_3 0
58 # define NUM_RCU_LVL_4 0
59 #elif NR_CPUS <= RCU_FANOUT_3
60 # define RCU_NUM_LVLS 3
61 # define NUM_RCU_LVL_0 1
62 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
63 # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
64 # define NUM_RCU_LVL_3 (NR_CPUS)
65 # define NUM_RCU_LVL_4 0
66 #elif NR_CPUS <= RCU_FANOUT_4
67 # define RCU_NUM_LVLS 4
68 # define NUM_RCU_LVL_0 1
69 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3)
70 # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
71 # define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
72 # define NUM_RCU_LVL_4 (NR_CPUS)
74 # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
75 #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */
77 #define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4)
78 #define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
80 extern int rcu_num_lvls;
81 extern int rcu_num_nodes;
84 * Dynticks per-CPU state.
87 long long dynticks_nesting; /* Track irq/process nesting level. */
88 /* Process level is worth LLONG_MAX/2. */
89 int dynticks_nmi_nesting; /* Track NMI nesting level. */
90 atomic_t dynticks; /* Even value for idle, else odd. */
91 #ifdef CONFIG_NO_HZ_FULL_SYSIDLE
92 long long dynticks_idle_nesting;
93 /* irq/process nesting level from idle. */
94 atomic_t dynticks_idle; /* Even value for idle, else odd. */
95 /* "Idle" excludes userspace execution. */
96 unsigned long dynticks_idle_jiffies;
97 /* End of last non-NMI non-idle period. */
98 #endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
99 #ifdef CONFIG_RCU_FAST_NO_HZ
100 bool all_lazy; /* Are all CPU's CBs lazy? */
101 unsigned long nonlazy_posted;
102 /* # times non-lazy CBs posted to CPU. */
103 unsigned long nonlazy_posted_snap;
104 /* idle-period nonlazy_posted snapshot. */
105 unsigned long last_accelerate;
106 /* Last jiffy CBs were accelerated. */
107 unsigned long last_advance_all;
108 /* Last jiffy CBs were all advanced. */
109 int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
110 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
113 /* RCU's kthread states for tracing. */
114 #define RCU_KTHREAD_STOPPED 0
115 #define RCU_KTHREAD_RUNNING 1
116 #define RCU_KTHREAD_WAITING 2
117 #define RCU_KTHREAD_OFFCPU 3
118 #define RCU_KTHREAD_YIELDING 4
119 #define RCU_KTHREAD_MAX 4
122 * Definition for node within the RCU grace-period-detection hierarchy.
125 raw_spinlock_t lock; /* Root rcu_node's lock protects some */
126 /* rcu_state fields as well as following. */
127 unsigned long gpnum; /* Current grace period for this node. */
128 /* This will either be equal to or one */
129 /* behind the root rcu_node's gpnum. */
130 unsigned long completed; /* Last GP completed for this node. */
131 /* This will either be equal to or one */
132 /* behind the root rcu_node's gpnum. */
133 unsigned long qsmask; /* CPUs or groups that need to switch in */
134 /* order for current grace period to proceed.*/
135 /* In leaf rcu_node, each bit corresponds to */
136 /* an rcu_data structure, otherwise, each */
137 /* bit corresponds to a child rcu_node */
139 unsigned long expmask; /* Groups that have ->blkd_tasks */
140 /* elements that need to drain to allow the */
141 /* current expedited grace period to */
142 /* complete (only for PREEMPT_RCU). */
143 unsigned long qsmaskinit;
144 /* Per-GP initial value for qsmask & expmask. */
145 /* Initialized from ->qsmaskinitnext at the */
146 /* beginning of each grace period. */
147 unsigned long qsmaskinitnext;
148 /* Online CPUs for next grace period. */
149 unsigned long grpmask; /* Mask to apply to parent qsmask. */
150 /* Only one bit will be set in this mask. */
151 int grplo; /* lowest-numbered CPU or group here. */
152 int grphi; /* highest-numbered CPU or group here. */
153 u8 grpnum; /* CPU/group number for next level up. */
154 u8 level; /* root is at level 0. */
155 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
156 /* exit RCU read-side critical sections */
157 /* before propagating offline up the */
159 struct rcu_node *parent;
160 struct list_head blkd_tasks;
161 /* Tasks blocked in RCU read-side critical */
162 /* section. Tasks are placed at the head */
163 /* of this list and age towards the tail. */
164 struct list_head *gp_tasks;
165 /* Pointer to the first task blocking the */
166 /* current grace period, or NULL if there */
167 /* is no such task. */
168 struct list_head *exp_tasks;
169 /* Pointer to the first task blocking the */
170 /* current expedited grace period, or NULL */
171 /* if there is no such task. If there */
172 /* is no current expedited grace period, */
173 /* then there can cannot be any such task. */
174 #ifdef CONFIG_RCU_BOOST
175 struct list_head *boost_tasks;
176 /* Pointer to first task that needs to be */
177 /* priority boosted, or NULL if no priority */
178 /* boosting is needed for this rcu_node */
179 /* structure. If there are no tasks */
180 /* queued on this rcu_node structure that */
181 /* are blocking the current grace period, */
182 /* there can be no such task. */
183 struct rt_mutex boost_mtx;
184 /* Used only for the priority-boosting */
185 /* side effect, not as a lock. */
186 unsigned long boost_time;
187 /* When to start boosting (jiffies). */
188 struct task_struct *boost_kthread_task;
189 /* kthread that takes care of priority */
190 /* boosting for this rcu_node structure. */
191 unsigned int boost_kthread_status;
192 /* State of boost_kthread_task for tracing. */
193 unsigned long n_tasks_boosted;
194 /* Total number of tasks boosted. */
195 unsigned long n_exp_boosts;
196 /* Number of tasks boosted for expedited GP. */
197 unsigned long n_normal_boosts;
198 /* Number of tasks boosted for normal GP. */
199 unsigned long n_balk_blkd_tasks;
200 /* Refused to boost: no blocked tasks. */
201 unsigned long n_balk_exp_gp_tasks;
202 /* Refused to boost: nothing blocking GP. */
203 unsigned long n_balk_boost_tasks;
204 /* Refused to boost: already boosting. */
205 unsigned long n_balk_notblocked;
206 /* Refused to boost: RCU RS CS still running. */
207 unsigned long n_balk_notyet;
208 /* Refused to boost: not yet time. */
209 unsigned long n_balk_nos;
210 /* Refused to boost: not sure why, though. */
211 /* This can happen due to race conditions. */
212 #endif /* #ifdef CONFIG_RCU_BOOST */
213 #ifdef CONFIG_RCU_NOCB_CPU
214 struct swait_head nocb_gp_wq[2];
215 /* Place for rcu_nocb_kthread() to wait GP. */
216 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
217 int need_future_gp[2];
218 /* Counts of upcoming no-CB GP requests. */
219 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
220 } ____cacheline_internodealigned_in_smp;
223 * Do a full breadth-first scan of the rcu_node structures for the
224 * specified rcu_state structure.
226 #define rcu_for_each_node_breadth_first(rsp, rnp) \
227 for ((rnp) = &(rsp)->node[0]; \
228 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
231 * Do a breadth-first scan of the non-leaf rcu_node structures for the
232 * specified rcu_state structure. Note that if there is a singleton
233 * rcu_node tree with but one rcu_node structure, this loop is a no-op.
235 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
236 for ((rnp) = &(rsp)->node[0]; \
237 (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++)
240 * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
241 * structure. Note that if there is a singleton rcu_node tree with but
242 * one rcu_node structure, this loop -will- visit the rcu_node structure.
243 * It is still a leaf node, even if it is also the root node.
245 #define rcu_for_each_leaf_node(rsp, rnp) \
246 for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \
247 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
249 /* Index values for nxttail array in struct rcu_data. */
250 #define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */
251 #define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */
252 #define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */
253 #define RCU_NEXT_TAIL 3
254 #define RCU_NEXT_SIZE 4
256 /* Per-CPU data for read-copy update. */
258 /* 1) quiescent-state and grace-period handling : */
259 unsigned long completed; /* Track rsp->completed gp number */
260 /* in order to detect GP end. */
261 unsigned long gpnum; /* Highest gp number that this CPU */
262 /* is aware of having started. */
263 unsigned long rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
264 /* for rcu_all_qs() invocations. */
265 bool passed_quiesce; /* User-mode/idle loop etc. */
266 bool qs_pending; /* Core waits for quiesc state. */
267 bool beenonline; /* CPU online at least once. */
268 bool gpwrap; /* Possible gpnum/completed wrap. */
269 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
270 unsigned long grpmask; /* Mask to apply to leaf qsmask. */
271 #ifdef CONFIG_RCU_CPU_STALL_INFO
272 unsigned long ticks_this_gp; /* The number of scheduling-clock */
273 /* ticks this CPU has handled */
274 /* during and after the last grace */
275 /* period it is aware of. */
276 #endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
278 /* 2) batch handling */
280 * If nxtlist is not NULL, it is partitioned as follows.
281 * Any of the partitions might be empty, in which case the
282 * pointer to that partition will be equal to the pointer for
283 * the following partition. When the list is empty, all of
284 * the nxttail elements point to the ->nxtlist pointer itself,
285 * which in that case is NULL.
287 * [nxtlist, *nxttail[RCU_DONE_TAIL]):
288 * Entries that batch # <= ->completed
289 * The grace period for these entries has completed, and
290 * the other grace-period-completed entries may be moved
291 * here temporarily in rcu_process_callbacks().
292 * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
293 * Entries that batch # <= ->completed - 1: waiting for current GP
294 * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
295 * Entries known to have arrived before current GP ended
296 * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]):
297 * Entries that might have arrived after current GP ended
298 * Note that the value of *nxttail[RCU_NEXT_TAIL] will
299 * always be NULL, as this is the end of the list.
301 struct rcu_head *nxtlist;
302 struct rcu_head **nxttail[RCU_NEXT_SIZE];
303 unsigned long nxtcompleted[RCU_NEXT_SIZE];
304 /* grace periods for sublists. */
305 long qlen_lazy; /* # of lazy queued callbacks */
306 long qlen; /* # of queued callbacks, incl lazy */
307 long qlen_last_fqs_check;
308 /* qlen at last check for QS forcing */
309 unsigned long n_cbs_invoked; /* count of RCU cbs invoked. */
310 unsigned long n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */
311 unsigned long n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */
312 unsigned long n_cbs_adopted; /* RCU cbs adopted from dying CPU */
313 unsigned long n_force_qs_snap;
314 /* did other CPU force QS recently? */
315 long blimit; /* Upper limit on a processed batch */
317 /* 3) dynticks interface. */
318 struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */
319 int dynticks_snap; /* Per-GP tracking for dynticks. */
321 /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
322 unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */
323 unsigned long offline_fqs; /* Kicked due to being offline. */
324 unsigned long cond_resched_completed;
325 /* Grace period that needs help */
326 /* from cond_resched(). */
328 /* 5) __rcu_pending() statistics. */
329 unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */
330 unsigned long n_rp_qs_pending;
331 unsigned long n_rp_report_qs;
332 unsigned long n_rp_cb_ready;
333 unsigned long n_rp_cpu_needs_gp;
334 unsigned long n_rp_gp_completed;
335 unsigned long n_rp_gp_started;
336 unsigned long n_rp_nocb_defer_wakeup;
337 unsigned long n_rp_need_nothing;
339 /* 6) _rcu_barrier() and OOM callbacks. */
340 struct rcu_head barrier_head;
341 #ifdef CONFIG_RCU_FAST_NO_HZ
342 struct rcu_head oom_head;
343 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
345 /* 7) Callback offloading. */
346 #ifdef CONFIG_RCU_NOCB_CPU
347 struct rcu_head *nocb_head; /* CBs waiting for kthread. */
348 struct rcu_head **nocb_tail;
349 atomic_long_t nocb_q_count; /* # CBs waiting for nocb */
350 atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */
351 struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
352 struct rcu_head **nocb_follower_tail;
353 struct swait_head nocb_wq; /* For nocb kthreads to sleep on. */
354 struct task_struct *nocb_kthread;
355 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
357 /* The following fields are used by the leader, hence own cacheline. */
358 struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
359 /* CBs waiting for GP. */
360 struct rcu_head **nocb_gp_tail;
361 bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */
362 struct rcu_data *nocb_next_follower;
363 /* Next follower in wakeup chain. */
365 /* The following fields are used by the follower, hence new cachline. */
366 struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp;
367 /* Leader CPU takes GP-end wakeups. */
368 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
370 /* 8) RCU CPU stall data. */
371 #ifdef CONFIG_RCU_CPU_STALL_INFO
372 unsigned int softirq_snap; /* Snapshot of softirq activity. */
373 #endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
376 struct rcu_state *rsp;
379 /* Values for fqs_state field in struct rcu_state. */
380 #define RCU_GP_IDLE 0 /* No grace period in progress. */
381 #define RCU_GP_INIT 1 /* Grace period being initialized. */
382 #define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */
383 #define RCU_FORCE_QS 3 /* Need to force quiescent state. */
384 #define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
386 /* Values for nocb_defer_wakeup field in struct rcu_data. */
387 #define RCU_NOGP_WAKE_NOT 0
388 #define RCU_NOGP_WAKE 1
389 #define RCU_NOGP_WAKE_FORCE 2
391 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
392 /* For jiffies_till_first_fqs and */
393 /* and jiffies_till_next_fqs. */
395 #define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
396 /* delay between bouts of */
397 /* quiescent-state forcing. */
399 #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
400 /* at least one scheduling clock */
401 /* irq before ratting on them. */
403 #define rcu_wait(cond) \
406 set_current_state(TASK_INTERRUPTIBLE); \
411 __set_current_state(TASK_RUNNING); \
415 * RCU global state, including node hierarchy. This hierarchy is
416 * represented in "heap" form in a dense array. The root (first level)
417 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
418 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
419 * and the third level in ->node[m+1] and following (->node[m+1] referenced
420 * by ->level[2]). The number of levels is determined by the number of
421 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
422 * consisting of a single rcu_node.
425 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
426 struct rcu_node *level[RCU_NUM_LVLS]; /* Hierarchy levels. */
427 u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */
428 u8 levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */
429 u8 flavor_mask; /* bit in flavor mask. */
430 struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */
431 void (*call)(struct rcu_head *head, /* call_rcu() flavor. */
432 void (*func)(struct rcu_head *head));
434 /* The following fields are guarded by the root rcu_node's lock. */
436 u8 fqs_state ____cacheline_internodealigned_in_smp;
437 /* Force QS state. */
438 u8 boost; /* Subject to priority boost. */
439 unsigned long gpnum; /* Current gp number. */
440 unsigned long completed; /* # of last completed gp. */
441 struct task_struct *gp_kthread; /* Task for grace periods. */
442 struct swait_head gp_wq; /* Where GP task waits. */
443 short gp_flags; /* Commands for GP task. */
444 short gp_state; /* GP kthread sleep state. */
446 /* End of fields guarded by root rcu_node's lock. */
448 raw_spinlock_t orphan_lock ____cacheline_internodealigned_in_smp;
449 /* Protect following fields. */
450 struct rcu_head *orphan_nxtlist; /* Orphaned callbacks that */
451 /* need a grace period. */
452 struct rcu_head **orphan_nxttail; /* Tail of above. */
453 struct rcu_head *orphan_donelist; /* Orphaned callbacks that */
454 /* are ready to invoke. */
455 struct rcu_head **orphan_donetail; /* Tail of above. */
456 long qlen_lazy; /* Number of lazy callbacks. */
457 long qlen; /* Total number of callbacks. */
458 /* End of fields guarded by orphan_lock. */
460 struct mutex barrier_mutex; /* Guards barrier fields. */
461 atomic_t barrier_cpu_count; /* # CPUs waiting on. */
462 struct completion barrier_completion; /* Wake at barrier end. */
463 unsigned long n_barrier_done; /* ++ at start and end of */
464 /* _rcu_barrier(). */
465 /* End of fields guarded by barrier_mutex. */
467 atomic_long_t expedited_start; /* Starting ticket. */
468 atomic_long_t expedited_done; /* Done ticket. */
469 atomic_long_t expedited_wrap; /* # near-wrap incidents. */
470 atomic_long_t expedited_tryfail; /* # acquisition failures. */
471 atomic_long_t expedited_workdone1; /* # done by others #1. */
472 atomic_long_t expedited_workdone2; /* # done by others #2. */
473 atomic_long_t expedited_normal; /* # fallbacks to normal. */
474 atomic_long_t expedited_stoppedcpus; /* # successful stop_cpus. */
475 atomic_long_t expedited_done_tries; /* # tries to update _done. */
476 atomic_long_t expedited_done_lost; /* # times beaten to _done. */
477 atomic_long_t expedited_done_exit; /* # times exited _done loop. */
479 unsigned long jiffies_force_qs; /* Time at which to invoke */
480 /* force_quiescent_state(). */
481 unsigned long n_force_qs; /* Number of calls to */
482 /* force_quiescent_state(). */
483 unsigned long n_force_qs_lh; /* ~Number of calls leaving */
484 /* due to lock unavailable. */
485 unsigned long n_force_qs_ngp; /* Number of calls leaving */
486 /* due to no GP active. */
487 unsigned long gp_start; /* Time at which GP started, */
488 /* but in jiffies. */
489 unsigned long gp_activity; /* Time of last GP kthread */
490 /* activity in jiffies. */
491 unsigned long jiffies_stall; /* Time at which to check */
492 /* for CPU stalls. */
493 unsigned long jiffies_resched; /* Time at which to resched */
494 /* a reluctant CPU. */
495 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
497 unsigned long gp_max; /* Maximum GP duration in */
499 const char *name; /* Name of structure. */
500 char abbr; /* Abbreviated name. */
501 struct list_head flavors; /* List of RCU flavors. */
504 /* Values for rcu_state structure's gp_flags field. */
505 #define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
506 #define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
508 /* Values for rcu_state structure's gp_flags field. */
509 #define RCU_GP_WAIT_INIT 0 /* Initial state. */
510 #define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
511 #define RCU_GP_WAIT_FQS 2 /* Wait for force-quiescent-state time. */
513 extern struct list_head rcu_struct_flavors;
515 /* Sequence through rcu_state structures for each RCU flavor. */
516 #define for_each_rcu_flavor(rsp) \
517 list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
520 * RCU implementation internal declarations:
522 extern struct rcu_state rcu_sched_state;
523 DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
525 extern struct rcu_state rcu_bh_state;
526 DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
528 #ifdef CONFIG_PREEMPT_RCU
529 extern struct rcu_state rcu_preempt_state;
530 DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
531 #endif /* #ifdef CONFIG_PREEMPT_RCU */
533 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
534 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
535 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
536 DECLARE_PER_CPU(char, rcu_cpu_has_work);
538 #ifndef RCU_TREE_NONCORE
540 /* Forward declarations for rcutree_plugin.h */
541 static void rcu_bootup_announce(void);
542 static void rcu_preempt_note_context_switch(void);
543 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
544 #ifdef CONFIG_HOTPLUG_CPU
545 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
546 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
547 static void rcu_print_detail_task_stall(struct rcu_state *rsp);
548 static int rcu_print_task_stall(struct rcu_node *rnp);
549 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
550 static void rcu_preempt_check_callbacks(void);
551 void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
552 static void __init __rcu_init_preempt(void);
553 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
554 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
555 static bool rcu_is_callbacks_kthread(void);
556 static void rcu_cpu_kthread_setup(unsigned int cpu);
557 #ifdef CONFIG_RCU_BOOST
558 static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
559 struct rcu_node *rnp);
560 #endif /* #ifdef CONFIG_RCU_BOOST */
561 static void __init rcu_spawn_boost_kthreads(void);
562 static void rcu_prepare_kthreads(int cpu);
563 static void rcu_cleanup_after_idle(void);
564 static void rcu_prepare_for_idle(void);
565 static void rcu_idle_count_callbacks_posted(void);
566 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
567 static void print_cpu_stall_info_begin(void);
568 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
569 static void print_cpu_stall_info_end(void);
570 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
571 static void increment_cpu_stall_ticks(void);
572 static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
573 static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
574 static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp);
575 static void rcu_init_one_nocb(struct rcu_node *rnp);
576 static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
577 bool lazy, unsigned long flags);
578 static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
579 struct rcu_data *rdp,
580 unsigned long flags);
581 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
582 static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
583 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
584 static void rcu_spawn_all_nocb_kthreads(int cpu);
585 static void __init rcu_spawn_nocb_kthreads(void);
586 #ifdef CONFIG_RCU_NOCB_CPU
587 static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
588 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
589 static void __maybe_unused rcu_kick_nohz_cpu(int cpu);
590 static bool init_nocb_callback_list(struct rcu_data *rdp);
591 static void rcu_sysidle_enter(int irq);
592 static void rcu_sysidle_exit(int irq);
593 static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
594 unsigned long *maxj);
595 static bool is_sysidle_rcu_state(struct rcu_state *rsp);
596 static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle,
598 static void rcu_bind_gp_kthread(void);
599 static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp);
600 static bool rcu_nohz_full_cpu(struct rcu_state *rsp);
601 static void rcu_dynticks_task_enter(void);
602 static void rcu_dynticks_task_exit(void);
604 #endif /* #ifndef RCU_TREE_NONCORE */
606 #ifdef CONFIG_RCU_TRACE
607 /* Read out queue lengths for tracing. */
608 static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
610 #ifdef CONFIG_RCU_NOCB_CPU
611 *ql = atomic_long_read(&rdp->nocb_q_count);
612 *qll = atomic_long_read(&rdp->nocb_q_count_lazy);
613 #else /* #ifdef CONFIG_RCU_NOCB_CPU */
616 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
618 #endif /* #ifdef CONFIG_RCU_TRACE */