1 | /* SPDX-License-Identifier: GPL-2.0+ */ |
2 | /* |
3 | * RCU expedited grace periods |
4 | * |
5 | * Copyright IBM Corporation, 2016 |
6 | * |
7 | * Authors: Paul E. McKenney <paulmck@linux.ibm.com> |
8 | */ |
9 | |
10 | #include <linux/lockdep.h> |
11 | |
12 | static void rcu_exp_handler(void *unused); |
13 | static int rcu_print_task_exp_stall(struct rcu_node *rnp); |
14 | static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp); |
15 | |
16 | /* |
17 | * Record the start of an expedited grace period. |
18 | */ |
19 | static void rcu_exp_gp_seq_start(void) |
20 | { |
21 | rcu_seq_start(sp: &rcu_state.expedited_sequence); |
22 | rcu_poll_gp_seq_start_unlocked(snap: &rcu_state.gp_seq_polled_exp_snap); |
23 | } |
24 | |
25 | /* |
26 | * Return the value that the expedited-grace-period counter will have |
27 | * at the end of the current grace period. |
28 | */ |
29 | static __maybe_unused unsigned long rcu_exp_gp_seq_endval(void) |
30 | { |
31 | return rcu_seq_endval(sp: &rcu_state.expedited_sequence); |
32 | } |
33 | |
34 | /* |
35 | * Record the end of an expedited grace period. |
36 | */ |
37 | static void rcu_exp_gp_seq_end(void) |
38 | { |
39 | rcu_poll_gp_seq_end_unlocked(snap: &rcu_state.gp_seq_polled_exp_snap); |
40 | rcu_seq_end(sp: &rcu_state.expedited_sequence); |
41 | smp_mb(); /* Ensure that consecutive grace periods serialize. */ |
42 | } |
43 | |
44 | /* |
45 | * Take a snapshot of the expedited-grace-period counter, which is the |
46 | * earliest value that will indicate that a full grace period has |
47 | * elapsed since the current time. |
48 | */ |
49 | static unsigned long rcu_exp_gp_seq_snap(void) |
50 | { |
51 | unsigned long s; |
52 | |
53 | smp_mb(); /* Caller's modifications seen first by other CPUs. */ |
54 | s = rcu_seq_snap(sp: &rcu_state.expedited_sequence); |
55 | trace_rcu_exp_grace_period(rcuname: rcu_state.name, gpseq: s, TPS("snap" )); |
56 | return s; |
57 | } |
58 | |
59 | /* |
60 | * Given a counter snapshot from rcu_exp_gp_seq_snap(), return true |
61 | * if a full expedited grace period has elapsed since that snapshot |
62 | * was taken. |
63 | */ |
64 | static bool rcu_exp_gp_seq_done(unsigned long s) |
65 | { |
66 | return rcu_seq_done(sp: &rcu_state.expedited_sequence, s); |
67 | } |
68 | |
69 | /* |
70 | * Reset the ->expmaskinit values in the rcu_node tree to reflect any |
71 | * recent CPU-online activity. Note that these masks are not cleared |
72 | * when CPUs go offline, so they reflect the union of all CPUs that have |
73 | * ever been online. This means that this function normally takes its |
74 | * no-work-to-do fastpath. |
75 | */ |
76 | static void sync_exp_reset_tree_hotplug(void) |
77 | { |
78 | bool done; |
79 | unsigned long flags; |
80 | unsigned long mask; |
81 | unsigned long oldmask; |
82 | int ncpus = smp_load_acquire(&rcu_state.ncpus); /* Order vs. locking. */ |
83 | struct rcu_node *rnp; |
84 | struct rcu_node *rnp_up; |
85 | |
86 | /* If no new CPUs onlined since last time, nothing to do. */ |
87 | if (likely(ncpus == rcu_state.ncpus_snap)) |
88 | return; |
89 | rcu_state.ncpus_snap = ncpus; |
90 | |
91 | /* |
92 | * Each pass through the following loop propagates newly onlined |
93 | * CPUs for the current rcu_node structure up the rcu_node tree. |
94 | */ |
95 | rcu_for_each_leaf_node(rnp) { |
96 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
97 | if (rnp->expmaskinit == rnp->expmaskinitnext) { |
98 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
99 | continue; /* No new CPUs, nothing to do. */ |
100 | } |
101 | |
102 | /* Update this node's mask, track old value for propagation. */ |
103 | oldmask = rnp->expmaskinit; |
104 | rnp->expmaskinit = rnp->expmaskinitnext; |
105 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
106 | |
107 | /* If was already nonzero, nothing to propagate. */ |
108 | if (oldmask) |
109 | continue; |
110 | |
111 | /* Propagate the new CPU up the tree. */ |
112 | mask = rnp->grpmask; |
113 | rnp_up = rnp->parent; |
114 | done = false; |
115 | while (rnp_up) { |
116 | raw_spin_lock_irqsave_rcu_node(rnp_up, flags); |
117 | if (rnp_up->expmaskinit) |
118 | done = true; |
119 | rnp_up->expmaskinit |= mask; |
120 | raw_spin_unlock_irqrestore_rcu_node(rnp_up, flags); |
121 | if (done) |
122 | break; |
123 | mask = rnp_up->grpmask; |
124 | rnp_up = rnp_up->parent; |
125 | } |
126 | } |
127 | } |
128 | |
129 | /* |
130 | * Reset the ->expmask values in the rcu_node tree in preparation for |
131 | * a new expedited grace period. |
132 | */ |
133 | static void __maybe_unused sync_exp_reset_tree(void) |
134 | { |
135 | unsigned long flags; |
136 | struct rcu_node *rnp; |
137 | |
138 | sync_exp_reset_tree_hotplug(); |
139 | rcu_for_each_node_breadth_first(rnp) { |
140 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
141 | WARN_ON_ONCE(rnp->expmask); |
142 | WRITE_ONCE(rnp->expmask, rnp->expmaskinit); |
143 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
144 | } |
145 | } |
146 | |
147 | /* |
148 | * Return non-zero if there is no RCU expedited grace period in progress |
149 | * for the specified rcu_node structure, in other words, if all CPUs and |
150 | * tasks covered by the specified rcu_node structure have done their bit |
151 | * for the current expedited grace period. |
152 | */ |
153 | static bool sync_rcu_exp_done(struct rcu_node *rnp) |
154 | { |
155 | raw_lockdep_assert_held_rcu_node(rnp); |
156 | return READ_ONCE(rnp->exp_tasks) == NULL && |
157 | READ_ONCE(rnp->expmask) == 0; |
158 | } |
159 | |
160 | /* |
161 | * Like sync_rcu_exp_done(), but where the caller does not hold the |
162 | * rcu_node's ->lock. |
163 | */ |
164 | static bool sync_rcu_exp_done_unlocked(struct rcu_node *rnp) |
165 | { |
166 | unsigned long flags; |
167 | bool ret; |
168 | |
169 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
170 | ret = sync_rcu_exp_done(rnp); |
171 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
172 | |
173 | return ret; |
174 | } |
175 | |
176 | |
177 | /* |
178 | * Report the exit from RCU read-side critical section for the last task |
179 | * that queued itself during or before the current expedited preemptible-RCU |
180 | * grace period. This event is reported either to the rcu_node structure on |
181 | * which the task was queued or to one of that rcu_node structure's ancestors, |
182 | * recursively up the tree. (Calm down, calm down, we do the recursion |
183 | * iteratively!) |
184 | */ |
185 | static void __rcu_report_exp_rnp(struct rcu_node *rnp, |
186 | bool wake, unsigned long flags) |
187 | __releases(rnp->lock) |
188 | { |
189 | unsigned long mask; |
190 | |
191 | raw_lockdep_assert_held_rcu_node(rnp); |
192 | for (;;) { |
193 | if (!sync_rcu_exp_done(rnp)) { |
194 | if (!rnp->expmask) |
195 | rcu_initiate_boost(rnp, flags); |
196 | else |
197 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
198 | break; |
199 | } |
200 | if (rnp->parent == NULL) { |
201 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
202 | if (wake) { |
203 | smp_mb(); /* EGP done before wake_up(). */ |
204 | swake_up_one(q: &rcu_state.expedited_wq); |
205 | } |
206 | break; |
207 | } |
208 | mask = rnp->grpmask; |
209 | raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled */ |
210 | rnp = rnp->parent; |
211 | raw_spin_lock_rcu_node(rnp); /* irqs already disabled */ |
212 | WARN_ON_ONCE(!(rnp->expmask & mask)); |
213 | WRITE_ONCE(rnp->expmask, rnp->expmask & ~mask); |
214 | } |
215 | } |
216 | |
217 | /* |
218 | * Report expedited quiescent state for specified node. This is a |
219 | * lock-acquisition wrapper function for __rcu_report_exp_rnp(). |
220 | */ |
221 | static void __maybe_unused rcu_report_exp_rnp(struct rcu_node *rnp, bool wake) |
222 | { |
223 | unsigned long flags; |
224 | |
225 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
226 | __rcu_report_exp_rnp(rnp, wake, flags); |
227 | } |
228 | |
229 | /* |
230 | * Report expedited quiescent state for multiple CPUs, all covered by the |
231 | * specified leaf rcu_node structure. |
232 | */ |
233 | static void rcu_report_exp_cpu_mult(struct rcu_node *rnp, |
234 | unsigned long mask, bool wake) |
235 | { |
236 | int cpu; |
237 | unsigned long flags; |
238 | struct rcu_data *rdp; |
239 | |
240 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
241 | if (!(rnp->expmask & mask)) { |
242 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
243 | return; |
244 | } |
245 | WRITE_ONCE(rnp->expmask, rnp->expmask & ~mask); |
246 | for_each_leaf_node_cpu_mask(rnp, cpu, mask) { |
247 | rdp = per_cpu_ptr(&rcu_data, cpu); |
248 | if (!IS_ENABLED(CONFIG_NO_HZ_FULL) || !rdp->rcu_forced_tick_exp) |
249 | continue; |
250 | rdp->rcu_forced_tick_exp = false; |
251 | tick_dep_clear_cpu(cpu, bit: TICK_DEP_BIT_RCU_EXP); |
252 | } |
253 | __rcu_report_exp_rnp(rnp, wake, flags); /* Releases rnp->lock. */ |
254 | } |
255 | |
256 | /* |
257 | * Report expedited quiescent state for specified rcu_data (CPU). |
258 | */ |
259 | static void rcu_report_exp_rdp(struct rcu_data *rdp) |
260 | { |
261 | WRITE_ONCE(rdp->cpu_no_qs.b.exp, false); |
262 | rcu_report_exp_cpu_mult(rnp: rdp->mynode, mask: rdp->grpmask, wake: true); |
263 | } |
264 | |
265 | /* Common code for work-done checking. */ |
266 | static bool sync_exp_work_done(unsigned long s) |
267 | { |
268 | if (rcu_exp_gp_seq_done(s)) { |
269 | trace_rcu_exp_grace_period(rcuname: rcu_state.name, gpseq: s, TPS("done" )); |
270 | smp_mb(); /* Ensure test happens before caller kfree(). */ |
271 | return true; |
272 | } |
273 | return false; |
274 | } |
275 | |
276 | /* |
277 | * Funnel-lock acquisition for expedited grace periods. Returns true |
278 | * if some other task completed an expedited grace period that this task |
279 | * can piggy-back on, and with no mutex held. Otherwise, returns false |
280 | * with the mutex held, indicating that the caller must actually do the |
281 | * expedited grace period. |
282 | */ |
283 | static bool exp_funnel_lock(unsigned long s) |
284 | { |
285 | struct rcu_data *rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id()); |
286 | struct rcu_node *rnp = rdp->mynode; |
287 | struct rcu_node *rnp_root = rcu_get_root(); |
288 | |
289 | /* Low-contention fastpath. */ |
290 | if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) && |
291 | (rnp == rnp_root || |
292 | ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) && |
293 | mutex_trylock(lock: &rcu_state.exp_mutex)) |
294 | goto fastpath; |
295 | |
296 | /* |
297 | * Each pass through the following loop works its way up |
298 | * the rcu_node tree, returning if others have done the work or |
299 | * otherwise falls through to acquire ->exp_mutex. The mapping |
300 | * from CPU to rcu_node structure can be inexact, as it is just |
301 | * promoting locality and is not strictly needed for correctness. |
302 | */ |
303 | for (; rnp != NULL; rnp = rnp->parent) { |
304 | if (sync_exp_work_done(s)) |
305 | return true; |
306 | |
307 | /* Work not done, either wait here or go up. */ |
308 | spin_lock(lock: &rnp->exp_lock); |
309 | if (ULONG_CMP_GE(rnp->exp_seq_rq, s)) { |
310 | |
311 | /* Someone else doing GP, so wait for them. */ |
312 | spin_unlock(lock: &rnp->exp_lock); |
313 | trace_rcu_exp_funnel_lock(rcuname: rcu_state.name, level: rnp->level, |
314 | grplo: rnp->grplo, grphi: rnp->grphi, |
315 | TPS("wait" )); |
316 | wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], |
317 | sync_exp_work_done(s)); |
318 | return true; |
319 | } |
320 | WRITE_ONCE(rnp->exp_seq_rq, s); /* Followers can wait on us. */ |
321 | spin_unlock(lock: &rnp->exp_lock); |
322 | trace_rcu_exp_funnel_lock(rcuname: rcu_state.name, level: rnp->level, |
323 | grplo: rnp->grplo, grphi: rnp->grphi, TPS("nxtlvl" )); |
324 | } |
325 | mutex_lock(&rcu_state.exp_mutex); |
326 | fastpath: |
327 | if (sync_exp_work_done(s)) { |
328 | mutex_unlock(lock: &rcu_state.exp_mutex); |
329 | return true; |
330 | } |
331 | rcu_exp_gp_seq_start(); |
332 | trace_rcu_exp_grace_period(rcuname: rcu_state.name, gpseq: s, TPS("start" )); |
333 | return false; |
334 | } |
335 | |
336 | /* |
337 | * Select the CPUs within the specified rcu_node that the upcoming |
338 | * expedited grace period needs to wait for. |
339 | */ |
340 | static void __sync_rcu_exp_select_node_cpus(struct rcu_exp_work *rewp) |
341 | { |
342 | int cpu; |
343 | unsigned long flags; |
344 | unsigned long mask_ofl_test; |
345 | unsigned long mask_ofl_ipi; |
346 | int ret; |
347 | struct rcu_node *rnp = container_of(rewp, struct rcu_node, rew); |
348 | |
349 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
350 | |
351 | /* Each pass checks a CPU for identity, offline, and idle. */ |
352 | mask_ofl_test = 0; |
353 | for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) { |
354 | struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
355 | unsigned long mask = rdp->grpmask; |
356 | int snap; |
357 | |
358 | if (raw_smp_processor_id() == cpu || |
359 | !(rnp->qsmaskinitnext & mask)) { |
360 | mask_ofl_test |= mask; |
361 | } else { |
362 | snap = rcu_dynticks_snap(cpu); |
363 | if (rcu_dynticks_in_eqs(snap)) |
364 | mask_ofl_test |= mask; |
365 | else |
366 | rdp->exp_dynticks_snap = snap; |
367 | } |
368 | } |
369 | mask_ofl_ipi = rnp->expmask & ~mask_ofl_test; |
370 | |
371 | /* |
372 | * Need to wait for any blocked tasks as well. Note that |
373 | * additional blocking tasks will also block the expedited GP |
374 | * until such time as the ->expmask bits are cleared. |
375 | */ |
376 | if (rcu_preempt_has_tasks(rnp)) |
377 | WRITE_ONCE(rnp->exp_tasks, rnp->blkd_tasks.next); |
378 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
379 | |
380 | /* IPI the remaining CPUs for expedited quiescent state. */ |
381 | for_each_leaf_node_cpu_mask(rnp, cpu, mask_ofl_ipi) { |
382 | struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
383 | unsigned long mask = rdp->grpmask; |
384 | |
385 | retry_ipi: |
386 | if (rcu_dynticks_in_eqs_since(rdp, snap: rdp->exp_dynticks_snap)) { |
387 | mask_ofl_test |= mask; |
388 | continue; |
389 | } |
390 | if (get_cpu() == cpu) { |
391 | mask_ofl_test |= mask; |
392 | put_cpu(); |
393 | continue; |
394 | } |
395 | ret = smp_call_function_single(cpuid: cpu, func: rcu_exp_handler, NULL, wait: 0); |
396 | put_cpu(); |
397 | /* The CPU will report the QS in response to the IPI. */ |
398 | if (!ret) |
399 | continue; |
400 | |
401 | /* Failed, raced with CPU hotplug operation. */ |
402 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
403 | if ((rnp->qsmaskinitnext & mask) && |
404 | (rnp->expmask & mask)) { |
405 | /* Online, so delay for a bit and try again. */ |
406 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
407 | trace_rcu_exp_grace_period(rcuname: rcu_state.name, gpseq: rcu_exp_gp_seq_endval(), TPS("selectofl" )); |
408 | schedule_timeout_idle(timeout: 1); |
409 | goto retry_ipi; |
410 | } |
411 | /* CPU really is offline, so we must report its QS. */ |
412 | if (rnp->expmask & mask) |
413 | mask_ofl_test |= mask; |
414 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
415 | } |
416 | /* Report quiescent states for those that went offline. */ |
417 | if (mask_ofl_test) |
418 | rcu_report_exp_cpu_mult(rnp, mask: mask_ofl_test, wake: false); |
419 | } |
420 | |
421 | static void rcu_exp_sel_wait_wake(unsigned long s); |
422 | |
423 | #ifdef CONFIG_RCU_EXP_KTHREAD |
424 | static void sync_rcu_exp_select_node_cpus(struct kthread_work *wp) |
425 | { |
426 | struct rcu_exp_work *rewp = |
427 | container_of(wp, struct rcu_exp_work, rew_work); |
428 | |
429 | __sync_rcu_exp_select_node_cpus(rewp); |
430 | } |
431 | |
432 | static inline bool rcu_gp_par_worker_started(void) |
433 | { |
434 | return !!READ_ONCE(rcu_exp_par_gp_kworker); |
435 | } |
436 | |
437 | static inline void sync_rcu_exp_select_cpus_queue_work(struct rcu_node *rnp) |
438 | { |
439 | kthread_init_work(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus); |
440 | /* |
441 | * Use rcu_exp_par_gp_kworker, because flushing a work item from |
442 | * another work item on the same kthread worker can result in |
443 | * deadlock. |
444 | */ |
445 | kthread_queue_work(worker: rcu_exp_par_gp_kworker, work: &rnp->rew.rew_work); |
446 | } |
447 | |
448 | static inline void sync_rcu_exp_select_cpus_flush_work(struct rcu_node *rnp) |
449 | { |
450 | kthread_flush_work(work: &rnp->rew.rew_work); |
451 | } |
452 | |
453 | /* |
454 | * Work-queue handler to drive an expedited grace period forward. |
455 | */ |
456 | static void wait_rcu_exp_gp(struct kthread_work *wp) |
457 | { |
458 | struct rcu_exp_work *rewp; |
459 | |
460 | rewp = container_of(wp, struct rcu_exp_work, rew_work); |
461 | rcu_exp_sel_wait_wake(s: rewp->rew_s); |
462 | } |
463 | |
464 | static inline void synchronize_rcu_expedited_queue_work(struct rcu_exp_work *rew) |
465 | { |
466 | kthread_init_work(&rew->rew_work, wait_rcu_exp_gp); |
467 | kthread_queue_work(worker: rcu_exp_gp_kworker, work: &rew->rew_work); |
468 | } |
469 | |
470 | static inline void synchronize_rcu_expedited_destroy_work(struct rcu_exp_work *rew) |
471 | { |
472 | } |
473 | #else /* !CONFIG_RCU_EXP_KTHREAD */ |
474 | static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) |
475 | { |
476 | struct rcu_exp_work *rewp = |
477 | container_of(wp, struct rcu_exp_work, rew_work); |
478 | |
479 | __sync_rcu_exp_select_node_cpus(rewp); |
480 | } |
481 | |
482 | static inline bool rcu_gp_par_worker_started(void) |
483 | { |
484 | return !!READ_ONCE(rcu_par_gp_wq); |
485 | } |
486 | |
487 | static inline void sync_rcu_exp_select_cpus_queue_work(struct rcu_node *rnp) |
488 | { |
489 | int cpu = find_next_bit(&rnp->ffmask, BITS_PER_LONG, -1); |
490 | |
491 | INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus); |
492 | /* If all offline, queue the work on an unbound CPU. */ |
493 | if (unlikely(cpu > rnp->grphi - rnp->grplo)) |
494 | cpu = WORK_CPU_UNBOUND; |
495 | else |
496 | cpu += rnp->grplo; |
497 | queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work); |
498 | } |
499 | |
500 | static inline void sync_rcu_exp_select_cpus_flush_work(struct rcu_node *rnp) |
501 | { |
502 | flush_work(&rnp->rew.rew_work); |
503 | } |
504 | |
505 | /* |
506 | * Work-queue handler to drive an expedited grace period forward. |
507 | */ |
508 | static void wait_rcu_exp_gp(struct work_struct *wp) |
509 | { |
510 | struct rcu_exp_work *rewp; |
511 | |
512 | rewp = container_of(wp, struct rcu_exp_work, rew_work); |
513 | rcu_exp_sel_wait_wake(rewp->rew_s); |
514 | } |
515 | |
516 | static inline void synchronize_rcu_expedited_queue_work(struct rcu_exp_work *rew) |
517 | { |
518 | INIT_WORK_ONSTACK(&rew->rew_work, wait_rcu_exp_gp); |
519 | queue_work(rcu_gp_wq, &rew->rew_work); |
520 | } |
521 | |
522 | static inline void synchronize_rcu_expedited_destroy_work(struct rcu_exp_work *rew) |
523 | { |
524 | destroy_work_on_stack(&rew->rew_work); |
525 | } |
526 | #endif /* CONFIG_RCU_EXP_KTHREAD */ |
527 | |
528 | /* |
529 | * Select the nodes that the upcoming expedited grace period needs |
530 | * to wait for. |
531 | */ |
532 | static void sync_rcu_exp_select_cpus(void) |
533 | { |
534 | struct rcu_node *rnp; |
535 | |
536 | trace_rcu_exp_grace_period(rcuname: rcu_state.name, gpseq: rcu_exp_gp_seq_endval(), TPS("reset" )); |
537 | sync_exp_reset_tree(); |
538 | trace_rcu_exp_grace_period(rcuname: rcu_state.name, gpseq: rcu_exp_gp_seq_endval(), TPS("select" )); |
539 | |
540 | /* Schedule work for each leaf rcu_node structure. */ |
541 | rcu_for_each_leaf_node(rnp) { |
542 | rnp->exp_need_flush = false; |
543 | if (!READ_ONCE(rnp->expmask)) |
544 | continue; /* Avoid early boot non-existent wq. */ |
545 | if (!rcu_gp_par_worker_started() || |
546 | rcu_scheduler_active != RCU_SCHEDULER_RUNNING || |
547 | rcu_is_last_leaf_node(rnp)) { |
548 | /* No worker started yet or last leaf, do direct call. */ |
549 | sync_rcu_exp_select_node_cpus(wp: &rnp->rew.rew_work); |
550 | continue; |
551 | } |
552 | sync_rcu_exp_select_cpus_queue_work(rnp); |
553 | rnp->exp_need_flush = true; |
554 | } |
555 | |
556 | /* Wait for jobs (if any) to complete. */ |
557 | rcu_for_each_leaf_node(rnp) |
558 | if (rnp->exp_need_flush) |
559 | sync_rcu_exp_select_cpus_flush_work(rnp); |
560 | } |
561 | |
562 | /* |
563 | * Wait for the expedited grace period to elapse, within time limit. |
564 | * If the time limit is exceeded without the grace period elapsing, |
565 | * return false, otherwise return true. |
566 | */ |
567 | static bool synchronize_rcu_expedited_wait_once(long tlimit) |
568 | { |
569 | int t; |
570 | struct rcu_node *rnp_root = rcu_get_root(); |
571 | |
572 | t = swait_event_timeout_exclusive(rcu_state.expedited_wq, |
573 | sync_rcu_exp_done_unlocked(rnp_root), |
574 | tlimit); |
575 | // Workqueues should not be signaled. |
576 | if (t > 0 || sync_rcu_exp_done_unlocked(rnp: rnp_root)) |
577 | return true; |
578 | WARN_ON(t < 0); /* workqueues should not be signaled. */ |
579 | return false; |
580 | } |
581 | |
582 | /* |
583 | * Wait for the expedited grace period to elapse, issuing any needed |
584 | * RCU CPU stall warnings along the way. |
585 | */ |
586 | static void synchronize_rcu_expedited_wait(void) |
587 | { |
588 | int cpu; |
589 | unsigned long j; |
590 | unsigned long jiffies_stall; |
591 | unsigned long jiffies_start; |
592 | unsigned long mask; |
593 | int ndetected; |
594 | struct rcu_data *rdp; |
595 | struct rcu_node *rnp; |
596 | struct rcu_node *rnp_root = rcu_get_root(); |
597 | unsigned long flags; |
598 | |
599 | trace_rcu_exp_grace_period(rcuname: rcu_state.name, gpseq: rcu_exp_gp_seq_endval(), TPS("startwait" )); |
600 | jiffies_stall = rcu_exp_jiffies_till_stall_check(); |
601 | jiffies_start = jiffies; |
602 | if (tick_nohz_full_enabled() && rcu_inkernel_boot_has_ended()) { |
603 | if (synchronize_rcu_expedited_wait_once(tlimit: 1)) |
604 | return; |
605 | rcu_for_each_leaf_node(rnp) { |
606 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
607 | mask = READ_ONCE(rnp->expmask); |
608 | for_each_leaf_node_cpu_mask(rnp, cpu, mask) { |
609 | rdp = per_cpu_ptr(&rcu_data, cpu); |
610 | if (rdp->rcu_forced_tick_exp) |
611 | continue; |
612 | rdp->rcu_forced_tick_exp = true; |
613 | if (cpu_online(cpu)) |
614 | tick_dep_set_cpu(cpu, bit: TICK_DEP_BIT_RCU_EXP); |
615 | } |
616 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
617 | } |
618 | j = READ_ONCE(jiffies_till_first_fqs); |
619 | if (synchronize_rcu_expedited_wait_once(tlimit: j + HZ)) |
620 | return; |
621 | } |
622 | |
623 | for (;;) { |
624 | unsigned long j; |
625 | |
626 | if (synchronize_rcu_expedited_wait_once(tlimit: jiffies_stall)) |
627 | return; |
628 | if (rcu_stall_is_suppressed()) |
629 | continue; |
630 | j = jiffies; |
631 | rcu_stall_notifier_call_chain(RCU_STALL_NOTIFY_EXP, v: (void *)(j - jiffies_start)); |
632 | trace_rcu_stall_warning(rcuname: rcu_state.name, TPS("ExpeditedStall" )); |
633 | pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {" , |
634 | rcu_state.name); |
635 | ndetected = 0; |
636 | rcu_for_each_leaf_node(rnp) { |
637 | ndetected += rcu_print_task_exp_stall(rnp); |
638 | for_each_leaf_node_possible_cpu(rnp, cpu) { |
639 | struct rcu_data *rdp; |
640 | |
641 | mask = leaf_node_cpu_bit(rnp, cpu); |
642 | if (!(READ_ONCE(rnp->expmask) & mask)) |
643 | continue; |
644 | ndetected++; |
645 | rdp = per_cpu_ptr(&rcu_data, cpu); |
646 | pr_cont(" %d-%c%c%c%c" , cpu, |
647 | "O." [!!cpu_online(cpu)], |
648 | "o." [!!(rdp->grpmask & rnp->expmaskinit)], |
649 | "N." [!!(rdp->grpmask & rnp->expmaskinitnext)], |
650 | "D." [!!data_race(rdp->cpu_no_qs.b.exp)]); |
651 | } |
652 | } |
653 | pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n" , |
654 | j - jiffies_start, rcu_state.expedited_sequence, |
655 | data_race(rnp_root->expmask), |
656 | ".T" [!!data_race(rnp_root->exp_tasks)]); |
657 | if (ndetected) { |
658 | pr_err("blocking rcu_node structures (internal RCU debug):" ); |
659 | rcu_for_each_node_breadth_first(rnp) { |
660 | if (rnp == rnp_root) |
661 | continue; /* printed unconditionally */ |
662 | if (sync_rcu_exp_done_unlocked(rnp)) |
663 | continue; |
664 | pr_cont(" l=%u:%d-%d:%#lx/%c" , |
665 | rnp->level, rnp->grplo, rnp->grphi, |
666 | data_race(rnp->expmask), |
667 | ".T" [!!data_race(rnp->exp_tasks)]); |
668 | } |
669 | pr_cont("\n" ); |
670 | } |
671 | rcu_for_each_leaf_node(rnp) { |
672 | for_each_leaf_node_possible_cpu(rnp, cpu) { |
673 | mask = leaf_node_cpu_bit(rnp, cpu); |
674 | if (!(READ_ONCE(rnp->expmask) & mask)) |
675 | continue; |
676 | preempt_disable(); // For smp_processor_id() in dump_cpu_task(). |
677 | dump_cpu_task(cpu); |
678 | preempt_enable(); |
679 | } |
680 | rcu_exp_print_detail_task_stall_rnp(rnp); |
681 | } |
682 | jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3; |
683 | panic_on_rcu_stall(); |
684 | } |
685 | } |
686 | |
687 | /* |
688 | * Wait for the current expedited grace period to complete, and then |
689 | * wake up everyone who piggybacked on the just-completed expedited |
690 | * grace period. Also update all the ->exp_seq_rq counters as needed |
691 | * in order to avoid counter-wrap problems. |
692 | */ |
693 | static void rcu_exp_wait_wake(unsigned long s) |
694 | { |
695 | struct rcu_node *rnp; |
696 | |
697 | synchronize_rcu_expedited_wait(); |
698 | |
699 | // Switch over to wakeup mode, allowing the next GP to proceed. |
700 | // End the previous grace period only after acquiring the mutex |
701 | // to ensure that only one GP runs concurrently with wakeups. |
702 | mutex_lock(&rcu_state.exp_wake_mutex); |
703 | rcu_exp_gp_seq_end(); |
704 | trace_rcu_exp_grace_period(rcuname: rcu_state.name, gpseq: s, TPS("end" )); |
705 | |
706 | rcu_for_each_node_breadth_first(rnp) { |
707 | if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s)) { |
708 | spin_lock(lock: &rnp->exp_lock); |
709 | /* Recheck, avoid hang in case someone just arrived. */ |
710 | if (ULONG_CMP_LT(rnp->exp_seq_rq, s)) |
711 | WRITE_ONCE(rnp->exp_seq_rq, s); |
712 | spin_unlock(lock: &rnp->exp_lock); |
713 | } |
714 | smp_mb(); /* All above changes before wakeup. */ |
715 | wake_up_all(&rnp->exp_wq[rcu_seq_ctr(s) & 0x3]); |
716 | } |
717 | trace_rcu_exp_grace_period(rcuname: rcu_state.name, gpseq: s, TPS("endwake" )); |
718 | mutex_unlock(lock: &rcu_state.exp_wake_mutex); |
719 | } |
720 | |
721 | /* |
722 | * Common code to drive an expedited grace period forward, used by |
723 | * workqueues and mid-boot-time tasks. |
724 | */ |
725 | static void rcu_exp_sel_wait_wake(unsigned long s) |
726 | { |
727 | /* Initialize the rcu_node tree in preparation for the wait. */ |
728 | sync_rcu_exp_select_cpus(); |
729 | |
730 | /* Wait and clean up, including waking everyone. */ |
731 | rcu_exp_wait_wake(s); |
732 | } |
733 | |
734 | #ifdef CONFIG_PREEMPT_RCU |
735 | |
736 | /* |
737 | * Remote handler for smp_call_function_single(). If there is an |
738 | * RCU read-side critical section in effect, request that the |
739 | * next rcu_read_unlock() record the quiescent state up the |
740 | * ->expmask fields in the rcu_node tree. Otherwise, immediately |
741 | * report the quiescent state. |
742 | */ |
743 | static void rcu_exp_handler(void *unused) |
744 | { |
745 | int depth = rcu_preempt_depth(); |
746 | unsigned long flags; |
747 | struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
748 | struct rcu_node *rnp = rdp->mynode; |
749 | struct task_struct *t = current; |
750 | |
751 | /* |
752 | * First, the common case of not being in an RCU read-side |
753 | * critical section. If also enabled or idle, immediately |
754 | * report the quiescent state, otherwise defer. |
755 | */ |
756 | if (!depth) { |
757 | if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) || |
758 | rcu_is_cpu_rrupt_from_idle()) { |
759 | rcu_report_exp_rdp(rdp); |
760 | } else { |
761 | WRITE_ONCE(rdp->cpu_no_qs.b.exp, true); |
762 | set_tsk_need_resched(t); |
763 | set_preempt_need_resched(); |
764 | } |
765 | return; |
766 | } |
767 | |
768 | /* |
769 | * Second, the less-common case of being in an RCU read-side |
770 | * critical section. In this case we can count on a future |
771 | * rcu_read_unlock(). However, this rcu_read_unlock() might |
772 | * execute on some other CPU, but in that case there will be |
773 | * a future context switch. Either way, if the expedited |
774 | * grace period is still waiting on this CPU, set ->deferred_qs |
775 | * so that the eventual quiescent state will be reported. |
776 | * Note that there is a large group of race conditions that |
777 | * can have caused this quiescent state to already have been |
778 | * reported, so we really do need to check ->expmask. |
779 | */ |
780 | if (depth > 0) { |
781 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
782 | if (rnp->expmask & rdp->grpmask) { |
783 | WRITE_ONCE(rdp->cpu_no_qs.b.exp, true); |
784 | t->rcu_read_unlock_special.b.exp_hint = true; |
785 | } |
786 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
787 | return; |
788 | } |
789 | |
790 | // Finally, negative nesting depth should not happen. |
791 | WARN_ON_ONCE(1); |
792 | } |
793 | |
794 | /* PREEMPTION=y, so no PREEMPTION=n expedited grace period to clean up after. */ |
795 | static void sync_sched_exp_online_cleanup(int cpu) |
796 | { |
797 | } |
798 | |
799 | /* |
800 | * Scan the current list of tasks blocked within RCU read-side critical |
801 | * sections, printing out the tid of each that is blocking the current |
802 | * expedited grace period. |
803 | */ |
804 | static int rcu_print_task_exp_stall(struct rcu_node *rnp) |
805 | { |
806 | unsigned long flags; |
807 | int ndetected = 0; |
808 | struct task_struct *t; |
809 | |
810 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
811 | if (!rnp->exp_tasks) { |
812 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
813 | return 0; |
814 | } |
815 | t = list_entry(rnp->exp_tasks->prev, |
816 | struct task_struct, rcu_node_entry); |
817 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
818 | pr_cont(" P%d" , t->pid); |
819 | ndetected++; |
820 | } |
821 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
822 | return ndetected; |
823 | } |
824 | |
825 | /* |
826 | * Scan the current list of tasks blocked within RCU read-side critical |
827 | * sections, dumping the stack of each that is blocking the current |
828 | * expedited grace period. |
829 | */ |
830 | static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp) |
831 | { |
832 | unsigned long flags; |
833 | struct task_struct *t; |
834 | |
835 | if (!rcu_exp_stall_task_details) |
836 | return; |
837 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
838 | if (!READ_ONCE(rnp->exp_tasks)) { |
839 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
840 | return; |
841 | } |
842 | t = list_entry(rnp->exp_tasks->prev, |
843 | struct task_struct, rcu_node_entry); |
844 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
845 | /* |
846 | * We could be printing a lot while holding a spinlock. |
847 | * Avoid triggering hard lockup. |
848 | */ |
849 | touch_nmi_watchdog(); |
850 | sched_show_task(p: t); |
851 | } |
852 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
853 | } |
854 | |
855 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
856 | |
857 | /* Request an expedited quiescent state. */ |
858 | static void rcu_exp_need_qs(void) |
859 | { |
860 | __this_cpu_write(rcu_data.cpu_no_qs.b.exp, true); |
861 | /* Store .exp before .rcu_urgent_qs. */ |
862 | smp_store_release(this_cpu_ptr(&rcu_data.rcu_urgent_qs), true); |
863 | set_tsk_need_resched(current); |
864 | set_preempt_need_resched(); |
865 | } |
866 | |
867 | /* Invoked on each online non-idle CPU for expedited quiescent state. */ |
868 | static void rcu_exp_handler(void *unused) |
869 | { |
870 | struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
871 | struct rcu_node *rnp = rdp->mynode; |
872 | bool preempt_bh_enabled = !(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)); |
873 | |
874 | if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) || |
875 | __this_cpu_read(rcu_data.cpu_no_qs.b.exp)) |
876 | return; |
877 | if (rcu_is_cpu_rrupt_from_idle() || |
878 | (IS_ENABLED(CONFIG_PREEMPT_COUNT) && preempt_bh_enabled)) { |
879 | rcu_report_exp_rdp(this_cpu_ptr(&rcu_data)); |
880 | return; |
881 | } |
882 | rcu_exp_need_qs(); |
883 | } |
884 | |
885 | /* Send IPI for expedited cleanup if needed at end of CPU-hotplug operation. */ |
886 | static void sync_sched_exp_online_cleanup(int cpu) |
887 | { |
888 | unsigned long flags; |
889 | int my_cpu; |
890 | struct rcu_data *rdp; |
891 | int ret; |
892 | struct rcu_node *rnp; |
893 | |
894 | rdp = per_cpu_ptr(&rcu_data, cpu); |
895 | rnp = rdp->mynode; |
896 | my_cpu = get_cpu(); |
897 | /* Quiescent state either not needed or already requested, leave. */ |
898 | if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) || |
899 | READ_ONCE(rdp->cpu_no_qs.b.exp)) { |
900 | put_cpu(); |
901 | return; |
902 | } |
903 | /* Quiescent state needed on current CPU, so set it up locally. */ |
904 | if (my_cpu == cpu) { |
905 | local_irq_save(flags); |
906 | rcu_exp_need_qs(); |
907 | local_irq_restore(flags); |
908 | put_cpu(); |
909 | return; |
910 | } |
911 | /* Quiescent state needed on some other CPU, send IPI. */ |
912 | ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0); |
913 | put_cpu(); |
914 | WARN_ON_ONCE(ret); |
915 | } |
916 | |
917 | /* |
918 | * Because preemptible RCU does not exist, we never have to check for |
919 | * tasks blocked within RCU read-side critical sections that are |
920 | * blocking the current expedited grace period. |
921 | */ |
922 | static int rcu_print_task_exp_stall(struct rcu_node *rnp) |
923 | { |
924 | return 0; |
925 | } |
926 | |
927 | /* |
928 | * Because preemptible RCU does not exist, we never have to print out |
929 | * tasks blocked within RCU read-side critical sections that are blocking |
930 | * the current expedited grace period. |
931 | */ |
932 | static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp) |
933 | { |
934 | } |
935 | |
936 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
937 | |
938 | /** |
939 | * synchronize_rcu_expedited - Brute-force RCU grace period |
940 | * |
941 | * Wait for an RCU grace period, but expedite it. The basic idea is to |
942 | * IPI all non-idle non-nohz online CPUs. The IPI handler checks whether |
943 | * the CPU is in an RCU critical section, and if so, it sets a flag that |
944 | * causes the outermost rcu_read_unlock() to report the quiescent state |
945 | * for RCU-preempt or asks the scheduler for help for RCU-sched. On the |
946 | * other hand, if the CPU is not in an RCU read-side critical section, |
947 | * the IPI handler reports the quiescent state immediately. |
948 | * |
949 | * Although this is a great improvement over previous expedited |
950 | * implementations, it is still unfriendly to real-time workloads, so is |
951 | * thus not recommended for any sort of common-case code. In fact, if |
952 | * you are using synchronize_rcu_expedited() in a loop, please restructure |
953 | * your code to batch your updates, and then use a single synchronize_rcu() |
954 | * instead. |
955 | * |
956 | * This has the same semantics as (but is more brutal than) synchronize_rcu(). |
957 | */ |
958 | void synchronize_rcu_expedited(void) |
959 | { |
960 | bool boottime = (rcu_scheduler_active == RCU_SCHEDULER_INIT); |
961 | unsigned long flags; |
962 | struct rcu_exp_work rew; |
963 | struct rcu_node *rnp; |
964 | unsigned long s; |
965 | |
966 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
967 | lock_is_held(&rcu_lock_map) || |
968 | lock_is_held(&rcu_sched_lock_map), |
969 | "Illegal synchronize_rcu_expedited() in RCU read-side critical section" ); |
970 | |
971 | /* Is the state is such that the call is a grace period? */ |
972 | if (rcu_blocking_is_gp()) { |
973 | // Note well that this code runs with !PREEMPT && !SMP. |
974 | // In addition, all code that advances grace periods runs |
975 | // at process level. Therefore, this expedited GP overlaps |
976 | // with other expedited GPs only by being fully nested within |
977 | // them, which allows reuse of ->gp_seq_polled_exp_snap. |
978 | rcu_poll_gp_seq_start_unlocked(snap: &rcu_state.gp_seq_polled_exp_snap); |
979 | rcu_poll_gp_seq_end_unlocked(snap: &rcu_state.gp_seq_polled_exp_snap); |
980 | |
981 | local_irq_save(flags); |
982 | WARN_ON_ONCE(num_online_cpus() > 1); |
983 | rcu_state.expedited_sequence += (1 << RCU_SEQ_CTR_SHIFT); |
984 | local_irq_restore(flags); |
985 | return; // Context allows vacuous grace periods. |
986 | } |
987 | |
988 | /* If expedited grace periods are prohibited, fall back to normal. */ |
989 | if (rcu_gp_is_normal()) { |
990 | wait_rcu_gp(call_rcu_hurry); |
991 | return; |
992 | } |
993 | |
994 | /* Take a snapshot of the sequence number. */ |
995 | s = rcu_exp_gp_seq_snap(); |
996 | if (exp_funnel_lock(s)) |
997 | return; /* Someone else did our work for us. */ |
998 | |
999 | /* Ensure that load happens before action based on it. */ |
1000 | if (unlikely(boottime)) { |
1001 | /* Direct call during scheduler init and early_initcalls(). */ |
1002 | rcu_exp_sel_wait_wake(s); |
1003 | } else { |
1004 | /* Marshall arguments & schedule the expedited grace period. */ |
1005 | rew.rew_s = s; |
1006 | synchronize_rcu_expedited_queue_work(rew: &rew); |
1007 | } |
1008 | |
1009 | /* Wait for expedited grace period to complete. */ |
1010 | rnp = rcu_get_root(); |
1011 | wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], |
1012 | sync_exp_work_done(s)); |
1013 | smp_mb(); /* Work actions happen before return. */ |
1014 | |
1015 | /* Let the next expedited grace period start. */ |
1016 | mutex_unlock(lock: &rcu_state.exp_mutex); |
1017 | |
1018 | if (likely(!boottime)) |
1019 | synchronize_rcu_expedited_destroy_work(rew: &rew); |
1020 | } |
1021 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
1022 | |
1023 | /* |
1024 | * Ensure that start_poll_synchronize_rcu_expedited() has the expedited |
1025 | * RCU grace periods that it needs. |
1026 | */ |
1027 | static void sync_rcu_do_polled_gp(struct work_struct *wp) |
1028 | { |
1029 | unsigned long flags; |
1030 | int i = 0; |
1031 | struct rcu_node *rnp = container_of(wp, struct rcu_node, exp_poll_wq); |
1032 | unsigned long s; |
1033 | |
1034 | raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags); |
1035 | s = rnp->exp_seq_poll_rq; |
1036 | rnp->exp_seq_poll_rq = RCU_GET_STATE_COMPLETED; |
1037 | raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags); |
1038 | if (s == RCU_GET_STATE_COMPLETED) |
1039 | return; |
1040 | while (!poll_state_synchronize_rcu(s)) { |
1041 | synchronize_rcu_expedited(); |
1042 | if (i == 10 || i == 20) |
1043 | pr_info("%s: i = %d s = %lx gp_seq_polled = %lx\n" , __func__, i, s, READ_ONCE(rcu_state.gp_seq_polled)); |
1044 | i++; |
1045 | } |
1046 | raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags); |
1047 | s = rnp->exp_seq_poll_rq; |
1048 | if (poll_state_synchronize_rcu(s)) |
1049 | rnp->exp_seq_poll_rq = RCU_GET_STATE_COMPLETED; |
1050 | raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags); |
1051 | } |
1052 | |
1053 | /** |
1054 | * start_poll_synchronize_rcu_expedited - Snapshot current RCU state and start expedited grace period |
1055 | * |
1056 | * Returns a cookie to pass to a call to cond_synchronize_rcu(), |
1057 | * cond_synchronize_rcu_expedited(), or poll_state_synchronize_rcu(), |
1058 | * allowing them to determine whether or not any sort of grace period has |
1059 | * elapsed in the meantime. If the needed expedited grace period is not |
1060 | * already slated to start, initiates that grace period. |
1061 | */ |
1062 | unsigned long start_poll_synchronize_rcu_expedited(void) |
1063 | { |
1064 | unsigned long flags; |
1065 | struct rcu_data *rdp; |
1066 | struct rcu_node *rnp; |
1067 | unsigned long s; |
1068 | |
1069 | s = get_state_synchronize_rcu(); |
1070 | rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id()); |
1071 | rnp = rdp->mynode; |
1072 | if (rcu_init_invoked()) |
1073 | raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags); |
1074 | if (!poll_state_synchronize_rcu(s)) { |
1075 | if (rcu_init_invoked()) { |
1076 | rnp->exp_seq_poll_rq = s; |
1077 | queue_work(wq: rcu_gp_wq, work: &rnp->exp_poll_wq); |
1078 | } |
1079 | } |
1080 | if (rcu_init_invoked()) |
1081 | raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags); |
1082 | |
1083 | return s; |
1084 | } |
1085 | EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu_expedited); |
1086 | |
1087 | /** |
1088 | * start_poll_synchronize_rcu_expedited_full - Take a full snapshot and start expedited grace period |
1089 | * @rgosp: Place to put snapshot of grace-period state |
1090 | * |
1091 | * Places the normal and expedited grace-period states in rgosp. This |
1092 | * state value can be passed to a later call to cond_synchronize_rcu_full() |
1093 | * or poll_state_synchronize_rcu_full() to determine whether or not a |
1094 | * grace period (whether normal or expedited) has elapsed in the meantime. |
1095 | * If the needed expedited grace period is not already slated to start, |
1096 | * initiates that grace period. |
1097 | */ |
1098 | void start_poll_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp) |
1099 | { |
1100 | get_state_synchronize_rcu_full(rgosp); |
1101 | (void)start_poll_synchronize_rcu_expedited(); |
1102 | } |
1103 | EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu_expedited_full); |
1104 | |
1105 | /** |
1106 | * cond_synchronize_rcu_expedited - Conditionally wait for an expedited RCU grace period |
1107 | * |
1108 | * @oldstate: value from get_state_synchronize_rcu(), start_poll_synchronize_rcu(), or start_poll_synchronize_rcu_expedited() |
1109 | * |
1110 | * If any type of full RCU grace period has elapsed since the earlier |
1111 | * call to get_state_synchronize_rcu(), start_poll_synchronize_rcu(), |
1112 | * or start_poll_synchronize_rcu_expedited(), just return. Otherwise, |
1113 | * invoke synchronize_rcu_expedited() to wait for a full grace period. |
1114 | * |
1115 | * Yes, this function does not take counter wrap into account. |
1116 | * But counter wrap is harmless. If the counter wraps, we have waited for |
1117 | * more than 2 billion grace periods (and way more on a 64-bit system!), |
1118 | * so waiting for a couple of additional grace periods should be just fine. |
1119 | * |
1120 | * This function provides the same memory-ordering guarantees that |
1121 | * would be provided by a synchronize_rcu() that was invoked at the call |
1122 | * to the function that provided @oldstate and that returned at the end |
1123 | * of this function. |
1124 | */ |
1125 | void cond_synchronize_rcu_expedited(unsigned long oldstate) |
1126 | { |
1127 | if (!poll_state_synchronize_rcu(oldstate)) |
1128 | synchronize_rcu_expedited(); |
1129 | } |
1130 | EXPORT_SYMBOL_GPL(cond_synchronize_rcu_expedited); |
1131 | |
1132 | /** |
1133 | * cond_synchronize_rcu_expedited_full - Conditionally wait for an expedited RCU grace period |
1134 | * @rgosp: value from get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(), or start_poll_synchronize_rcu_expedited_full() |
1135 | * |
1136 | * If a full RCU grace period has elapsed since the call to |
1137 | * get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(), |
1138 | * or start_poll_synchronize_rcu_expedited_full() from which @rgosp was |
1139 | * obtained, just return. Otherwise, invoke synchronize_rcu_expedited() |
1140 | * to wait for a full grace period. |
1141 | * |
1142 | * Yes, this function does not take counter wrap into account. |
1143 | * But counter wrap is harmless. If the counter wraps, we have waited for |
1144 | * more than 2 billion grace periods (and way more on a 64-bit system!), |
1145 | * so waiting for a couple of additional grace periods should be just fine. |
1146 | * |
1147 | * This function provides the same memory-ordering guarantees that |
1148 | * would be provided by a synchronize_rcu() that was invoked at the call |
1149 | * to the function that provided @rgosp and that returned at the end of |
1150 | * this function. |
1151 | */ |
1152 | void cond_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp) |
1153 | { |
1154 | if (!poll_state_synchronize_rcu_full(rgosp)) |
1155 | synchronize_rcu_expedited(); |
1156 | } |
1157 | EXPORT_SYMBOL_GPL(cond_synchronize_rcu_expedited_full); |
1158 | |