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f41d911f PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion (tree-based version) | |
3 | * Internal non-public definitions that provide either classic | |
6cc68793 | 4 | * or preemptible semantics. |
f41d911f PM |
5 | * |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License as published by | |
8 | * the Free Software Foundation; either version 2 of the License, or | |
9 | * (at your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | * GNU General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
87de1cfd PM |
17 | * along with this program; if not, you can access it online at |
18 | * http://www.gnu.org/licenses/gpl-2.0.html. | |
f41d911f PM |
19 | * |
20 | * Copyright Red Hat, 2009 | |
21 | * Copyright IBM Corporation, 2009 | |
22 | * | |
23 | * Author: Ingo Molnar <mingo@elte.hu> | |
24 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> | |
25 | */ | |
26 | ||
d9a3da06 | 27 | #include <linux/delay.h> |
3fbfbf7a | 28 | #include <linux/gfp.h> |
b626c1b6 | 29 | #include <linux/oom.h> |
62ab7072 | 30 | #include <linux/smpboot.h> |
4102adab | 31 | #include "../time/tick-internal.h" |
f41d911f | 32 | |
5b61b0ba | 33 | #ifdef CONFIG_RCU_BOOST |
61cfd097 | 34 | |
abaa93d9 | 35 | #include "../locking/rtmutex_common.h" |
21871d7e CW |
36 | |
37 | /* rcuc/rcub kthread realtime priority */ | |
38 | static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO; | |
39 | module_param(kthread_prio, int, 0644); | |
61cfd097 PM |
40 | |
41 | /* | |
42 | * Control variables for per-CPU and per-rcu_node kthreads. These | |
43 | * handle all flavors of RCU. | |
44 | */ | |
45 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); | |
46 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); | |
47 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); | |
48 | DEFINE_PER_CPU(char, rcu_cpu_has_work); | |
49 | ||
21871d7e | 50 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
5b61b0ba | 51 | |
3fbfbf7a PM |
52 | #ifdef CONFIG_RCU_NOCB_CPU |
53 | static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ | |
54 | static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */ | |
1b0048a4 | 55 | static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ |
3fbfbf7a PM |
56 | static char __initdata nocb_buf[NR_CPUS * 5]; |
57 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ | |
58 | ||
26845c28 PM |
59 | /* |
60 | * Check the RCU kernel configuration parameters and print informative | |
61 | * messages about anything out of the ordinary. If you like #ifdef, you | |
62 | * will love this function. | |
63 | */ | |
64 | static void __init rcu_bootup_announce_oddness(void) | |
65 | { | |
66 | #ifdef CONFIG_RCU_TRACE | |
efc151c3 | 67 | pr_info("\tRCU debugfs-based tracing is enabled.\n"); |
26845c28 PM |
68 | #endif |
69 | #if (defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) || (!defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32) | |
efc151c3 | 70 | pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n", |
26845c28 PM |
71 | CONFIG_RCU_FANOUT); |
72 | #endif | |
73 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
efc151c3 | 74 | pr_info("\tHierarchical RCU autobalancing is disabled.\n"); |
26845c28 PM |
75 | #endif |
76 | #ifdef CONFIG_RCU_FAST_NO_HZ | |
efc151c3 | 77 | pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n"); |
26845c28 PM |
78 | #endif |
79 | #ifdef CONFIG_PROVE_RCU | |
efc151c3 | 80 | pr_info("\tRCU lockdep checking is enabled.\n"); |
26845c28 PM |
81 | #endif |
82 | #ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE | |
efc151c3 | 83 | pr_info("\tRCU torture testing starts during boot.\n"); |
26845c28 | 84 | #endif |
a858af28 | 85 | #if defined(CONFIG_RCU_CPU_STALL_INFO) |
efc151c3 | 86 | pr_info("\tAdditional per-CPU info printed with stalls.\n"); |
26845c28 PM |
87 | #endif |
88 | #if NUM_RCU_LVL_4 != 0 | |
efc151c3 | 89 | pr_info("\tFour-level hierarchy is enabled.\n"); |
26845c28 | 90 | #endif |
f885b7f2 | 91 | if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF) |
9a5739d7 | 92 | pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf); |
cca6f393 | 93 | if (nr_cpu_ids != NR_CPUS) |
efc151c3 | 94 | pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); |
21871d7e CW |
95 | #ifdef CONFIG_RCU_BOOST |
96 | pr_info("\tRCU kthread priority: %d.\n", kthread_prio); | |
97 | #endif | |
26845c28 PM |
98 | } |
99 | ||
28f6569a | 100 | #ifdef CONFIG_PREEMPT_RCU |
f41d911f | 101 | |
a41bfeb2 | 102 | RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); |
e534165b | 103 | static struct rcu_state *rcu_state_p = &rcu_preempt_state; |
f41d911f | 104 | |
d9a3da06 | 105 | static int rcu_preempted_readers_exp(struct rcu_node *rnp); |
d19fb8d1 PM |
106 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
107 | bool wake); | |
d9a3da06 | 108 | |
f41d911f PM |
109 | /* |
110 | * Tell them what RCU they are running. | |
111 | */ | |
0e0fc1c2 | 112 | static void __init rcu_bootup_announce(void) |
f41d911f | 113 | { |
efc151c3 | 114 | pr_info("Preemptible hierarchical RCU implementation.\n"); |
26845c28 | 115 | rcu_bootup_announce_oddness(); |
f41d911f PM |
116 | } |
117 | ||
118 | /* | |
119 | * Return the number of RCU-preempt batches processed thus far | |
120 | * for debug and statistics. | |
121 | */ | |
bf33eb1a | 122 | static long rcu_batches_completed_preempt(void) |
f41d911f PM |
123 | { |
124 | return rcu_preempt_state.completed; | |
125 | } | |
126 | EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt); | |
127 | ||
128 | /* | |
129 | * Return the number of RCU batches processed thus far for debug & stats. | |
130 | */ | |
131 | long rcu_batches_completed(void) | |
132 | { | |
133 | return rcu_batches_completed_preempt(); | |
134 | } | |
135 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
136 | ||
137 | /* | |
6cc68793 | 138 | * Record a preemptible-RCU quiescent state for the specified CPU. Note |
f41d911f PM |
139 | * that this just means that the task currently running on the CPU is |
140 | * not in a quiescent state. There might be any number of tasks blocked | |
141 | * while in an RCU read-side critical section. | |
25502a6c | 142 | * |
1d082fd0 PM |
143 | * As with the other rcu_*_qs() functions, callers to this function |
144 | * must disable preemption. | |
f41d911f | 145 | */ |
284a8c93 | 146 | static void rcu_preempt_qs(void) |
f41d911f | 147 | { |
284a8c93 PM |
148 | if (!__this_cpu_read(rcu_preempt_data.passed_quiesce)) { |
149 | trace_rcu_grace_period(TPS("rcu_preempt"), | |
150 | __this_cpu_read(rcu_preempt_data.gpnum), | |
151 | TPS("cpuqs")); | |
152 | __this_cpu_write(rcu_preempt_data.passed_quiesce, 1); | |
153 | barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */ | |
154 | current->rcu_read_unlock_special.b.need_qs = false; | |
155 | } | |
f41d911f PM |
156 | } |
157 | ||
158 | /* | |
c3422bea PM |
159 | * We have entered the scheduler, and the current task might soon be |
160 | * context-switched away from. If this task is in an RCU read-side | |
161 | * critical section, we will no longer be able to rely on the CPU to | |
12f5f524 PM |
162 | * record that fact, so we enqueue the task on the blkd_tasks list. |
163 | * The task will dequeue itself when it exits the outermost enclosing | |
164 | * RCU read-side critical section. Therefore, the current grace period | |
165 | * cannot be permitted to complete until the blkd_tasks list entries | |
166 | * predating the current grace period drain, in other words, until | |
167 | * rnp->gp_tasks becomes NULL. | |
c3422bea PM |
168 | * |
169 | * Caller must disable preemption. | |
f41d911f | 170 | */ |
38200cf2 | 171 | static void rcu_preempt_note_context_switch(void) |
f41d911f PM |
172 | { |
173 | struct task_struct *t = current; | |
c3422bea | 174 | unsigned long flags; |
f41d911f PM |
175 | struct rcu_data *rdp; |
176 | struct rcu_node *rnp; | |
177 | ||
10f39bb1 | 178 | if (t->rcu_read_lock_nesting > 0 && |
1d082fd0 | 179 | !t->rcu_read_unlock_special.b.blocked) { |
f41d911f PM |
180 | |
181 | /* Possibly blocking in an RCU read-side critical section. */ | |
38200cf2 | 182 | rdp = this_cpu_ptr(rcu_preempt_state.rda); |
f41d911f | 183 | rnp = rdp->mynode; |
1304afb2 | 184 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 185 | smp_mb__after_unlock_lock(); |
1d082fd0 | 186 | t->rcu_read_unlock_special.b.blocked = true; |
86848966 | 187 | t->rcu_blocked_node = rnp; |
f41d911f PM |
188 | |
189 | /* | |
190 | * If this CPU has already checked in, then this task | |
191 | * will hold up the next grace period rather than the | |
192 | * current grace period. Queue the task accordingly. | |
193 | * If the task is queued for the current grace period | |
194 | * (i.e., this CPU has not yet passed through a quiescent | |
195 | * state for the current grace period), then as long | |
196 | * as that task remains queued, the current grace period | |
12f5f524 PM |
197 | * cannot end. Note that there is some uncertainty as |
198 | * to exactly when the current grace period started. | |
199 | * We take a conservative approach, which can result | |
200 | * in unnecessarily waiting on tasks that started very | |
201 | * slightly after the current grace period began. C'est | |
202 | * la vie!!! | |
b0e165c0 PM |
203 | * |
204 | * But first, note that the current CPU must still be | |
205 | * on line! | |
f41d911f | 206 | */ |
b0e165c0 | 207 | WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0); |
e7d8842e | 208 | WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); |
12f5f524 PM |
209 | if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) { |
210 | list_add(&t->rcu_node_entry, rnp->gp_tasks->prev); | |
211 | rnp->gp_tasks = &t->rcu_node_entry; | |
27f4d280 PM |
212 | #ifdef CONFIG_RCU_BOOST |
213 | if (rnp->boost_tasks != NULL) | |
214 | rnp->boost_tasks = rnp->gp_tasks; | |
215 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
12f5f524 PM |
216 | } else { |
217 | list_add(&t->rcu_node_entry, &rnp->blkd_tasks); | |
218 | if (rnp->qsmask & rdp->grpmask) | |
219 | rnp->gp_tasks = &t->rcu_node_entry; | |
220 | } | |
d4c08f2a PM |
221 | trace_rcu_preempt_task(rdp->rsp->name, |
222 | t->pid, | |
223 | (rnp->qsmask & rdp->grpmask) | |
224 | ? rnp->gpnum | |
225 | : rnp->gpnum + 1); | |
1304afb2 | 226 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
10f39bb1 | 227 | } else if (t->rcu_read_lock_nesting < 0 && |
1d082fd0 | 228 | t->rcu_read_unlock_special.s) { |
10f39bb1 PM |
229 | |
230 | /* | |
231 | * Complete exit from RCU read-side critical section on | |
232 | * behalf of preempted instance of __rcu_read_unlock(). | |
233 | */ | |
234 | rcu_read_unlock_special(t); | |
f41d911f PM |
235 | } |
236 | ||
237 | /* | |
238 | * Either we were not in an RCU read-side critical section to | |
239 | * begin with, or we have now recorded that critical section | |
240 | * globally. Either way, we can now note a quiescent state | |
241 | * for this CPU. Again, if we were in an RCU read-side critical | |
242 | * section, and if that critical section was blocking the current | |
243 | * grace period, then the fact that the task has been enqueued | |
244 | * means that we continue to block the current grace period. | |
245 | */ | |
284a8c93 | 246 | rcu_preempt_qs(); |
f41d911f PM |
247 | } |
248 | ||
fc2219d4 PM |
249 | /* |
250 | * Check for preempted RCU readers blocking the current grace period | |
251 | * for the specified rcu_node structure. If the caller needs a reliable | |
252 | * answer, it must hold the rcu_node's ->lock. | |
253 | */ | |
27f4d280 | 254 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
fc2219d4 | 255 | { |
12f5f524 | 256 | return rnp->gp_tasks != NULL; |
fc2219d4 PM |
257 | } |
258 | ||
b668c9cf PM |
259 | /* |
260 | * Record a quiescent state for all tasks that were previously queued | |
261 | * on the specified rcu_node structure and that were blocking the current | |
262 | * RCU grace period. The caller must hold the specified rnp->lock with | |
263 | * irqs disabled, and this lock is released upon return, but irqs remain | |
264 | * disabled. | |
265 | */ | |
d3f6bad3 | 266 | static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
b668c9cf PM |
267 | __releases(rnp->lock) |
268 | { | |
269 | unsigned long mask; | |
270 | struct rcu_node *rnp_p; | |
271 | ||
27f4d280 | 272 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
1304afb2 | 273 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b668c9cf PM |
274 | return; /* Still need more quiescent states! */ |
275 | } | |
276 | ||
277 | rnp_p = rnp->parent; | |
278 | if (rnp_p == NULL) { | |
279 | /* | |
280 | * Either there is only one rcu_node in the tree, | |
281 | * or tasks were kicked up to root rcu_node due to | |
282 | * CPUs going offline. | |
283 | */ | |
d3f6bad3 | 284 | rcu_report_qs_rsp(&rcu_preempt_state, flags); |
b668c9cf PM |
285 | return; |
286 | } | |
287 | ||
288 | /* Report up the rest of the hierarchy. */ | |
289 | mask = rnp->grpmask; | |
1304afb2 PM |
290 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
291 | raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */ | |
6303b9c8 | 292 | smp_mb__after_unlock_lock(); |
d3f6bad3 | 293 | rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags); |
b668c9cf PM |
294 | } |
295 | ||
12f5f524 PM |
296 | /* |
297 | * Advance a ->blkd_tasks-list pointer to the next entry, instead | |
298 | * returning NULL if at the end of the list. | |
299 | */ | |
300 | static struct list_head *rcu_next_node_entry(struct task_struct *t, | |
301 | struct rcu_node *rnp) | |
302 | { | |
303 | struct list_head *np; | |
304 | ||
305 | np = t->rcu_node_entry.next; | |
306 | if (np == &rnp->blkd_tasks) | |
307 | np = NULL; | |
308 | return np; | |
309 | } | |
310 | ||
8af3a5e7 PM |
311 | /* |
312 | * Return true if the specified rcu_node structure has tasks that were | |
313 | * preempted within an RCU read-side critical section. | |
314 | */ | |
315 | static bool rcu_preempt_has_tasks(struct rcu_node *rnp) | |
316 | { | |
317 | return !list_empty(&rnp->blkd_tasks); | |
318 | } | |
319 | ||
b668c9cf PM |
320 | /* |
321 | * Handle special cases during rcu_read_unlock(), such as needing to | |
322 | * notify RCU core processing or task having blocked during the RCU | |
323 | * read-side critical section. | |
324 | */ | |
2a3fa843 | 325 | void rcu_read_unlock_special(struct task_struct *t) |
f41d911f | 326 | { |
b6a932d1 PM |
327 | bool empty; |
328 | bool empty_exp; | |
329 | bool empty_norm; | |
330 | bool empty_exp_now; | |
f41d911f | 331 | unsigned long flags; |
12f5f524 | 332 | struct list_head *np; |
82e78d80 | 333 | #ifdef CONFIG_RCU_BOOST |
abaa93d9 | 334 | bool drop_boost_mutex = false; |
82e78d80 | 335 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
f41d911f | 336 | struct rcu_node *rnp; |
1d082fd0 | 337 | union rcu_special special; |
f41d911f PM |
338 | |
339 | /* NMI handlers cannot block and cannot safely manipulate state. */ | |
340 | if (in_nmi()) | |
341 | return; | |
342 | ||
343 | local_irq_save(flags); | |
344 | ||
345 | /* | |
346 | * If RCU core is waiting for this CPU to exit critical section, | |
1d082fd0 PM |
347 | * let it know that we have done so. Because irqs are disabled, |
348 | * t->rcu_read_unlock_special cannot change. | |
f41d911f PM |
349 | */ |
350 | special = t->rcu_read_unlock_special; | |
1d082fd0 | 351 | if (special.b.need_qs) { |
284a8c93 | 352 | rcu_preempt_qs(); |
1d082fd0 | 353 | if (!t->rcu_read_unlock_special.s) { |
79a62f95 LJ |
354 | local_irq_restore(flags); |
355 | return; | |
356 | } | |
f41d911f PM |
357 | } |
358 | ||
79a62f95 LJ |
359 | /* Hardware IRQ handlers cannot block, complain if they get here. */ |
360 | if (WARN_ON_ONCE(in_irq() || in_serving_softirq())) { | |
f41d911f PM |
361 | local_irq_restore(flags); |
362 | return; | |
363 | } | |
364 | ||
365 | /* Clean up if blocked during RCU read-side critical section. */ | |
1d082fd0 PM |
366 | if (special.b.blocked) { |
367 | t->rcu_read_unlock_special.b.blocked = false; | |
f41d911f | 368 | |
dd5d19ba PM |
369 | /* |
370 | * Remove this task from the list it blocked on. The | |
371 | * task can migrate while we acquire the lock, but at | |
372 | * most one time. So at most two passes through loop. | |
373 | */ | |
374 | for (;;) { | |
86848966 | 375 | rnp = t->rcu_blocked_node; |
1304afb2 | 376 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
6303b9c8 | 377 | smp_mb__after_unlock_lock(); |
86848966 | 378 | if (rnp == t->rcu_blocked_node) |
dd5d19ba | 379 | break; |
1304afb2 | 380 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
dd5d19ba | 381 | } |
b6a932d1 | 382 | empty = !rcu_preempt_has_tasks(rnp); |
74e871ac | 383 | empty_norm = !rcu_preempt_blocked_readers_cgp(rnp); |
d9a3da06 PM |
384 | empty_exp = !rcu_preempted_readers_exp(rnp); |
385 | smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ | |
12f5f524 | 386 | np = rcu_next_node_entry(t, rnp); |
f41d911f | 387 | list_del_init(&t->rcu_node_entry); |
82e78d80 | 388 | t->rcu_blocked_node = NULL; |
f7f7bac9 | 389 | trace_rcu_unlock_preempted_task(TPS("rcu_preempt"), |
d4c08f2a | 390 | rnp->gpnum, t->pid); |
12f5f524 PM |
391 | if (&t->rcu_node_entry == rnp->gp_tasks) |
392 | rnp->gp_tasks = np; | |
393 | if (&t->rcu_node_entry == rnp->exp_tasks) | |
394 | rnp->exp_tasks = np; | |
27f4d280 PM |
395 | #ifdef CONFIG_RCU_BOOST |
396 | if (&t->rcu_node_entry == rnp->boost_tasks) | |
397 | rnp->boost_tasks = np; | |
abaa93d9 PM |
398 | /* Snapshot ->boost_mtx ownership with rcu_node lock held. */ |
399 | drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t; | |
27f4d280 | 400 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
f41d911f | 401 | |
b6a932d1 PM |
402 | /* |
403 | * If this was the last task on the list, go see if we | |
404 | * need to propagate ->qsmaskinit bit clearing up the | |
405 | * rcu_node tree. | |
406 | */ | |
407 | if (!empty && !rcu_preempt_has_tasks(rnp)) | |
408 | rcu_cleanup_dead_rnp(rnp); | |
409 | ||
f41d911f PM |
410 | /* |
411 | * If this was the last task on the current list, and if | |
412 | * we aren't waiting on any CPUs, report the quiescent state. | |
389abd48 PM |
413 | * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, |
414 | * so we must take a snapshot of the expedited state. | |
f41d911f | 415 | */ |
389abd48 | 416 | empty_exp_now = !rcu_preempted_readers_exp(rnp); |
74e871ac | 417 | if (!empty_norm && !rcu_preempt_blocked_readers_cgp(rnp)) { |
f7f7bac9 | 418 | trace_rcu_quiescent_state_report(TPS("preempt_rcu"), |
d4c08f2a PM |
419 | rnp->gpnum, |
420 | 0, rnp->qsmask, | |
421 | rnp->level, | |
422 | rnp->grplo, | |
423 | rnp->grphi, | |
424 | !!rnp->gp_tasks); | |
d3f6bad3 | 425 | rcu_report_unblock_qs_rnp(rnp, flags); |
c701d5d9 | 426 | } else { |
d4c08f2a | 427 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c701d5d9 | 428 | } |
d9a3da06 | 429 | |
27f4d280 PM |
430 | #ifdef CONFIG_RCU_BOOST |
431 | /* Unboost if we were boosted. */ | |
abaa93d9 PM |
432 | if (drop_boost_mutex) { |
433 | rt_mutex_unlock(&rnp->boost_mtx); | |
dfeb9765 PM |
434 | complete(&rnp->boost_completion); |
435 | } | |
27f4d280 PM |
436 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
437 | ||
d9a3da06 PM |
438 | /* |
439 | * If this was the last task on the expedited lists, | |
440 | * then we need to report up the rcu_node hierarchy. | |
441 | */ | |
389abd48 | 442 | if (!empty_exp && empty_exp_now) |
b40d293e | 443 | rcu_report_exp_rnp(&rcu_preempt_state, rnp, true); |
b668c9cf PM |
444 | } else { |
445 | local_irq_restore(flags); | |
f41d911f | 446 | } |
f41d911f PM |
447 | } |
448 | ||
1ed509a2 PM |
449 | /* |
450 | * Dump detailed information for all tasks blocking the current RCU | |
451 | * grace period on the specified rcu_node structure. | |
452 | */ | |
453 | static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) | |
454 | { | |
455 | unsigned long flags; | |
1ed509a2 PM |
456 | struct task_struct *t; |
457 | ||
12f5f524 | 458 | raw_spin_lock_irqsave(&rnp->lock, flags); |
5fd4dc06 PM |
459 | if (!rcu_preempt_blocked_readers_cgp(rnp)) { |
460 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
461 | return; | |
462 | } | |
12f5f524 PM |
463 | t = list_entry(rnp->gp_tasks, |
464 | struct task_struct, rcu_node_entry); | |
465 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) | |
466 | sched_show_task(t); | |
467 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1ed509a2 PM |
468 | } |
469 | ||
470 | /* | |
471 | * Dump detailed information for all tasks blocking the current RCU | |
472 | * grace period. | |
473 | */ | |
474 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) | |
475 | { | |
476 | struct rcu_node *rnp = rcu_get_root(rsp); | |
477 | ||
478 | rcu_print_detail_task_stall_rnp(rnp); | |
479 | rcu_for_each_leaf_node(rsp, rnp) | |
480 | rcu_print_detail_task_stall_rnp(rnp); | |
481 | } | |
482 | ||
a858af28 PM |
483 | #ifdef CONFIG_RCU_CPU_STALL_INFO |
484 | ||
485 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) | |
486 | { | |
efc151c3 | 487 | pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", |
a858af28 PM |
488 | rnp->level, rnp->grplo, rnp->grphi); |
489 | } | |
490 | ||
491 | static void rcu_print_task_stall_end(void) | |
492 | { | |
efc151c3 | 493 | pr_cont("\n"); |
a858af28 PM |
494 | } |
495 | ||
496 | #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
497 | ||
498 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) | |
499 | { | |
500 | } | |
501 | ||
502 | static void rcu_print_task_stall_end(void) | |
503 | { | |
504 | } | |
505 | ||
506 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
507 | ||
f41d911f PM |
508 | /* |
509 | * Scan the current list of tasks blocked within RCU read-side critical | |
510 | * sections, printing out the tid of each. | |
511 | */ | |
9bc8b558 | 512 | static int rcu_print_task_stall(struct rcu_node *rnp) |
f41d911f | 513 | { |
f41d911f | 514 | struct task_struct *t; |
9bc8b558 | 515 | int ndetected = 0; |
f41d911f | 516 | |
27f4d280 | 517 | if (!rcu_preempt_blocked_readers_cgp(rnp)) |
9bc8b558 | 518 | return 0; |
a858af28 | 519 | rcu_print_task_stall_begin(rnp); |
12f5f524 PM |
520 | t = list_entry(rnp->gp_tasks, |
521 | struct task_struct, rcu_node_entry); | |
9bc8b558 | 522 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
efc151c3 | 523 | pr_cont(" P%d", t->pid); |
9bc8b558 PM |
524 | ndetected++; |
525 | } | |
a858af28 | 526 | rcu_print_task_stall_end(); |
9bc8b558 | 527 | return ndetected; |
f41d911f PM |
528 | } |
529 | ||
b0e165c0 PM |
530 | /* |
531 | * Check that the list of blocked tasks for the newly completed grace | |
532 | * period is in fact empty. It is a serious bug to complete a grace | |
533 | * period that still has RCU readers blocked! This function must be | |
534 | * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock | |
535 | * must be held by the caller. | |
12f5f524 PM |
536 | * |
537 | * Also, if there are blocked tasks on the list, they automatically | |
538 | * block the newly created grace period, so set up ->gp_tasks accordingly. | |
b0e165c0 PM |
539 | */ |
540 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) | |
541 | { | |
27f4d280 | 542 | WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
96e92021 | 543 | if (rcu_preempt_has_tasks(rnp)) |
12f5f524 | 544 | rnp->gp_tasks = rnp->blkd_tasks.next; |
28ecd580 | 545 | WARN_ON_ONCE(rnp->qsmask); |
b0e165c0 PM |
546 | } |
547 | ||
33f76148 PM |
548 | #ifdef CONFIG_HOTPLUG_CPU |
549 | ||
e5601400 PM |
550 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
551 | ||
f41d911f PM |
552 | /* |
553 | * Check for a quiescent state from the current CPU. When a task blocks, | |
554 | * the task is recorded in the corresponding CPU's rcu_node structure, | |
555 | * which is checked elsewhere. | |
556 | * | |
557 | * Caller must disable hard irqs. | |
558 | */ | |
86aea0e6 | 559 | static void rcu_preempt_check_callbacks(void) |
f41d911f PM |
560 | { |
561 | struct task_struct *t = current; | |
562 | ||
563 | if (t->rcu_read_lock_nesting == 0) { | |
284a8c93 | 564 | rcu_preempt_qs(); |
f41d911f PM |
565 | return; |
566 | } | |
10f39bb1 | 567 | if (t->rcu_read_lock_nesting > 0 && |
86aea0e6 PM |
568 | __this_cpu_read(rcu_preempt_data.qs_pending) && |
569 | !__this_cpu_read(rcu_preempt_data.passed_quiesce)) | |
1d082fd0 | 570 | t->rcu_read_unlock_special.b.need_qs = true; |
f41d911f PM |
571 | } |
572 | ||
a46e0899 PM |
573 | #ifdef CONFIG_RCU_BOOST |
574 | ||
09223371 SL |
575 | static void rcu_preempt_do_callbacks(void) |
576 | { | |
c9d4b0af | 577 | rcu_do_batch(&rcu_preempt_state, this_cpu_ptr(&rcu_preempt_data)); |
09223371 SL |
578 | } |
579 | ||
a46e0899 PM |
580 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
581 | ||
f41d911f | 582 | /* |
6cc68793 | 583 | * Queue a preemptible-RCU callback for invocation after a grace period. |
f41d911f PM |
584 | */ |
585 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
586 | { | |
3fbfbf7a | 587 | __call_rcu(head, func, &rcu_preempt_state, -1, 0); |
f41d911f PM |
588 | } |
589 | EXPORT_SYMBOL_GPL(call_rcu); | |
590 | ||
6ebb237b PM |
591 | /** |
592 | * synchronize_rcu - wait until a grace period has elapsed. | |
593 | * | |
594 | * Control will return to the caller some time after a full grace | |
595 | * period has elapsed, in other words after all currently executing RCU | |
77d8485a PM |
596 | * read-side critical sections have completed. Note, however, that |
597 | * upon return from synchronize_rcu(), the caller might well be executing | |
598 | * concurrently with new RCU read-side critical sections that began while | |
599 | * synchronize_rcu() was waiting. RCU read-side critical sections are | |
600 | * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. | |
f0a0e6f2 PM |
601 | * |
602 | * See the description of synchronize_sched() for more detailed information | |
603 | * on memory ordering guarantees. | |
6ebb237b PM |
604 | */ |
605 | void synchronize_rcu(void) | |
606 | { | |
fe15d706 PM |
607 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
608 | !lock_is_held(&rcu_lock_map) && | |
609 | !lock_is_held(&rcu_sched_lock_map), | |
610 | "Illegal synchronize_rcu() in RCU read-side critical section"); | |
6ebb237b PM |
611 | if (!rcu_scheduler_active) |
612 | return; | |
3705b88d AM |
613 | if (rcu_expedited) |
614 | synchronize_rcu_expedited(); | |
615 | else | |
616 | wait_rcu_gp(call_rcu); | |
6ebb237b PM |
617 | } |
618 | EXPORT_SYMBOL_GPL(synchronize_rcu); | |
619 | ||
d9a3da06 | 620 | static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); |
bcfa57ce | 621 | static unsigned long sync_rcu_preempt_exp_count; |
d9a3da06 PM |
622 | static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); |
623 | ||
624 | /* | |
625 | * Return non-zero if there are any tasks in RCU read-side critical | |
626 | * sections blocking the current preemptible-RCU expedited grace period. | |
627 | * If there is no preemptible-RCU expedited grace period currently in | |
628 | * progress, returns zero unconditionally. | |
629 | */ | |
630 | static int rcu_preempted_readers_exp(struct rcu_node *rnp) | |
631 | { | |
12f5f524 | 632 | return rnp->exp_tasks != NULL; |
d9a3da06 PM |
633 | } |
634 | ||
635 | /* | |
636 | * return non-zero if there is no RCU expedited grace period in progress | |
637 | * for the specified rcu_node structure, in other words, if all CPUs and | |
638 | * tasks covered by the specified rcu_node structure have done their bit | |
639 | * for the current expedited grace period. Works only for preemptible | |
640 | * RCU -- other RCU implementation use other means. | |
641 | * | |
642 | * Caller must hold sync_rcu_preempt_exp_mutex. | |
643 | */ | |
644 | static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) | |
645 | { | |
646 | return !rcu_preempted_readers_exp(rnp) && | |
647 | ACCESS_ONCE(rnp->expmask) == 0; | |
648 | } | |
649 | ||
650 | /* | |
651 | * Report the exit from RCU read-side critical section for the last task | |
652 | * that queued itself during or before the current expedited preemptible-RCU | |
653 | * grace period. This event is reported either to the rcu_node structure on | |
654 | * which the task was queued or to one of that rcu_node structure's ancestors, | |
655 | * recursively up the tree. (Calm down, calm down, we do the recursion | |
656 | * iteratively!) | |
657 | * | |
b40d293e TG |
658 | * Most callers will set the "wake" flag, but the task initiating the |
659 | * expedited grace period need not wake itself. | |
660 | * | |
d9a3da06 PM |
661 | * Caller must hold sync_rcu_preempt_exp_mutex. |
662 | */ | |
b40d293e TG |
663 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
664 | bool wake) | |
d9a3da06 PM |
665 | { |
666 | unsigned long flags; | |
667 | unsigned long mask; | |
668 | ||
1304afb2 | 669 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 670 | smp_mb__after_unlock_lock(); |
d9a3da06 | 671 | for (;;) { |
131906b0 PM |
672 | if (!sync_rcu_preempt_exp_done(rnp)) { |
673 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
d9a3da06 | 674 | break; |
131906b0 | 675 | } |
d9a3da06 | 676 | if (rnp->parent == NULL) { |
131906b0 | 677 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
78e4bc34 PM |
678 | if (wake) { |
679 | smp_mb(); /* EGP done before wake_up(). */ | |
b40d293e | 680 | wake_up(&sync_rcu_preempt_exp_wq); |
78e4bc34 | 681 | } |
d9a3da06 PM |
682 | break; |
683 | } | |
684 | mask = rnp->grpmask; | |
1304afb2 | 685 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
d9a3da06 | 686 | rnp = rnp->parent; |
1304afb2 | 687 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
6303b9c8 | 688 | smp_mb__after_unlock_lock(); |
d9a3da06 PM |
689 | rnp->expmask &= ~mask; |
690 | } | |
d9a3da06 PM |
691 | } |
692 | ||
693 | /* | |
694 | * Snapshot the tasks blocking the newly started preemptible-RCU expedited | |
695 | * grace period for the specified rcu_node structure. If there are no such | |
696 | * tasks, report it up the rcu_node hierarchy. | |
697 | * | |
7b2e6011 PM |
698 | * Caller must hold sync_rcu_preempt_exp_mutex and must exclude |
699 | * CPU hotplug operations. | |
d9a3da06 PM |
700 | */ |
701 | static void | |
702 | sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp) | |
703 | { | |
1217ed1b | 704 | unsigned long flags; |
12f5f524 | 705 | int must_wait = 0; |
d9a3da06 | 706 | |
1217ed1b | 707 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 708 | smp_mb__after_unlock_lock(); |
96e92021 | 709 | if (!rcu_preempt_has_tasks(rnp)) { |
1217ed1b | 710 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c701d5d9 | 711 | } else { |
12f5f524 | 712 | rnp->exp_tasks = rnp->blkd_tasks.next; |
1217ed1b | 713 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
12f5f524 PM |
714 | must_wait = 1; |
715 | } | |
d9a3da06 | 716 | if (!must_wait) |
b40d293e | 717 | rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */ |
d9a3da06 PM |
718 | } |
719 | ||
236fefaf PM |
720 | /** |
721 | * synchronize_rcu_expedited - Brute-force RCU grace period | |
722 | * | |
723 | * Wait for an RCU-preempt grace period, but expedite it. The basic | |
724 | * idea is to invoke synchronize_sched_expedited() to push all the tasks to | |
725 | * the ->blkd_tasks lists and wait for this list to drain. This consumes | |
726 | * significant time on all CPUs and is unfriendly to real-time workloads, | |
727 | * so is thus not recommended for any sort of common-case code. | |
728 | * In fact, if you are using synchronize_rcu_expedited() in a loop, | |
729 | * please restructure your code to batch your updates, and then Use a | |
730 | * single synchronize_rcu() instead. | |
019129d5 PM |
731 | */ |
732 | void synchronize_rcu_expedited(void) | |
733 | { | |
d9a3da06 PM |
734 | unsigned long flags; |
735 | struct rcu_node *rnp; | |
736 | struct rcu_state *rsp = &rcu_preempt_state; | |
bcfa57ce | 737 | unsigned long snap; |
d9a3da06 PM |
738 | int trycount = 0; |
739 | ||
740 | smp_mb(); /* Caller's modifications seen first by other CPUs. */ | |
741 | snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1; | |
742 | smp_mb(); /* Above access cannot bleed into critical section. */ | |
743 | ||
1943c89d PM |
744 | /* |
745 | * Block CPU-hotplug operations. This means that any CPU-hotplug | |
746 | * operation that finds an rcu_node structure with tasks in the | |
747 | * process of being boosted will know that all tasks blocking | |
748 | * this expedited grace period will already be in the process of | |
749 | * being boosted. This simplifies the process of moving tasks | |
750 | * from leaf to root rcu_node structures. | |
751 | */ | |
dd56af42 PM |
752 | if (!try_get_online_cpus()) { |
753 | /* CPU-hotplug operation in flight, fall back to normal GP. */ | |
754 | wait_rcu_gp(call_rcu); | |
755 | return; | |
756 | } | |
1943c89d | 757 | |
d9a3da06 PM |
758 | /* |
759 | * Acquire lock, falling back to synchronize_rcu() if too many | |
760 | * lock-acquisition failures. Of course, if someone does the | |
761 | * expedited grace period for us, just leave. | |
762 | */ | |
763 | while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) { | |
1943c89d PM |
764 | if (ULONG_CMP_LT(snap, |
765 | ACCESS_ONCE(sync_rcu_preempt_exp_count))) { | |
766 | put_online_cpus(); | |
767 | goto mb_ret; /* Others did our work for us. */ | |
768 | } | |
c701d5d9 | 769 | if (trycount++ < 10) { |
d9a3da06 | 770 | udelay(trycount * num_online_cpus()); |
c701d5d9 | 771 | } else { |
1943c89d | 772 | put_online_cpus(); |
3705b88d | 773 | wait_rcu_gp(call_rcu); |
d9a3da06 PM |
774 | return; |
775 | } | |
d9a3da06 | 776 | } |
1943c89d PM |
777 | if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) { |
778 | put_online_cpus(); | |
d9a3da06 | 779 | goto unlock_mb_ret; /* Others did our work for us. */ |
1943c89d | 780 | } |
d9a3da06 | 781 | |
12f5f524 | 782 | /* force all RCU readers onto ->blkd_tasks lists. */ |
d9a3da06 PM |
783 | synchronize_sched_expedited(); |
784 | ||
d9a3da06 PM |
785 | /* Initialize ->expmask for all non-leaf rcu_node structures. */ |
786 | rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) { | |
1943c89d | 787 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 788 | smp_mb__after_unlock_lock(); |
d9a3da06 | 789 | rnp->expmask = rnp->qsmaskinit; |
1943c89d | 790 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da06 PM |
791 | } |
792 | ||
12f5f524 | 793 | /* Snapshot current state of ->blkd_tasks lists. */ |
d9a3da06 PM |
794 | rcu_for_each_leaf_node(rsp, rnp) |
795 | sync_rcu_preempt_exp_init(rsp, rnp); | |
796 | if (NUM_RCU_NODES > 1) | |
797 | sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp)); | |
798 | ||
1943c89d | 799 | put_online_cpus(); |
d9a3da06 | 800 | |
12f5f524 | 801 | /* Wait for snapshotted ->blkd_tasks lists to drain. */ |
d9a3da06 PM |
802 | rnp = rcu_get_root(rsp); |
803 | wait_event(sync_rcu_preempt_exp_wq, | |
804 | sync_rcu_preempt_exp_done(rnp)); | |
805 | ||
806 | /* Clean up and exit. */ | |
807 | smp_mb(); /* ensure expedited GP seen before counter increment. */ | |
4de376a1 PK |
808 | ACCESS_ONCE(sync_rcu_preempt_exp_count) = |
809 | sync_rcu_preempt_exp_count + 1; | |
d9a3da06 PM |
810 | unlock_mb_ret: |
811 | mutex_unlock(&sync_rcu_preempt_exp_mutex); | |
812 | mb_ret: | |
813 | smp_mb(); /* ensure subsequent action seen after grace period. */ | |
019129d5 PM |
814 | } |
815 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
816 | ||
e74f4c45 PM |
817 | /** |
818 | * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. | |
f0a0e6f2 PM |
819 | * |
820 | * Note that this primitive does not necessarily wait for an RCU grace period | |
821 | * to complete. For example, if there are no RCU callbacks queued anywhere | |
822 | * in the system, then rcu_barrier() is within its rights to return | |
823 | * immediately, without waiting for anything, much less an RCU grace period. | |
e74f4c45 PM |
824 | */ |
825 | void rcu_barrier(void) | |
826 | { | |
037b64ed | 827 | _rcu_barrier(&rcu_preempt_state); |
e74f4c45 PM |
828 | } |
829 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
830 | ||
1eba8f84 | 831 | /* |
6cc68793 | 832 | * Initialize preemptible RCU's state structures. |
1eba8f84 PM |
833 | */ |
834 | static void __init __rcu_init_preempt(void) | |
835 | { | |
394f99a9 | 836 | rcu_init_one(&rcu_preempt_state, &rcu_preempt_data); |
1eba8f84 PM |
837 | } |
838 | ||
2439b696 PM |
839 | /* |
840 | * Check for a task exiting while in a preemptible-RCU read-side | |
841 | * critical section, clean up if so. No need to issue warnings, | |
842 | * as debug_check_no_locks_held() already does this if lockdep | |
843 | * is enabled. | |
844 | */ | |
845 | void exit_rcu(void) | |
846 | { | |
847 | struct task_struct *t = current; | |
848 | ||
849 | if (likely(list_empty(¤t->rcu_node_entry))) | |
850 | return; | |
851 | t->rcu_read_lock_nesting = 1; | |
852 | barrier(); | |
1d082fd0 | 853 | t->rcu_read_unlock_special.b.blocked = true; |
2439b696 PM |
854 | __rcu_read_unlock(); |
855 | } | |
856 | ||
28f6569a | 857 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
f41d911f | 858 | |
e534165b | 859 | static struct rcu_state *rcu_state_p = &rcu_sched_state; |
27f4d280 | 860 | |
f41d911f PM |
861 | /* |
862 | * Tell them what RCU they are running. | |
863 | */ | |
0e0fc1c2 | 864 | static void __init rcu_bootup_announce(void) |
f41d911f | 865 | { |
efc151c3 | 866 | pr_info("Hierarchical RCU implementation.\n"); |
26845c28 | 867 | rcu_bootup_announce_oddness(); |
f41d911f PM |
868 | } |
869 | ||
870 | /* | |
871 | * Return the number of RCU batches processed thus far for debug & stats. | |
872 | */ | |
873 | long rcu_batches_completed(void) | |
874 | { | |
875 | return rcu_batches_completed_sched(); | |
876 | } | |
877 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
878 | ||
cba6d0d6 PM |
879 | /* |
880 | * Because preemptible RCU does not exist, we never have to check for | |
881 | * CPUs being in quiescent states. | |
882 | */ | |
38200cf2 | 883 | static void rcu_preempt_note_context_switch(void) |
cba6d0d6 PM |
884 | { |
885 | } | |
886 | ||
fc2219d4 | 887 | /* |
6cc68793 | 888 | * Because preemptible RCU does not exist, there are never any preempted |
fc2219d4 PM |
889 | * RCU readers. |
890 | */ | |
27f4d280 | 891 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
fc2219d4 PM |
892 | { |
893 | return 0; | |
894 | } | |
895 | ||
b668c9cf PM |
896 | #ifdef CONFIG_HOTPLUG_CPU |
897 | ||
8af3a5e7 PM |
898 | /* |
899 | * Because there is no preemptible RCU, there can be no readers blocked. | |
900 | */ | |
901 | static bool rcu_preempt_has_tasks(struct rcu_node *rnp) | |
902 | { | |
903 | return false; | |
904 | } | |
905 | ||
b668c9cf PM |
906 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
907 | ||
1ed509a2 | 908 | /* |
6cc68793 | 909 | * Because preemptible RCU does not exist, we never have to check for |
1ed509a2 PM |
910 | * tasks blocked within RCU read-side critical sections. |
911 | */ | |
912 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) | |
913 | { | |
914 | } | |
915 | ||
f41d911f | 916 | /* |
6cc68793 | 917 | * Because preemptible RCU does not exist, we never have to check for |
f41d911f PM |
918 | * tasks blocked within RCU read-side critical sections. |
919 | */ | |
9bc8b558 | 920 | static int rcu_print_task_stall(struct rcu_node *rnp) |
f41d911f | 921 | { |
9bc8b558 | 922 | return 0; |
f41d911f PM |
923 | } |
924 | ||
b0e165c0 | 925 | /* |
6cc68793 | 926 | * Because there is no preemptible RCU, there can be no readers blocked, |
49e29126 PM |
927 | * so there is no need to check for blocked tasks. So check only for |
928 | * bogus qsmask values. | |
b0e165c0 PM |
929 | */ |
930 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) | |
931 | { | |
49e29126 | 932 | WARN_ON_ONCE(rnp->qsmask); |
b0e165c0 PM |
933 | } |
934 | ||
f41d911f | 935 | /* |
6cc68793 | 936 | * Because preemptible RCU does not exist, it never has any callbacks |
f41d911f PM |
937 | * to check. |
938 | */ | |
86aea0e6 | 939 | static void rcu_preempt_check_callbacks(void) |
f41d911f PM |
940 | { |
941 | } | |
942 | ||
019129d5 PM |
943 | /* |
944 | * Wait for an rcu-preempt grace period, but make it happen quickly. | |
6cc68793 | 945 | * But because preemptible RCU does not exist, map to rcu-sched. |
019129d5 PM |
946 | */ |
947 | void synchronize_rcu_expedited(void) | |
948 | { | |
949 | synchronize_sched_expedited(); | |
950 | } | |
951 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
952 | ||
e74f4c45 | 953 | /* |
6cc68793 | 954 | * Because preemptible RCU does not exist, rcu_barrier() is just |
e74f4c45 PM |
955 | * another name for rcu_barrier_sched(). |
956 | */ | |
957 | void rcu_barrier(void) | |
958 | { | |
959 | rcu_barrier_sched(); | |
960 | } | |
961 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
962 | ||
1eba8f84 | 963 | /* |
6cc68793 | 964 | * Because preemptible RCU does not exist, it need not be initialized. |
1eba8f84 PM |
965 | */ |
966 | static void __init __rcu_init_preempt(void) | |
967 | { | |
968 | } | |
969 | ||
2439b696 PM |
970 | /* |
971 | * Because preemptible RCU does not exist, tasks cannot possibly exit | |
972 | * while in preemptible RCU read-side critical sections. | |
973 | */ | |
974 | void exit_rcu(void) | |
975 | { | |
976 | } | |
977 | ||
28f6569a | 978 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
8bd93a2c | 979 | |
27f4d280 PM |
980 | #ifdef CONFIG_RCU_BOOST |
981 | ||
1696a8be | 982 | #include "../locking/rtmutex_common.h" |
27f4d280 | 983 | |
0ea1f2eb PM |
984 | #ifdef CONFIG_RCU_TRACE |
985 | ||
986 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) | |
987 | { | |
96e92021 | 988 | if (!rcu_preempt_has_tasks(rnp)) |
0ea1f2eb PM |
989 | rnp->n_balk_blkd_tasks++; |
990 | else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL) | |
991 | rnp->n_balk_exp_gp_tasks++; | |
992 | else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL) | |
993 | rnp->n_balk_boost_tasks++; | |
994 | else if (rnp->gp_tasks != NULL && rnp->qsmask != 0) | |
995 | rnp->n_balk_notblocked++; | |
996 | else if (rnp->gp_tasks != NULL && | |
a9f4793d | 997 | ULONG_CMP_LT(jiffies, rnp->boost_time)) |
0ea1f2eb PM |
998 | rnp->n_balk_notyet++; |
999 | else | |
1000 | rnp->n_balk_nos++; | |
1001 | } | |
1002 | ||
1003 | #else /* #ifdef CONFIG_RCU_TRACE */ | |
1004 | ||
1005 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) | |
1006 | { | |
1007 | } | |
1008 | ||
1009 | #endif /* #else #ifdef CONFIG_RCU_TRACE */ | |
1010 | ||
5d01bbd1 TG |
1011 | static void rcu_wake_cond(struct task_struct *t, int status) |
1012 | { | |
1013 | /* | |
1014 | * If the thread is yielding, only wake it when this | |
1015 | * is invoked from idle | |
1016 | */ | |
1017 | if (status != RCU_KTHREAD_YIELDING || is_idle_task(current)) | |
1018 | wake_up_process(t); | |
1019 | } | |
1020 | ||
27f4d280 PM |
1021 | /* |
1022 | * Carry out RCU priority boosting on the task indicated by ->exp_tasks | |
1023 | * or ->boost_tasks, advancing the pointer to the next task in the | |
1024 | * ->blkd_tasks list. | |
1025 | * | |
1026 | * Note that irqs must be enabled: boosting the task can block. | |
1027 | * Returns 1 if there are more tasks needing to be boosted. | |
1028 | */ | |
1029 | static int rcu_boost(struct rcu_node *rnp) | |
1030 | { | |
1031 | unsigned long flags; | |
27f4d280 PM |
1032 | struct task_struct *t; |
1033 | struct list_head *tb; | |
1034 | ||
b08ea27d PM |
1035 | if (ACCESS_ONCE(rnp->exp_tasks) == NULL && |
1036 | ACCESS_ONCE(rnp->boost_tasks) == NULL) | |
27f4d280 PM |
1037 | return 0; /* Nothing left to boost. */ |
1038 | ||
1039 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 1040 | smp_mb__after_unlock_lock(); |
27f4d280 PM |
1041 | |
1042 | /* | |
1043 | * Recheck under the lock: all tasks in need of boosting | |
1044 | * might exit their RCU read-side critical sections on their own. | |
1045 | */ | |
1046 | if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { | |
1047 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1048 | return 0; | |
1049 | } | |
1050 | ||
1051 | /* | |
1052 | * Preferentially boost tasks blocking expedited grace periods. | |
1053 | * This cannot starve the normal grace periods because a second | |
1054 | * expedited grace period must boost all blocked tasks, including | |
1055 | * those blocking the pre-existing normal grace period. | |
1056 | */ | |
0ea1f2eb | 1057 | if (rnp->exp_tasks != NULL) { |
27f4d280 | 1058 | tb = rnp->exp_tasks; |
0ea1f2eb PM |
1059 | rnp->n_exp_boosts++; |
1060 | } else { | |
27f4d280 | 1061 | tb = rnp->boost_tasks; |
0ea1f2eb PM |
1062 | rnp->n_normal_boosts++; |
1063 | } | |
1064 | rnp->n_tasks_boosted++; | |
27f4d280 PM |
1065 | |
1066 | /* | |
1067 | * We boost task t by manufacturing an rt_mutex that appears to | |
1068 | * be held by task t. We leave a pointer to that rt_mutex where | |
1069 | * task t can find it, and task t will release the mutex when it | |
1070 | * exits its outermost RCU read-side critical section. Then | |
1071 | * simply acquiring this artificial rt_mutex will boost task | |
1072 | * t's priority. (Thanks to tglx for suggesting this approach!) | |
1073 | * | |
1074 | * Note that task t must acquire rnp->lock to remove itself from | |
1075 | * the ->blkd_tasks list, which it will do from exit() if from | |
1076 | * nowhere else. We therefore are guaranteed that task t will | |
1077 | * stay around at least until we drop rnp->lock. Note that | |
1078 | * rnp->lock also resolves races between our priority boosting | |
1079 | * and task t's exiting its outermost RCU read-side critical | |
1080 | * section. | |
1081 | */ | |
1082 | t = container_of(tb, struct task_struct, rcu_node_entry); | |
abaa93d9 | 1083 | rt_mutex_init_proxy_locked(&rnp->boost_mtx, t); |
dfeb9765 | 1084 | init_completion(&rnp->boost_completion); |
27f4d280 | 1085 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
abaa93d9 PM |
1086 | /* Lock only for side effect: boosts task t's priority. */ |
1087 | rt_mutex_lock(&rnp->boost_mtx); | |
1088 | rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ | |
27f4d280 | 1089 | |
abaa93d9 | 1090 | /* Wait for boostee to be done w/boost_mtx before reinitializing. */ |
dfeb9765 | 1091 | wait_for_completion(&rnp->boost_completion); |
27f4d280 | 1092 | |
4f89b336 PM |
1093 | return ACCESS_ONCE(rnp->exp_tasks) != NULL || |
1094 | ACCESS_ONCE(rnp->boost_tasks) != NULL; | |
27f4d280 PM |
1095 | } |
1096 | ||
27f4d280 PM |
1097 | /* |
1098 | * Priority-boosting kthread. One per leaf rcu_node and one for the | |
1099 | * root rcu_node. | |
1100 | */ | |
1101 | static int rcu_boost_kthread(void *arg) | |
1102 | { | |
1103 | struct rcu_node *rnp = (struct rcu_node *)arg; | |
1104 | int spincnt = 0; | |
1105 | int more2boost; | |
1106 | ||
f7f7bac9 | 1107 | trace_rcu_utilization(TPS("Start boost kthread@init")); |
27f4d280 | 1108 | for (;;) { |
d71df90e | 1109 | rnp->boost_kthread_status = RCU_KTHREAD_WAITING; |
f7f7bac9 | 1110 | trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); |
08bca60a | 1111 | rcu_wait(rnp->boost_tasks || rnp->exp_tasks); |
f7f7bac9 | 1112 | trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); |
d71df90e | 1113 | rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; |
27f4d280 PM |
1114 | more2boost = rcu_boost(rnp); |
1115 | if (more2boost) | |
1116 | spincnt++; | |
1117 | else | |
1118 | spincnt = 0; | |
1119 | if (spincnt > 10) { | |
5d01bbd1 | 1120 | rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; |
f7f7bac9 | 1121 | trace_rcu_utilization(TPS("End boost kthread@rcu_yield")); |
5d01bbd1 | 1122 | schedule_timeout_interruptible(2); |
f7f7bac9 | 1123 | trace_rcu_utilization(TPS("Start boost kthread@rcu_yield")); |
27f4d280 PM |
1124 | spincnt = 0; |
1125 | } | |
1126 | } | |
1217ed1b | 1127 | /* NOTREACHED */ |
f7f7bac9 | 1128 | trace_rcu_utilization(TPS("End boost kthread@notreached")); |
27f4d280 PM |
1129 | return 0; |
1130 | } | |
1131 | ||
1132 | /* | |
1133 | * Check to see if it is time to start boosting RCU readers that are | |
1134 | * blocking the current grace period, and, if so, tell the per-rcu_node | |
1135 | * kthread to start boosting them. If there is an expedited grace | |
1136 | * period in progress, it is always time to boost. | |
1137 | * | |
b065a853 PM |
1138 | * The caller must hold rnp->lock, which this function releases. |
1139 | * The ->boost_kthread_task is immortal, so we don't need to worry | |
1140 | * about it going away. | |
27f4d280 | 1141 | */ |
1217ed1b | 1142 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
615e41c6 | 1143 | __releases(rnp->lock) |
27f4d280 PM |
1144 | { |
1145 | struct task_struct *t; | |
1146 | ||
0ea1f2eb PM |
1147 | if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { |
1148 | rnp->n_balk_exp_gp_tasks++; | |
1217ed1b | 1149 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d280 | 1150 | return; |
0ea1f2eb | 1151 | } |
27f4d280 PM |
1152 | if (rnp->exp_tasks != NULL || |
1153 | (rnp->gp_tasks != NULL && | |
1154 | rnp->boost_tasks == NULL && | |
1155 | rnp->qsmask == 0 && | |
1156 | ULONG_CMP_GE(jiffies, rnp->boost_time))) { | |
1157 | if (rnp->exp_tasks == NULL) | |
1158 | rnp->boost_tasks = rnp->gp_tasks; | |
1217ed1b | 1159 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d280 | 1160 | t = rnp->boost_kthread_task; |
5d01bbd1 TG |
1161 | if (t) |
1162 | rcu_wake_cond(t, rnp->boost_kthread_status); | |
1217ed1b | 1163 | } else { |
0ea1f2eb | 1164 | rcu_initiate_boost_trace(rnp); |
1217ed1b PM |
1165 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1166 | } | |
27f4d280 PM |
1167 | } |
1168 | ||
a46e0899 PM |
1169 | /* |
1170 | * Wake up the per-CPU kthread to invoke RCU callbacks. | |
1171 | */ | |
1172 | static void invoke_rcu_callbacks_kthread(void) | |
1173 | { | |
1174 | unsigned long flags; | |
1175 | ||
1176 | local_irq_save(flags); | |
1177 | __this_cpu_write(rcu_cpu_has_work, 1); | |
1eb52121 | 1178 | if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && |
5d01bbd1 TG |
1179 | current != __this_cpu_read(rcu_cpu_kthread_task)) { |
1180 | rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), | |
1181 | __this_cpu_read(rcu_cpu_kthread_status)); | |
1182 | } | |
a46e0899 PM |
1183 | local_irq_restore(flags); |
1184 | } | |
1185 | ||
dff1672d PM |
1186 | /* |
1187 | * Is the current CPU running the RCU-callbacks kthread? | |
1188 | * Caller must have preemption disabled. | |
1189 | */ | |
1190 | static bool rcu_is_callbacks_kthread(void) | |
1191 | { | |
c9d4b0af | 1192 | return __this_cpu_read(rcu_cpu_kthread_task) == current; |
dff1672d PM |
1193 | } |
1194 | ||
27f4d280 PM |
1195 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
1196 | ||
1197 | /* | |
1198 | * Do priority-boost accounting for the start of a new grace period. | |
1199 | */ | |
1200 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) | |
1201 | { | |
1202 | rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; | |
1203 | } | |
1204 | ||
27f4d280 PM |
1205 | /* |
1206 | * Create an RCU-boost kthread for the specified node if one does not | |
1207 | * already exist. We only create this kthread for preemptible RCU. | |
1208 | * Returns zero if all is well, a negated errno otherwise. | |
1209 | */ | |
49fb4c62 | 1210 | static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, |
5d01bbd1 | 1211 | struct rcu_node *rnp) |
27f4d280 | 1212 | { |
5d01bbd1 | 1213 | int rnp_index = rnp - &rsp->node[0]; |
27f4d280 PM |
1214 | unsigned long flags; |
1215 | struct sched_param sp; | |
1216 | struct task_struct *t; | |
1217 | ||
1218 | if (&rcu_preempt_state != rsp) | |
1219 | return 0; | |
5d01bbd1 TG |
1220 | |
1221 | if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0) | |
1222 | return 0; | |
1223 | ||
a46e0899 | 1224 | rsp->boost = 1; |
27f4d280 PM |
1225 | if (rnp->boost_kthread_task != NULL) |
1226 | return 0; | |
1227 | t = kthread_create(rcu_boost_kthread, (void *)rnp, | |
5b61b0ba | 1228 | "rcub/%d", rnp_index); |
27f4d280 PM |
1229 | if (IS_ERR(t)) |
1230 | return PTR_ERR(t); | |
1231 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 1232 | smp_mb__after_unlock_lock(); |
27f4d280 PM |
1233 | rnp->boost_kthread_task = t; |
1234 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
21871d7e | 1235 | sp.sched_priority = kthread_prio; |
27f4d280 | 1236 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
9a432736 | 1237 | wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ |
27f4d280 PM |
1238 | return 0; |
1239 | } | |
1240 | ||
f8b7fc6b PM |
1241 | static void rcu_kthread_do_work(void) |
1242 | { | |
c9d4b0af CL |
1243 | rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data)); |
1244 | rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data)); | |
f8b7fc6b PM |
1245 | rcu_preempt_do_callbacks(); |
1246 | } | |
1247 | ||
62ab7072 | 1248 | static void rcu_cpu_kthread_setup(unsigned int cpu) |
f8b7fc6b | 1249 | { |
f8b7fc6b | 1250 | struct sched_param sp; |
f8b7fc6b | 1251 | |
21871d7e | 1252 | sp.sched_priority = kthread_prio; |
62ab7072 | 1253 | sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); |
f8b7fc6b PM |
1254 | } |
1255 | ||
62ab7072 | 1256 | static void rcu_cpu_kthread_park(unsigned int cpu) |
f8b7fc6b | 1257 | { |
62ab7072 | 1258 | per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; |
f8b7fc6b PM |
1259 | } |
1260 | ||
62ab7072 | 1261 | static int rcu_cpu_kthread_should_run(unsigned int cpu) |
f8b7fc6b | 1262 | { |
c9d4b0af | 1263 | return __this_cpu_read(rcu_cpu_has_work); |
f8b7fc6b PM |
1264 | } |
1265 | ||
1266 | /* | |
1267 | * Per-CPU kernel thread that invokes RCU callbacks. This replaces the | |
e0f23060 PM |
1268 | * RCU softirq used in flavors and configurations of RCU that do not |
1269 | * support RCU priority boosting. | |
f8b7fc6b | 1270 | */ |
62ab7072 | 1271 | static void rcu_cpu_kthread(unsigned int cpu) |
f8b7fc6b | 1272 | { |
c9d4b0af CL |
1273 | unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status); |
1274 | char work, *workp = this_cpu_ptr(&rcu_cpu_has_work); | |
62ab7072 | 1275 | int spincnt; |
f8b7fc6b | 1276 | |
62ab7072 | 1277 | for (spincnt = 0; spincnt < 10; spincnt++) { |
f7f7bac9 | 1278 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); |
f8b7fc6b | 1279 | local_bh_disable(); |
f8b7fc6b | 1280 | *statusp = RCU_KTHREAD_RUNNING; |
62ab7072 PM |
1281 | this_cpu_inc(rcu_cpu_kthread_loops); |
1282 | local_irq_disable(); | |
f8b7fc6b PM |
1283 | work = *workp; |
1284 | *workp = 0; | |
62ab7072 | 1285 | local_irq_enable(); |
f8b7fc6b PM |
1286 | if (work) |
1287 | rcu_kthread_do_work(); | |
1288 | local_bh_enable(); | |
62ab7072 | 1289 | if (*workp == 0) { |
f7f7bac9 | 1290 | trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); |
62ab7072 PM |
1291 | *statusp = RCU_KTHREAD_WAITING; |
1292 | return; | |
f8b7fc6b PM |
1293 | } |
1294 | } | |
62ab7072 | 1295 | *statusp = RCU_KTHREAD_YIELDING; |
f7f7bac9 | 1296 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield")); |
62ab7072 | 1297 | schedule_timeout_interruptible(2); |
f7f7bac9 | 1298 | trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); |
62ab7072 | 1299 | *statusp = RCU_KTHREAD_WAITING; |
f8b7fc6b PM |
1300 | } |
1301 | ||
1302 | /* | |
1303 | * Set the per-rcu_node kthread's affinity to cover all CPUs that are | |
1304 | * served by the rcu_node in question. The CPU hotplug lock is still | |
1305 | * held, so the value of rnp->qsmaskinit will be stable. | |
1306 | * | |
1307 | * We don't include outgoingcpu in the affinity set, use -1 if there is | |
1308 | * no outgoing CPU. If there are no CPUs left in the affinity set, | |
1309 | * this function allows the kthread to execute on any CPU. | |
1310 | */ | |
5d01bbd1 | 1311 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
f8b7fc6b | 1312 | { |
5d01bbd1 TG |
1313 | struct task_struct *t = rnp->boost_kthread_task; |
1314 | unsigned long mask = rnp->qsmaskinit; | |
f8b7fc6b PM |
1315 | cpumask_var_t cm; |
1316 | int cpu; | |
f8b7fc6b | 1317 | |
5d01bbd1 | 1318 | if (!t) |
f8b7fc6b | 1319 | return; |
5d01bbd1 | 1320 | if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) |
f8b7fc6b | 1321 | return; |
f8b7fc6b PM |
1322 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) |
1323 | if ((mask & 0x1) && cpu != outgoingcpu) | |
1324 | cpumask_set_cpu(cpu, cm); | |
1325 | if (cpumask_weight(cm) == 0) { | |
1326 | cpumask_setall(cm); | |
1327 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) | |
1328 | cpumask_clear_cpu(cpu, cm); | |
1329 | WARN_ON_ONCE(cpumask_weight(cm) == 0); | |
1330 | } | |
5d01bbd1 | 1331 | set_cpus_allowed_ptr(t, cm); |
f8b7fc6b PM |
1332 | free_cpumask_var(cm); |
1333 | } | |
1334 | ||
62ab7072 PM |
1335 | static struct smp_hotplug_thread rcu_cpu_thread_spec = { |
1336 | .store = &rcu_cpu_kthread_task, | |
1337 | .thread_should_run = rcu_cpu_kthread_should_run, | |
1338 | .thread_fn = rcu_cpu_kthread, | |
1339 | .thread_comm = "rcuc/%u", | |
1340 | .setup = rcu_cpu_kthread_setup, | |
1341 | .park = rcu_cpu_kthread_park, | |
1342 | }; | |
f8b7fc6b PM |
1343 | |
1344 | /* | |
9386c0b7 | 1345 | * Spawn boost kthreads -- called as soon as the scheduler is running. |
f8b7fc6b | 1346 | */ |
9386c0b7 | 1347 | static void __init rcu_spawn_boost_kthreads(void) |
f8b7fc6b | 1348 | { |
f8b7fc6b | 1349 | struct rcu_node *rnp; |
5d01bbd1 | 1350 | int cpu; |
f8b7fc6b | 1351 | |
62ab7072 | 1352 | for_each_possible_cpu(cpu) |
f8b7fc6b | 1353 | per_cpu(rcu_cpu_has_work, cpu) = 0; |
62ab7072 | 1354 | BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); |
3e9f5c70 PM |
1355 | rcu_for_each_leaf_node(rcu_state_p, rnp) |
1356 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); | |
f8b7fc6b | 1357 | } |
f8b7fc6b | 1358 | |
49fb4c62 | 1359 | static void rcu_prepare_kthreads(int cpu) |
f8b7fc6b | 1360 | { |
e534165b | 1361 | struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
f8b7fc6b PM |
1362 | struct rcu_node *rnp = rdp->mynode; |
1363 | ||
1364 | /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ | |
62ab7072 | 1365 | if (rcu_scheduler_fully_active) |
e534165b | 1366 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); |
f8b7fc6b PM |
1367 | } |
1368 | ||
27f4d280 PM |
1369 | #else /* #ifdef CONFIG_RCU_BOOST */ |
1370 | ||
1217ed1b | 1371 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
615e41c6 | 1372 | __releases(rnp->lock) |
27f4d280 | 1373 | { |
1217ed1b | 1374 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d280 PM |
1375 | } |
1376 | ||
a46e0899 | 1377 | static void invoke_rcu_callbacks_kthread(void) |
27f4d280 | 1378 | { |
a46e0899 | 1379 | WARN_ON_ONCE(1); |
27f4d280 PM |
1380 | } |
1381 | ||
dff1672d PM |
1382 | static bool rcu_is_callbacks_kthread(void) |
1383 | { | |
1384 | return false; | |
1385 | } | |
1386 | ||
27f4d280 PM |
1387 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) |
1388 | { | |
1389 | } | |
1390 | ||
5d01bbd1 | 1391 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
f8b7fc6b PM |
1392 | { |
1393 | } | |
1394 | ||
9386c0b7 | 1395 | static void __init rcu_spawn_boost_kthreads(void) |
b0d30417 | 1396 | { |
b0d30417 | 1397 | } |
b0d30417 | 1398 | |
49fb4c62 | 1399 | static void rcu_prepare_kthreads(int cpu) |
f8b7fc6b PM |
1400 | { |
1401 | } | |
1402 | ||
27f4d280 PM |
1403 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ |
1404 | ||
8bd93a2c PM |
1405 | #if !defined(CONFIG_RCU_FAST_NO_HZ) |
1406 | ||
1407 | /* | |
1408 | * Check to see if any future RCU-related work will need to be done | |
1409 | * by the current CPU, even if none need be done immediately, returning | |
1410 | * 1 if so. This function is part of the RCU implementation; it is -not- | |
1411 | * an exported member of the RCU API. | |
1412 | * | |
7cb92499 PM |
1413 | * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs |
1414 | * any flavor of RCU. | |
8bd93a2c | 1415 | */ |
ffa83fb5 | 1416 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
aa6da514 | 1417 | int rcu_needs_cpu(unsigned long *delta_jiffies) |
8bd93a2c | 1418 | { |
aa9b1630 | 1419 | *delta_jiffies = ULONG_MAX; |
aa6da514 | 1420 | return rcu_cpu_has_callbacks(NULL); |
7cb92499 | 1421 | } |
ffa83fb5 | 1422 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
7cb92499 PM |
1423 | |
1424 | /* | |
1425 | * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up | |
1426 | * after it. | |
1427 | */ | |
8fa7845d | 1428 | static void rcu_cleanup_after_idle(void) |
7cb92499 PM |
1429 | { |
1430 | } | |
1431 | ||
aea1b35e | 1432 | /* |
a858af28 | 1433 | * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, |
aea1b35e PM |
1434 | * is nothing. |
1435 | */ | |
198bbf81 | 1436 | static void rcu_prepare_for_idle(void) |
aea1b35e PM |
1437 | { |
1438 | } | |
1439 | ||
c57afe80 PM |
1440 | /* |
1441 | * Don't bother keeping a running count of the number of RCU callbacks | |
1442 | * posted because CONFIG_RCU_FAST_NO_HZ=n. | |
1443 | */ | |
1444 | static void rcu_idle_count_callbacks_posted(void) | |
1445 | { | |
1446 | } | |
1447 | ||
8bd93a2c PM |
1448 | #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
1449 | ||
f23f7fa1 PM |
1450 | /* |
1451 | * This code is invoked when a CPU goes idle, at which point we want | |
1452 | * to have the CPU do everything required for RCU so that it can enter | |
1453 | * the energy-efficient dyntick-idle mode. This is handled by a | |
1454 | * state machine implemented by rcu_prepare_for_idle() below. | |
1455 | * | |
1456 | * The following three proprocessor symbols control this state machine: | |
1457 | * | |
f23f7fa1 PM |
1458 | * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted |
1459 | * to sleep in dyntick-idle mode with RCU callbacks pending. This | |
1460 | * is sized to be roughly one RCU grace period. Those energy-efficiency | |
1461 | * benchmarkers who might otherwise be tempted to set this to a large | |
1462 | * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your | |
1463 | * system. And if you are -that- concerned about energy efficiency, | |
1464 | * just power the system down and be done with it! | |
778d250a PM |
1465 | * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is |
1466 | * permitted to sleep in dyntick-idle mode with only lazy RCU | |
1467 | * callbacks pending. Setting this too high can OOM your system. | |
f23f7fa1 PM |
1468 | * |
1469 | * The values below work well in practice. If future workloads require | |
1470 | * adjustment, they can be converted into kernel config parameters, though | |
1471 | * making the state machine smarter might be a better option. | |
1472 | */ | |
e84c48ae | 1473 | #define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ |
778d250a | 1474 | #define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ |
f23f7fa1 | 1475 | |
5e44ce35 PM |
1476 | static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY; |
1477 | module_param(rcu_idle_gp_delay, int, 0644); | |
1478 | static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY; | |
1479 | module_param(rcu_idle_lazy_gp_delay, int, 0644); | |
486e2593 | 1480 | |
d689fe22 | 1481 | extern int tick_nohz_active; |
486e2593 PM |
1482 | |
1483 | /* | |
c229828c PM |
1484 | * Try to advance callbacks for all flavors of RCU on the current CPU, but |
1485 | * only if it has been awhile since the last time we did so. Afterwards, | |
1486 | * if there are any callbacks ready for immediate invocation, return true. | |
486e2593 | 1487 | */ |
f1f399d1 | 1488 | static bool __maybe_unused rcu_try_advance_all_cbs(void) |
486e2593 | 1489 | { |
c0f4dfd4 PM |
1490 | bool cbs_ready = false; |
1491 | struct rcu_data *rdp; | |
c229828c | 1492 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
c0f4dfd4 PM |
1493 | struct rcu_node *rnp; |
1494 | struct rcu_state *rsp; | |
486e2593 | 1495 | |
c229828c PM |
1496 | /* Exit early if we advanced recently. */ |
1497 | if (jiffies == rdtp->last_advance_all) | |
d0bc90fd | 1498 | return false; |
c229828c PM |
1499 | rdtp->last_advance_all = jiffies; |
1500 | ||
c0f4dfd4 PM |
1501 | for_each_rcu_flavor(rsp) { |
1502 | rdp = this_cpu_ptr(rsp->rda); | |
1503 | rnp = rdp->mynode; | |
486e2593 | 1504 | |
c0f4dfd4 PM |
1505 | /* |
1506 | * Don't bother checking unless a grace period has | |
1507 | * completed since we last checked and there are | |
1508 | * callbacks not yet ready to invoke. | |
1509 | */ | |
1510 | if (rdp->completed != rnp->completed && | |
1511 | rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL]) | |
470716fc | 1512 | note_gp_changes(rsp, rdp); |
486e2593 | 1513 | |
c0f4dfd4 PM |
1514 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
1515 | cbs_ready = true; | |
1516 | } | |
1517 | return cbs_ready; | |
486e2593 PM |
1518 | } |
1519 | ||
aa9b1630 | 1520 | /* |
c0f4dfd4 PM |
1521 | * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready |
1522 | * to invoke. If the CPU has callbacks, try to advance them. Tell the | |
1523 | * caller to set the timeout based on whether or not there are non-lazy | |
1524 | * callbacks. | |
aa9b1630 | 1525 | * |
c0f4dfd4 | 1526 | * The caller must have disabled interrupts. |
aa9b1630 | 1527 | */ |
ffa83fb5 | 1528 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
aa6da514 | 1529 | int rcu_needs_cpu(unsigned long *dj) |
aa9b1630 | 1530 | { |
aa6da514 | 1531 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
aa9b1630 | 1532 | |
c0f4dfd4 PM |
1533 | /* Snapshot to detect later posting of non-lazy callback. */ |
1534 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; | |
1535 | ||
aa9b1630 | 1536 | /* If no callbacks, RCU doesn't need the CPU. */ |
aa6da514 | 1537 | if (!rcu_cpu_has_callbacks(&rdtp->all_lazy)) { |
c0f4dfd4 | 1538 | *dj = ULONG_MAX; |
aa9b1630 PM |
1539 | return 0; |
1540 | } | |
c0f4dfd4 PM |
1541 | |
1542 | /* Attempt to advance callbacks. */ | |
1543 | if (rcu_try_advance_all_cbs()) { | |
1544 | /* Some ready to invoke, so initiate later invocation. */ | |
1545 | invoke_rcu_core(); | |
aa9b1630 PM |
1546 | return 1; |
1547 | } | |
c0f4dfd4 PM |
1548 | rdtp->last_accelerate = jiffies; |
1549 | ||
1550 | /* Request timer delay depending on laziness, and round. */ | |
6faf7283 | 1551 | if (!rdtp->all_lazy) { |
c0f4dfd4 PM |
1552 | *dj = round_up(rcu_idle_gp_delay + jiffies, |
1553 | rcu_idle_gp_delay) - jiffies; | |
e84c48ae | 1554 | } else { |
c0f4dfd4 | 1555 | *dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; |
e84c48ae | 1556 | } |
aa9b1630 PM |
1557 | return 0; |
1558 | } | |
ffa83fb5 | 1559 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
aa9b1630 | 1560 | |
21e52e15 | 1561 | /* |
c0f4dfd4 PM |
1562 | * Prepare a CPU for idle from an RCU perspective. The first major task |
1563 | * is to sense whether nohz mode has been enabled or disabled via sysfs. | |
1564 | * The second major task is to check to see if a non-lazy callback has | |
1565 | * arrived at a CPU that previously had only lazy callbacks. The third | |
1566 | * major task is to accelerate (that is, assign grace-period numbers to) | |
1567 | * any recently arrived callbacks. | |
aea1b35e PM |
1568 | * |
1569 | * The caller must have disabled interrupts. | |
8bd93a2c | 1570 | */ |
198bbf81 | 1571 | static void rcu_prepare_for_idle(void) |
8bd93a2c | 1572 | { |
f1f399d1 | 1573 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
48a7639c | 1574 | bool needwake; |
c0f4dfd4 | 1575 | struct rcu_data *rdp; |
198bbf81 | 1576 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
c0f4dfd4 PM |
1577 | struct rcu_node *rnp; |
1578 | struct rcu_state *rsp; | |
9d2ad243 PM |
1579 | int tne; |
1580 | ||
1581 | /* Handle nohz enablement switches conservatively. */ | |
d689fe22 | 1582 | tne = ACCESS_ONCE(tick_nohz_active); |
9d2ad243 | 1583 | if (tne != rdtp->tick_nohz_enabled_snap) { |
aa6da514 | 1584 | if (rcu_cpu_has_callbacks(NULL)) |
9d2ad243 PM |
1585 | invoke_rcu_core(); /* force nohz to see update. */ |
1586 | rdtp->tick_nohz_enabled_snap = tne; | |
1587 | return; | |
1588 | } | |
1589 | if (!tne) | |
1590 | return; | |
f511fc62 | 1591 | |
c0f4dfd4 | 1592 | /* If this is a no-CBs CPU, no callbacks, just return. */ |
198bbf81 | 1593 | if (rcu_is_nocb_cpu(smp_processor_id())) |
9a0c6fef | 1594 | return; |
9a0c6fef | 1595 | |
c57afe80 | 1596 | /* |
c0f4dfd4 PM |
1597 | * If a non-lazy callback arrived at a CPU having only lazy |
1598 | * callbacks, invoke RCU core for the side-effect of recalculating | |
1599 | * idle duration on re-entry to idle. | |
c57afe80 | 1600 | */ |
c0f4dfd4 PM |
1601 | if (rdtp->all_lazy && |
1602 | rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) { | |
c337f8f5 PM |
1603 | rdtp->all_lazy = false; |
1604 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; | |
c0f4dfd4 | 1605 | invoke_rcu_core(); |
c57afe80 PM |
1606 | return; |
1607 | } | |
c57afe80 | 1608 | |
3084f2f8 | 1609 | /* |
c0f4dfd4 PM |
1610 | * If we have not yet accelerated this jiffy, accelerate all |
1611 | * callbacks on this CPU. | |
3084f2f8 | 1612 | */ |
c0f4dfd4 | 1613 | if (rdtp->last_accelerate == jiffies) |
aea1b35e | 1614 | return; |
c0f4dfd4 PM |
1615 | rdtp->last_accelerate = jiffies; |
1616 | for_each_rcu_flavor(rsp) { | |
198bbf81 | 1617 | rdp = this_cpu_ptr(rsp->rda); |
c0f4dfd4 PM |
1618 | if (!*rdp->nxttail[RCU_DONE_TAIL]) |
1619 | continue; | |
1620 | rnp = rdp->mynode; | |
1621 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
6303b9c8 | 1622 | smp_mb__after_unlock_lock(); |
48a7639c | 1623 | needwake = rcu_accelerate_cbs(rsp, rnp, rdp); |
c0f4dfd4 | 1624 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
48a7639c PM |
1625 | if (needwake) |
1626 | rcu_gp_kthread_wake(rsp); | |
77e38ed3 | 1627 | } |
f1f399d1 | 1628 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
c0f4dfd4 | 1629 | } |
3084f2f8 | 1630 | |
c0f4dfd4 PM |
1631 | /* |
1632 | * Clean up for exit from idle. Attempt to advance callbacks based on | |
1633 | * any grace periods that elapsed while the CPU was idle, and if any | |
1634 | * callbacks are now ready to invoke, initiate invocation. | |
1635 | */ | |
8fa7845d | 1636 | static void rcu_cleanup_after_idle(void) |
c0f4dfd4 | 1637 | { |
f1f399d1 | 1638 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
8fa7845d | 1639 | if (rcu_is_nocb_cpu(smp_processor_id())) |
aea1b35e | 1640 | return; |
7a497c96 PM |
1641 | if (rcu_try_advance_all_cbs()) |
1642 | invoke_rcu_core(); | |
f1f399d1 | 1643 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
8bd93a2c PM |
1644 | } |
1645 | ||
c57afe80 | 1646 | /* |
98248a0e PM |
1647 | * Keep a running count of the number of non-lazy callbacks posted |
1648 | * on this CPU. This running counter (which is never decremented) allows | |
1649 | * rcu_prepare_for_idle() to detect when something out of the idle loop | |
1650 | * posts a callback, even if an equal number of callbacks are invoked. | |
1651 | * Of course, callbacks should only be posted from within a trace event | |
1652 | * designed to be called from idle or from within RCU_NONIDLE(). | |
c57afe80 PM |
1653 | */ |
1654 | static void rcu_idle_count_callbacks_posted(void) | |
1655 | { | |
5955f7ee | 1656 | __this_cpu_add(rcu_dynticks.nonlazy_posted, 1); |
c57afe80 PM |
1657 | } |
1658 | ||
b626c1b6 PM |
1659 | /* |
1660 | * Data for flushing lazy RCU callbacks at OOM time. | |
1661 | */ | |
1662 | static atomic_t oom_callback_count; | |
1663 | static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq); | |
1664 | ||
1665 | /* | |
1666 | * RCU OOM callback -- decrement the outstanding count and deliver the | |
1667 | * wake-up if we are the last one. | |
1668 | */ | |
1669 | static void rcu_oom_callback(struct rcu_head *rhp) | |
1670 | { | |
1671 | if (atomic_dec_and_test(&oom_callback_count)) | |
1672 | wake_up(&oom_callback_wq); | |
1673 | } | |
1674 | ||
1675 | /* | |
1676 | * Post an rcu_oom_notify callback on the current CPU if it has at | |
1677 | * least one lazy callback. This will unnecessarily post callbacks | |
1678 | * to CPUs that already have a non-lazy callback at the end of their | |
1679 | * callback list, but this is an infrequent operation, so accept some | |
1680 | * extra overhead to keep things simple. | |
1681 | */ | |
1682 | static void rcu_oom_notify_cpu(void *unused) | |
1683 | { | |
1684 | struct rcu_state *rsp; | |
1685 | struct rcu_data *rdp; | |
1686 | ||
1687 | for_each_rcu_flavor(rsp) { | |
fa07a58f | 1688 | rdp = raw_cpu_ptr(rsp->rda); |
b626c1b6 PM |
1689 | if (rdp->qlen_lazy != 0) { |
1690 | atomic_inc(&oom_callback_count); | |
1691 | rsp->call(&rdp->oom_head, rcu_oom_callback); | |
1692 | } | |
1693 | } | |
1694 | } | |
1695 | ||
1696 | /* | |
1697 | * If low on memory, ensure that each CPU has a non-lazy callback. | |
1698 | * This will wake up CPUs that have only lazy callbacks, in turn | |
1699 | * ensuring that they free up the corresponding memory in a timely manner. | |
1700 | * Because an uncertain amount of memory will be freed in some uncertain | |
1701 | * timeframe, we do not claim to have freed anything. | |
1702 | */ | |
1703 | static int rcu_oom_notify(struct notifier_block *self, | |
1704 | unsigned long notused, void *nfreed) | |
1705 | { | |
1706 | int cpu; | |
1707 | ||
1708 | /* Wait for callbacks from earlier instance to complete. */ | |
1709 | wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0); | |
78e4bc34 | 1710 | smp_mb(); /* Ensure callback reuse happens after callback invocation. */ |
b626c1b6 PM |
1711 | |
1712 | /* | |
1713 | * Prevent premature wakeup: ensure that all increments happen | |
1714 | * before there is a chance of the counter reaching zero. | |
1715 | */ | |
1716 | atomic_set(&oom_callback_count, 1); | |
1717 | ||
1718 | get_online_cpus(); | |
1719 | for_each_online_cpu(cpu) { | |
1720 | smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); | |
bde6c3aa | 1721 | cond_resched_rcu_qs(); |
b626c1b6 PM |
1722 | } |
1723 | put_online_cpus(); | |
1724 | ||
1725 | /* Unconditionally decrement: no need to wake ourselves up. */ | |
1726 | atomic_dec(&oom_callback_count); | |
1727 | ||
1728 | return NOTIFY_OK; | |
1729 | } | |
1730 | ||
1731 | static struct notifier_block rcu_oom_nb = { | |
1732 | .notifier_call = rcu_oom_notify | |
1733 | }; | |
1734 | ||
1735 | static int __init rcu_register_oom_notifier(void) | |
1736 | { | |
1737 | register_oom_notifier(&rcu_oom_nb); | |
1738 | return 0; | |
1739 | } | |
1740 | early_initcall(rcu_register_oom_notifier); | |
1741 | ||
8bd93a2c | 1742 | #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
a858af28 PM |
1743 | |
1744 | #ifdef CONFIG_RCU_CPU_STALL_INFO | |
1745 | ||
1746 | #ifdef CONFIG_RCU_FAST_NO_HZ | |
1747 | ||
1748 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) | |
1749 | { | |
5955f7ee | 1750 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
c0f4dfd4 | 1751 | unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap; |
a858af28 | 1752 | |
c0f4dfd4 PM |
1753 | sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", |
1754 | rdtp->last_accelerate & 0xffff, jiffies & 0xffff, | |
1755 | ulong2long(nlpd), | |
1756 | rdtp->all_lazy ? 'L' : '.', | |
1757 | rdtp->tick_nohz_enabled_snap ? '.' : 'D'); | |
a858af28 PM |
1758 | } |
1759 | ||
1760 | #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ | |
1761 | ||
1762 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) | |
1763 | { | |
1c17e4d4 | 1764 | *cp = '\0'; |
a858af28 PM |
1765 | } |
1766 | ||
1767 | #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ | |
1768 | ||
1769 | /* Initiate the stall-info list. */ | |
1770 | static void print_cpu_stall_info_begin(void) | |
1771 | { | |
efc151c3 | 1772 | pr_cont("\n"); |
a858af28 PM |
1773 | } |
1774 | ||
1775 | /* | |
1776 | * Print out diagnostic information for the specified stalled CPU. | |
1777 | * | |
1778 | * If the specified CPU is aware of the current RCU grace period | |
1779 | * (flavor specified by rsp), then print the number of scheduling | |
1780 | * clock interrupts the CPU has taken during the time that it has | |
1781 | * been aware. Otherwise, print the number of RCU grace periods | |
1782 | * that this CPU is ignorant of, for example, "1" if the CPU was | |
1783 | * aware of the previous grace period. | |
1784 | * | |
1785 | * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. | |
1786 | */ | |
1787 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) | |
1788 | { | |
1789 | char fast_no_hz[72]; | |
1790 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
1791 | struct rcu_dynticks *rdtp = rdp->dynticks; | |
1792 | char *ticks_title; | |
1793 | unsigned long ticks_value; | |
1794 | ||
1795 | if (rsp->gpnum == rdp->gpnum) { | |
1796 | ticks_title = "ticks this GP"; | |
1797 | ticks_value = rdp->ticks_this_gp; | |
1798 | } else { | |
1799 | ticks_title = "GPs behind"; | |
1800 | ticks_value = rsp->gpnum - rdp->gpnum; | |
1801 | } | |
1802 | print_cpu_stall_fast_no_hz(fast_no_hz, cpu); | |
efc151c3 | 1803 | pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u %s\n", |
a858af28 PM |
1804 | cpu, ticks_value, ticks_title, |
1805 | atomic_read(&rdtp->dynticks) & 0xfff, | |
1806 | rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, | |
6231069b | 1807 | rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), |
a858af28 PM |
1808 | fast_no_hz); |
1809 | } | |
1810 | ||
1811 | /* Terminate the stall-info list. */ | |
1812 | static void print_cpu_stall_info_end(void) | |
1813 | { | |
efc151c3 | 1814 | pr_err("\t"); |
a858af28 PM |
1815 | } |
1816 | ||
1817 | /* Zero ->ticks_this_gp for all flavors of RCU. */ | |
1818 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) | |
1819 | { | |
1820 | rdp->ticks_this_gp = 0; | |
6231069b | 1821 | rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); |
a858af28 PM |
1822 | } |
1823 | ||
1824 | /* Increment ->ticks_this_gp for all flavors of RCU. */ | |
1825 | static void increment_cpu_stall_ticks(void) | |
1826 | { | |
115f7a7c PM |
1827 | struct rcu_state *rsp; |
1828 | ||
1829 | for_each_rcu_flavor(rsp) | |
fa07a58f | 1830 | raw_cpu_inc(rsp->rda->ticks_this_gp); |
a858af28 PM |
1831 | } |
1832 | ||
1833 | #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
1834 | ||
1835 | static void print_cpu_stall_info_begin(void) | |
1836 | { | |
efc151c3 | 1837 | pr_cont(" {"); |
a858af28 PM |
1838 | } |
1839 | ||
1840 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) | |
1841 | { | |
efc151c3 | 1842 | pr_cont(" %d", cpu); |
a858af28 PM |
1843 | } |
1844 | ||
1845 | static void print_cpu_stall_info_end(void) | |
1846 | { | |
efc151c3 | 1847 | pr_cont("} "); |
a858af28 PM |
1848 | } |
1849 | ||
1850 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) | |
1851 | { | |
1852 | } | |
1853 | ||
1854 | static void increment_cpu_stall_ticks(void) | |
1855 | { | |
1856 | } | |
1857 | ||
1858 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
3fbfbf7a PM |
1859 | |
1860 | #ifdef CONFIG_RCU_NOCB_CPU | |
1861 | ||
1862 | /* | |
1863 | * Offload callback processing from the boot-time-specified set of CPUs | |
1864 | * specified by rcu_nocb_mask. For each CPU in the set, there is a | |
1865 | * kthread created that pulls the callbacks from the corresponding CPU, | |
1866 | * waits for a grace period to elapse, and invokes the callbacks. | |
1867 | * The no-CBs CPUs do a wake_up() on their kthread when they insert | |
1868 | * a callback into any empty list, unless the rcu_nocb_poll boot parameter | |
1869 | * has been specified, in which case each kthread actively polls its | |
1870 | * CPU. (Which isn't so great for energy efficiency, but which does | |
1871 | * reduce RCU's overhead on that CPU.) | |
1872 | * | |
1873 | * This is intended to be used in conjunction with Frederic Weisbecker's | |
1874 | * adaptive-idle work, which would seriously reduce OS jitter on CPUs | |
1875 | * running CPU-bound user-mode computations. | |
1876 | * | |
1877 | * Offloading of callback processing could also in theory be used as | |
1878 | * an energy-efficiency measure because CPUs with no RCU callbacks | |
1879 | * queued are more aggressive about entering dyntick-idle mode. | |
1880 | */ | |
1881 | ||
1882 | ||
1883 | /* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */ | |
1884 | static int __init rcu_nocb_setup(char *str) | |
1885 | { | |
1886 | alloc_bootmem_cpumask_var(&rcu_nocb_mask); | |
1887 | have_rcu_nocb_mask = true; | |
1888 | cpulist_parse(str, rcu_nocb_mask); | |
1889 | return 1; | |
1890 | } | |
1891 | __setup("rcu_nocbs=", rcu_nocb_setup); | |
1892 | ||
1b0048a4 PG |
1893 | static int __init parse_rcu_nocb_poll(char *arg) |
1894 | { | |
1895 | rcu_nocb_poll = 1; | |
1896 | return 0; | |
1897 | } | |
1898 | early_param("rcu_nocb_poll", parse_rcu_nocb_poll); | |
1899 | ||
dae6e64d | 1900 | /* |
0446be48 PM |
1901 | * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended |
1902 | * grace period. | |
dae6e64d | 1903 | */ |
0446be48 | 1904 | static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
dae6e64d | 1905 | { |
0446be48 | 1906 | wake_up_all(&rnp->nocb_gp_wq[rnp->completed & 0x1]); |
dae6e64d PM |
1907 | } |
1908 | ||
1909 | /* | |
8b425aa8 | 1910 | * Set the root rcu_node structure's ->need_future_gp field |
dae6e64d PM |
1911 | * based on the sum of those of all rcu_node structures. This does |
1912 | * double-count the root rcu_node structure's requests, but this | |
1913 | * is necessary to handle the possibility of a rcu_nocb_kthread() | |
1914 | * having awakened during the time that the rcu_node structures | |
1915 | * were being updated for the end of the previous grace period. | |
34ed6246 | 1916 | */ |
dae6e64d PM |
1917 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
1918 | { | |
8b425aa8 | 1919 | rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq; |
dae6e64d PM |
1920 | } |
1921 | ||
1922 | static void rcu_init_one_nocb(struct rcu_node *rnp) | |
34ed6246 | 1923 | { |
dae6e64d PM |
1924 | init_waitqueue_head(&rnp->nocb_gp_wq[0]); |
1925 | init_waitqueue_head(&rnp->nocb_gp_wq[1]); | |
34ed6246 PM |
1926 | } |
1927 | ||
2f33b512 | 1928 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
24342c96 | 1929 | /* Is the specified CPU a no-CBs CPU? */ |
d1e43fa5 | 1930 | bool rcu_is_nocb_cpu(int cpu) |
3fbfbf7a PM |
1931 | { |
1932 | if (have_rcu_nocb_mask) | |
1933 | return cpumask_test_cpu(cpu, rcu_nocb_mask); | |
1934 | return false; | |
1935 | } | |
2f33b512 | 1936 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
3fbfbf7a | 1937 | |
fbce7497 PM |
1938 | /* |
1939 | * Kick the leader kthread for this NOCB group. | |
1940 | */ | |
1941 | static void wake_nocb_leader(struct rcu_data *rdp, bool force) | |
1942 | { | |
1943 | struct rcu_data *rdp_leader = rdp->nocb_leader; | |
1944 | ||
1945 | if (!ACCESS_ONCE(rdp_leader->nocb_kthread)) | |
1946 | return; | |
11ed7f93 | 1947 | if (ACCESS_ONCE(rdp_leader->nocb_leader_sleep) || force) { |
39953dfd | 1948 | /* Prior smp_mb__after_atomic() orders against prior enqueue. */ |
11ed7f93 | 1949 | ACCESS_ONCE(rdp_leader->nocb_leader_sleep) = false; |
fbce7497 PM |
1950 | wake_up(&rdp_leader->nocb_wq); |
1951 | } | |
1952 | } | |
1953 | ||
d7e29933 PM |
1954 | /* |
1955 | * Does the specified CPU need an RCU callback for the specified flavor | |
1956 | * of rcu_barrier()? | |
1957 | */ | |
1958 | static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) | |
1959 | { | |
1960 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
1961 | struct rcu_head *rhp; | |
1962 | ||
1963 | /* No-CBs CPUs might have callbacks on any of three lists. */ | |
1964 | rhp = ACCESS_ONCE(rdp->nocb_head); | |
1965 | if (!rhp) | |
1966 | rhp = ACCESS_ONCE(rdp->nocb_gp_head); | |
1967 | if (!rhp) | |
1968 | rhp = ACCESS_ONCE(rdp->nocb_follower_head); | |
1969 | ||
1970 | /* Having no rcuo kthread but CBs after scheduler starts is bad! */ | |
1971 | if (!ACCESS_ONCE(rdp->nocb_kthread) && rhp) { | |
1972 | /* RCU callback enqueued before CPU first came online??? */ | |
1973 | pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n", | |
1974 | cpu, rhp->func); | |
1975 | WARN_ON_ONCE(1); | |
1976 | } | |
1977 | ||
1978 | return !!rhp; | |
1979 | } | |
1980 | ||
3fbfbf7a PM |
1981 | /* |
1982 | * Enqueue the specified string of rcu_head structures onto the specified | |
1983 | * CPU's no-CBs lists. The CPU is specified by rdp, the head of the | |
1984 | * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy | |
1985 | * counts are supplied by rhcount and rhcount_lazy. | |
1986 | * | |
1987 | * If warranted, also wake up the kthread servicing this CPUs queues. | |
1988 | */ | |
1989 | static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, | |
1990 | struct rcu_head *rhp, | |
1991 | struct rcu_head **rhtp, | |
96d3fd0d PM |
1992 | int rhcount, int rhcount_lazy, |
1993 | unsigned long flags) | |
3fbfbf7a PM |
1994 | { |
1995 | int len; | |
1996 | struct rcu_head **old_rhpp; | |
1997 | struct task_struct *t; | |
1998 | ||
1999 | /* Enqueue the callback on the nocb list and update counts. */ | |
2000 | old_rhpp = xchg(&rdp->nocb_tail, rhtp); | |
2001 | ACCESS_ONCE(*old_rhpp) = rhp; | |
2002 | atomic_long_add(rhcount, &rdp->nocb_q_count); | |
2003 | atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy); | |
39953dfd | 2004 | smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */ |
3fbfbf7a PM |
2005 | |
2006 | /* If we are not being polled and there is a kthread, awaken it ... */ | |
2007 | t = ACCESS_ONCE(rdp->nocb_kthread); | |
25e03a74 | 2008 | if (rcu_nocb_poll || !t) { |
9261dd0d PM |
2009 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2010 | TPS("WakeNotPoll")); | |
3fbfbf7a | 2011 | return; |
9261dd0d | 2012 | } |
3fbfbf7a PM |
2013 | len = atomic_long_read(&rdp->nocb_q_count); |
2014 | if (old_rhpp == &rdp->nocb_head) { | |
96d3fd0d | 2015 | if (!irqs_disabled_flags(flags)) { |
fbce7497 PM |
2016 | /* ... if queue was empty ... */ |
2017 | wake_nocb_leader(rdp, false); | |
96d3fd0d PM |
2018 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2019 | TPS("WakeEmpty")); | |
2020 | } else { | |
9fdd3bc9 | 2021 | rdp->nocb_defer_wakeup = RCU_NOGP_WAKE; |
96d3fd0d PM |
2022 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2023 | TPS("WakeEmptyIsDeferred")); | |
2024 | } | |
3fbfbf7a PM |
2025 | rdp->qlen_last_fqs_check = 0; |
2026 | } else if (len > rdp->qlen_last_fqs_check + qhimark) { | |
fbce7497 | 2027 | /* ... or if many callbacks queued. */ |
9fdd3bc9 PM |
2028 | if (!irqs_disabled_flags(flags)) { |
2029 | wake_nocb_leader(rdp, true); | |
2030 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2031 | TPS("WakeOvf")); | |
2032 | } else { | |
2033 | rdp->nocb_defer_wakeup = RCU_NOGP_WAKE_FORCE; | |
2034 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2035 | TPS("WakeOvfIsDeferred")); | |
2036 | } | |
3fbfbf7a | 2037 | rdp->qlen_last_fqs_check = LONG_MAX / 2; |
9261dd0d PM |
2038 | } else { |
2039 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot")); | |
3fbfbf7a PM |
2040 | } |
2041 | return; | |
2042 | } | |
2043 | ||
2044 | /* | |
2045 | * This is a helper for __call_rcu(), which invokes this when the normal | |
2046 | * callback queue is inoperable. If this is not a no-CBs CPU, this | |
2047 | * function returns failure back to __call_rcu(), which can complain | |
2048 | * appropriately. | |
2049 | * | |
2050 | * Otherwise, this function queues the callback where the corresponding | |
2051 | * "rcuo" kthread can find it. | |
2052 | */ | |
2053 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, | |
96d3fd0d | 2054 | bool lazy, unsigned long flags) |
3fbfbf7a PM |
2055 | { |
2056 | ||
d1e43fa5 | 2057 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
c271d3a9 | 2058 | return false; |
96d3fd0d | 2059 | __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy, flags); |
21e7a608 PM |
2060 | if (__is_kfree_rcu_offset((unsigned long)rhp->func)) |
2061 | trace_rcu_kfree_callback(rdp->rsp->name, rhp, | |
2062 | (unsigned long)rhp->func, | |
756cbf6b PM |
2063 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
2064 | -atomic_long_read(&rdp->nocb_q_count)); | |
21e7a608 PM |
2065 | else |
2066 | trace_rcu_callback(rdp->rsp->name, rhp, | |
756cbf6b PM |
2067 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
2068 | -atomic_long_read(&rdp->nocb_q_count)); | |
1772947b PM |
2069 | |
2070 | /* | |
2071 | * If called from an extended quiescent state with interrupts | |
2072 | * disabled, invoke the RCU core in order to allow the idle-entry | |
2073 | * deferred-wakeup check to function. | |
2074 | */ | |
2075 | if (irqs_disabled_flags(flags) && | |
2076 | !rcu_is_watching() && | |
2077 | cpu_online(smp_processor_id())) | |
2078 | invoke_rcu_core(); | |
2079 | ||
c271d3a9 | 2080 | return true; |
3fbfbf7a PM |
2081 | } |
2082 | ||
2083 | /* | |
2084 | * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is | |
2085 | * not a no-CBs CPU. | |
2086 | */ | |
2087 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, | |
96d3fd0d PM |
2088 | struct rcu_data *rdp, |
2089 | unsigned long flags) | |
3fbfbf7a PM |
2090 | { |
2091 | long ql = rsp->qlen; | |
2092 | long qll = rsp->qlen_lazy; | |
2093 | ||
2094 | /* If this is not a no-CBs CPU, tell the caller to do it the old way. */ | |
d1e43fa5 | 2095 | if (!rcu_is_nocb_cpu(smp_processor_id())) |
0a9e1e11 | 2096 | return false; |
3fbfbf7a PM |
2097 | rsp->qlen = 0; |
2098 | rsp->qlen_lazy = 0; | |
2099 | ||
2100 | /* First, enqueue the donelist, if any. This preserves CB ordering. */ | |
2101 | if (rsp->orphan_donelist != NULL) { | |
2102 | __call_rcu_nocb_enqueue(rdp, rsp->orphan_donelist, | |
96d3fd0d | 2103 | rsp->orphan_donetail, ql, qll, flags); |
3fbfbf7a PM |
2104 | ql = qll = 0; |
2105 | rsp->orphan_donelist = NULL; | |
2106 | rsp->orphan_donetail = &rsp->orphan_donelist; | |
2107 | } | |
2108 | if (rsp->orphan_nxtlist != NULL) { | |
2109 | __call_rcu_nocb_enqueue(rdp, rsp->orphan_nxtlist, | |
96d3fd0d | 2110 | rsp->orphan_nxttail, ql, qll, flags); |
3fbfbf7a PM |
2111 | ql = qll = 0; |
2112 | rsp->orphan_nxtlist = NULL; | |
2113 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; | |
2114 | } | |
0a9e1e11 | 2115 | return true; |
3fbfbf7a PM |
2116 | } |
2117 | ||
2118 | /* | |
34ed6246 PM |
2119 | * If necessary, kick off a new grace period, and either way wait |
2120 | * for a subsequent grace period to complete. | |
3fbfbf7a | 2121 | */ |
34ed6246 | 2122 | static void rcu_nocb_wait_gp(struct rcu_data *rdp) |
3fbfbf7a | 2123 | { |
34ed6246 | 2124 | unsigned long c; |
dae6e64d | 2125 | bool d; |
34ed6246 | 2126 | unsigned long flags; |
48a7639c | 2127 | bool needwake; |
34ed6246 PM |
2128 | struct rcu_node *rnp = rdp->mynode; |
2129 | ||
2130 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 2131 | smp_mb__after_unlock_lock(); |
48a7639c | 2132 | needwake = rcu_start_future_gp(rnp, rdp, &c); |
0446be48 | 2133 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
48a7639c PM |
2134 | if (needwake) |
2135 | rcu_gp_kthread_wake(rdp->rsp); | |
3fbfbf7a PM |
2136 | |
2137 | /* | |
34ed6246 PM |
2138 | * Wait for the grace period. Do so interruptibly to avoid messing |
2139 | * up the load average. | |
3fbfbf7a | 2140 | */ |
f7f7bac9 | 2141 | trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait")); |
34ed6246 | 2142 | for (;;) { |
dae6e64d PM |
2143 | wait_event_interruptible( |
2144 | rnp->nocb_gp_wq[c & 0x1], | |
2145 | (d = ULONG_CMP_GE(ACCESS_ONCE(rnp->completed), c))); | |
2146 | if (likely(d)) | |
34ed6246 | 2147 | break; |
73a860cd | 2148 | WARN_ON(signal_pending(current)); |
f7f7bac9 | 2149 | trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait")); |
34ed6246 | 2150 | } |
f7f7bac9 | 2151 | trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait")); |
34ed6246 | 2152 | smp_mb(); /* Ensure that CB invocation happens after GP end. */ |
3fbfbf7a PM |
2153 | } |
2154 | ||
fbce7497 PM |
2155 | /* |
2156 | * Leaders come here to wait for additional callbacks to show up. | |
2157 | * This function does not return until callbacks appear. | |
2158 | */ | |
2159 | static void nocb_leader_wait(struct rcu_data *my_rdp) | |
2160 | { | |
2161 | bool firsttime = true; | |
2162 | bool gotcbs; | |
2163 | struct rcu_data *rdp; | |
2164 | struct rcu_head **tail; | |
2165 | ||
2166 | wait_again: | |
2167 | ||
2168 | /* Wait for callbacks to appear. */ | |
2169 | if (!rcu_nocb_poll) { | |
2170 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep"); | |
2171 | wait_event_interruptible(my_rdp->nocb_wq, | |
11ed7f93 | 2172 | !ACCESS_ONCE(my_rdp->nocb_leader_sleep)); |
fbce7497 PM |
2173 | /* Memory barrier handled by smp_mb() calls below and repoll. */ |
2174 | } else if (firsttime) { | |
2175 | firsttime = false; /* Don't drown trace log with "Poll"! */ | |
2176 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Poll"); | |
2177 | } | |
2178 | ||
2179 | /* | |
2180 | * Each pass through the following loop checks a follower for CBs. | |
2181 | * We are our own first follower. Any CBs found are moved to | |
2182 | * nocb_gp_head, where they await a grace period. | |
2183 | */ | |
2184 | gotcbs = false; | |
2185 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { | |
2186 | rdp->nocb_gp_head = ACCESS_ONCE(rdp->nocb_head); | |
2187 | if (!rdp->nocb_gp_head) | |
2188 | continue; /* No CBs here, try next follower. */ | |
2189 | ||
2190 | /* Move callbacks to wait-for-GP list, which is empty. */ | |
2191 | ACCESS_ONCE(rdp->nocb_head) = NULL; | |
2192 | rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head); | |
2193 | rdp->nocb_gp_count = atomic_long_xchg(&rdp->nocb_q_count, 0); | |
2194 | rdp->nocb_gp_count_lazy = | |
2195 | atomic_long_xchg(&rdp->nocb_q_count_lazy, 0); | |
2196 | gotcbs = true; | |
2197 | } | |
2198 | ||
2199 | /* | |
2200 | * If there were no callbacks, sleep a bit, rescan after a | |
2201 | * memory barrier, and go retry. | |
2202 | */ | |
2203 | if (unlikely(!gotcbs)) { | |
2204 | if (!rcu_nocb_poll) | |
2205 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, | |
2206 | "WokeEmpty"); | |
73a860cd | 2207 | WARN_ON(signal_pending(current)); |
fbce7497 PM |
2208 | schedule_timeout_interruptible(1); |
2209 | ||
2210 | /* Rescan in case we were a victim of memory ordering. */ | |
11ed7f93 PK |
2211 | my_rdp->nocb_leader_sleep = true; |
2212 | smp_mb(); /* Ensure _sleep true before scan. */ | |
fbce7497 PM |
2213 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) |
2214 | if (ACCESS_ONCE(rdp->nocb_head)) { | |
2215 | /* Found CB, so short-circuit next wait. */ | |
11ed7f93 | 2216 | my_rdp->nocb_leader_sleep = false; |
fbce7497 PM |
2217 | break; |
2218 | } | |
2219 | goto wait_again; | |
2220 | } | |
2221 | ||
2222 | /* Wait for one grace period. */ | |
2223 | rcu_nocb_wait_gp(my_rdp); | |
2224 | ||
2225 | /* | |
11ed7f93 PK |
2226 | * We left ->nocb_leader_sleep unset to reduce cache thrashing. |
2227 | * We set it now, but recheck for new callbacks while | |
fbce7497 PM |
2228 | * traversing our follower list. |
2229 | */ | |
11ed7f93 PK |
2230 | my_rdp->nocb_leader_sleep = true; |
2231 | smp_mb(); /* Ensure _sleep true before scan of ->nocb_head. */ | |
fbce7497 PM |
2232 | |
2233 | /* Each pass through the following loop wakes a follower, if needed. */ | |
2234 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { | |
2235 | if (ACCESS_ONCE(rdp->nocb_head)) | |
11ed7f93 | 2236 | my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/ |
fbce7497 PM |
2237 | if (!rdp->nocb_gp_head) |
2238 | continue; /* No CBs, so no need to wake follower. */ | |
2239 | ||
2240 | /* Append callbacks to follower's "done" list. */ | |
2241 | tail = xchg(&rdp->nocb_follower_tail, rdp->nocb_gp_tail); | |
2242 | *tail = rdp->nocb_gp_head; | |
2243 | atomic_long_add(rdp->nocb_gp_count, &rdp->nocb_follower_count); | |
2244 | atomic_long_add(rdp->nocb_gp_count_lazy, | |
2245 | &rdp->nocb_follower_count_lazy); | |
c847f142 | 2246 | smp_mb__after_atomic(); /* Store *tail before wakeup. */ |
fbce7497 PM |
2247 | if (rdp != my_rdp && tail == &rdp->nocb_follower_head) { |
2248 | /* | |
2249 | * List was empty, wake up the follower. | |
2250 | * Memory barriers supplied by atomic_long_add(). | |
2251 | */ | |
2252 | wake_up(&rdp->nocb_wq); | |
2253 | } | |
2254 | } | |
2255 | ||
2256 | /* If we (the leader) don't have CBs, go wait some more. */ | |
2257 | if (!my_rdp->nocb_follower_head) | |
2258 | goto wait_again; | |
2259 | } | |
2260 | ||
2261 | /* | |
2262 | * Followers come here to wait for additional callbacks to show up. | |
2263 | * This function does not return until callbacks appear. | |
2264 | */ | |
2265 | static void nocb_follower_wait(struct rcu_data *rdp) | |
2266 | { | |
2267 | bool firsttime = true; | |
2268 | ||
2269 | for (;;) { | |
2270 | if (!rcu_nocb_poll) { | |
2271 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2272 | "FollowerSleep"); | |
2273 | wait_event_interruptible(rdp->nocb_wq, | |
2274 | ACCESS_ONCE(rdp->nocb_follower_head)); | |
2275 | } else if (firsttime) { | |
2276 | /* Don't drown trace log with "Poll"! */ | |
2277 | firsttime = false; | |
2278 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "Poll"); | |
2279 | } | |
2280 | if (smp_load_acquire(&rdp->nocb_follower_head)) { | |
2281 | /* ^^^ Ensure CB invocation follows _head test. */ | |
2282 | return; | |
2283 | } | |
2284 | if (!rcu_nocb_poll) | |
2285 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2286 | "WokeEmpty"); | |
73a860cd | 2287 | WARN_ON(signal_pending(current)); |
fbce7497 PM |
2288 | schedule_timeout_interruptible(1); |
2289 | } | |
2290 | } | |
2291 | ||
3fbfbf7a PM |
2292 | /* |
2293 | * Per-rcu_data kthread, but only for no-CBs CPUs. Each kthread invokes | |
fbce7497 PM |
2294 | * callbacks queued by the corresponding no-CBs CPU, however, there is |
2295 | * an optional leader-follower relationship so that the grace-period | |
2296 | * kthreads don't have to do quite so many wakeups. | |
3fbfbf7a PM |
2297 | */ |
2298 | static int rcu_nocb_kthread(void *arg) | |
2299 | { | |
2300 | int c, cl; | |
2301 | struct rcu_head *list; | |
2302 | struct rcu_head *next; | |
2303 | struct rcu_head **tail; | |
2304 | struct rcu_data *rdp = arg; | |
2305 | ||
2306 | /* Each pass through this loop invokes one batch of callbacks */ | |
2307 | for (;;) { | |
fbce7497 PM |
2308 | /* Wait for callbacks. */ |
2309 | if (rdp->nocb_leader == rdp) | |
2310 | nocb_leader_wait(rdp); | |
2311 | else | |
2312 | nocb_follower_wait(rdp); | |
2313 | ||
2314 | /* Pull the ready-to-invoke callbacks onto local list. */ | |
2315 | list = ACCESS_ONCE(rdp->nocb_follower_head); | |
2316 | BUG_ON(!list); | |
2317 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty"); | |
2318 | ACCESS_ONCE(rdp->nocb_follower_head) = NULL; | |
2319 | tail = xchg(&rdp->nocb_follower_tail, &rdp->nocb_follower_head); | |
2320 | c = atomic_long_xchg(&rdp->nocb_follower_count, 0); | |
2321 | cl = atomic_long_xchg(&rdp->nocb_follower_count_lazy, 0); | |
2322 | rdp->nocb_p_count += c; | |
2323 | rdp->nocb_p_count_lazy += cl; | |
3fbfbf7a PM |
2324 | |
2325 | /* Each pass through the following loop invokes a callback. */ | |
2326 | trace_rcu_batch_start(rdp->rsp->name, cl, c, -1); | |
2327 | c = cl = 0; | |
2328 | while (list) { | |
2329 | next = list->next; | |
2330 | /* Wait for enqueuing to complete, if needed. */ | |
2331 | while (next == NULL && &list->next != tail) { | |
69a79bb1 PM |
2332 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2333 | TPS("WaitQueue")); | |
3fbfbf7a | 2334 | schedule_timeout_interruptible(1); |
69a79bb1 PM |
2335 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2336 | TPS("WokeQueue")); | |
3fbfbf7a PM |
2337 | next = list->next; |
2338 | } | |
2339 | debug_rcu_head_unqueue(list); | |
2340 | local_bh_disable(); | |
2341 | if (__rcu_reclaim(rdp->rsp->name, list)) | |
2342 | cl++; | |
2343 | c++; | |
2344 | local_bh_enable(); | |
2345 | list = next; | |
2346 | } | |
2347 | trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); | |
4de376a1 PK |
2348 | ACCESS_ONCE(rdp->nocb_p_count) = rdp->nocb_p_count - c; |
2349 | ACCESS_ONCE(rdp->nocb_p_count_lazy) = | |
2350 | rdp->nocb_p_count_lazy - cl; | |
c635a4e1 | 2351 | rdp->n_nocbs_invoked += c; |
3fbfbf7a PM |
2352 | } |
2353 | return 0; | |
2354 | } | |
2355 | ||
96d3fd0d | 2356 | /* Is a deferred wakeup of rcu_nocb_kthread() required? */ |
9fdd3bc9 | 2357 | static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) |
96d3fd0d PM |
2358 | { |
2359 | return ACCESS_ONCE(rdp->nocb_defer_wakeup); | |
2360 | } | |
2361 | ||
2362 | /* Do a deferred wakeup of rcu_nocb_kthread(). */ | |
2363 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) | |
2364 | { | |
9fdd3bc9 PM |
2365 | int ndw; |
2366 | ||
96d3fd0d PM |
2367 | if (!rcu_nocb_need_deferred_wakeup(rdp)) |
2368 | return; | |
9fdd3bc9 PM |
2369 | ndw = ACCESS_ONCE(rdp->nocb_defer_wakeup); |
2370 | ACCESS_ONCE(rdp->nocb_defer_wakeup) = RCU_NOGP_WAKE_NOT; | |
2371 | wake_nocb_leader(rdp, ndw == RCU_NOGP_WAKE_FORCE); | |
2372 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("DeferredWake")); | |
96d3fd0d PM |
2373 | } |
2374 | ||
f4579fc5 PM |
2375 | void __init rcu_init_nohz(void) |
2376 | { | |
2377 | int cpu; | |
2378 | bool need_rcu_nocb_mask = true; | |
2379 | struct rcu_state *rsp; | |
2380 | ||
2381 | #ifdef CONFIG_RCU_NOCB_CPU_NONE | |
2382 | need_rcu_nocb_mask = false; | |
2383 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */ | |
2384 | ||
2385 | #if defined(CONFIG_NO_HZ_FULL) | |
2386 | if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask)) | |
2387 | need_rcu_nocb_mask = true; | |
2388 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ | |
2389 | ||
2390 | if (!have_rcu_nocb_mask && need_rcu_nocb_mask) { | |
949cccdb PK |
2391 | if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { |
2392 | pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); | |
2393 | return; | |
2394 | } | |
f4579fc5 PM |
2395 | have_rcu_nocb_mask = true; |
2396 | } | |
2397 | if (!have_rcu_nocb_mask) | |
2398 | return; | |
2399 | ||
2400 | #ifdef CONFIG_RCU_NOCB_CPU_ZERO | |
2401 | pr_info("\tOffload RCU callbacks from CPU 0\n"); | |
2402 | cpumask_set_cpu(0, rcu_nocb_mask); | |
2403 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */ | |
2404 | #ifdef CONFIG_RCU_NOCB_CPU_ALL | |
2405 | pr_info("\tOffload RCU callbacks from all CPUs\n"); | |
2406 | cpumask_copy(rcu_nocb_mask, cpu_possible_mask); | |
2407 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ | |
2408 | #if defined(CONFIG_NO_HZ_FULL) | |
2409 | if (tick_nohz_full_running) | |
2410 | cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); | |
2411 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ | |
2412 | ||
2413 | if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { | |
2414 | pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n"); | |
2415 | cpumask_and(rcu_nocb_mask, cpu_possible_mask, | |
2416 | rcu_nocb_mask); | |
2417 | } | |
2418 | cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask); | |
2419 | pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf); | |
2420 | if (rcu_nocb_poll) | |
2421 | pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); | |
2422 | ||
2423 | for_each_rcu_flavor(rsp) { | |
2424 | for_each_cpu(cpu, rcu_nocb_mask) { | |
2425 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
2426 | ||
2427 | /* | |
2428 | * If there are early callbacks, they will need | |
2429 | * to be moved to the nocb lists. | |
2430 | */ | |
2431 | WARN_ON_ONCE(rdp->nxttail[RCU_NEXT_TAIL] != | |
2432 | &rdp->nxtlist && | |
2433 | rdp->nxttail[RCU_NEXT_TAIL] != NULL); | |
2434 | init_nocb_callback_list(rdp); | |
2435 | } | |
35ce7f29 | 2436 | rcu_organize_nocb_kthreads(rsp); |
f4579fc5 | 2437 | } |
96d3fd0d PM |
2438 | } |
2439 | ||
3fbfbf7a PM |
2440 | /* Initialize per-rcu_data variables for no-CBs CPUs. */ |
2441 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) | |
2442 | { | |
2443 | rdp->nocb_tail = &rdp->nocb_head; | |
2444 | init_waitqueue_head(&rdp->nocb_wq); | |
fbce7497 | 2445 | rdp->nocb_follower_tail = &rdp->nocb_follower_head; |
3fbfbf7a PM |
2446 | } |
2447 | ||
35ce7f29 PM |
2448 | /* |
2449 | * If the specified CPU is a no-CBs CPU that does not already have its | |
2450 | * rcuo kthread for the specified RCU flavor, spawn it. If the CPUs are | |
2451 | * brought online out of order, this can require re-organizing the | |
2452 | * leader-follower relationships. | |
2453 | */ | |
2454 | static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu) | |
2455 | { | |
2456 | struct rcu_data *rdp; | |
2457 | struct rcu_data *rdp_last; | |
2458 | struct rcu_data *rdp_old_leader; | |
2459 | struct rcu_data *rdp_spawn = per_cpu_ptr(rsp->rda, cpu); | |
2460 | struct task_struct *t; | |
2461 | ||
2462 | /* | |
2463 | * If this isn't a no-CBs CPU or if it already has an rcuo kthread, | |
2464 | * then nothing to do. | |
2465 | */ | |
2466 | if (!rcu_is_nocb_cpu(cpu) || rdp_spawn->nocb_kthread) | |
2467 | return; | |
2468 | ||
2469 | /* If we didn't spawn the leader first, reorganize! */ | |
2470 | rdp_old_leader = rdp_spawn->nocb_leader; | |
2471 | if (rdp_old_leader != rdp_spawn && !rdp_old_leader->nocb_kthread) { | |
2472 | rdp_last = NULL; | |
2473 | rdp = rdp_old_leader; | |
2474 | do { | |
2475 | rdp->nocb_leader = rdp_spawn; | |
2476 | if (rdp_last && rdp != rdp_spawn) | |
2477 | rdp_last->nocb_next_follower = rdp; | |
bbe5d7a9 PM |
2478 | if (rdp == rdp_spawn) { |
2479 | rdp = rdp->nocb_next_follower; | |
2480 | } else { | |
2481 | rdp_last = rdp; | |
2482 | rdp = rdp->nocb_next_follower; | |
2483 | rdp_last->nocb_next_follower = NULL; | |
2484 | } | |
35ce7f29 PM |
2485 | } while (rdp); |
2486 | rdp_spawn->nocb_next_follower = rdp_old_leader; | |
2487 | } | |
2488 | ||
2489 | /* Spawn the kthread for this CPU and RCU flavor. */ | |
2490 | t = kthread_run(rcu_nocb_kthread, rdp_spawn, | |
2491 | "rcuo%c/%d", rsp->abbr, cpu); | |
2492 | BUG_ON(IS_ERR(t)); | |
2493 | ACCESS_ONCE(rdp_spawn->nocb_kthread) = t; | |
2494 | } | |
2495 | ||
2496 | /* | |
2497 | * If the specified CPU is a no-CBs CPU that does not already have its | |
2498 | * rcuo kthreads, spawn them. | |
2499 | */ | |
2500 | static void rcu_spawn_all_nocb_kthreads(int cpu) | |
2501 | { | |
2502 | struct rcu_state *rsp; | |
2503 | ||
2504 | if (rcu_scheduler_fully_active) | |
2505 | for_each_rcu_flavor(rsp) | |
2506 | rcu_spawn_one_nocb_kthread(rsp, cpu); | |
2507 | } | |
2508 | ||
2509 | /* | |
2510 | * Once the scheduler is running, spawn rcuo kthreads for all online | |
2511 | * no-CBs CPUs. This assumes that the early_initcall()s happen before | |
2512 | * non-boot CPUs come online -- if this changes, we will need to add | |
2513 | * some mutual exclusion. | |
2514 | */ | |
2515 | static void __init rcu_spawn_nocb_kthreads(void) | |
2516 | { | |
2517 | int cpu; | |
2518 | ||
2519 | for_each_online_cpu(cpu) | |
2520 | rcu_spawn_all_nocb_kthreads(cpu); | |
2521 | } | |
2522 | ||
fbce7497 PM |
2523 | /* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids). */ |
2524 | static int rcu_nocb_leader_stride = -1; | |
2525 | module_param(rcu_nocb_leader_stride, int, 0444); | |
2526 | ||
2527 | /* | |
35ce7f29 | 2528 | * Initialize leader-follower relationships for all no-CBs CPU. |
fbce7497 | 2529 | */ |
35ce7f29 | 2530 | static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) |
3fbfbf7a PM |
2531 | { |
2532 | int cpu; | |
fbce7497 PM |
2533 | int ls = rcu_nocb_leader_stride; |
2534 | int nl = 0; /* Next leader. */ | |
3fbfbf7a | 2535 | struct rcu_data *rdp; |
fbce7497 PM |
2536 | struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ |
2537 | struct rcu_data *rdp_prev = NULL; | |
3fbfbf7a | 2538 | |
22c2f669 | 2539 | if (!have_rcu_nocb_mask) |
3fbfbf7a | 2540 | return; |
fbce7497 PM |
2541 | if (ls == -1) { |
2542 | ls = int_sqrt(nr_cpu_ids); | |
2543 | rcu_nocb_leader_stride = ls; | |
2544 | } | |
2545 | ||
2546 | /* | |
2547 | * Each pass through this loop sets up one rcu_data structure and | |
2548 | * spawns one rcu_nocb_kthread(). | |
2549 | */ | |
3fbfbf7a PM |
2550 | for_each_cpu(cpu, rcu_nocb_mask) { |
2551 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
fbce7497 PM |
2552 | if (rdp->cpu >= nl) { |
2553 | /* New leader, set up for followers & next leader. */ | |
2554 | nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls; | |
2555 | rdp->nocb_leader = rdp; | |
2556 | rdp_leader = rdp; | |
2557 | } else { | |
2558 | /* Another follower, link to previous leader. */ | |
2559 | rdp->nocb_leader = rdp_leader; | |
2560 | rdp_prev->nocb_next_follower = rdp; | |
2561 | } | |
2562 | rdp_prev = rdp; | |
3fbfbf7a PM |
2563 | } |
2564 | } | |
2565 | ||
2566 | /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ | |
34ed6246 | 2567 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
3fbfbf7a | 2568 | { |
22c2f669 | 2569 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
34ed6246 | 2570 | return false; |
22c2f669 | 2571 | |
3fbfbf7a | 2572 | rdp->nxttail[RCU_NEXT_TAIL] = NULL; |
34ed6246 | 2573 | return true; |
3fbfbf7a PM |
2574 | } |
2575 | ||
34ed6246 PM |
2576 | #else /* #ifdef CONFIG_RCU_NOCB_CPU */ |
2577 | ||
d7e29933 PM |
2578 | static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) |
2579 | { | |
2580 | WARN_ON_ONCE(1); /* Should be dead code. */ | |
2581 | return false; | |
2582 | } | |
2583 | ||
0446be48 | 2584 | static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
3fbfbf7a | 2585 | { |
3fbfbf7a PM |
2586 | } |
2587 | ||
dae6e64d PM |
2588 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
2589 | { | |
2590 | } | |
2591 | ||
2592 | static void rcu_init_one_nocb(struct rcu_node *rnp) | |
2593 | { | |
2594 | } | |
3fbfbf7a | 2595 | |
3fbfbf7a | 2596 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, |
96d3fd0d | 2597 | bool lazy, unsigned long flags) |
3fbfbf7a | 2598 | { |
4afc7e26 | 2599 | return false; |
3fbfbf7a PM |
2600 | } |
2601 | ||
2602 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, | |
96d3fd0d PM |
2603 | struct rcu_data *rdp, |
2604 | unsigned long flags) | |
3fbfbf7a | 2605 | { |
f4aa84ba | 2606 | return false; |
3fbfbf7a PM |
2607 | } |
2608 | ||
3fbfbf7a PM |
2609 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) |
2610 | { | |
2611 | } | |
2612 | ||
9fdd3bc9 | 2613 | static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) |
96d3fd0d PM |
2614 | { |
2615 | return false; | |
2616 | } | |
2617 | ||
2618 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) | |
2619 | { | |
2620 | } | |
2621 | ||
35ce7f29 PM |
2622 | static void rcu_spawn_all_nocb_kthreads(int cpu) |
2623 | { | |
2624 | } | |
2625 | ||
2626 | static void __init rcu_spawn_nocb_kthreads(void) | |
3fbfbf7a PM |
2627 | { |
2628 | } | |
2629 | ||
34ed6246 | 2630 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
3fbfbf7a | 2631 | { |
34ed6246 | 2632 | return false; |
3fbfbf7a PM |
2633 | } |
2634 | ||
2635 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ | |
65d798f0 PM |
2636 | |
2637 | /* | |
2638 | * An adaptive-ticks CPU can potentially execute in kernel mode for an | |
2639 | * arbitrarily long period of time with the scheduling-clock tick turned | |
2640 | * off. RCU will be paying attention to this CPU because it is in the | |
2641 | * kernel, but the CPU cannot be guaranteed to be executing the RCU state | |
2642 | * machine because the scheduling-clock tick has been disabled. Therefore, | |
2643 | * if an adaptive-ticks CPU is failing to respond to the current grace | |
2644 | * period and has not be idle from an RCU perspective, kick it. | |
2645 | */ | |
4a81e832 | 2646 | static void __maybe_unused rcu_kick_nohz_cpu(int cpu) |
65d798f0 PM |
2647 | { |
2648 | #ifdef CONFIG_NO_HZ_FULL | |
2649 | if (tick_nohz_full_cpu(cpu)) | |
2650 | smp_send_reschedule(cpu); | |
2651 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ | |
2652 | } | |
2333210b PM |
2653 | |
2654 | ||
2655 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE | |
2656 | ||
0edd1b17 | 2657 | static int full_sysidle_state; /* Current system-idle state. */ |
d4bd54fb PM |
2658 | #define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ |
2659 | #define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ | |
2660 | #define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ | |
2661 | #define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ | |
2662 | #define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ | |
2663 | ||
eb348b89 PM |
2664 | /* |
2665 | * Invoked to note exit from irq or task transition to idle. Note that | |
2666 | * usermode execution does -not- count as idle here! After all, we want | |
2667 | * to detect full-system idle states, not RCU quiescent states and grace | |
2668 | * periods. The caller must have disabled interrupts. | |
2669 | */ | |
28ced795 | 2670 | static void rcu_sysidle_enter(int irq) |
eb348b89 PM |
2671 | { |
2672 | unsigned long j; | |
28ced795 | 2673 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
eb348b89 | 2674 | |
663e1310 PM |
2675 | /* If there are no nohz_full= CPUs, no need to track this. */ |
2676 | if (!tick_nohz_full_enabled()) | |
2677 | return; | |
2678 | ||
eb348b89 PM |
2679 | /* Adjust nesting, check for fully idle. */ |
2680 | if (irq) { | |
2681 | rdtp->dynticks_idle_nesting--; | |
2682 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); | |
2683 | if (rdtp->dynticks_idle_nesting != 0) | |
2684 | return; /* Still not fully idle. */ | |
2685 | } else { | |
2686 | if ((rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) == | |
2687 | DYNTICK_TASK_NEST_VALUE) { | |
2688 | rdtp->dynticks_idle_nesting = 0; | |
2689 | } else { | |
2690 | rdtp->dynticks_idle_nesting -= DYNTICK_TASK_NEST_VALUE; | |
2691 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); | |
2692 | return; /* Still not fully idle. */ | |
2693 | } | |
2694 | } | |
2695 | ||
2696 | /* Record start of fully idle period. */ | |
2697 | j = jiffies; | |
2698 | ACCESS_ONCE(rdtp->dynticks_idle_jiffies) = j; | |
4e857c58 | 2699 | smp_mb__before_atomic(); |
eb348b89 | 2700 | atomic_inc(&rdtp->dynticks_idle); |
4e857c58 | 2701 | smp_mb__after_atomic(); |
eb348b89 PM |
2702 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks_idle) & 0x1); |
2703 | } | |
2704 | ||
0edd1b17 PM |
2705 | /* |
2706 | * Unconditionally force exit from full system-idle state. This is | |
2707 | * invoked when a normal CPU exits idle, but must be called separately | |
2708 | * for the timekeeping CPU (tick_do_timer_cpu). The reason for this | |
2709 | * is that the timekeeping CPU is permitted to take scheduling-clock | |
2710 | * interrupts while the system is in system-idle state, and of course | |
2711 | * rcu_sysidle_exit() has no way of distinguishing a scheduling-clock | |
2712 | * interrupt from any other type of interrupt. | |
2713 | */ | |
2714 | void rcu_sysidle_force_exit(void) | |
2715 | { | |
2716 | int oldstate = ACCESS_ONCE(full_sysidle_state); | |
2717 | int newoldstate; | |
2718 | ||
2719 | /* | |
2720 | * Each pass through the following loop attempts to exit full | |
2721 | * system-idle state. If contention proves to be a problem, | |
2722 | * a trylock-based contention tree could be used here. | |
2723 | */ | |
2724 | while (oldstate > RCU_SYSIDLE_SHORT) { | |
2725 | newoldstate = cmpxchg(&full_sysidle_state, | |
2726 | oldstate, RCU_SYSIDLE_NOT); | |
2727 | if (oldstate == newoldstate && | |
2728 | oldstate == RCU_SYSIDLE_FULL_NOTED) { | |
2729 | rcu_kick_nohz_cpu(tick_do_timer_cpu); | |
2730 | return; /* We cleared it, done! */ | |
2731 | } | |
2732 | oldstate = newoldstate; | |
2733 | } | |
2734 | smp_mb(); /* Order initial oldstate fetch vs. later non-idle work. */ | |
2735 | } | |
2736 | ||
eb348b89 PM |
2737 | /* |
2738 | * Invoked to note entry to irq or task transition from idle. Note that | |
2739 | * usermode execution does -not- count as idle here! The caller must | |
2740 | * have disabled interrupts. | |
2741 | */ | |
28ced795 | 2742 | static void rcu_sysidle_exit(int irq) |
eb348b89 | 2743 | { |
28ced795 CL |
2744 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
2745 | ||
663e1310 PM |
2746 | /* If there are no nohz_full= CPUs, no need to track this. */ |
2747 | if (!tick_nohz_full_enabled()) | |
2748 | return; | |
2749 | ||
eb348b89 PM |
2750 | /* Adjust nesting, check for already non-idle. */ |
2751 | if (irq) { | |
2752 | rdtp->dynticks_idle_nesting++; | |
2753 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); | |
2754 | if (rdtp->dynticks_idle_nesting != 1) | |
2755 | return; /* Already non-idle. */ | |
2756 | } else { | |
2757 | /* | |
2758 | * Allow for irq misnesting. Yes, it really is possible | |
2759 | * to enter an irq handler then never leave it, and maybe | |
2760 | * also vice versa. Handle both possibilities. | |
2761 | */ | |
2762 | if (rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) { | |
2763 | rdtp->dynticks_idle_nesting += DYNTICK_TASK_NEST_VALUE; | |
2764 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); | |
2765 | return; /* Already non-idle. */ | |
2766 | } else { | |
2767 | rdtp->dynticks_idle_nesting = DYNTICK_TASK_EXIT_IDLE; | |
2768 | } | |
2769 | } | |
2770 | ||
2771 | /* Record end of idle period. */ | |
4e857c58 | 2772 | smp_mb__before_atomic(); |
eb348b89 | 2773 | atomic_inc(&rdtp->dynticks_idle); |
4e857c58 | 2774 | smp_mb__after_atomic(); |
eb348b89 | 2775 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks_idle) & 0x1)); |
0edd1b17 PM |
2776 | |
2777 | /* | |
2778 | * If we are the timekeeping CPU, we are permitted to be non-idle | |
2779 | * during a system-idle state. This must be the case, because | |
2780 | * the timekeeping CPU has to take scheduling-clock interrupts | |
2781 | * during the time that the system is transitioning to full | |
2782 | * system-idle state. This means that the timekeeping CPU must | |
2783 | * invoke rcu_sysidle_force_exit() directly if it does anything | |
2784 | * more than take a scheduling-clock interrupt. | |
2785 | */ | |
2786 | if (smp_processor_id() == tick_do_timer_cpu) | |
2787 | return; | |
2788 | ||
2789 | /* Update system-idle state: We are clearly no longer fully idle! */ | |
2790 | rcu_sysidle_force_exit(); | |
2791 | } | |
2792 | ||
2793 | /* | |
2794 | * Check to see if the current CPU is idle. Note that usermode execution | |
2795 | * does not count as idle. The caller must have disabled interrupts. | |
2796 | */ | |
2797 | static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, | |
2798 | unsigned long *maxj) | |
2799 | { | |
2800 | int cur; | |
2801 | unsigned long j; | |
2802 | struct rcu_dynticks *rdtp = rdp->dynticks; | |
2803 | ||
663e1310 PM |
2804 | /* If there are no nohz_full= CPUs, don't check system-wide idleness. */ |
2805 | if (!tick_nohz_full_enabled()) | |
2806 | return; | |
2807 | ||
0edd1b17 PM |
2808 | /* |
2809 | * If some other CPU has already reported non-idle, if this is | |
2810 | * not the flavor of RCU that tracks sysidle state, or if this | |
2811 | * is an offline or the timekeeping CPU, nothing to do. | |
2812 | */ | |
417e8d26 | 2813 | if (!*isidle || rdp->rsp != rcu_state_p || |
0edd1b17 PM |
2814 | cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) |
2815 | return; | |
eb75767b PM |
2816 | if (rcu_gp_in_progress(rdp->rsp)) |
2817 | WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); | |
0edd1b17 PM |
2818 | |
2819 | /* Pick up current idle and NMI-nesting counter and check. */ | |
2820 | cur = atomic_read(&rdtp->dynticks_idle); | |
2821 | if (cur & 0x1) { | |
2822 | *isidle = false; /* We are not idle! */ | |
2823 | return; | |
2824 | } | |
2825 | smp_mb(); /* Read counters before timestamps. */ | |
2826 | ||
2827 | /* Pick up timestamps. */ | |
2828 | j = ACCESS_ONCE(rdtp->dynticks_idle_jiffies); | |
2829 | /* If this CPU entered idle more recently, update maxj timestamp. */ | |
2830 | if (ULONG_CMP_LT(*maxj, j)) | |
2831 | *maxj = j; | |
2832 | } | |
2833 | ||
2834 | /* | |
2835 | * Is this the flavor of RCU that is handling full-system idle? | |
2836 | */ | |
2837 | static bool is_sysidle_rcu_state(struct rcu_state *rsp) | |
2838 | { | |
417e8d26 | 2839 | return rsp == rcu_state_p; |
0edd1b17 PM |
2840 | } |
2841 | ||
2842 | /* | |
2843 | * Return a delay in jiffies based on the number of CPUs, rcu_node | |
2844 | * leaf fanout, and jiffies tick rate. The idea is to allow larger | |
2845 | * systems more time to transition to full-idle state in order to | |
2846 | * avoid the cache thrashing that otherwise occur on the state variable. | |
2847 | * Really small systems (less than a couple of tens of CPUs) should | |
2848 | * instead use a single global atomically incremented counter, and later | |
2849 | * versions of this will automatically reconfigure themselves accordingly. | |
2850 | */ | |
2851 | static unsigned long rcu_sysidle_delay(void) | |
2852 | { | |
2853 | if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) | |
2854 | return 0; | |
2855 | return DIV_ROUND_UP(nr_cpu_ids * HZ, rcu_fanout_leaf * 1000); | |
2856 | } | |
2857 | ||
2858 | /* | |
2859 | * Advance the full-system-idle state. This is invoked when all of | |
2860 | * the non-timekeeping CPUs are idle. | |
2861 | */ | |
2862 | static void rcu_sysidle(unsigned long j) | |
2863 | { | |
2864 | /* Check the current state. */ | |
2865 | switch (ACCESS_ONCE(full_sysidle_state)) { | |
2866 | case RCU_SYSIDLE_NOT: | |
2867 | ||
2868 | /* First time all are idle, so note a short idle period. */ | |
2869 | ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_SHORT; | |
2870 | break; | |
2871 | ||
2872 | case RCU_SYSIDLE_SHORT: | |
2873 | ||
2874 | /* | |
2875 | * Idle for a bit, time to advance to next state? | |
2876 | * cmpxchg failure means race with non-idle, let them win. | |
2877 | */ | |
2878 | if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) | |
2879 | (void)cmpxchg(&full_sysidle_state, | |
2880 | RCU_SYSIDLE_SHORT, RCU_SYSIDLE_LONG); | |
2881 | break; | |
2882 | ||
2883 | case RCU_SYSIDLE_LONG: | |
2884 | ||
2885 | /* | |
2886 | * Do an additional check pass before advancing to full. | |
2887 | * cmpxchg failure means race with non-idle, let them win. | |
2888 | */ | |
2889 | if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) | |
2890 | (void)cmpxchg(&full_sysidle_state, | |
2891 | RCU_SYSIDLE_LONG, RCU_SYSIDLE_FULL); | |
2892 | break; | |
2893 | ||
2894 | default: | |
2895 | break; | |
2896 | } | |
2897 | } | |
2898 | ||
2899 | /* | |
2900 | * Found a non-idle non-timekeeping CPU, so kick the system-idle state | |
2901 | * back to the beginning. | |
2902 | */ | |
2903 | static void rcu_sysidle_cancel(void) | |
2904 | { | |
2905 | smp_mb(); | |
becb41bf PM |
2906 | if (full_sysidle_state > RCU_SYSIDLE_SHORT) |
2907 | ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT; | |
0edd1b17 PM |
2908 | } |
2909 | ||
2910 | /* | |
2911 | * Update the sysidle state based on the results of a force-quiescent-state | |
2912 | * scan of the CPUs' dyntick-idle state. | |
2913 | */ | |
2914 | static void rcu_sysidle_report(struct rcu_state *rsp, int isidle, | |
2915 | unsigned long maxj, bool gpkt) | |
2916 | { | |
417e8d26 | 2917 | if (rsp != rcu_state_p) |
0edd1b17 PM |
2918 | return; /* Wrong flavor, ignore. */ |
2919 | if (gpkt && nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) | |
2920 | return; /* Running state machine from timekeeping CPU. */ | |
2921 | if (isidle) | |
2922 | rcu_sysidle(maxj); /* More idle! */ | |
2923 | else | |
2924 | rcu_sysidle_cancel(); /* Idle is over. */ | |
2925 | } | |
2926 | ||
2927 | /* | |
2928 | * Wrapper for rcu_sysidle_report() when called from the grace-period | |
2929 | * kthread's context. | |
2930 | */ | |
2931 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, | |
2932 | unsigned long maxj) | |
2933 | { | |
663e1310 PM |
2934 | /* If there are no nohz_full= CPUs, no need to track this. */ |
2935 | if (!tick_nohz_full_enabled()) | |
2936 | return; | |
2937 | ||
0edd1b17 PM |
2938 | rcu_sysidle_report(rsp, isidle, maxj, true); |
2939 | } | |
2940 | ||
2941 | /* Callback and function for forcing an RCU grace period. */ | |
2942 | struct rcu_sysidle_head { | |
2943 | struct rcu_head rh; | |
2944 | int inuse; | |
2945 | }; | |
2946 | ||
2947 | static void rcu_sysidle_cb(struct rcu_head *rhp) | |
2948 | { | |
2949 | struct rcu_sysidle_head *rshp; | |
2950 | ||
2951 | /* | |
2952 | * The following memory barrier is needed to replace the | |
2953 | * memory barriers that would normally be in the memory | |
2954 | * allocator. | |
2955 | */ | |
2956 | smp_mb(); /* grace period precedes setting inuse. */ | |
2957 | ||
2958 | rshp = container_of(rhp, struct rcu_sysidle_head, rh); | |
2959 | ACCESS_ONCE(rshp->inuse) = 0; | |
2960 | } | |
2961 | ||
2962 | /* | |
2963 | * Check to see if the system is fully idle, other than the timekeeping CPU. | |
663e1310 PM |
2964 | * The caller must have disabled interrupts. This is not intended to be |
2965 | * called unless tick_nohz_full_enabled(). | |
0edd1b17 PM |
2966 | */ |
2967 | bool rcu_sys_is_idle(void) | |
2968 | { | |
2969 | static struct rcu_sysidle_head rsh; | |
2970 | int rss = ACCESS_ONCE(full_sysidle_state); | |
2971 | ||
2972 | if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu)) | |
2973 | return false; | |
2974 | ||
2975 | /* Handle small-system case by doing a full scan of CPUs. */ | |
2976 | if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) { | |
2977 | int oldrss = rss - 1; | |
2978 | ||
2979 | /* | |
2980 | * One pass to advance to each state up to _FULL. | |
2981 | * Give up if any pass fails to advance the state. | |
2982 | */ | |
2983 | while (rss < RCU_SYSIDLE_FULL && oldrss < rss) { | |
2984 | int cpu; | |
2985 | bool isidle = true; | |
2986 | unsigned long maxj = jiffies - ULONG_MAX / 4; | |
2987 | struct rcu_data *rdp; | |
2988 | ||
2989 | /* Scan all the CPUs looking for nonidle CPUs. */ | |
2990 | for_each_possible_cpu(cpu) { | |
417e8d26 | 2991 | rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
0edd1b17 PM |
2992 | rcu_sysidle_check_cpu(rdp, &isidle, &maxj); |
2993 | if (!isidle) | |
2994 | break; | |
2995 | } | |
417e8d26 | 2996 | rcu_sysidle_report(rcu_state_p, isidle, maxj, false); |
0edd1b17 PM |
2997 | oldrss = rss; |
2998 | rss = ACCESS_ONCE(full_sysidle_state); | |
2999 | } | |
3000 | } | |
3001 | ||
3002 | /* If this is the first observation of an idle period, record it. */ | |
3003 | if (rss == RCU_SYSIDLE_FULL) { | |
3004 | rss = cmpxchg(&full_sysidle_state, | |
3005 | RCU_SYSIDLE_FULL, RCU_SYSIDLE_FULL_NOTED); | |
3006 | return rss == RCU_SYSIDLE_FULL; | |
3007 | } | |
3008 | ||
3009 | smp_mb(); /* ensure rss load happens before later caller actions. */ | |
3010 | ||
3011 | /* If already fully idle, tell the caller (in case of races). */ | |
3012 | if (rss == RCU_SYSIDLE_FULL_NOTED) | |
3013 | return true; | |
3014 | ||
3015 | /* | |
3016 | * If we aren't there yet, and a grace period is not in flight, | |
3017 | * initiate a grace period. Either way, tell the caller that | |
3018 | * we are not there yet. We use an xchg() rather than an assignment | |
3019 | * to make up for the memory barriers that would otherwise be | |
3020 | * provided by the memory allocator. | |
3021 | */ | |
3022 | if (nr_cpu_ids > CONFIG_NO_HZ_FULL_SYSIDLE_SMALL && | |
417e8d26 | 3023 | !rcu_gp_in_progress(rcu_state_p) && |
0edd1b17 PM |
3024 | !rsh.inuse && xchg(&rsh.inuse, 1) == 0) |
3025 | call_rcu(&rsh.rh, rcu_sysidle_cb); | |
3026 | return false; | |
eb348b89 PM |
3027 | } |
3028 | ||
2333210b PM |
3029 | /* |
3030 | * Initialize dynticks sysidle state for CPUs coming online. | |
3031 | */ | |
3032 | static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) | |
3033 | { | |
3034 | rdtp->dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE; | |
3035 | } | |
3036 | ||
3037 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
3038 | ||
28ced795 | 3039 | static void rcu_sysidle_enter(int irq) |
eb348b89 PM |
3040 | { |
3041 | } | |
3042 | ||
28ced795 | 3043 | static void rcu_sysidle_exit(int irq) |
eb348b89 PM |
3044 | { |
3045 | } | |
3046 | ||
0edd1b17 PM |
3047 | static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, |
3048 | unsigned long *maxj) | |
3049 | { | |
3050 | } | |
3051 | ||
3052 | static bool is_sysidle_rcu_state(struct rcu_state *rsp) | |
3053 | { | |
3054 | return false; | |
3055 | } | |
3056 | ||
3057 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, | |
3058 | unsigned long maxj) | |
3059 | { | |
3060 | } | |
3061 | ||
2333210b PM |
3062 | static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) |
3063 | { | |
3064 | } | |
3065 | ||
3066 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
a096932f PM |
3067 | |
3068 | /* | |
3069 | * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the | |
3070 | * grace-period kthread will do force_quiescent_state() processing? | |
3071 | * The idea is to avoid waking up RCU core processing on such a | |
3072 | * CPU unless the grace period has extended for too long. | |
3073 | * | |
3074 | * This code relies on the fact that all NO_HZ_FULL CPUs are also | |
52e2bb95 | 3075 | * CONFIG_RCU_NOCB_CPU CPUs. |
a096932f PM |
3076 | */ |
3077 | static bool rcu_nohz_full_cpu(struct rcu_state *rsp) | |
3078 | { | |
3079 | #ifdef CONFIG_NO_HZ_FULL | |
3080 | if (tick_nohz_full_cpu(smp_processor_id()) && | |
3081 | (!rcu_gp_in_progress(rsp) || | |
3082 | ULONG_CMP_LT(jiffies, ACCESS_ONCE(rsp->gp_start) + HZ))) | |
3083 | return 1; | |
3084 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ | |
3085 | return 0; | |
3086 | } | |
5057f55e PM |
3087 | |
3088 | /* | |
3089 | * Bind the grace-period kthread for the sysidle flavor of RCU to the | |
3090 | * timekeeping CPU. | |
3091 | */ | |
3092 | static void rcu_bind_gp_kthread(void) | |
3093 | { | |
c0f489d2 | 3094 | int __maybe_unused cpu; |
5057f55e | 3095 | |
c0f489d2 | 3096 | if (!tick_nohz_full_enabled()) |
5057f55e | 3097 | return; |
c0f489d2 PM |
3098 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
3099 | cpu = tick_do_timer_cpu; | |
3100 | if (cpu >= 0 && cpu < nr_cpu_ids && raw_smp_processor_id() != cpu) | |
5057f55e | 3101 | set_cpus_allowed_ptr(current, cpumask_of(cpu)); |
c0f489d2 PM |
3102 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
3103 | if (!is_housekeeping_cpu(raw_smp_processor_id())) | |
3104 | housekeeping_affine(current); | |
3105 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
5057f55e | 3106 | } |
176f8f7a PM |
3107 | |
3108 | /* Record the current task on dyntick-idle entry. */ | |
3109 | static void rcu_dynticks_task_enter(void) | |
3110 | { | |
3111 | #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) | |
3112 | ACCESS_ONCE(current->rcu_tasks_idle_cpu) = smp_processor_id(); | |
3113 | #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ | |
3114 | } | |
3115 | ||
3116 | /* Record no current task on dyntick-idle exit. */ | |
3117 | static void rcu_dynticks_task_exit(void) | |
3118 | { | |
3119 | #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) | |
3120 | ACCESS_ONCE(current->rcu_tasks_idle_cpu) = -1; | |
3121 | #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ | |
3122 | } |