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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 MG |
33 | #define RCU_KTHREAD_PRIO 1 |
34 | ||
35 | #ifdef CONFIG_RCU_BOOST | |
abaa93d9 | 36 | #include "../locking/rtmutex_common.h" |
5b61b0ba MG |
37 | #define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO |
38 | #else | |
39 | #define RCU_BOOST_PRIO RCU_KTHREAD_PRIO | |
40 | #endif | |
41 | ||
3fbfbf7a PM |
42 | #ifdef CONFIG_RCU_NOCB_CPU |
43 | static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ | |
44 | static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */ | |
1b0048a4 | 45 | static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ |
3fbfbf7a PM |
46 | static char __initdata nocb_buf[NR_CPUS * 5]; |
47 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ | |
48 | ||
26845c28 PM |
49 | /* |
50 | * Check the RCU kernel configuration parameters and print informative | |
51 | * messages about anything out of the ordinary. If you like #ifdef, you | |
52 | * will love this function. | |
53 | */ | |
54 | static void __init rcu_bootup_announce_oddness(void) | |
55 | { | |
56 | #ifdef CONFIG_RCU_TRACE | |
efc151c3 | 57 | pr_info("\tRCU debugfs-based tracing is enabled.\n"); |
26845c28 PM |
58 | #endif |
59 | #if (defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) || (!defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32) | |
efc151c3 | 60 | pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n", |
26845c28 PM |
61 | CONFIG_RCU_FANOUT); |
62 | #endif | |
63 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
efc151c3 | 64 | pr_info("\tHierarchical RCU autobalancing is disabled.\n"); |
26845c28 PM |
65 | #endif |
66 | #ifdef CONFIG_RCU_FAST_NO_HZ | |
efc151c3 | 67 | pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n"); |
26845c28 PM |
68 | #endif |
69 | #ifdef CONFIG_PROVE_RCU | |
efc151c3 | 70 | pr_info("\tRCU lockdep checking is enabled.\n"); |
26845c28 PM |
71 | #endif |
72 | #ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE | |
efc151c3 | 73 | pr_info("\tRCU torture testing starts during boot.\n"); |
26845c28 | 74 | #endif |
81a294c4 | 75 | #if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE) |
efc151c3 | 76 | pr_info("\tDump stacks of tasks blocking RCU-preempt GP.\n"); |
a858af28 PM |
77 | #endif |
78 | #if defined(CONFIG_RCU_CPU_STALL_INFO) | |
efc151c3 | 79 | pr_info("\tAdditional per-CPU info printed with stalls.\n"); |
26845c28 PM |
80 | #endif |
81 | #if NUM_RCU_LVL_4 != 0 | |
efc151c3 | 82 | pr_info("\tFour-level hierarchy is enabled.\n"); |
26845c28 | 83 | #endif |
f885b7f2 | 84 | if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF) |
9a5739d7 | 85 | pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf); |
cca6f393 | 86 | if (nr_cpu_ids != NR_CPUS) |
efc151c3 | 87 | pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); |
26845c28 PM |
88 | } |
89 | ||
f41d911f PM |
90 | #ifdef CONFIG_TREE_PREEMPT_RCU |
91 | ||
a41bfeb2 | 92 | RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); |
e534165b | 93 | static struct rcu_state *rcu_state_p = &rcu_preempt_state; |
f41d911f | 94 | |
d9a3da06 PM |
95 | static int rcu_preempted_readers_exp(struct rcu_node *rnp); |
96 | ||
f41d911f PM |
97 | /* |
98 | * Tell them what RCU they are running. | |
99 | */ | |
0e0fc1c2 | 100 | static void __init rcu_bootup_announce(void) |
f41d911f | 101 | { |
efc151c3 | 102 | pr_info("Preemptible hierarchical RCU implementation.\n"); |
26845c28 | 103 | rcu_bootup_announce_oddness(); |
f41d911f PM |
104 | } |
105 | ||
106 | /* | |
107 | * Return the number of RCU-preempt batches processed thus far | |
108 | * for debug and statistics. | |
109 | */ | |
110 | long rcu_batches_completed_preempt(void) | |
111 | { | |
112 | return rcu_preempt_state.completed; | |
113 | } | |
114 | EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt); | |
115 | ||
116 | /* | |
117 | * Return the number of RCU batches processed thus far for debug & stats. | |
118 | */ | |
119 | long rcu_batches_completed(void) | |
120 | { | |
121 | return rcu_batches_completed_preempt(); | |
122 | } | |
123 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
124 | ||
125 | /* | |
6cc68793 | 126 | * Record a preemptible-RCU quiescent state for the specified CPU. Note |
f41d911f PM |
127 | * that this just means that the task currently running on the CPU is |
128 | * not in a quiescent state. There might be any number of tasks blocked | |
129 | * while in an RCU read-side critical section. | |
25502a6c PM |
130 | * |
131 | * Unlike the other rcu_*_qs() functions, callers to this function | |
132 | * must disable irqs in order to protect the assignment to | |
133 | * ->rcu_read_unlock_special. | |
f41d911f | 134 | */ |
c3422bea | 135 | static void rcu_preempt_qs(int cpu) |
f41d911f PM |
136 | { |
137 | struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); | |
25502a6c | 138 | |
e4cc1f22 | 139 | if (rdp->passed_quiesce == 0) |
f7f7bac9 | 140 | trace_rcu_grace_period(TPS("rcu_preempt"), rdp->gpnum, TPS("cpuqs")); |
e4cc1f22 | 141 | rdp->passed_quiesce = 1; |
25502a6c | 142 | current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; |
f41d911f PM |
143 | } |
144 | ||
145 | /* | |
c3422bea PM |
146 | * We have entered the scheduler, and the current task might soon be |
147 | * context-switched away from. If this task is in an RCU read-side | |
148 | * critical section, we will no longer be able to rely on the CPU to | |
12f5f524 PM |
149 | * record that fact, so we enqueue the task on the blkd_tasks list. |
150 | * The task will dequeue itself when it exits the outermost enclosing | |
151 | * RCU read-side critical section. Therefore, the current grace period | |
152 | * cannot be permitted to complete until the blkd_tasks list entries | |
153 | * predating the current grace period drain, in other words, until | |
154 | * rnp->gp_tasks becomes NULL. | |
c3422bea PM |
155 | * |
156 | * Caller must disable preemption. | |
f41d911f | 157 | */ |
cba6d0d6 | 158 | static void rcu_preempt_note_context_switch(int cpu) |
f41d911f PM |
159 | { |
160 | struct task_struct *t = current; | |
c3422bea | 161 | unsigned long flags; |
f41d911f PM |
162 | struct rcu_data *rdp; |
163 | struct rcu_node *rnp; | |
164 | ||
10f39bb1 | 165 | if (t->rcu_read_lock_nesting > 0 && |
f41d911f PM |
166 | (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { |
167 | ||
168 | /* Possibly blocking in an RCU read-side critical section. */ | |
cba6d0d6 | 169 | rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu); |
f41d911f | 170 | rnp = rdp->mynode; |
1304afb2 | 171 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 172 | smp_mb__after_unlock_lock(); |
f41d911f | 173 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; |
86848966 | 174 | t->rcu_blocked_node = rnp; |
f41d911f PM |
175 | |
176 | /* | |
177 | * If this CPU has already checked in, then this task | |
178 | * will hold up the next grace period rather than the | |
179 | * current grace period. Queue the task accordingly. | |
180 | * If the task is queued for the current grace period | |
181 | * (i.e., this CPU has not yet passed through a quiescent | |
182 | * state for the current grace period), then as long | |
183 | * as that task remains queued, the current grace period | |
12f5f524 PM |
184 | * cannot end. Note that there is some uncertainty as |
185 | * to exactly when the current grace period started. | |
186 | * We take a conservative approach, which can result | |
187 | * in unnecessarily waiting on tasks that started very | |
188 | * slightly after the current grace period began. C'est | |
189 | * la vie!!! | |
b0e165c0 PM |
190 | * |
191 | * But first, note that the current CPU must still be | |
192 | * on line! | |
f41d911f | 193 | */ |
b0e165c0 | 194 | WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0); |
e7d8842e | 195 | WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); |
12f5f524 PM |
196 | if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) { |
197 | list_add(&t->rcu_node_entry, rnp->gp_tasks->prev); | |
198 | rnp->gp_tasks = &t->rcu_node_entry; | |
27f4d280 PM |
199 | #ifdef CONFIG_RCU_BOOST |
200 | if (rnp->boost_tasks != NULL) | |
201 | rnp->boost_tasks = rnp->gp_tasks; | |
202 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
12f5f524 PM |
203 | } else { |
204 | list_add(&t->rcu_node_entry, &rnp->blkd_tasks); | |
205 | if (rnp->qsmask & rdp->grpmask) | |
206 | rnp->gp_tasks = &t->rcu_node_entry; | |
207 | } | |
d4c08f2a PM |
208 | trace_rcu_preempt_task(rdp->rsp->name, |
209 | t->pid, | |
210 | (rnp->qsmask & rdp->grpmask) | |
211 | ? rnp->gpnum | |
212 | : rnp->gpnum + 1); | |
1304afb2 | 213 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
10f39bb1 PM |
214 | } else if (t->rcu_read_lock_nesting < 0 && |
215 | t->rcu_read_unlock_special) { | |
216 | ||
217 | /* | |
218 | * Complete exit from RCU read-side critical section on | |
219 | * behalf of preempted instance of __rcu_read_unlock(). | |
220 | */ | |
221 | rcu_read_unlock_special(t); | |
f41d911f PM |
222 | } |
223 | ||
224 | /* | |
225 | * Either we were not in an RCU read-side critical section to | |
226 | * begin with, or we have now recorded that critical section | |
227 | * globally. Either way, we can now note a quiescent state | |
228 | * for this CPU. Again, if we were in an RCU read-side critical | |
229 | * section, and if that critical section was blocking the current | |
230 | * grace period, then the fact that the task has been enqueued | |
231 | * means that we continue to block the current grace period. | |
232 | */ | |
e7d8842e | 233 | local_irq_save(flags); |
cba6d0d6 | 234 | rcu_preempt_qs(cpu); |
e7d8842e | 235 | local_irq_restore(flags); |
f41d911f PM |
236 | } |
237 | ||
fc2219d4 PM |
238 | /* |
239 | * Check for preempted RCU readers blocking the current grace period | |
240 | * for the specified rcu_node structure. If the caller needs a reliable | |
241 | * answer, it must hold the rcu_node's ->lock. | |
242 | */ | |
27f4d280 | 243 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
fc2219d4 | 244 | { |
12f5f524 | 245 | return rnp->gp_tasks != NULL; |
fc2219d4 PM |
246 | } |
247 | ||
b668c9cf PM |
248 | /* |
249 | * Record a quiescent state for all tasks that were previously queued | |
250 | * on the specified rcu_node structure and that were blocking the current | |
251 | * RCU grace period. The caller must hold the specified rnp->lock with | |
252 | * irqs disabled, and this lock is released upon return, but irqs remain | |
253 | * disabled. | |
254 | */ | |
d3f6bad3 | 255 | static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
b668c9cf PM |
256 | __releases(rnp->lock) |
257 | { | |
258 | unsigned long mask; | |
259 | struct rcu_node *rnp_p; | |
260 | ||
27f4d280 | 261 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
1304afb2 | 262 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b668c9cf PM |
263 | return; /* Still need more quiescent states! */ |
264 | } | |
265 | ||
266 | rnp_p = rnp->parent; | |
267 | if (rnp_p == NULL) { | |
268 | /* | |
269 | * Either there is only one rcu_node in the tree, | |
270 | * or tasks were kicked up to root rcu_node due to | |
271 | * CPUs going offline. | |
272 | */ | |
d3f6bad3 | 273 | rcu_report_qs_rsp(&rcu_preempt_state, flags); |
b668c9cf PM |
274 | return; |
275 | } | |
276 | ||
277 | /* Report up the rest of the hierarchy. */ | |
278 | mask = rnp->grpmask; | |
1304afb2 PM |
279 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
280 | raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */ | |
6303b9c8 | 281 | smp_mb__after_unlock_lock(); |
d3f6bad3 | 282 | rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags); |
b668c9cf PM |
283 | } |
284 | ||
12f5f524 PM |
285 | /* |
286 | * Advance a ->blkd_tasks-list pointer to the next entry, instead | |
287 | * returning NULL if at the end of the list. | |
288 | */ | |
289 | static struct list_head *rcu_next_node_entry(struct task_struct *t, | |
290 | struct rcu_node *rnp) | |
291 | { | |
292 | struct list_head *np; | |
293 | ||
294 | np = t->rcu_node_entry.next; | |
295 | if (np == &rnp->blkd_tasks) | |
296 | np = NULL; | |
297 | return np; | |
298 | } | |
299 | ||
b668c9cf PM |
300 | /* |
301 | * Handle special cases during rcu_read_unlock(), such as needing to | |
302 | * notify RCU core processing or task having blocked during the RCU | |
303 | * read-side critical section. | |
304 | */ | |
2a3fa843 | 305 | void rcu_read_unlock_special(struct task_struct *t) |
f41d911f PM |
306 | { |
307 | int empty; | |
d9a3da06 | 308 | int empty_exp; |
389abd48 | 309 | int empty_exp_now; |
f41d911f | 310 | unsigned long flags; |
12f5f524 | 311 | struct list_head *np; |
82e78d80 | 312 | #ifdef CONFIG_RCU_BOOST |
abaa93d9 | 313 | bool drop_boost_mutex = false; |
82e78d80 | 314 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
f41d911f PM |
315 | struct rcu_node *rnp; |
316 | int special; | |
317 | ||
318 | /* NMI handlers cannot block and cannot safely manipulate state. */ | |
319 | if (in_nmi()) | |
320 | return; | |
321 | ||
322 | local_irq_save(flags); | |
323 | ||
324 | /* | |
325 | * If RCU core is waiting for this CPU to exit critical section, | |
326 | * let it know that we have done so. | |
327 | */ | |
328 | special = t->rcu_read_unlock_special; | |
329 | if (special & RCU_READ_UNLOCK_NEED_QS) { | |
c3422bea | 330 | rcu_preempt_qs(smp_processor_id()); |
79a62f95 LJ |
331 | if (!t->rcu_read_unlock_special) { |
332 | local_irq_restore(flags); | |
333 | return; | |
334 | } | |
f41d911f PM |
335 | } |
336 | ||
79a62f95 LJ |
337 | /* Hardware IRQ handlers cannot block, complain if they get here. */ |
338 | if (WARN_ON_ONCE(in_irq() || in_serving_softirq())) { | |
f41d911f PM |
339 | local_irq_restore(flags); |
340 | return; | |
341 | } | |
342 | ||
343 | /* Clean up if blocked during RCU read-side critical section. */ | |
344 | if (special & RCU_READ_UNLOCK_BLOCKED) { | |
345 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; | |
346 | ||
dd5d19ba PM |
347 | /* |
348 | * Remove this task from the list it blocked on. The | |
349 | * task can migrate while we acquire the lock, but at | |
350 | * most one time. So at most two passes through loop. | |
351 | */ | |
352 | for (;;) { | |
86848966 | 353 | rnp = t->rcu_blocked_node; |
1304afb2 | 354 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
6303b9c8 | 355 | smp_mb__after_unlock_lock(); |
86848966 | 356 | if (rnp == t->rcu_blocked_node) |
dd5d19ba | 357 | break; |
1304afb2 | 358 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
dd5d19ba | 359 | } |
27f4d280 | 360 | empty = !rcu_preempt_blocked_readers_cgp(rnp); |
d9a3da06 PM |
361 | empty_exp = !rcu_preempted_readers_exp(rnp); |
362 | smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ | |
12f5f524 | 363 | np = rcu_next_node_entry(t, rnp); |
f41d911f | 364 | list_del_init(&t->rcu_node_entry); |
82e78d80 | 365 | t->rcu_blocked_node = NULL; |
f7f7bac9 | 366 | trace_rcu_unlock_preempted_task(TPS("rcu_preempt"), |
d4c08f2a | 367 | rnp->gpnum, t->pid); |
12f5f524 PM |
368 | if (&t->rcu_node_entry == rnp->gp_tasks) |
369 | rnp->gp_tasks = np; | |
370 | if (&t->rcu_node_entry == rnp->exp_tasks) | |
371 | rnp->exp_tasks = np; | |
27f4d280 PM |
372 | #ifdef CONFIG_RCU_BOOST |
373 | if (&t->rcu_node_entry == rnp->boost_tasks) | |
374 | rnp->boost_tasks = np; | |
abaa93d9 PM |
375 | /* Snapshot ->boost_mtx ownership with rcu_node lock held. */ |
376 | drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t; | |
27f4d280 | 377 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
f41d911f PM |
378 | |
379 | /* | |
380 | * If this was the last task on the current list, and if | |
381 | * we aren't waiting on any CPUs, report the quiescent state. | |
389abd48 PM |
382 | * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, |
383 | * so we must take a snapshot of the expedited state. | |
f41d911f | 384 | */ |
389abd48 | 385 | empty_exp_now = !rcu_preempted_readers_exp(rnp); |
d4c08f2a | 386 | if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) { |
f7f7bac9 | 387 | trace_rcu_quiescent_state_report(TPS("preempt_rcu"), |
d4c08f2a PM |
388 | rnp->gpnum, |
389 | 0, rnp->qsmask, | |
390 | rnp->level, | |
391 | rnp->grplo, | |
392 | rnp->grphi, | |
393 | !!rnp->gp_tasks); | |
d3f6bad3 | 394 | rcu_report_unblock_qs_rnp(rnp, flags); |
c701d5d9 | 395 | } else { |
d4c08f2a | 396 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c701d5d9 | 397 | } |
d9a3da06 | 398 | |
27f4d280 PM |
399 | #ifdef CONFIG_RCU_BOOST |
400 | /* Unboost if we were boosted. */ | |
abaa93d9 PM |
401 | if (drop_boost_mutex) { |
402 | rt_mutex_unlock(&rnp->boost_mtx); | |
dfeb9765 PM |
403 | complete(&rnp->boost_completion); |
404 | } | |
27f4d280 PM |
405 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
406 | ||
d9a3da06 PM |
407 | /* |
408 | * If this was the last task on the expedited lists, | |
409 | * then we need to report up the rcu_node hierarchy. | |
410 | */ | |
389abd48 | 411 | if (!empty_exp && empty_exp_now) |
b40d293e | 412 | rcu_report_exp_rnp(&rcu_preempt_state, rnp, true); |
b668c9cf PM |
413 | } else { |
414 | local_irq_restore(flags); | |
f41d911f | 415 | } |
f41d911f PM |
416 | } |
417 | ||
1ed509a2 PM |
418 | #ifdef CONFIG_RCU_CPU_STALL_VERBOSE |
419 | ||
420 | /* | |
421 | * Dump detailed information for all tasks blocking the current RCU | |
422 | * grace period on the specified rcu_node structure. | |
423 | */ | |
424 | static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) | |
425 | { | |
426 | unsigned long flags; | |
1ed509a2 PM |
427 | struct task_struct *t; |
428 | ||
12f5f524 | 429 | raw_spin_lock_irqsave(&rnp->lock, flags); |
5fd4dc06 PM |
430 | if (!rcu_preempt_blocked_readers_cgp(rnp)) { |
431 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
432 | return; | |
433 | } | |
12f5f524 PM |
434 | t = list_entry(rnp->gp_tasks, |
435 | struct task_struct, rcu_node_entry); | |
436 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) | |
437 | sched_show_task(t); | |
438 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1ed509a2 PM |
439 | } |
440 | ||
441 | /* | |
442 | * Dump detailed information for all tasks blocking the current RCU | |
443 | * grace period. | |
444 | */ | |
445 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) | |
446 | { | |
447 | struct rcu_node *rnp = rcu_get_root(rsp); | |
448 | ||
449 | rcu_print_detail_task_stall_rnp(rnp); | |
450 | rcu_for_each_leaf_node(rsp, rnp) | |
451 | rcu_print_detail_task_stall_rnp(rnp); | |
452 | } | |
453 | ||
454 | #else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ | |
455 | ||
456 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) | |
457 | { | |
458 | } | |
459 | ||
460 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ | |
461 | ||
a858af28 PM |
462 | #ifdef CONFIG_RCU_CPU_STALL_INFO |
463 | ||
464 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) | |
465 | { | |
efc151c3 | 466 | pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", |
a858af28 PM |
467 | rnp->level, rnp->grplo, rnp->grphi); |
468 | } | |
469 | ||
470 | static void rcu_print_task_stall_end(void) | |
471 | { | |
efc151c3 | 472 | pr_cont("\n"); |
a858af28 PM |
473 | } |
474 | ||
475 | #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
476 | ||
477 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) | |
478 | { | |
479 | } | |
480 | ||
481 | static void rcu_print_task_stall_end(void) | |
482 | { | |
483 | } | |
484 | ||
485 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
486 | ||
f41d911f PM |
487 | /* |
488 | * Scan the current list of tasks blocked within RCU read-side critical | |
489 | * sections, printing out the tid of each. | |
490 | */ | |
9bc8b558 | 491 | static int rcu_print_task_stall(struct rcu_node *rnp) |
f41d911f | 492 | { |
f41d911f | 493 | struct task_struct *t; |
9bc8b558 | 494 | int ndetected = 0; |
f41d911f | 495 | |
27f4d280 | 496 | if (!rcu_preempt_blocked_readers_cgp(rnp)) |
9bc8b558 | 497 | return 0; |
a858af28 | 498 | rcu_print_task_stall_begin(rnp); |
12f5f524 PM |
499 | t = list_entry(rnp->gp_tasks, |
500 | struct task_struct, rcu_node_entry); | |
9bc8b558 | 501 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
efc151c3 | 502 | pr_cont(" P%d", t->pid); |
9bc8b558 PM |
503 | ndetected++; |
504 | } | |
a858af28 | 505 | rcu_print_task_stall_end(); |
9bc8b558 | 506 | return ndetected; |
f41d911f PM |
507 | } |
508 | ||
b0e165c0 PM |
509 | /* |
510 | * Check that the list of blocked tasks for the newly completed grace | |
511 | * period is in fact empty. It is a serious bug to complete a grace | |
512 | * period that still has RCU readers blocked! This function must be | |
513 | * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock | |
514 | * must be held by the caller. | |
12f5f524 PM |
515 | * |
516 | * Also, if there are blocked tasks on the list, they automatically | |
517 | * block the newly created grace period, so set up ->gp_tasks accordingly. | |
b0e165c0 PM |
518 | */ |
519 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) | |
520 | { | |
27f4d280 | 521 | WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
12f5f524 PM |
522 | if (!list_empty(&rnp->blkd_tasks)) |
523 | rnp->gp_tasks = rnp->blkd_tasks.next; | |
28ecd580 | 524 | WARN_ON_ONCE(rnp->qsmask); |
b0e165c0 PM |
525 | } |
526 | ||
33f76148 PM |
527 | #ifdef CONFIG_HOTPLUG_CPU |
528 | ||
dd5d19ba PM |
529 | /* |
530 | * Handle tasklist migration for case in which all CPUs covered by the | |
531 | * specified rcu_node have gone offline. Move them up to the root | |
532 | * rcu_node. The reason for not just moving them to the immediate | |
533 | * parent is to remove the need for rcu_read_unlock_special() to | |
534 | * make more than two attempts to acquire the target rcu_node's lock. | |
b668c9cf PM |
535 | * Returns true if there were tasks blocking the current RCU grace |
536 | * period. | |
dd5d19ba | 537 | * |
237c80c5 PM |
538 | * Returns 1 if there was previously a task blocking the current grace |
539 | * period on the specified rcu_node structure. | |
540 | * | |
dd5d19ba PM |
541 | * The caller must hold rnp->lock with irqs disabled. |
542 | */ | |
237c80c5 PM |
543 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
544 | struct rcu_node *rnp, | |
545 | struct rcu_data *rdp) | |
dd5d19ba | 546 | { |
dd5d19ba PM |
547 | struct list_head *lp; |
548 | struct list_head *lp_root; | |
d9a3da06 | 549 | int retval = 0; |
dd5d19ba | 550 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
12f5f524 | 551 | struct task_struct *t; |
dd5d19ba | 552 | |
86848966 PM |
553 | if (rnp == rnp_root) { |
554 | WARN_ONCE(1, "Last CPU thought to be offlined?"); | |
237c80c5 | 555 | return 0; /* Shouldn't happen: at least one CPU online. */ |
86848966 | 556 | } |
12f5f524 PM |
557 | |
558 | /* If we are on an internal node, complain bitterly. */ | |
559 | WARN_ON_ONCE(rnp != rdp->mynode); | |
dd5d19ba PM |
560 | |
561 | /* | |
12f5f524 PM |
562 | * Move tasks up to root rcu_node. Don't try to get fancy for |
563 | * this corner-case operation -- just put this node's tasks | |
564 | * at the head of the root node's list, and update the root node's | |
565 | * ->gp_tasks and ->exp_tasks pointers to those of this node's, | |
566 | * if non-NULL. This might result in waiting for more tasks than | |
567 | * absolutely necessary, but this is a good performance/complexity | |
568 | * tradeoff. | |
dd5d19ba | 569 | */ |
2036d94a | 570 | if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0) |
d9a3da06 PM |
571 | retval |= RCU_OFL_TASKS_NORM_GP; |
572 | if (rcu_preempted_readers_exp(rnp)) | |
573 | retval |= RCU_OFL_TASKS_EXP_GP; | |
12f5f524 PM |
574 | lp = &rnp->blkd_tasks; |
575 | lp_root = &rnp_root->blkd_tasks; | |
576 | while (!list_empty(lp)) { | |
577 | t = list_entry(lp->next, typeof(*t), rcu_node_entry); | |
578 | raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ | |
6303b9c8 | 579 | smp_mb__after_unlock_lock(); |
12f5f524 PM |
580 | list_del(&t->rcu_node_entry); |
581 | t->rcu_blocked_node = rnp_root; | |
582 | list_add(&t->rcu_node_entry, lp_root); | |
583 | if (&t->rcu_node_entry == rnp->gp_tasks) | |
584 | rnp_root->gp_tasks = rnp->gp_tasks; | |
585 | if (&t->rcu_node_entry == rnp->exp_tasks) | |
586 | rnp_root->exp_tasks = rnp->exp_tasks; | |
27f4d280 PM |
587 | #ifdef CONFIG_RCU_BOOST |
588 | if (&t->rcu_node_entry == rnp->boost_tasks) | |
589 | rnp_root->boost_tasks = rnp->boost_tasks; | |
590 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
12f5f524 | 591 | raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ |
dd5d19ba | 592 | } |
27f4d280 | 593 | |
1e3fd2b3 PM |
594 | rnp->gp_tasks = NULL; |
595 | rnp->exp_tasks = NULL; | |
27f4d280 | 596 | #ifdef CONFIG_RCU_BOOST |
1e3fd2b3 | 597 | rnp->boost_tasks = NULL; |
5cc900cf PM |
598 | /* |
599 | * In case root is being boosted and leaf was not. Make sure | |
600 | * that we boost the tasks blocking the current grace period | |
601 | * in this case. | |
602 | */ | |
27f4d280 | 603 | raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ |
6303b9c8 | 604 | smp_mb__after_unlock_lock(); |
27f4d280 | 605 | if (rnp_root->boost_tasks != NULL && |
5cc900cf PM |
606 | rnp_root->boost_tasks != rnp_root->gp_tasks && |
607 | rnp_root->boost_tasks != rnp_root->exp_tasks) | |
27f4d280 PM |
608 | rnp_root->boost_tasks = rnp_root->gp_tasks; |
609 | raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ | |
610 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
611 | ||
237c80c5 | 612 | return retval; |
dd5d19ba PM |
613 | } |
614 | ||
e5601400 PM |
615 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
616 | ||
f41d911f PM |
617 | /* |
618 | * Check for a quiescent state from the current CPU. When a task blocks, | |
619 | * the task is recorded in the corresponding CPU's rcu_node structure, | |
620 | * which is checked elsewhere. | |
621 | * | |
622 | * Caller must disable hard irqs. | |
623 | */ | |
624 | static void rcu_preempt_check_callbacks(int cpu) | |
625 | { | |
626 | struct task_struct *t = current; | |
627 | ||
628 | if (t->rcu_read_lock_nesting == 0) { | |
c3422bea | 629 | rcu_preempt_qs(cpu); |
f41d911f PM |
630 | return; |
631 | } | |
10f39bb1 PM |
632 | if (t->rcu_read_lock_nesting > 0 && |
633 | per_cpu(rcu_preempt_data, cpu).qs_pending) | |
c3422bea | 634 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
f41d911f PM |
635 | } |
636 | ||
a46e0899 PM |
637 | #ifdef CONFIG_RCU_BOOST |
638 | ||
09223371 SL |
639 | static void rcu_preempt_do_callbacks(void) |
640 | { | |
c9d4b0af | 641 | rcu_do_batch(&rcu_preempt_state, this_cpu_ptr(&rcu_preempt_data)); |
09223371 SL |
642 | } |
643 | ||
a46e0899 PM |
644 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
645 | ||
f41d911f | 646 | /* |
6cc68793 | 647 | * Queue a preemptible-RCU callback for invocation after a grace period. |
f41d911f PM |
648 | */ |
649 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
650 | { | |
3fbfbf7a | 651 | __call_rcu(head, func, &rcu_preempt_state, -1, 0); |
f41d911f PM |
652 | } |
653 | EXPORT_SYMBOL_GPL(call_rcu); | |
654 | ||
6ebb237b PM |
655 | /** |
656 | * synchronize_rcu - wait until a grace period has elapsed. | |
657 | * | |
658 | * Control will return to the caller some time after a full grace | |
659 | * period has elapsed, in other words after all currently executing RCU | |
77d8485a PM |
660 | * read-side critical sections have completed. Note, however, that |
661 | * upon return from synchronize_rcu(), the caller might well be executing | |
662 | * concurrently with new RCU read-side critical sections that began while | |
663 | * synchronize_rcu() was waiting. RCU read-side critical sections are | |
664 | * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. | |
f0a0e6f2 PM |
665 | * |
666 | * See the description of synchronize_sched() for more detailed information | |
667 | * on memory ordering guarantees. | |
6ebb237b PM |
668 | */ |
669 | void synchronize_rcu(void) | |
670 | { | |
fe15d706 PM |
671 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
672 | !lock_is_held(&rcu_lock_map) && | |
673 | !lock_is_held(&rcu_sched_lock_map), | |
674 | "Illegal synchronize_rcu() in RCU read-side critical section"); | |
6ebb237b PM |
675 | if (!rcu_scheduler_active) |
676 | return; | |
3705b88d AM |
677 | if (rcu_expedited) |
678 | synchronize_rcu_expedited(); | |
679 | else | |
680 | wait_rcu_gp(call_rcu); | |
6ebb237b PM |
681 | } |
682 | EXPORT_SYMBOL_GPL(synchronize_rcu); | |
683 | ||
d9a3da06 | 684 | static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); |
bcfa57ce | 685 | static unsigned long sync_rcu_preempt_exp_count; |
d9a3da06 PM |
686 | static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); |
687 | ||
688 | /* | |
689 | * Return non-zero if there are any tasks in RCU read-side critical | |
690 | * sections blocking the current preemptible-RCU expedited grace period. | |
691 | * If there is no preemptible-RCU expedited grace period currently in | |
692 | * progress, returns zero unconditionally. | |
693 | */ | |
694 | static int rcu_preempted_readers_exp(struct rcu_node *rnp) | |
695 | { | |
12f5f524 | 696 | return rnp->exp_tasks != NULL; |
d9a3da06 PM |
697 | } |
698 | ||
699 | /* | |
700 | * return non-zero if there is no RCU expedited grace period in progress | |
701 | * for the specified rcu_node structure, in other words, if all CPUs and | |
702 | * tasks covered by the specified rcu_node structure have done their bit | |
703 | * for the current expedited grace period. Works only for preemptible | |
704 | * RCU -- other RCU implementation use other means. | |
705 | * | |
706 | * Caller must hold sync_rcu_preempt_exp_mutex. | |
707 | */ | |
708 | static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) | |
709 | { | |
710 | return !rcu_preempted_readers_exp(rnp) && | |
711 | ACCESS_ONCE(rnp->expmask) == 0; | |
712 | } | |
713 | ||
714 | /* | |
715 | * Report the exit from RCU read-side critical section for the last task | |
716 | * that queued itself during or before the current expedited preemptible-RCU | |
717 | * grace period. This event is reported either to the rcu_node structure on | |
718 | * which the task was queued or to one of that rcu_node structure's ancestors, | |
719 | * recursively up the tree. (Calm down, calm down, we do the recursion | |
720 | * iteratively!) | |
721 | * | |
b40d293e TG |
722 | * Most callers will set the "wake" flag, but the task initiating the |
723 | * expedited grace period need not wake itself. | |
724 | * | |
d9a3da06 PM |
725 | * Caller must hold sync_rcu_preempt_exp_mutex. |
726 | */ | |
b40d293e TG |
727 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
728 | bool wake) | |
d9a3da06 PM |
729 | { |
730 | unsigned long flags; | |
731 | unsigned long mask; | |
732 | ||
1304afb2 | 733 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 734 | smp_mb__after_unlock_lock(); |
d9a3da06 | 735 | for (;;) { |
131906b0 PM |
736 | if (!sync_rcu_preempt_exp_done(rnp)) { |
737 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
d9a3da06 | 738 | break; |
131906b0 | 739 | } |
d9a3da06 | 740 | if (rnp->parent == NULL) { |
131906b0 | 741 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
78e4bc34 PM |
742 | if (wake) { |
743 | smp_mb(); /* EGP done before wake_up(). */ | |
b40d293e | 744 | wake_up(&sync_rcu_preempt_exp_wq); |
78e4bc34 | 745 | } |
d9a3da06 PM |
746 | break; |
747 | } | |
748 | mask = rnp->grpmask; | |
1304afb2 | 749 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
d9a3da06 | 750 | rnp = rnp->parent; |
1304afb2 | 751 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
6303b9c8 | 752 | smp_mb__after_unlock_lock(); |
d9a3da06 PM |
753 | rnp->expmask &= ~mask; |
754 | } | |
d9a3da06 PM |
755 | } |
756 | ||
757 | /* | |
758 | * Snapshot the tasks blocking the newly started preemptible-RCU expedited | |
759 | * grace period for the specified rcu_node structure. If there are no such | |
760 | * tasks, report it up the rcu_node hierarchy. | |
761 | * | |
7b2e6011 PM |
762 | * Caller must hold sync_rcu_preempt_exp_mutex and must exclude |
763 | * CPU hotplug operations. | |
d9a3da06 PM |
764 | */ |
765 | static void | |
766 | sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp) | |
767 | { | |
1217ed1b | 768 | unsigned long flags; |
12f5f524 | 769 | int must_wait = 0; |
d9a3da06 | 770 | |
1217ed1b | 771 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 772 | smp_mb__after_unlock_lock(); |
c701d5d9 | 773 | if (list_empty(&rnp->blkd_tasks)) { |
1217ed1b | 774 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c701d5d9 | 775 | } else { |
12f5f524 | 776 | rnp->exp_tasks = rnp->blkd_tasks.next; |
1217ed1b | 777 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
12f5f524 PM |
778 | must_wait = 1; |
779 | } | |
d9a3da06 | 780 | if (!must_wait) |
b40d293e | 781 | rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */ |
d9a3da06 PM |
782 | } |
783 | ||
236fefaf PM |
784 | /** |
785 | * synchronize_rcu_expedited - Brute-force RCU grace period | |
786 | * | |
787 | * Wait for an RCU-preempt grace period, but expedite it. The basic | |
788 | * idea is to invoke synchronize_sched_expedited() to push all the tasks to | |
789 | * the ->blkd_tasks lists and wait for this list to drain. This consumes | |
790 | * significant time on all CPUs and is unfriendly to real-time workloads, | |
791 | * so is thus not recommended for any sort of common-case code. | |
792 | * In fact, if you are using synchronize_rcu_expedited() in a loop, | |
793 | * please restructure your code to batch your updates, and then Use a | |
794 | * single synchronize_rcu() instead. | |
795 | * | |
796 | * Note that it is illegal to call this function while holding any lock | |
797 | * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal | |
798 | * to call this function from a CPU-hotplug notifier. Failing to observe | |
799 | * these restriction will result in deadlock. | |
019129d5 PM |
800 | */ |
801 | void synchronize_rcu_expedited(void) | |
802 | { | |
d9a3da06 PM |
803 | unsigned long flags; |
804 | struct rcu_node *rnp; | |
805 | struct rcu_state *rsp = &rcu_preempt_state; | |
bcfa57ce | 806 | unsigned long snap; |
d9a3da06 PM |
807 | int trycount = 0; |
808 | ||
809 | smp_mb(); /* Caller's modifications seen first by other CPUs. */ | |
810 | snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1; | |
811 | smp_mb(); /* Above access cannot bleed into critical section. */ | |
812 | ||
1943c89d PM |
813 | /* |
814 | * Block CPU-hotplug operations. This means that any CPU-hotplug | |
815 | * operation that finds an rcu_node structure with tasks in the | |
816 | * process of being boosted will know that all tasks blocking | |
817 | * this expedited grace period will already be in the process of | |
818 | * being boosted. This simplifies the process of moving tasks | |
819 | * from leaf to root rcu_node structures. | |
820 | */ | |
821 | get_online_cpus(); | |
822 | ||
d9a3da06 PM |
823 | /* |
824 | * Acquire lock, falling back to synchronize_rcu() if too many | |
825 | * lock-acquisition failures. Of course, if someone does the | |
826 | * expedited grace period for us, just leave. | |
827 | */ | |
828 | while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) { | |
1943c89d PM |
829 | if (ULONG_CMP_LT(snap, |
830 | ACCESS_ONCE(sync_rcu_preempt_exp_count))) { | |
831 | put_online_cpus(); | |
832 | goto mb_ret; /* Others did our work for us. */ | |
833 | } | |
c701d5d9 | 834 | if (trycount++ < 10) { |
d9a3da06 | 835 | udelay(trycount * num_online_cpus()); |
c701d5d9 | 836 | } else { |
1943c89d | 837 | put_online_cpus(); |
3705b88d | 838 | wait_rcu_gp(call_rcu); |
d9a3da06 PM |
839 | return; |
840 | } | |
d9a3da06 | 841 | } |
1943c89d PM |
842 | if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) { |
843 | put_online_cpus(); | |
d9a3da06 | 844 | goto unlock_mb_ret; /* Others did our work for us. */ |
1943c89d | 845 | } |
d9a3da06 | 846 | |
12f5f524 | 847 | /* force all RCU readers onto ->blkd_tasks lists. */ |
d9a3da06 PM |
848 | synchronize_sched_expedited(); |
849 | ||
d9a3da06 PM |
850 | /* Initialize ->expmask for all non-leaf rcu_node structures. */ |
851 | rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) { | |
1943c89d | 852 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 853 | smp_mb__after_unlock_lock(); |
d9a3da06 | 854 | rnp->expmask = rnp->qsmaskinit; |
1943c89d | 855 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da06 PM |
856 | } |
857 | ||
12f5f524 | 858 | /* Snapshot current state of ->blkd_tasks lists. */ |
d9a3da06 PM |
859 | rcu_for_each_leaf_node(rsp, rnp) |
860 | sync_rcu_preempt_exp_init(rsp, rnp); | |
861 | if (NUM_RCU_NODES > 1) | |
862 | sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp)); | |
863 | ||
1943c89d | 864 | put_online_cpus(); |
d9a3da06 | 865 | |
12f5f524 | 866 | /* Wait for snapshotted ->blkd_tasks lists to drain. */ |
d9a3da06 PM |
867 | rnp = rcu_get_root(rsp); |
868 | wait_event(sync_rcu_preempt_exp_wq, | |
869 | sync_rcu_preempt_exp_done(rnp)); | |
870 | ||
871 | /* Clean up and exit. */ | |
872 | smp_mb(); /* ensure expedited GP seen before counter increment. */ | |
873 | ACCESS_ONCE(sync_rcu_preempt_exp_count)++; | |
874 | unlock_mb_ret: | |
875 | mutex_unlock(&sync_rcu_preempt_exp_mutex); | |
876 | mb_ret: | |
877 | smp_mb(); /* ensure subsequent action seen after grace period. */ | |
019129d5 PM |
878 | } |
879 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
880 | ||
e74f4c45 PM |
881 | /** |
882 | * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. | |
f0a0e6f2 PM |
883 | * |
884 | * Note that this primitive does not necessarily wait for an RCU grace period | |
885 | * to complete. For example, if there are no RCU callbacks queued anywhere | |
886 | * in the system, then rcu_barrier() is within its rights to return | |
887 | * immediately, without waiting for anything, much less an RCU grace period. | |
e74f4c45 PM |
888 | */ |
889 | void rcu_barrier(void) | |
890 | { | |
037b64ed | 891 | _rcu_barrier(&rcu_preempt_state); |
e74f4c45 PM |
892 | } |
893 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
894 | ||
1eba8f84 | 895 | /* |
6cc68793 | 896 | * Initialize preemptible RCU's state structures. |
1eba8f84 PM |
897 | */ |
898 | static void __init __rcu_init_preempt(void) | |
899 | { | |
394f99a9 | 900 | rcu_init_one(&rcu_preempt_state, &rcu_preempt_data); |
1eba8f84 PM |
901 | } |
902 | ||
2439b696 PM |
903 | /* |
904 | * Check for a task exiting while in a preemptible-RCU read-side | |
905 | * critical section, clean up if so. No need to issue warnings, | |
906 | * as debug_check_no_locks_held() already does this if lockdep | |
907 | * is enabled. | |
908 | */ | |
909 | void exit_rcu(void) | |
910 | { | |
911 | struct task_struct *t = current; | |
912 | ||
913 | if (likely(list_empty(¤t->rcu_node_entry))) | |
914 | return; | |
915 | t->rcu_read_lock_nesting = 1; | |
916 | barrier(); | |
917 | t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED; | |
918 | __rcu_read_unlock(); | |
919 | } | |
920 | ||
f41d911f PM |
921 | #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
922 | ||
e534165b | 923 | static struct rcu_state *rcu_state_p = &rcu_sched_state; |
27f4d280 | 924 | |
f41d911f PM |
925 | /* |
926 | * Tell them what RCU they are running. | |
927 | */ | |
0e0fc1c2 | 928 | static void __init rcu_bootup_announce(void) |
f41d911f | 929 | { |
efc151c3 | 930 | pr_info("Hierarchical RCU implementation.\n"); |
26845c28 | 931 | rcu_bootup_announce_oddness(); |
f41d911f PM |
932 | } |
933 | ||
934 | /* | |
935 | * Return the number of RCU batches processed thus far for debug & stats. | |
936 | */ | |
937 | long rcu_batches_completed(void) | |
938 | { | |
939 | return rcu_batches_completed_sched(); | |
940 | } | |
941 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
942 | ||
cba6d0d6 PM |
943 | /* |
944 | * Because preemptible RCU does not exist, we never have to check for | |
945 | * CPUs being in quiescent states. | |
946 | */ | |
947 | static void rcu_preempt_note_context_switch(int cpu) | |
948 | { | |
949 | } | |
950 | ||
fc2219d4 | 951 | /* |
6cc68793 | 952 | * Because preemptible RCU does not exist, there are never any preempted |
fc2219d4 PM |
953 | * RCU readers. |
954 | */ | |
27f4d280 | 955 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
fc2219d4 PM |
956 | { |
957 | return 0; | |
958 | } | |
959 | ||
b668c9cf PM |
960 | #ifdef CONFIG_HOTPLUG_CPU |
961 | ||
962 | /* Because preemptible RCU does not exist, no quieting of tasks. */ | |
d3f6bad3 | 963 | static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
b41d1b92 | 964 | __releases(rnp->lock) |
b668c9cf | 965 | { |
1304afb2 | 966 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b668c9cf PM |
967 | } |
968 | ||
969 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ | |
970 | ||
1ed509a2 | 971 | /* |
6cc68793 | 972 | * Because preemptible RCU does not exist, we never have to check for |
1ed509a2 PM |
973 | * tasks blocked within RCU read-side critical sections. |
974 | */ | |
975 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) | |
976 | { | |
977 | } | |
978 | ||
f41d911f | 979 | /* |
6cc68793 | 980 | * Because preemptible RCU does not exist, we never have to check for |
f41d911f PM |
981 | * tasks blocked within RCU read-side critical sections. |
982 | */ | |
9bc8b558 | 983 | static int rcu_print_task_stall(struct rcu_node *rnp) |
f41d911f | 984 | { |
9bc8b558 | 985 | return 0; |
f41d911f PM |
986 | } |
987 | ||
b0e165c0 | 988 | /* |
6cc68793 | 989 | * Because there is no preemptible RCU, there can be no readers blocked, |
49e29126 PM |
990 | * so there is no need to check for blocked tasks. So check only for |
991 | * bogus qsmask values. | |
b0e165c0 PM |
992 | */ |
993 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) | |
994 | { | |
49e29126 | 995 | WARN_ON_ONCE(rnp->qsmask); |
b0e165c0 PM |
996 | } |
997 | ||
33f76148 PM |
998 | #ifdef CONFIG_HOTPLUG_CPU |
999 | ||
dd5d19ba | 1000 | /* |
6cc68793 | 1001 | * Because preemptible RCU does not exist, it never needs to migrate |
237c80c5 PM |
1002 | * tasks that were blocked within RCU read-side critical sections, and |
1003 | * such non-existent tasks cannot possibly have been blocking the current | |
1004 | * grace period. | |
dd5d19ba | 1005 | */ |
237c80c5 PM |
1006 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
1007 | struct rcu_node *rnp, | |
1008 | struct rcu_data *rdp) | |
dd5d19ba | 1009 | { |
237c80c5 | 1010 | return 0; |
dd5d19ba PM |
1011 | } |
1012 | ||
e5601400 PM |
1013 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
1014 | ||
f41d911f | 1015 | /* |
6cc68793 | 1016 | * Because preemptible RCU does not exist, it never has any callbacks |
f41d911f PM |
1017 | * to check. |
1018 | */ | |
1eba8f84 | 1019 | static void rcu_preempt_check_callbacks(int cpu) |
f41d911f PM |
1020 | { |
1021 | } | |
1022 | ||
019129d5 PM |
1023 | /* |
1024 | * Wait for an rcu-preempt grace period, but make it happen quickly. | |
6cc68793 | 1025 | * But because preemptible RCU does not exist, map to rcu-sched. |
019129d5 PM |
1026 | */ |
1027 | void synchronize_rcu_expedited(void) | |
1028 | { | |
1029 | synchronize_sched_expedited(); | |
1030 | } | |
1031 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
1032 | ||
d9a3da06 PM |
1033 | #ifdef CONFIG_HOTPLUG_CPU |
1034 | ||
1035 | /* | |
6cc68793 | 1036 | * Because preemptible RCU does not exist, there is never any need to |
d9a3da06 PM |
1037 | * report on tasks preempted in RCU read-side critical sections during |
1038 | * expedited RCU grace periods. | |
1039 | */ | |
b40d293e TG |
1040 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
1041 | bool wake) | |
d9a3da06 | 1042 | { |
d9a3da06 PM |
1043 | } |
1044 | ||
1045 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ | |
1046 | ||
e74f4c45 | 1047 | /* |
6cc68793 | 1048 | * Because preemptible RCU does not exist, rcu_barrier() is just |
e74f4c45 PM |
1049 | * another name for rcu_barrier_sched(). |
1050 | */ | |
1051 | void rcu_barrier(void) | |
1052 | { | |
1053 | rcu_barrier_sched(); | |
1054 | } | |
1055 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
1056 | ||
1eba8f84 | 1057 | /* |
6cc68793 | 1058 | * Because preemptible RCU does not exist, it need not be initialized. |
1eba8f84 PM |
1059 | */ |
1060 | static void __init __rcu_init_preempt(void) | |
1061 | { | |
1062 | } | |
1063 | ||
2439b696 PM |
1064 | /* |
1065 | * Because preemptible RCU does not exist, tasks cannot possibly exit | |
1066 | * while in preemptible RCU read-side critical sections. | |
1067 | */ | |
1068 | void exit_rcu(void) | |
1069 | { | |
1070 | } | |
1071 | ||
f41d911f | 1072 | #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ |
8bd93a2c | 1073 | |
27f4d280 PM |
1074 | #ifdef CONFIG_RCU_BOOST |
1075 | ||
1696a8be | 1076 | #include "../locking/rtmutex_common.h" |
27f4d280 | 1077 | |
0ea1f2eb PM |
1078 | #ifdef CONFIG_RCU_TRACE |
1079 | ||
1080 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) | |
1081 | { | |
1082 | if (list_empty(&rnp->blkd_tasks)) | |
1083 | rnp->n_balk_blkd_tasks++; | |
1084 | else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL) | |
1085 | rnp->n_balk_exp_gp_tasks++; | |
1086 | else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL) | |
1087 | rnp->n_balk_boost_tasks++; | |
1088 | else if (rnp->gp_tasks != NULL && rnp->qsmask != 0) | |
1089 | rnp->n_balk_notblocked++; | |
1090 | else if (rnp->gp_tasks != NULL && | |
a9f4793d | 1091 | ULONG_CMP_LT(jiffies, rnp->boost_time)) |
0ea1f2eb PM |
1092 | rnp->n_balk_notyet++; |
1093 | else | |
1094 | rnp->n_balk_nos++; | |
1095 | } | |
1096 | ||
1097 | #else /* #ifdef CONFIG_RCU_TRACE */ | |
1098 | ||
1099 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) | |
1100 | { | |
1101 | } | |
1102 | ||
1103 | #endif /* #else #ifdef CONFIG_RCU_TRACE */ | |
1104 | ||
5d01bbd1 TG |
1105 | static void rcu_wake_cond(struct task_struct *t, int status) |
1106 | { | |
1107 | /* | |
1108 | * If the thread is yielding, only wake it when this | |
1109 | * is invoked from idle | |
1110 | */ | |
1111 | if (status != RCU_KTHREAD_YIELDING || is_idle_task(current)) | |
1112 | wake_up_process(t); | |
1113 | } | |
1114 | ||
27f4d280 PM |
1115 | /* |
1116 | * Carry out RCU priority boosting on the task indicated by ->exp_tasks | |
1117 | * or ->boost_tasks, advancing the pointer to the next task in the | |
1118 | * ->blkd_tasks list. | |
1119 | * | |
1120 | * Note that irqs must be enabled: boosting the task can block. | |
1121 | * Returns 1 if there are more tasks needing to be boosted. | |
1122 | */ | |
1123 | static int rcu_boost(struct rcu_node *rnp) | |
1124 | { | |
1125 | unsigned long flags; | |
27f4d280 PM |
1126 | struct task_struct *t; |
1127 | struct list_head *tb; | |
1128 | ||
1129 | if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) | |
1130 | return 0; /* Nothing left to boost. */ | |
1131 | ||
1132 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 1133 | smp_mb__after_unlock_lock(); |
27f4d280 PM |
1134 | |
1135 | /* | |
1136 | * Recheck under the lock: all tasks in need of boosting | |
1137 | * might exit their RCU read-side critical sections on their own. | |
1138 | */ | |
1139 | if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { | |
1140 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1141 | return 0; | |
1142 | } | |
1143 | ||
1144 | /* | |
1145 | * Preferentially boost tasks blocking expedited grace periods. | |
1146 | * This cannot starve the normal grace periods because a second | |
1147 | * expedited grace period must boost all blocked tasks, including | |
1148 | * those blocking the pre-existing normal grace period. | |
1149 | */ | |
0ea1f2eb | 1150 | if (rnp->exp_tasks != NULL) { |
27f4d280 | 1151 | tb = rnp->exp_tasks; |
0ea1f2eb PM |
1152 | rnp->n_exp_boosts++; |
1153 | } else { | |
27f4d280 | 1154 | tb = rnp->boost_tasks; |
0ea1f2eb PM |
1155 | rnp->n_normal_boosts++; |
1156 | } | |
1157 | rnp->n_tasks_boosted++; | |
27f4d280 PM |
1158 | |
1159 | /* | |
1160 | * We boost task t by manufacturing an rt_mutex that appears to | |
1161 | * be held by task t. We leave a pointer to that rt_mutex where | |
1162 | * task t can find it, and task t will release the mutex when it | |
1163 | * exits its outermost RCU read-side critical section. Then | |
1164 | * simply acquiring this artificial rt_mutex will boost task | |
1165 | * t's priority. (Thanks to tglx for suggesting this approach!) | |
1166 | * | |
1167 | * Note that task t must acquire rnp->lock to remove itself from | |
1168 | * the ->blkd_tasks list, which it will do from exit() if from | |
1169 | * nowhere else. We therefore are guaranteed that task t will | |
1170 | * stay around at least until we drop rnp->lock. Note that | |
1171 | * rnp->lock also resolves races between our priority boosting | |
1172 | * and task t's exiting its outermost RCU read-side critical | |
1173 | * section. | |
1174 | */ | |
1175 | t = container_of(tb, struct task_struct, rcu_node_entry); | |
abaa93d9 | 1176 | rt_mutex_init_proxy_locked(&rnp->boost_mtx, t); |
dfeb9765 | 1177 | init_completion(&rnp->boost_completion); |
27f4d280 | 1178 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
abaa93d9 PM |
1179 | /* Lock only for side effect: boosts task t's priority. */ |
1180 | rt_mutex_lock(&rnp->boost_mtx); | |
1181 | rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ | |
27f4d280 | 1182 | |
abaa93d9 | 1183 | /* Wait for boostee to be done w/boost_mtx before reinitializing. */ |
dfeb9765 | 1184 | wait_for_completion(&rnp->boost_completion); |
27f4d280 | 1185 | |
4f89b336 PM |
1186 | return ACCESS_ONCE(rnp->exp_tasks) != NULL || |
1187 | ACCESS_ONCE(rnp->boost_tasks) != NULL; | |
27f4d280 PM |
1188 | } |
1189 | ||
27f4d280 PM |
1190 | /* |
1191 | * Priority-boosting kthread. One per leaf rcu_node and one for the | |
1192 | * root rcu_node. | |
1193 | */ | |
1194 | static int rcu_boost_kthread(void *arg) | |
1195 | { | |
1196 | struct rcu_node *rnp = (struct rcu_node *)arg; | |
1197 | int spincnt = 0; | |
1198 | int more2boost; | |
1199 | ||
f7f7bac9 | 1200 | trace_rcu_utilization(TPS("Start boost kthread@init")); |
27f4d280 | 1201 | for (;;) { |
d71df90e | 1202 | rnp->boost_kthread_status = RCU_KTHREAD_WAITING; |
f7f7bac9 | 1203 | trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); |
08bca60a | 1204 | rcu_wait(rnp->boost_tasks || rnp->exp_tasks); |
f7f7bac9 | 1205 | trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); |
d71df90e | 1206 | rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; |
27f4d280 PM |
1207 | more2boost = rcu_boost(rnp); |
1208 | if (more2boost) | |
1209 | spincnt++; | |
1210 | else | |
1211 | spincnt = 0; | |
1212 | if (spincnt > 10) { | |
5d01bbd1 | 1213 | rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; |
f7f7bac9 | 1214 | trace_rcu_utilization(TPS("End boost kthread@rcu_yield")); |
5d01bbd1 | 1215 | schedule_timeout_interruptible(2); |
f7f7bac9 | 1216 | trace_rcu_utilization(TPS("Start boost kthread@rcu_yield")); |
27f4d280 PM |
1217 | spincnt = 0; |
1218 | } | |
1219 | } | |
1217ed1b | 1220 | /* NOTREACHED */ |
f7f7bac9 | 1221 | trace_rcu_utilization(TPS("End boost kthread@notreached")); |
27f4d280 PM |
1222 | return 0; |
1223 | } | |
1224 | ||
1225 | /* | |
1226 | * Check to see if it is time to start boosting RCU readers that are | |
1227 | * blocking the current grace period, and, if so, tell the per-rcu_node | |
1228 | * kthread to start boosting them. If there is an expedited grace | |
1229 | * period in progress, it is always time to boost. | |
1230 | * | |
b065a853 PM |
1231 | * The caller must hold rnp->lock, which this function releases. |
1232 | * The ->boost_kthread_task is immortal, so we don't need to worry | |
1233 | * about it going away. | |
27f4d280 | 1234 | */ |
1217ed1b | 1235 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
615e41c6 | 1236 | __releases(rnp->lock) |
27f4d280 PM |
1237 | { |
1238 | struct task_struct *t; | |
1239 | ||
0ea1f2eb PM |
1240 | if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { |
1241 | rnp->n_balk_exp_gp_tasks++; | |
1217ed1b | 1242 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d280 | 1243 | return; |
0ea1f2eb | 1244 | } |
27f4d280 PM |
1245 | if (rnp->exp_tasks != NULL || |
1246 | (rnp->gp_tasks != NULL && | |
1247 | rnp->boost_tasks == NULL && | |
1248 | rnp->qsmask == 0 && | |
1249 | ULONG_CMP_GE(jiffies, rnp->boost_time))) { | |
1250 | if (rnp->exp_tasks == NULL) | |
1251 | rnp->boost_tasks = rnp->gp_tasks; | |
1217ed1b | 1252 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d280 | 1253 | t = rnp->boost_kthread_task; |
5d01bbd1 TG |
1254 | if (t) |
1255 | rcu_wake_cond(t, rnp->boost_kthread_status); | |
1217ed1b | 1256 | } else { |
0ea1f2eb | 1257 | rcu_initiate_boost_trace(rnp); |
1217ed1b PM |
1258 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1259 | } | |
27f4d280 PM |
1260 | } |
1261 | ||
a46e0899 PM |
1262 | /* |
1263 | * Wake up the per-CPU kthread to invoke RCU callbacks. | |
1264 | */ | |
1265 | static void invoke_rcu_callbacks_kthread(void) | |
1266 | { | |
1267 | unsigned long flags; | |
1268 | ||
1269 | local_irq_save(flags); | |
1270 | __this_cpu_write(rcu_cpu_has_work, 1); | |
1eb52121 | 1271 | if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && |
5d01bbd1 TG |
1272 | current != __this_cpu_read(rcu_cpu_kthread_task)) { |
1273 | rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), | |
1274 | __this_cpu_read(rcu_cpu_kthread_status)); | |
1275 | } | |
a46e0899 PM |
1276 | local_irq_restore(flags); |
1277 | } | |
1278 | ||
dff1672d PM |
1279 | /* |
1280 | * Is the current CPU running the RCU-callbacks kthread? | |
1281 | * Caller must have preemption disabled. | |
1282 | */ | |
1283 | static bool rcu_is_callbacks_kthread(void) | |
1284 | { | |
c9d4b0af | 1285 | return __this_cpu_read(rcu_cpu_kthread_task) == current; |
dff1672d PM |
1286 | } |
1287 | ||
27f4d280 PM |
1288 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
1289 | ||
1290 | /* | |
1291 | * Do priority-boost accounting for the start of a new grace period. | |
1292 | */ | |
1293 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) | |
1294 | { | |
1295 | rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; | |
1296 | } | |
1297 | ||
27f4d280 PM |
1298 | /* |
1299 | * Create an RCU-boost kthread for the specified node if one does not | |
1300 | * already exist. We only create this kthread for preemptible RCU. | |
1301 | * Returns zero if all is well, a negated errno otherwise. | |
1302 | */ | |
49fb4c62 | 1303 | static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, |
5d01bbd1 | 1304 | struct rcu_node *rnp) |
27f4d280 | 1305 | { |
5d01bbd1 | 1306 | int rnp_index = rnp - &rsp->node[0]; |
27f4d280 PM |
1307 | unsigned long flags; |
1308 | struct sched_param sp; | |
1309 | struct task_struct *t; | |
1310 | ||
1311 | if (&rcu_preempt_state != rsp) | |
1312 | return 0; | |
5d01bbd1 TG |
1313 | |
1314 | if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0) | |
1315 | return 0; | |
1316 | ||
a46e0899 | 1317 | rsp->boost = 1; |
27f4d280 PM |
1318 | if (rnp->boost_kthread_task != NULL) |
1319 | return 0; | |
1320 | t = kthread_create(rcu_boost_kthread, (void *)rnp, | |
5b61b0ba | 1321 | "rcub/%d", rnp_index); |
27f4d280 PM |
1322 | if (IS_ERR(t)) |
1323 | return PTR_ERR(t); | |
1324 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 1325 | smp_mb__after_unlock_lock(); |
27f4d280 PM |
1326 | rnp->boost_kthread_task = t; |
1327 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
5b61b0ba | 1328 | sp.sched_priority = RCU_BOOST_PRIO; |
27f4d280 | 1329 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
9a432736 | 1330 | wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ |
27f4d280 PM |
1331 | return 0; |
1332 | } | |
1333 | ||
f8b7fc6b PM |
1334 | static void rcu_kthread_do_work(void) |
1335 | { | |
c9d4b0af CL |
1336 | rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data)); |
1337 | rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data)); | |
f8b7fc6b PM |
1338 | rcu_preempt_do_callbacks(); |
1339 | } | |
1340 | ||
62ab7072 | 1341 | static void rcu_cpu_kthread_setup(unsigned int cpu) |
f8b7fc6b | 1342 | { |
f8b7fc6b | 1343 | struct sched_param sp; |
f8b7fc6b | 1344 | |
62ab7072 PM |
1345 | sp.sched_priority = RCU_KTHREAD_PRIO; |
1346 | sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); | |
f8b7fc6b PM |
1347 | } |
1348 | ||
62ab7072 | 1349 | static void rcu_cpu_kthread_park(unsigned int cpu) |
f8b7fc6b | 1350 | { |
62ab7072 | 1351 | per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; |
f8b7fc6b PM |
1352 | } |
1353 | ||
62ab7072 | 1354 | static int rcu_cpu_kthread_should_run(unsigned int cpu) |
f8b7fc6b | 1355 | { |
c9d4b0af | 1356 | return __this_cpu_read(rcu_cpu_has_work); |
f8b7fc6b PM |
1357 | } |
1358 | ||
1359 | /* | |
1360 | * Per-CPU kernel thread that invokes RCU callbacks. This replaces the | |
e0f23060 PM |
1361 | * RCU softirq used in flavors and configurations of RCU that do not |
1362 | * support RCU priority boosting. | |
f8b7fc6b | 1363 | */ |
62ab7072 | 1364 | static void rcu_cpu_kthread(unsigned int cpu) |
f8b7fc6b | 1365 | { |
c9d4b0af CL |
1366 | unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status); |
1367 | char work, *workp = this_cpu_ptr(&rcu_cpu_has_work); | |
62ab7072 | 1368 | int spincnt; |
f8b7fc6b | 1369 | |
62ab7072 | 1370 | for (spincnt = 0; spincnt < 10; spincnt++) { |
f7f7bac9 | 1371 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); |
f8b7fc6b | 1372 | local_bh_disable(); |
f8b7fc6b | 1373 | *statusp = RCU_KTHREAD_RUNNING; |
62ab7072 PM |
1374 | this_cpu_inc(rcu_cpu_kthread_loops); |
1375 | local_irq_disable(); | |
f8b7fc6b PM |
1376 | work = *workp; |
1377 | *workp = 0; | |
62ab7072 | 1378 | local_irq_enable(); |
f8b7fc6b PM |
1379 | if (work) |
1380 | rcu_kthread_do_work(); | |
1381 | local_bh_enable(); | |
62ab7072 | 1382 | if (*workp == 0) { |
f7f7bac9 | 1383 | trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); |
62ab7072 PM |
1384 | *statusp = RCU_KTHREAD_WAITING; |
1385 | return; | |
f8b7fc6b PM |
1386 | } |
1387 | } | |
62ab7072 | 1388 | *statusp = RCU_KTHREAD_YIELDING; |
f7f7bac9 | 1389 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield")); |
62ab7072 | 1390 | schedule_timeout_interruptible(2); |
f7f7bac9 | 1391 | trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); |
62ab7072 | 1392 | *statusp = RCU_KTHREAD_WAITING; |
f8b7fc6b PM |
1393 | } |
1394 | ||
1395 | /* | |
1396 | * Set the per-rcu_node kthread's affinity to cover all CPUs that are | |
1397 | * served by the rcu_node in question. The CPU hotplug lock is still | |
1398 | * held, so the value of rnp->qsmaskinit will be stable. | |
1399 | * | |
1400 | * We don't include outgoingcpu in the affinity set, use -1 if there is | |
1401 | * no outgoing CPU. If there are no CPUs left in the affinity set, | |
1402 | * this function allows the kthread to execute on any CPU. | |
1403 | */ | |
5d01bbd1 | 1404 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
f8b7fc6b | 1405 | { |
5d01bbd1 TG |
1406 | struct task_struct *t = rnp->boost_kthread_task; |
1407 | unsigned long mask = rnp->qsmaskinit; | |
f8b7fc6b PM |
1408 | cpumask_var_t cm; |
1409 | int cpu; | |
f8b7fc6b | 1410 | |
5d01bbd1 | 1411 | if (!t) |
f8b7fc6b | 1412 | return; |
5d01bbd1 | 1413 | if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) |
f8b7fc6b | 1414 | return; |
f8b7fc6b PM |
1415 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) |
1416 | if ((mask & 0x1) && cpu != outgoingcpu) | |
1417 | cpumask_set_cpu(cpu, cm); | |
1418 | if (cpumask_weight(cm) == 0) { | |
1419 | cpumask_setall(cm); | |
1420 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) | |
1421 | cpumask_clear_cpu(cpu, cm); | |
1422 | WARN_ON_ONCE(cpumask_weight(cm) == 0); | |
1423 | } | |
5d01bbd1 | 1424 | set_cpus_allowed_ptr(t, cm); |
f8b7fc6b PM |
1425 | free_cpumask_var(cm); |
1426 | } | |
1427 | ||
62ab7072 PM |
1428 | static struct smp_hotplug_thread rcu_cpu_thread_spec = { |
1429 | .store = &rcu_cpu_kthread_task, | |
1430 | .thread_should_run = rcu_cpu_kthread_should_run, | |
1431 | .thread_fn = rcu_cpu_kthread, | |
1432 | .thread_comm = "rcuc/%u", | |
1433 | .setup = rcu_cpu_kthread_setup, | |
1434 | .park = rcu_cpu_kthread_park, | |
1435 | }; | |
f8b7fc6b PM |
1436 | |
1437 | /* | |
9386c0b7 | 1438 | * Spawn boost kthreads -- called as soon as the scheduler is running. |
f8b7fc6b | 1439 | */ |
9386c0b7 | 1440 | static void __init rcu_spawn_boost_kthreads(void) |
f8b7fc6b | 1441 | { |
f8b7fc6b | 1442 | struct rcu_node *rnp; |
5d01bbd1 | 1443 | int cpu; |
f8b7fc6b | 1444 | |
62ab7072 | 1445 | for_each_possible_cpu(cpu) |
f8b7fc6b | 1446 | per_cpu(rcu_cpu_has_work, cpu) = 0; |
62ab7072 | 1447 | BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); |
e534165b US |
1448 | rnp = rcu_get_root(rcu_state_p); |
1449 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); | |
f8b7fc6b | 1450 | if (NUM_RCU_NODES > 1) { |
e534165b US |
1451 | rcu_for_each_leaf_node(rcu_state_p, rnp) |
1452 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); | |
f8b7fc6b | 1453 | } |
f8b7fc6b | 1454 | } |
f8b7fc6b | 1455 | |
49fb4c62 | 1456 | static void rcu_prepare_kthreads(int cpu) |
f8b7fc6b | 1457 | { |
e534165b | 1458 | struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
f8b7fc6b PM |
1459 | struct rcu_node *rnp = rdp->mynode; |
1460 | ||
1461 | /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ | |
62ab7072 | 1462 | if (rcu_scheduler_fully_active) |
e534165b | 1463 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); |
f8b7fc6b PM |
1464 | } |
1465 | ||
27f4d280 PM |
1466 | #else /* #ifdef CONFIG_RCU_BOOST */ |
1467 | ||
1217ed1b | 1468 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
615e41c6 | 1469 | __releases(rnp->lock) |
27f4d280 | 1470 | { |
1217ed1b | 1471 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d280 PM |
1472 | } |
1473 | ||
a46e0899 | 1474 | static void invoke_rcu_callbacks_kthread(void) |
27f4d280 | 1475 | { |
a46e0899 | 1476 | WARN_ON_ONCE(1); |
27f4d280 PM |
1477 | } |
1478 | ||
dff1672d PM |
1479 | static bool rcu_is_callbacks_kthread(void) |
1480 | { | |
1481 | return false; | |
1482 | } | |
1483 | ||
27f4d280 PM |
1484 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) |
1485 | { | |
1486 | } | |
1487 | ||
5d01bbd1 | 1488 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
f8b7fc6b PM |
1489 | { |
1490 | } | |
1491 | ||
9386c0b7 | 1492 | static void __init rcu_spawn_boost_kthreads(void) |
b0d30417 | 1493 | { |
b0d30417 | 1494 | } |
b0d30417 | 1495 | |
49fb4c62 | 1496 | static void rcu_prepare_kthreads(int cpu) |
f8b7fc6b PM |
1497 | { |
1498 | } | |
1499 | ||
27f4d280 PM |
1500 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ |
1501 | ||
8bd93a2c PM |
1502 | #if !defined(CONFIG_RCU_FAST_NO_HZ) |
1503 | ||
1504 | /* | |
1505 | * Check to see if any future RCU-related work will need to be done | |
1506 | * by the current CPU, even if none need be done immediately, returning | |
1507 | * 1 if so. This function is part of the RCU implementation; it is -not- | |
1508 | * an exported member of the RCU API. | |
1509 | * | |
7cb92499 PM |
1510 | * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs |
1511 | * any flavor of RCU. | |
8bd93a2c | 1512 | */ |
ffa83fb5 | 1513 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
aa9b1630 | 1514 | int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) |
8bd93a2c | 1515 | { |
aa9b1630 | 1516 | *delta_jiffies = ULONG_MAX; |
c0f4dfd4 | 1517 | return rcu_cpu_has_callbacks(cpu, NULL); |
7cb92499 | 1518 | } |
ffa83fb5 | 1519 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
7cb92499 PM |
1520 | |
1521 | /* | |
1522 | * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up | |
1523 | * after it. | |
1524 | */ | |
1525 | static void rcu_cleanup_after_idle(int cpu) | |
1526 | { | |
1527 | } | |
1528 | ||
aea1b35e | 1529 | /* |
a858af28 | 1530 | * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, |
aea1b35e PM |
1531 | * is nothing. |
1532 | */ | |
1533 | static void rcu_prepare_for_idle(int cpu) | |
1534 | { | |
1535 | } | |
1536 | ||
c57afe80 PM |
1537 | /* |
1538 | * Don't bother keeping a running count of the number of RCU callbacks | |
1539 | * posted because CONFIG_RCU_FAST_NO_HZ=n. | |
1540 | */ | |
1541 | static void rcu_idle_count_callbacks_posted(void) | |
1542 | { | |
1543 | } | |
1544 | ||
8bd93a2c PM |
1545 | #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
1546 | ||
f23f7fa1 PM |
1547 | /* |
1548 | * This code is invoked when a CPU goes idle, at which point we want | |
1549 | * to have the CPU do everything required for RCU so that it can enter | |
1550 | * the energy-efficient dyntick-idle mode. This is handled by a | |
1551 | * state machine implemented by rcu_prepare_for_idle() below. | |
1552 | * | |
1553 | * The following three proprocessor symbols control this state machine: | |
1554 | * | |
f23f7fa1 PM |
1555 | * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted |
1556 | * to sleep in dyntick-idle mode with RCU callbacks pending. This | |
1557 | * is sized to be roughly one RCU grace period. Those energy-efficiency | |
1558 | * benchmarkers who might otherwise be tempted to set this to a large | |
1559 | * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your | |
1560 | * system. And if you are -that- concerned about energy efficiency, | |
1561 | * just power the system down and be done with it! | |
778d250a PM |
1562 | * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is |
1563 | * permitted to sleep in dyntick-idle mode with only lazy RCU | |
1564 | * callbacks pending. Setting this too high can OOM your system. | |
f23f7fa1 PM |
1565 | * |
1566 | * The values below work well in practice. If future workloads require | |
1567 | * adjustment, they can be converted into kernel config parameters, though | |
1568 | * making the state machine smarter might be a better option. | |
1569 | */ | |
e84c48ae | 1570 | #define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ |
778d250a | 1571 | #define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ |
f23f7fa1 | 1572 | |
5e44ce35 PM |
1573 | static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY; |
1574 | module_param(rcu_idle_gp_delay, int, 0644); | |
1575 | static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY; | |
1576 | module_param(rcu_idle_lazy_gp_delay, int, 0644); | |
486e2593 | 1577 | |
d689fe22 | 1578 | extern int tick_nohz_active; |
486e2593 PM |
1579 | |
1580 | /* | |
c229828c PM |
1581 | * Try to advance callbacks for all flavors of RCU on the current CPU, but |
1582 | * only if it has been awhile since the last time we did so. Afterwards, | |
1583 | * if there are any callbacks ready for immediate invocation, return true. | |
486e2593 | 1584 | */ |
f1f399d1 | 1585 | static bool __maybe_unused rcu_try_advance_all_cbs(void) |
486e2593 | 1586 | { |
c0f4dfd4 PM |
1587 | bool cbs_ready = false; |
1588 | struct rcu_data *rdp; | |
c229828c | 1589 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
c0f4dfd4 PM |
1590 | struct rcu_node *rnp; |
1591 | struct rcu_state *rsp; | |
486e2593 | 1592 | |
c229828c PM |
1593 | /* Exit early if we advanced recently. */ |
1594 | if (jiffies == rdtp->last_advance_all) | |
1595 | return 0; | |
1596 | rdtp->last_advance_all = jiffies; | |
1597 | ||
c0f4dfd4 PM |
1598 | for_each_rcu_flavor(rsp) { |
1599 | rdp = this_cpu_ptr(rsp->rda); | |
1600 | rnp = rdp->mynode; | |
486e2593 | 1601 | |
c0f4dfd4 PM |
1602 | /* |
1603 | * Don't bother checking unless a grace period has | |
1604 | * completed since we last checked and there are | |
1605 | * callbacks not yet ready to invoke. | |
1606 | */ | |
1607 | if (rdp->completed != rnp->completed && | |
1608 | rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL]) | |
470716fc | 1609 | note_gp_changes(rsp, rdp); |
486e2593 | 1610 | |
c0f4dfd4 PM |
1611 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
1612 | cbs_ready = true; | |
1613 | } | |
1614 | return cbs_ready; | |
486e2593 PM |
1615 | } |
1616 | ||
aa9b1630 | 1617 | /* |
c0f4dfd4 PM |
1618 | * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready |
1619 | * to invoke. If the CPU has callbacks, try to advance them. Tell the | |
1620 | * caller to set the timeout based on whether or not there are non-lazy | |
1621 | * callbacks. | |
aa9b1630 | 1622 | * |
c0f4dfd4 | 1623 | * The caller must have disabled interrupts. |
aa9b1630 | 1624 | */ |
ffa83fb5 | 1625 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
c0f4dfd4 | 1626 | int rcu_needs_cpu(int cpu, unsigned long *dj) |
aa9b1630 PM |
1627 | { |
1628 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); | |
1629 | ||
c0f4dfd4 PM |
1630 | /* Snapshot to detect later posting of non-lazy callback. */ |
1631 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; | |
1632 | ||
aa9b1630 | 1633 | /* If no callbacks, RCU doesn't need the CPU. */ |
c0f4dfd4 PM |
1634 | if (!rcu_cpu_has_callbacks(cpu, &rdtp->all_lazy)) { |
1635 | *dj = ULONG_MAX; | |
aa9b1630 PM |
1636 | return 0; |
1637 | } | |
c0f4dfd4 PM |
1638 | |
1639 | /* Attempt to advance callbacks. */ | |
1640 | if (rcu_try_advance_all_cbs()) { | |
1641 | /* Some ready to invoke, so initiate later invocation. */ | |
1642 | invoke_rcu_core(); | |
aa9b1630 PM |
1643 | return 1; |
1644 | } | |
c0f4dfd4 PM |
1645 | rdtp->last_accelerate = jiffies; |
1646 | ||
1647 | /* Request timer delay depending on laziness, and round. */ | |
6faf7283 | 1648 | if (!rdtp->all_lazy) { |
c0f4dfd4 PM |
1649 | *dj = round_up(rcu_idle_gp_delay + jiffies, |
1650 | rcu_idle_gp_delay) - jiffies; | |
e84c48ae | 1651 | } else { |
c0f4dfd4 | 1652 | *dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; |
e84c48ae | 1653 | } |
aa9b1630 PM |
1654 | return 0; |
1655 | } | |
ffa83fb5 | 1656 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
aa9b1630 | 1657 | |
21e52e15 | 1658 | /* |
c0f4dfd4 PM |
1659 | * Prepare a CPU for idle from an RCU perspective. The first major task |
1660 | * is to sense whether nohz mode has been enabled or disabled via sysfs. | |
1661 | * The second major task is to check to see if a non-lazy callback has | |
1662 | * arrived at a CPU that previously had only lazy callbacks. The third | |
1663 | * major task is to accelerate (that is, assign grace-period numbers to) | |
1664 | * any recently arrived callbacks. | |
aea1b35e PM |
1665 | * |
1666 | * The caller must have disabled interrupts. | |
8bd93a2c | 1667 | */ |
aea1b35e | 1668 | static void rcu_prepare_for_idle(int cpu) |
8bd93a2c | 1669 | { |
f1f399d1 | 1670 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
48a7639c | 1671 | bool needwake; |
c0f4dfd4 | 1672 | struct rcu_data *rdp; |
5955f7ee | 1673 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
c0f4dfd4 PM |
1674 | struct rcu_node *rnp; |
1675 | struct rcu_state *rsp; | |
9d2ad243 PM |
1676 | int tne; |
1677 | ||
1678 | /* Handle nohz enablement switches conservatively. */ | |
d689fe22 | 1679 | tne = ACCESS_ONCE(tick_nohz_active); |
9d2ad243 | 1680 | if (tne != rdtp->tick_nohz_enabled_snap) { |
c0f4dfd4 | 1681 | if (rcu_cpu_has_callbacks(cpu, NULL)) |
9d2ad243 PM |
1682 | invoke_rcu_core(); /* force nohz to see update. */ |
1683 | rdtp->tick_nohz_enabled_snap = tne; | |
1684 | return; | |
1685 | } | |
1686 | if (!tne) | |
1687 | return; | |
f511fc62 | 1688 | |
c0f4dfd4 | 1689 | /* If this is a no-CBs CPU, no callbacks, just return. */ |
534c97b0 | 1690 | if (rcu_is_nocb_cpu(cpu)) |
9a0c6fef | 1691 | return; |
9a0c6fef | 1692 | |
c57afe80 | 1693 | /* |
c0f4dfd4 PM |
1694 | * If a non-lazy callback arrived at a CPU having only lazy |
1695 | * callbacks, invoke RCU core for the side-effect of recalculating | |
1696 | * idle duration on re-entry to idle. | |
c57afe80 | 1697 | */ |
c0f4dfd4 PM |
1698 | if (rdtp->all_lazy && |
1699 | rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) { | |
c337f8f5 PM |
1700 | rdtp->all_lazy = false; |
1701 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; | |
c0f4dfd4 | 1702 | invoke_rcu_core(); |
c57afe80 PM |
1703 | return; |
1704 | } | |
c57afe80 | 1705 | |
3084f2f8 | 1706 | /* |
c0f4dfd4 PM |
1707 | * If we have not yet accelerated this jiffy, accelerate all |
1708 | * callbacks on this CPU. | |
3084f2f8 | 1709 | */ |
c0f4dfd4 | 1710 | if (rdtp->last_accelerate == jiffies) |
aea1b35e | 1711 | return; |
c0f4dfd4 PM |
1712 | rdtp->last_accelerate = jiffies; |
1713 | for_each_rcu_flavor(rsp) { | |
1714 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
1715 | if (!*rdp->nxttail[RCU_DONE_TAIL]) | |
1716 | continue; | |
1717 | rnp = rdp->mynode; | |
1718 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
6303b9c8 | 1719 | smp_mb__after_unlock_lock(); |
48a7639c | 1720 | needwake = rcu_accelerate_cbs(rsp, rnp, rdp); |
c0f4dfd4 | 1721 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
48a7639c PM |
1722 | if (needwake) |
1723 | rcu_gp_kthread_wake(rsp); | |
77e38ed3 | 1724 | } |
f1f399d1 | 1725 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
c0f4dfd4 | 1726 | } |
3084f2f8 | 1727 | |
c0f4dfd4 PM |
1728 | /* |
1729 | * Clean up for exit from idle. Attempt to advance callbacks based on | |
1730 | * any grace periods that elapsed while the CPU was idle, and if any | |
1731 | * callbacks are now ready to invoke, initiate invocation. | |
1732 | */ | |
1733 | static void rcu_cleanup_after_idle(int cpu) | |
1734 | { | |
f1f399d1 | 1735 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
534c97b0 | 1736 | if (rcu_is_nocb_cpu(cpu)) |
aea1b35e | 1737 | return; |
7a497c96 PM |
1738 | if (rcu_try_advance_all_cbs()) |
1739 | invoke_rcu_core(); | |
f1f399d1 | 1740 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
8bd93a2c PM |
1741 | } |
1742 | ||
c57afe80 | 1743 | /* |
98248a0e PM |
1744 | * Keep a running count of the number of non-lazy callbacks posted |
1745 | * on this CPU. This running counter (which is never decremented) allows | |
1746 | * rcu_prepare_for_idle() to detect when something out of the idle loop | |
1747 | * posts a callback, even if an equal number of callbacks are invoked. | |
1748 | * Of course, callbacks should only be posted from within a trace event | |
1749 | * designed to be called from idle or from within RCU_NONIDLE(). | |
c57afe80 PM |
1750 | */ |
1751 | static void rcu_idle_count_callbacks_posted(void) | |
1752 | { | |
5955f7ee | 1753 | __this_cpu_add(rcu_dynticks.nonlazy_posted, 1); |
c57afe80 PM |
1754 | } |
1755 | ||
b626c1b6 PM |
1756 | /* |
1757 | * Data for flushing lazy RCU callbacks at OOM time. | |
1758 | */ | |
1759 | static atomic_t oom_callback_count; | |
1760 | static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq); | |
1761 | ||
1762 | /* | |
1763 | * RCU OOM callback -- decrement the outstanding count and deliver the | |
1764 | * wake-up if we are the last one. | |
1765 | */ | |
1766 | static void rcu_oom_callback(struct rcu_head *rhp) | |
1767 | { | |
1768 | if (atomic_dec_and_test(&oom_callback_count)) | |
1769 | wake_up(&oom_callback_wq); | |
1770 | } | |
1771 | ||
1772 | /* | |
1773 | * Post an rcu_oom_notify callback on the current CPU if it has at | |
1774 | * least one lazy callback. This will unnecessarily post callbacks | |
1775 | * to CPUs that already have a non-lazy callback at the end of their | |
1776 | * callback list, but this is an infrequent operation, so accept some | |
1777 | * extra overhead to keep things simple. | |
1778 | */ | |
1779 | static void rcu_oom_notify_cpu(void *unused) | |
1780 | { | |
1781 | struct rcu_state *rsp; | |
1782 | struct rcu_data *rdp; | |
1783 | ||
1784 | for_each_rcu_flavor(rsp) { | |
fa07a58f | 1785 | rdp = raw_cpu_ptr(rsp->rda); |
b626c1b6 PM |
1786 | if (rdp->qlen_lazy != 0) { |
1787 | atomic_inc(&oom_callback_count); | |
1788 | rsp->call(&rdp->oom_head, rcu_oom_callback); | |
1789 | } | |
1790 | } | |
1791 | } | |
1792 | ||
1793 | /* | |
1794 | * If low on memory, ensure that each CPU has a non-lazy callback. | |
1795 | * This will wake up CPUs that have only lazy callbacks, in turn | |
1796 | * ensuring that they free up the corresponding memory in a timely manner. | |
1797 | * Because an uncertain amount of memory will be freed in some uncertain | |
1798 | * timeframe, we do not claim to have freed anything. | |
1799 | */ | |
1800 | static int rcu_oom_notify(struct notifier_block *self, | |
1801 | unsigned long notused, void *nfreed) | |
1802 | { | |
1803 | int cpu; | |
1804 | ||
1805 | /* Wait for callbacks from earlier instance to complete. */ | |
1806 | wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0); | |
78e4bc34 | 1807 | smp_mb(); /* Ensure callback reuse happens after callback invocation. */ |
b626c1b6 PM |
1808 | |
1809 | /* | |
1810 | * Prevent premature wakeup: ensure that all increments happen | |
1811 | * before there is a chance of the counter reaching zero. | |
1812 | */ | |
1813 | atomic_set(&oom_callback_count, 1); | |
1814 | ||
1815 | get_online_cpus(); | |
1816 | for_each_online_cpu(cpu) { | |
1817 | smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); | |
1818 | cond_resched(); | |
1819 | } | |
1820 | put_online_cpus(); | |
1821 | ||
1822 | /* Unconditionally decrement: no need to wake ourselves up. */ | |
1823 | atomic_dec(&oom_callback_count); | |
1824 | ||
1825 | return NOTIFY_OK; | |
1826 | } | |
1827 | ||
1828 | static struct notifier_block rcu_oom_nb = { | |
1829 | .notifier_call = rcu_oom_notify | |
1830 | }; | |
1831 | ||
1832 | static int __init rcu_register_oom_notifier(void) | |
1833 | { | |
1834 | register_oom_notifier(&rcu_oom_nb); | |
1835 | return 0; | |
1836 | } | |
1837 | early_initcall(rcu_register_oom_notifier); | |
1838 | ||
8bd93a2c | 1839 | #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
a858af28 PM |
1840 | |
1841 | #ifdef CONFIG_RCU_CPU_STALL_INFO | |
1842 | ||
1843 | #ifdef CONFIG_RCU_FAST_NO_HZ | |
1844 | ||
1845 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) | |
1846 | { | |
5955f7ee | 1847 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
c0f4dfd4 | 1848 | unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap; |
a858af28 | 1849 | |
c0f4dfd4 PM |
1850 | sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", |
1851 | rdtp->last_accelerate & 0xffff, jiffies & 0xffff, | |
1852 | ulong2long(nlpd), | |
1853 | rdtp->all_lazy ? 'L' : '.', | |
1854 | rdtp->tick_nohz_enabled_snap ? '.' : 'D'); | |
a858af28 PM |
1855 | } |
1856 | ||
1857 | #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ | |
1858 | ||
1859 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) | |
1860 | { | |
1c17e4d4 | 1861 | *cp = '\0'; |
a858af28 PM |
1862 | } |
1863 | ||
1864 | #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ | |
1865 | ||
1866 | /* Initiate the stall-info list. */ | |
1867 | static void print_cpu_stall_info_begin(void) | |
1868 | { | |
efc151c3 | 1869 | pr_cont("\n"); |
a858af28 PM |
1870 | } |
1871 | ||
1872 | /* | |
1873 | * Print out diagnostic information for the specified stalled CPU. | |
1874 | * | |
1875 | * If the specified CPU is aware of the current RCU grace period | |
1876 | * (flavor specified by rsp), then print the number of scheduling | |
1877 | * clock interrupts the CPU has taken during the time that it has | |
1878 | * been aware. Otherwise, print the number of RCU grace periods | |
1879 | * that this CPU is ignorant of, for example, "1" if the CPU was | |
1880 | * aware of the previous grace period. | |
1881 | * | |
1882 | * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. | |
1883 | */ | |
1884 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) | |
1885 | { | |
1886 | char fast_no_hz[72]; | |
1887 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
1888 | struct rcu_dynticks *rdtp = rdp->dynticks; | |
1889 | char *ticks_title; | |
1890 | unsigned long ticks_value; | |
1891 | ||
1892 | if (rsp->gpnum == rdp->gpnum) { | |
1893 | ticks_title = "ticks this GP"; | |
1894 | ticks_value = rdp->ticks_this_gp; | |
1895 | } else { | |
1896 | ticks_title = "GPs behind"; | |
1897 | ticks_value = rsp->gpnum - rdp->gpnum; | |
1898 | } | |
1899 | print_cpu_stall_fast_no_hz(fast_no_hz, cpu); | |
efc151c3 | 1900 | pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u %s\n", |
a858af28 PM |
1901 | cpu, ticks_value, ticks_title, |
1902 | atomic_read(&rdtp->dynticks) & 0xfff, | |
1903 | rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, | |
6231069b | 1904 | rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), |
a858af28 PM |
1905 | fast_no_hz); |
1906 | } | |
1907 | ||
1908 | /* Terminate the stall-info list. */ | |
1909 | static void print_cpu_stall_info_end(void) | |
1910 | { | |
efc151c3 | 1911 | pr_err("\t"); |
a858af28 PM |
1912 | } |
1913 | ||
1914 | /* Zero ->ticks_this_gp for all flavors of RCU. */ | |
1915 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) | |
1916 | { | |
1917 | rdp->ticks_this_gp = 0; | |
6231069b | 1918 | rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); |
a858af28 PM |
1919 | } |
1920 | ||
1921 | /* Increment ->ticks_this_gp for all flavors of RCU. */ | |
1922 | static void increment_cpu_stall_ticks(void) | |
1923 | { | |
115f7a7c PM |
1924 | struct rcu_state *rsp; |
1925 | ||
1926 | for_each_rcu_flavor(rsp) | |
fa07a58f | 1927 | raw_cpu_inc(rsp->rda->ticks_this_gp); |
a858af28 PM |
1928 | } |
1929 | ||
1930 | #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
1931 | ||
1932 | static void print_cpu_stall_info_begin(void) | |
1933 | { | |
efc151c3 | 1934 | pr_cont(" {"); |
a858af28 PM |
1935 | } |
1936 | ||
1937 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) | |
1938 | { | |
efc151c3 | 1939 | pr_cont(" %d", cpu); |
a858af28 PM |
1940 | } |
1941 | ||
1942 | static void print_cpu_stall_info_end(void) | |
1943 | { | |
efc151c3 | 1944 | pr_cont("} "); |
a858af28 PM |
1945 | } |
1946 | ||
1947 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) | |
1948 | { | |
1949 | } | |
1950 | ||
1951 | static void increment_cpu_stall_ticks(void) | |
1952 | { | |
1953 | } | |
1954 | ||
1955 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
3fbfbf7a PM |
1956 | |
1957 | #ifdef CONFIG_RCU_NOCB_CPU | |
1958 | ||
1959 | /* | |
1960 | * Offload callback processing from the boot-time-specified set of CPUs | |
1961 | * specified by rcu_nocb_mask. For each CPU in the set, there is a | |
1962 | * kthread created that pulls the callbacks from the corresponding CPU, | |
1963 | * waits for a grace period to elapse, and invokes the callbacks. | |
1964 | * The no-CBs CPUs do a wake_up() on their kthread when they insert | |
1965 | * a callback into any empty list, unless the rcu_nocb_poll boot parameter | |
1966 | * has been specified, in which case each kthread actively polls its | |
1967 | * CPU. (Which isn't so great for energy efficiency, but which does | |
1968 | * reduce RCU's overhead on that CPU.) | |
1969 | * | |
1970 | * This is intended to be used in conjunction with Frederic Weisbecker's | |
1971 | * adaptive-idle work, which would seriously reduce OS jitter on CPUs | |
1972 | * running CPU-bound user-mode computations. | |
1973 | * | |
1974 | * Offloading of callback processing could also in theory be used as | |
1975 | * an energy-efficiency measure because CPUs with no RCU callbacks | |
1976 | * queued are more aggressive about entering dyntick-idle mode. | |
1977 | */ | |
1978 | ||
1979 | ||
1980 | /* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */ | |
1981 | static int __init rcu_nocb_setup(char *str) | |
1982 | { | |
1983 | alloc_bootmem_cpumask_var(&rcu_nocb_mask); | |
1984 | have_rcu_nocb_mask = true; | |
1985 | cpulist_parse(str, rcu_nocb_mask); | |
1986 | return 1; | |
1987 | } | |
1988 | __setup("rcu_nocbs=", rcu_nocb_setup); | |
1989 | ||
1b0048a4 PG |
1990 | static int __init parse_rcu_nocb_poll(char *arg) |
1991 | { | |
1992 | rcu_nocb_poll = 1; | |
1993 | return 0; | |
1994 | } | |
1995 | early_param("rcu_nocb_poll", parse_rcu_nocb_poll); | |
1996 | ||
dae6e64d | 1997 | /* |
0446be48 PM |
1998 | * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended |
1999 | * grace period. | |
dae6e64d | 2000 | */ |
0446be48 | 2001 | static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
dae6e64d | 2002 | { |
0446be48 | 2003 | wake_up_all(&rnp->nocb_gp_wq[rnp->completed & 0x1]); |
dae6e64d PM |
2004 | } |
2005 | ||
2006 | /* | |
8b425aa8 | 2007 | * Set the root rcu_node structure's ->need_future_gp field |
dae6e64d PM |
2008 | * based on the sum of those of all rcu_node structures. This does |
2009 | * double-count the root rcu_node structure's requests, but this | |
2010 | * is necessary to handle the possibility of a rcu_nocb_kthread() | |
2011 | * having awakened during the time that the rcu_node structures | |
2012 | * were being updated for the end of the previous grace period. | |
34ed6246 | 2013 | */ |
dae6e64d PM |
2014 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
2015 | { | |
8b425aa8 | 2016 | rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq; |
dae6e64d PM |
2017 | } |
2018 | ||
2019 | static void rcu_init_one_nocb(struct rcu_node *rnp) | |
34ed6246 | 2020 | { |
dae6e64d PM |
2021 | init_waitqueue_head(&rnp->nocb_gp_wq[0]); |
2022 | init_waitqueue_head(&rnp->nocb_gp_wq[1]); | |
34ed6246 PM |
2023 | } |
2024 | ||
2f33b512 | 2025 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
24342c96 | 2026 | /* Is the specified CPU a no-CBs CPU? */ |
d1e43fa5 | 2027 | bool rcu_is_nocb_cpu(int cpu) |
3fbfbf7a PM |
2028 | { |
2029 | if (have_rcu_nocb_mask) | |
2030 | return cpumask_test_cpu(cpu, rcu_nocb_mask); | |
2031 | return false; | |
2032 | } | |
2f33b512 | 2033 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
3fbfbf7a | 2034 | |
fbce7497 PM |
2035 | /* |
2036 | * Kick the leader kthread for this NOCB group. | |
2037 | */ | |
2038 | static void wake_nocb_leader(struct rcu_data *rdp, bool force) | |
2039 | { | |
2040 | struct rcu_data *rdp_leader = rdp->nocb_leader; | |
2041 | ||
2042 | if (!ACCESS_ONCE(rdp_leader->nocb_kthread)) | |
2043 | return; | |
11ed7f93 | 2044 | if (ACCESS_ONCE(rdp_leader->nocb_leader_sleep) || force) { |
39953dfd | 2045 | /* Prior smp_mb__after_atomic() orders against prior enqueue. */ |
11ed7f93 | 2046 | ACCESS_ONCE(rdp_leader->nocb_leader_sleep) = false; |
fbce7497 PM |
2047 | wake_up(&rdp_leader->nocb_wq); |
2048 | } | |
2049 | } | |
2050 | ||
3fbfbf7a PM |
2051 | /* |
2052 | * Enqueue the specified string of rcu_head structures onto the specified | |
2053 | * CPU's no-CBs lists. The CPU is specified by rdp, the head of the | |
2054 | * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy | |
2055 | * counts are supplied by rhcount and rhcount_lazy. | |
2056 | * | |
2057 | * If warranted, also wake up the kthread servicing this CPUs queues. | |
2058 | */ | |
2059 | static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, | |
2060 | struct rcu_head *rhp, | |
2061 | struct rcu_head **rhtp, | |
96d3fd0d PM |
2062 | int rhcount, int rhcount_lazy, |
2063 | unsigned long flags) | |
3fbfbf7a PM |
2064 | { |
2065 | int len; | |
2066 | struct rcu_head **old_rhpp; | |
2067 | struct task_struct *t; | |
2068 | ||
2069 | /* Enqueue the callback on the nocb list and update counts. */ | |
2070 | old_rhpp = xchg(&rdp->nocb_tail, rhtp); | |
2071 | ACCESS_ONCE(*old_rhpp) = rhp; | |
2072 | atomic_long_add(rhcount, &rdp->nocb_q_count); | |
2073 | atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy); | |
39953dfd | 2074 | smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */ |
3fbfbf7a PM |
2075 | |
2076 | /* If we are not being polled and there is a kthread, awaken it ... */ | |
2077 | t = ACCESS_ONCE(rdp->nocb_kthread); | |
25e03a74 | 2078 | if (rcu_nocb_poll || !t) { |
9261dd0d PM |
2079 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2080 | TPS("WakeNotPoll")); | |
3fbfbf7a | 2081 | return; |
9261dd0d | 2082 | } |
3fbfbf7a PM |
2083 | len = atomic_long_read(&rdp->nocb_q_count); |
2084 | if (old_rhpp == &rdp->nocb_head) { | |
96d3fd0d | 2085 | if (!irqs_disabled_flags(flags)) { |
fbce7497 PM |
2086 | /* ... if queue was empty ... */ |
2087 | wake_nocb_leader(rdp, false); | |
96d3fd0d PM |
2088 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2089 | TPS("WakeEmpty")); | |
2090 | } else { | |
2091 | rdp->nocb_defer_wakeup = true; | |
2092 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2093 | TPS("WakeEmptyIsDeferred")); | |
2094 | } | |
3fbfbf7a PM |
2095 | rdp->qlen_last_fqs_check = 0; |
2096 | } else if (len > rdp->qlen_last_fqs_check + qhimark) { | |
fbce7497 PM |
2097 | /* ... or if many callbacks queued. */ |
2098 | wake_nocb_leader(rdp, true); | |
3fbfbf7a | 2099 | rdp->qlen_last_fqs_check = LONG_MAX / 2; |
9261dd0d PM |
2100 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeOvf")); |
2101 | } else { | |
2102 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot")); | |
3fbfbf7a PM |
2103 | } |
2104 | return; | |
2105 | } | |
2106 | ||
2107 | /* | |
2108 | * This is a helper for __call_rcu(), which invokes this when the normal | |
2109 | * callback queue is inoperable. If this is not a no-CBs CPU, this | |
2110 | * function returns failure back to __call_rcu(), which can complain | |
2111 | * appropriately. | |
2112 | * | |
2113 | * Otherwise, this function queues the callback where the corresponding | |
2114 | * "rcuo" kthread can find it. | |
2115 | */ | |
2116 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, | |
96d3fd0d | 2117 | bool lazy, unsigned long flags) |
3fbfbf7a PM |
2118 | { |
2119 | ||
d1e43fa5 | 2120 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
c271d3a9 | 2121 | return false; |
96d3fd0d | 2122 | __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy, flags); |
21e7a608 PM |
2123 | if (__is_kfree_rcu_offset((unsigned long)rhp->func)) |
2124 | trace_rcu_kfree_callback(rdp->rsp->name, rhp, | |
2125 | (unsigned long)rhp->func, | |
756cbf6b PM |
2126 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
2127 | -atomic_long_read(&rdp->nocb_q_count)); | |
21e7a608 PM |
2128 | else |
2129 | trace_rcu_callback(rdp->rsp->name, rhp, | |
756cbf6b PM |
2130 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
2131 | -atomic_long_read(&rdp->nocb_q_count)); | |
c271d3a9 | 2132 | return true; |
3fbfbf7a PM |
2133 | } |
2134 | ||
2135 | /* | |
2136 | * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is | |
2137 | * not a no-CBs CPU. | |
2138 | */ | |
2139 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, | |
96d3fd0d PM |
2140 | struct rcu_data *rdp, |
2141 | unsigned long flags) | |
3fbfbf7a PM |
2142 | { |
2143 | long ql = rsp->qlen; | |
2144 | long qll = rsp->qlen_lazy; | |
2145 | ||
2146 | /* If this is not a no-CBs CPU, tell the caller to do it the old way. */ | |
d1e43fa5 | 2147 | if (!rcu_is_nocb_cpu(smp_processor_id())) |
0a9e1e11 | 2148 | return false; |
3fbfbf7a PM |
2149 | rsp->qlen = 0; |
2150 | rsp->qlen_lazy = 0; | |
2151 | ||
2152 | /* First, enqueue the donelist, if any. This preserves CB ordering. */ | |
2153 | if (rsp->orphan_donelist != NULL) { | |
2154 | __call_rcu_nocb_enqueue(rdp, rsp->orphan_donelist, | |
96d3fd0d | 2155 | rsp->orphan_donetail, ql, qll, flags); |
3fbfbf7a PM |
2156 | ql = qll = 0; |
2157 | rsp->orphan_donelist = NULL; | |
2158 | rsp->orphan_donetail = &rsp->orphan_donelist; | |
2159 | } | |
2160 | if (rsp->orphan_nxtlist != NULL) { | |
2161 | __call_rcu_nocb_enqueue(rdp, rsp->orphan_nxtlist, | |
96d3fd0d | 2162 | rsp->orphan_nxttail, ql, qll, flags); |
3fbfbf7a PM |
2163 | ql = qll = 0; |
2164 | rsp->orphan_nxtlist = NULL; | |
2165 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; | |
2166 | } | |
0a9e1e11 | 2167 | return true; |
3fbfbf7a PM |
2168 | } |
2169 | ||
2170 | /* | |
34ed6246 PM |
2171 | * If necessary, kick off a new grace period, and either way wait |
2172 | * for a subsequent grace period to complete. | |
3fbfbf7a | 2173 | */ |
34ed6246 | 2174 | static void rcu_nocb_wait_gp(struct rcu_data *rdp) |
3fbfbf7a | 2175 | { |
34ed6246 | 2176 | unsigned long c; |
dae6e64d | 2177 | bool d; |
34ed6246 | 2178 | unsigned long flags; |
48a7639c | 2179 | bool needwake; |
34ed6246 PM |
2180 | struct rcu_node *rnp = rdp->mynode; |
2181 | ||
2182 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 2183 | smp_mb__after_unlock_lock(); |
48a7639c | 2184 | needwake = rcu_start_future_gp(rnp, rdp, &c); |
0446be48 | 2185 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
48a7639c PM |
2186 | if (needwake) |
2187 | rcu_gp_kthread_wake(rdp->rsp); | |
3fbfbf7a PM |
2188 | |
2189 | /* | |
34ed6246 PM |
2190 | * Wait for the grace period. Do so interruptibly to avoid messing |
2191 | * up the load average. | |
3fbfbf7a | 2192 | */ |
f7f7bac9 | 2193 | trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait")); |
34ed6246 | 2194 | for (;;) { |
dae6e64d PM |
2195 | wait_event_interruptible( |
2196 | rnp->nocb_gp_wq[c & 0x1], | |
2197 | (d = ULONG_CMP_GE(ACCESS_ONCE(rnp->completed), c))); | |
2198 | if (likely(d)) | |
34ed6246 | 2199 | break; |
dae6e64d | 2200 | flush_signals(current); |
f7f7bac9 | 2201 | trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait")); |
34ed6246 | 2202 | } |
f7f7bac9 | 2203 | trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait")); |
34ed6246 | 2204 | smp_mb(); /* Ensure that CB invocation happens after GP end. */ |
3fbfbf7a PM |
2205 | } |
2206 | ||
fbce7497 PM |
2207 | /* |
2208 | * Leaders come here to wait for additional callbacks to show up. | |
2209 | * This function does not return until callbacks appear. | |
2210 | */ | |
2211 | static void nocb_leader_wait(struct rcu_data *my_rdp) | |
2212 | { | |
2213 | bool firsttime = true; | |
2214 | bool gotcbs; | |
2215 | struct rcu_data *rdp; | |
2216 | struct rcu_head **tail; | |
2217 | ||
2218 | wait_again: | |
2219 | ||
2220 | /* Wait for callbacks to appear. */ | |
2221 | if (!rcu_nocb_poll) { | |
2222 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep"); | |
2223 | wait_event_interruptible(my_rdp->nocb_wq, | |
11ed7f93 | 2224 | !ACCESS_ONCE(my_rdp->nocb_leader_sleep)); |
fbce7497 PM |
2225 | /* Memory barrier handled by smp_mb() calls below and repoll. */ |
2226 | } else if (firsttime) { | |
2227 | firsttime = false; /* Don't drown trace log with "Poll"! */ | |
2228 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Poll"); | |
2229 | } | |
2230 | ||
2231 | /* | |
2232 | * Each pass through the following loop checks a follower for CBs. | |
2233 | * We are our own first follower. Any CBs found are moved to | |
2234 | * nocb_gp_head, where they await a grace period. | |
2235 | */ | |
2236 | gotcbs = false; | |
2237 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { | |
2238 | rdp->nocb_gp_head = ACCESS_ONCE(rdp->nocb_head); | |
2239 | if (!rdp->nocb_gp_head) | |
2240 | continue; /* No CBs here, try next follower. */ | |
2241 | ||
2242 | /* Move callbacks to wait-for-GP list, which is empty. */ | |
2243 | ACCESS_ONCE(rdp->nocb_head) = NULL; | |
2244 | rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head); | |
2245 | rdp->nocb_gp_count = atomic_long_xchg(&rdp->nocb_q_count, 0); | |
2246 | rdp->nocb_gp_count_lazy = | |
2247 | atomic_long_xchg(&rdp->nocb_q_count_lazy, 0); | |
2248 | gotcbs = true; | |
2249 | } | |
2250 | ||
2251 | /* | |
2252 | * If there were no callbacks, sleep a bit, rescan after a | |
2253 | * memory barrier, and go retry. | |
2254 | */ | |
2255 | if (unlikely(!gotcbs)) { | |
2256 | if (!rcu_nocb_poll) | |
2257 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, | |
2258 | "WokeEmpty"); | |
2259 | flush_signals(current); | |
2260 | schedule_timeout_interruptible(1); | |
2261 | ||
2262 | /* Rescan in case we were a victim of memory ordering. */ | |
11ed7f93 PK |
2263 | my_rdp->nocb_leader_sleep = true; |
2264 | smp_mb(); /* Ensure _sleep true before scan. */ | |
fbce7497 PM |
2265 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) |
2266 | if (ACCESS_ONCE(rdp->nocb_head)) { | |
2267 | /* Found CB, so short-circuit next wait. */ | |
11ed7f93 | 2268 | my_rdp->nocb_leader_sleep = false; |
fbce7497 PM |
2269 | break; |
2270 | } | |
2271 | goto wait_again; | |
2272 | } | |
2273 | ||
2274 | /* Wait for one grace period. */ | |
2275 | rcu_nocb_wait_gp(my_rdp); | |
2276 | ||
2277 | /* | |
11ed7f93 PK |
2278 | * We left ->nocb_leader_sleep unset to reduce cache thrashing. |
2279 | * We set it now, but recheck for new callbacks while | |
fbce7497 PM |
2280 | * traversing our follower list. |
2281 | */ | |
11ed7f93 PK |
2282 | my_rdp->nocb_leader_sleep = true; |
2283 | smp_mb(); /* Ensure _sleep true before scan of ->nocb_head. */ | |
fbce7497 PM |
2284 | |
2285 | /* Each pass through the following loop wakes a follower, if needed. */ | |
2286 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { | |
2287 | if (ACCESS_ONCE(rdp->nocb_head)) | |
11ed7f93 | 2288 | my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/ |
fbce7497 PM |
2289 | if (!rdp->nocb_gp_head) |
2290 | continue; /* No CBs, so no need to wake follower. */ | |
2291 | ||
2292 | /* Append callbacks to follower's "done" list. */ | |
2293 | tail = xchg(&rdp->nocb_follower_tail, rdp->nocb_gp_tail); | |
2294 | *tail = rdp->nocb_gp_head; | |
2295 | atomic_long_add(rdp->nocb_gp_count, &rdp->nocb_follower_count); | |
2296 | atomic_long_add(rdp->nocb_gp_count_lazy, | |
2297 | &rdp->nocb_follower_count_lazy); | |
2298 | if (rdp != my_rdp && tail == &rdp->nocb_follower_head) { | |
2299 | /* | |
2300 | * List was empty, wake up the follower. | |
2301 | * Memory barriers supplied by atomic_long_add(). | |
2302 | */ | |
2303 | wake_up(&rdp->nocb_wq); | |
2304 | } | |
2305 | } | |
2306 | ||
2307 | /* If we (the leader) don't have CBs, go wait some more. */ | |
2308 | if (!my_rdp->nocb_follower_head) | |
2309 | goto wait_again; | |
2310 | } | |
2311 | ||
2312 | /* | |
2313 | * Followers come here to wait for additional callbacks to show up. | |
2314 | * This function does not return until callbacks appear. | |
2315 | */ | |
2316 | static void nocb_follower_wait(struct rcu_data *rdp) | |
2317 | { | |
2318 | bool firsttime = true; | |
2319 | ||
2320 | for (;;) { | |
2321 | if (!rcu_nocb_poll) { | |
2322 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2323 | "FollowerSleep"); | |
2324 | wait_event_interruptible(rdp->nocb_wq, | |
2325 | ACCESS_ONCE(rdp->nocb_follower_head)); | |
2326 | } else if (firsttime) { | |
2327 | /* Don't drown trace log with "Poll"! */ | |
2328 | firsttime = false; | |
2329 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "Poll"); | |
2330 | } | |
2331 | if (smp_load_acquire(&rdp->nocb_follower_head)) { | |
2332 | /* ^^^ Ensure CB invocation follows _head test. */ | |
2333 | return; | |
2334 | } | |
2335 | if (!rcu_nocb_poll) | |
2336 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2337 | "WokeEmpty"); | |
2338 | flush_signals(current); | |
2339 | schedule_timeout_interruptible(1); | |
2340 | } | |
2341 | } | |
2342 | ||
3fbfbf7a PM |
2343 | /* |
2344 | * Per-rcu_data kthread, but only for no-CBs CPUs. Each kthread invokes | |
fbce7497 PM |
2345 | * callbacks queued by the corresponding no-CBs CPU, however, there is |
2346 | * an optional leader-follower relationship so that the grace-period | |
2347 | * kthreads don't have to do quite so many wakeups. | |
3fbfbf7a PM |
2348 | */ |
2349 | static int rcu_nocb_kthread(void *arg) | |
2350 | { | |
2351 | int c, cl; | |
2352 | struct rcu_head *list; | |
2353 | struct rcu_head *next; | |
2354 | struct rcu_head **tail; | |
2355 | struct rcu_data *rdp = arg; | |
2356 | ||
2357 | /* Each pass through this loop invokes one batch of callbacks */ | |
2358 | for (;;) { | |
fbce7497 PM |
2359 | /* Wait for callbacks. */ |
2360 | if (rdp->nocb_leader == rdp) | |
2361 | nocb_leader_wait(rdp); | |
2362 | else | |
2363 | nocb_follower_wait(rdp); | |
2364 | ||
2365 | /* Pull the ready-to-invoke callbacks onto local list. */ | |
2366 | list = ACCESS_ONCE(rdp->nocb_follower_head); | |
2367 | BUG_ON(!list); | |
2368 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty"); | |
2369 | ACCESS_ONCE(rdp->nocb_follower_head) = NULL; | |
2370 | tail = xchg(&rdp->nocb_follower_tail, &rdp->nocb_follower_head); | |
2371 | c = atomic_long_xchg(&rdp->nocb_follower_count, 0); | |
2372 | cl = atomic_long_xchg(&rdp->nocb_follower_count_lazy, 0); | |
2373 | rdp->nocb_p_count += c; | |
2374 | rdp->nocb_p_count_lazy += cl; | |
3fbfbf7a PM |
2375 | |
2376 | /* Each pass through the following loop invokes a callback. */ | |
2377 | trace_rcu_batch_start(rdp->rsp->name, cl, c, -1); | |
2378 | c = cl = 0; | |
2379 | while (list) { | |
2380 | next = list->next; | |
2381 | /* Wait for enqueuing to complete, if needed. */ | |
2382 | while (next == NULL && &list->next != tail) { | |
69a79bb1 PM |
2383 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2384 | TPS("WaitQueue")); | |
3fbfbf7a | 2385 | schedule_timeout_interruptible(1); |
69a79bb1 PM |
2386 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2387 | TPS("WokeQueue")); | |
3fbfbf7a PM |
2388 | next = list->next; |
2389 | } | |
2390 | debug_rcu_head_unqueue(list); | |
2391 | local_bh_disable(); | |
2392 | if (__rcu_reclaim(rdp->rsp->name, list)) | |
2393 | cl++; | |
2394 | c++; | |
2395 | local_bh_enable(); | |
2396 | list = next; | |
2397 | } | |
2398 | trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); | |
2399 | ACCESS_ONCE(rdp->nocb_p_count) -= c; | |
2400 | ACCESS_ONCE(rdp->nocb_p_count_lazy) -= cl; | |
c635a4e1 | 2401 | rdp->n_nocbs_invoked += c; |
3fbfbf7a PM |
2402 | } |
2403 | return 0; | |
2404 | } | |
2405 | ||
96d3fd0d PM |
2406 | /* Is a deferred wakeup of rcu_nocb_kthread() required? */ |
2407 | static bool rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) | |
2408 | { | |
2409 | return ACCESS_ONCE(rdp->nocb_defer_wakeup); | |
2410 | } | |
2411 | ||
2412 | /* Do a deferred wakeup of rcu_nocb_kthread(). */ | |
2413 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) | |
2414 | { | |
2415 | if (!rcu_nocb_need_deferred_wakeup(rdp)) | |
2416 | return; | |
2417 | ACCESS_ONCE(rdp->nocb_defer_wakeup) = false; | |
fbce7497 | 2418 | wake_nocb_leader(rdp, false); |
96d3fd0d PM |
2419 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("DeferredWakeEmpty")); |
2420 | } | |
2421 | ||
f4579fc5 PM |
2422 | void __init rcu_init_nohz(void) |
2423 | { | |
2424 | int cpu; | |
2425 | bool need_rcu_nocb_mask = true; | |
2426 | struct rcu_state *rsp; | |
2427 | ||
2428 | #ifdef CONFIG_RCU_NOCB_CPU_NONE | |
2429 | need_rcu_nocb_mask = false; | |
2430 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */ | |
2431 | ||
2432 | #if defined(CONFIG_NO_HZ_FULL) | |
2433 | if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask)) | |
2434 | need_rcu_nocb_mask = true; | |
2435 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ | |
2436 | ||
2437 | if (!have_rcu_nocb_mask && need_rcu_nocb_mask) { | |
949cccdb PK |
2438 | if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { |
2439 | pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); | |
2440 | return; | |
2441 | } | |
f4579fc5 PM |
2442 | have_rcu_nocb_mask = true; |
2443 | } | |
2444 | if (!have_rcu_nocb_mask) | |
2445 | return; | |
2446 | ||
2447 | #ifdef CONFIG_RCU_NOCB_CPU_ZERO | |
2448 | pr_info("\tOffload RCU callbacks from CPU 0\n"); | |
2449 | cpumask_set_cpu(0, rcu_nocb_mask); | |
2450 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */ | |
2451 | #ifdef CONFIG_RCU_NOCB_CPU_ALL | |
2452 | pr_info("\tOffload RCU callbacks from all CPUs\n"); | |
2453 | cpumask_copy(rcu_nocb_mask, cpu_possible_mask); | |
2454 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ | |
2455 | #if defined(CONFIG_NO_HZ_FULL) | |
2456 | if (tick_nohz_full_running) | |
2457 | cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); | |
2458 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ | |
2459 | ||
2460 | if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { | |
2461 | pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n"); | |
2462 | cpumask_and(rcu_nocb_mask, cpu_possible_mask, | |
2463 | rcu_nocb_mask); | |
2464 | } | |
2465 | cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask); | |
2466 | pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf); | |
2467 | if (rcu_nocb_poll) | |
2468 | pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); | |
2469 | ||
2470 | for_each_rcu_flavor(rsp) { | |
2471 | for_each_cpu(cpu, rcu_nocb_mask) { | |
2472 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
2473 | ||
2474 | /* | |
2475 | * If there are early callbacks, they will need | |
2476 | * to be moved to the nocb lists. | |
2477 | */ | |
2478 | WARN_ON_ONCE(rdp->nxttail[RCU_NEXT_TAIL] != | |
2479 | &rdp->nxtlist && | |
2480 | rdp->nxttail[RCU_NEXT_TAIL] != NULL); | |
2481 | init_nocb_callback_list(rdp); | |
2482 | } | |
35ce7f29 | 2483 | rcu_organize_nocb_kthreads(rsp); |
f4579fc5 PM |
2484 | } |
2485 | } | |
2486 | ||
3fbfbf7a PM |
2487 | /* Initialize per-rcu_data variables for no-CBs CPUs. */ |
2488 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) | |
2489 | { | |
2490 | rdp->nocb_tail = &rdp->nocb_head; | |
2491 | init_waitqueue_head(&rdp->nocb_wq); | |
fbce7497 | 2492 | rdp->nocb_follower_tail = &rdp->nocb_follower_head; |
3fbfbf7a PM |
2493 | } |
2494 | ||
35ce7f29 PM |
2495 | /* |
2496 | * If the specified CPU is a no-CBs CPU that does not already have its | |
2497 | * rcuo kthread for the specified RCU flavor, spawn it. If the CPUs are | |
2498 | * brought online out of order, this can require re-organizing the | |
2499 | * leader-follower relationships. | |
2500 | */ | |
2501 | static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu) | |
2502 | { | |
2503 | struct rcu_data *rdp; | |
2504 | struct rcu_data *rdp_last; | |
2505 | struct rcu_data *rdp_old_leader; | |
2506 | struct rcu_data *rdp_spawn = per_cpu_ptr(rsp->rda, cpu); | |
2507 | struct task_struct *t; | |
2508 | ||
2509 | /* | |
2510 | * If this isn't a no-CBs CPU or if it already has an rcuo kthread, | |
2511 | * then nothing to do. | |
2512 | */ | |
2513 | if (!rcu_is_nocb_cpu(cpu) || rdp_spawn->nocb_kthread) | |
2514 | return; | |
2515 | ||
2516 | /* If we didn't spawn the leader first, reorganize! */ | |
2517 | rdp_old_leader = rdp_spawn->nocb_leader; | |
2518 | if (rdp_old_leader != rdp_spawn && !rdp_old_leader->nocb_kthread) { | |
2519 | rdp_last = NULL; | |
2520 | rdp = rdp_old_leader; | |
2521 | do { | |
2522 | rdp->nocb_leader = rdp_spawn; | |
2523 | if (rdp_last && rdp != rdp_spawn) | |
2524 | rdp_last->nocb_next_follower = rdp; | |
2525 | rdp_last = rdp; | |
2526 | rdp = rdp->nocb_next_follower; | |
2527 | rdp_last->nocb_next_follower = NULL; | |
2528 | } while (rdp); | |
2529 | rdp_spawn->nocb_next_follower = rdp_old_leader; | |
2530 | } | |
2531 | ||
2532 | /* Spawn the kthread for this CPU and RCU flavor. */ | |
2533 | t = kthread_run(rcu_nocb_kthread, rdp_spawn, | |
2534 | "rcuo%c/%d", rsp->abbr, cpu); | |
2535 | BUG_ON(IS_ERR(t)); | |
2536 | ACCESS_ONCE(rdp_spawn->nocb_kthread) = t; | |
2537 | } | |
2538 | ||
2539 | /* | |
2540 | * If the specified CPU is a no-CBs CPU that does not already have its | |
2541 | * rcuo kthreads, spawn them. | |
2542 | */ | |
2543 | static void rcu_spawn_all_nocb_kthreads(int cpu) | |
2544 | { | |
2545 | struct rcu_state *rsp; | |
2546 | ||
2547 | if (rcu_scheduler_fully_active) | |
2548 | for_each_rcu_flavor(rsp) | |
2549 | rcu_spawn_one_nocb_kthread(rsp, cpu); | |
2550 | } | |
2551 | ||
2552 | /* | |
2553 | * Once the scheduler is running, spawn rcuo kthreads for all online | |
2554 | * no-CBs CPUs. This assumes that the early_initcall()s happen before | |
2555 | * non-boot CPUs come online -- if this changes, we will need to add | |
2556 | * some mutual exclusion. | |
2557 | */ | |
2558 | static void __init rcu_spawn_nocb_kthreads(void) | |
2559 | { | |
2560 | int cpu; | |
2561 | ||
2562 | for_each_online_cpu(cpu) | |
2563 | rcu_spawn_all_nocb_kthreads(cpu); | |
2564 | } | |
2565 | ||
fbce7497 PM |
2566 | /* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids). */ |
2567 | static int rcu_nocb_leader_stride = -1; | |
2568 | module_param(rcu_nocb_leader_stride, int, 0444); | |
2569 | ||
2570 | /* | |
35ce7f29 | 2571 | * Initialize leader-follower relationships for all no-CBs CPU. |
fbce7497 | 2572 | */ |
35ce7f29 | 2573 | static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) |
3fbfbf7a PM |
2574 | { |
2575 | int cpu; | |
fbce7497 PM |
2576 | int ls = rcu_nocb_leader_stride; |
2577 | int nl = 0; /* Next leader. */ | |
3fbfbf7a | 2578 | struct rcu_data *rdp; |
fbce7497 PM |
2579 | struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ |
2580 | struct rcu_data *rdp_prev = NULL; | |
3fbfbf7a | 2581 | |
22c2f669 | 2582 | if (!have_rcu_nocb_mask) |
3fbfbf7a | 2583 | return; |
fbce7497 PM |
2584 | if (ls == -1) { |
2585 | ls = int_sqrt(nr_cpu_ids); | |
2586 | rcu_nocb_leader_stride = ls; | |
2587 | } | |
2588 | ||
2589 | /* | |
2590 | * Each pass through this loop sets up one rcu_data structure and | |
2591 | * spawns one rcu_nocb_kthread(). | |
2592 | */ | |
3fbfbf7a PM |
2593 | for_each_cpu(cpu, rcu_nocb_mask) { |
2594 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
fbce7497 PM |
2595 | if (rdp->cpu >= nl) { |
2596 | /* New leader, set up for followers & next leader. */ | |
2597 | nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls; | |
2598 | rdp->nocb_leader = rdp; | |
2599 | rdp_leader = rdp; | |
2600 | } else { | |
2601 | /* Another follower, link to previous leader. */ | |
2602 | rdp->nocb_leader = rdp_leader; | |
2603 | rdp_prev->nocb_next_follower = rdp; | |
2604 | } | |
2605 | rdp_prev = rdp; | |
3fbfbf7a PM |
2606 | } |
2607 | } | |
2608 | ||
2609 | /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ | |
34ed6246 | 2610 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
3fbfbf7a | 2611 | { |
22c2f669 | 2612 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
34ed6246 | 2613 | return false; |
22c2f669 | 2614 | |
3fbfbf7a | 2615 | rdp->nxttail[RCU_NEXT_TAIL] = NULL; |
34ed6246 | 2616 | return true; |
3fbfbf7a PM |
2617 | } |
2618 | ||
34ed6246 PM |
2619 | #else /* #ifdef CONFIG_RCU_NOCB_CPU */ |
2620 | ||
0446be48 | 2621 | static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
3fbfbf7a | 2622 | { |
3fbfbf7a PM |
2623 | } |
2624 | ||
dae6e64d PM |
2625 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
2626 | { | |
2627 | } | |
2628 | ||
2629 | static void rcu_init_one_nocb(struct rcu_node *rnp) | |
2630 | { | |
2631 | } | |
3fbfbf7a | 2632 | |
3fbfbf7a | 2633 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, |
96d3fd0d | 2634 | bool lazy, unsigned long flags) |
3fbfbf7a | 2635 | { |
4afc7e26 | 2636 | return false; |
3fbfbf7a PM |
2637 | } |
2638 | ||
2639 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, | |
96d3fd0d PM |
2640 | struct rcu_data *rdp, |
2641 | unsigned long flags) | |
3fbfbf7a | 2642 | { |
f4aa84ba | 2643 | return false; |
3fbfbf7a PM |
2644 | } |
2645 | ||
3fbfbf7a PM |
2646 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) |
2647 | { | |
2648 | } | |
2649 | ||
96d3fd0d PM |
2650 | static bool rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) |
2651 | { | |
2652 | return false; | |
2653 | } | |
2654 | ||
2655 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) | |
2656 | { | |
2657 | } | |
2658 | ||
35ce7f29 PM |
2659 | static void rcu_spawn_all_nocb_kthreads(int cpu) |
2660 | { | |
2661 | } | |
2662 | ||
2663 | static void __init rcu_spawn_nocb_kthreads(void) | |
3fbfbf7a PM |
2664 | { |
2665 | } | |
2666 | ||
34ed6246 | 2667 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
3fbfbf7a | 2668 | { |
34ed6246 | 2669 | return false; |
3fbfbf7a PM |
2670 | } |
2671 | ||
2672 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ | |
65d798f0 PM |
2673 | |
2674 | /* | |
2675 | * An adaptive-ticks CPU can potentially execute in kernel mode for an | |
2676 | * arbitrarily long period of time with the scheduling-clock tick turned | |
2677 | * off. RCU will be paying attention to this CPU because it is in the | |
2678 | * kernel, but the CPU cannot be guaranteed to be executing the RCU state | |
2679 | * machine because the scheduling-clock tick has been disabled. Therefore, | |
2680 | * if an adaptive-ticks CPU is failing to respond to the current grace | |
2681 | * period and has not be idle from an RCU perspective, kick it. | |
2682 | */ | |
4a81e832 | 2683 | static void __maybe_unused rcu_kick_nohz_cpu(int cpu) |
65d798f0 PM |
2684 | { |
2685 | #ifdef CONFIG_NO_HZ_FULL | |
2686 | if (tick_nohz_full_cpu(cpu)) | |
2687 | smp_send_reschedule(cpu); | |
2688 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ | |
2689 | } | |
2333210b PM |
2690 | |
2691 | ||
2692 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE | |
2693 | ||
0edd1b17 | 2694 | static int full_sysidle_state; /* Current system-idle state. */ |
d4bd54fb PM |
2695 | #define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ |
2696 | #define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ | |
2697 | #define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ | |
2698 | #define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ | |
2699 | #define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ | |
2700 | ||
eb348b89 PM |
2701 | /* |
2702 | * Invoked to note exit from irq or task transition to idle. Note that | |
2703 | * usermode execution does -not- count as idle here! After all, we want | |
2704 | * to detect full-system idle states, not RCU quiescent states and grace | |
2705 | * periods. The caller must have disabled interrupts. | |
2706 | */ | |
2707 | static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq) | |
2708 | { | |
2709 | unsigned long j; | |
2710 | ||
663e1310 PM |
2711 | /* If there are no nohz_full= CPUs, no need to track this. */ |
2712 | if (!tick_nohz_full_enabled()) | |
2713 | return; | |
2714 | ||
eb348b89 PM |
2715 | /* Adjust nesting, check for fully idle. */ |
2716 | if (irq) { | |
2717 | rdtp->dynticks_idle_nesting--; | |
2718 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); | |
2719 | if (rdtp->dynticks_idle_nesting != 0) | |
2720 | return; /* Still not fully idle. */ | |
2721 | } else { | |
2722 | if ((rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) == | |
2723 | DYNTICK_TASK_NEST_VALUE) { | |
2724 | rdtp->dynticks_idle_nesting = 0; | |
2725 | } else { | |
2726 | rdtp->dynticks_idle_nesting -= DYNTICK_TASK_NEST_VALUE; | |
2727 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); | |
2728 | return; /* Still not fully idle. */ | |
2729 | } | |
2730 | } | |
2731 | ||
2732 | /* Record start of fully idle period. */ | |
2733 | j = jiffies; | |
2734 | ACCESS_ONCE(rdtp->dynticks_idle_jiffies) = j; | |
4e857c58 | 2735 | smp_mb__before_atomic(); |
eb348b89 | 2736 | atomic_inc(&rdtp->dynticks_idle); |
4e857c58 | 2737 | smp_mb__after_atomic(); |
eb348b89 PM |
2738 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks_idle) & 0x1); |
2739 | } | |
2740 | ||
0edd1b17 PM |
2741 | /* |
2742 | * Unconditionally force exit from full system-idle state. This is | |
2743 | * invoked when a normal CPU exits idle, but must be called separately | |
2744 | * for the timekeeping CPU (tick_do_timer_cpu). The reason for this | |
2745 | * is that the timekeeping CPU is permitted to take scheduling-clock | |
2746 | * interrupts while the system is in system-idle state, and of course | |
2747 | * rcu_sysidle_exit() has no way of distinguishing a scheduling-clock | |
2748 | * interrupt from any other type of interrupt. | |
2749 | */ | |
2750 | void rcu_sysidle_force_exit(void) | |
2751 | { | |
2752 | int oldstate = ACCESS_ONCE(full_sysidle_state); | |
2753 | int newoldstate; | |
2754 | ||
2755 | /* | |
2756 | * Each pass through the following loop attempts to exit full | |
2757 | * system-idle state. If contention proves to be a problem, | |
2758 | * a trylock-based contention tree could be used here. | |
2759 | */ | |
2760 | while (oldstate > RCU_SYSIDLE_SHORT) { | |
2761 | newoldstate = cmpxchg(&full_sysidle_state, | |
2762 | oldstate, RCU_SYSIDLE_NOT); | |
2763 | if (oldstate == newoldstate && | |
2764 | oldstate == RCU_SYSIDLE_FULL_NOTED) { | |
2765 | rcu_kick_nohz_cpu(tick_do_timer_cpu); | |
2766 | return; /* We cleared it, done! */ | |
2767 | } | |
2768 | oldstate = newoldstate; | |
2769 | } | |
2770 | smp_mb(); /* Order initial oldstate fetch vs. later non-idle work. */ | |
2771 | } | |
2772 | ||
eb348b89 PM |
2773 | /* |
2774 | * Invoked to note entry to irq or task transition from idle. Note that | |
2775 | * usermode execution does -not- count as idle here! The caller must | |
2776 | * have disabled interrupts. | |
2777 | */ | |
2778 | static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq) | |
2779 | { | |
663e1310 PM |
2780 | /* If there are no nohz_full= CPUs, no need to track this. */ |
2781 | if (!tick_nohz_full_enabled()) | |
2782 | return; | |
2783 | ||
eb348b89 PM |
2784 | /* Adjust nesting, check for already non-idle. */ |
2785 | if (irq) { | |
2786 | rdtp->dynticks_idle_nesting++; | |
2787 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); | |
2788 | if (rdtp->dynticks_idle_nesting != 1) | |
2789 | return; /* Already non-idle. */ | |
2790 | } else { | |
2791 | /* | |
2792 | * Allow for irq misnesting. Yes, it really is possible | |
2793 | * to enter an irq handler then never leave it, and maybe | |
2794 | * also vice versa. Handle both possibilities. | |
2795 | */ | |
2796 | if (rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) { | |
2797 | rdtp->dynticks_idle_nesting += DYNTICK_TASK_NEST_VALUE; | |
2798 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); | |
2799 | return; /* Already non-idle. */ | |
2800 | } else { | |
2801 | rdtp->dynticks_idle_nesting = DYNTICK_TASK_EXIT_IDLE; | |
2802 | } | |
2803 | } | |
2804 | ||
2805 | /* Record end of idle period. */ | |
4e857c58 | 2806 | smp_mb__before_atomic(); |
eb348b89 | 2807 | atomic_inc(&rdtp->dynticks_idle); |
4e857c58 | 2808 | smp_mb__after_atomic(); |
eb348b89 | 2809 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks_idle) & 0x1)); |
0edd1b17 PM |
2810 | |
2811 | /* | |
2812 | * If we are the timekeeping CPU, we are permitted to be non-idle | |
2813 | * during a system-idle state. This must be the case, because | |
2814 | * the timekeeping CPU has to take scheduling-clock interrupts | |
2815 | * during the time that the system is transitioning to full | |
2816 | * system-idle state. This means that the timekeeping CPU must | |
2817 | * invoke rcu_sysidle_force_exit() directly if it does anything | |
2818 | * more than take a scheduling-clock interrupt. | |
2819 | */ | |
2820 | if (smp_processor_id() == tick_do_timer_cpu) | |
2821 | return; | |
2822 | ||
2823 | /* Update system-idle state: We are clearly no longer fully idle! */ | |
2824 | rcu_sysidle_force_exit(); | |
2825 | } | |
2826 | ||
2827 | /* | |
2828 | * Check to see if the current CPU is idle. Note that usermode execution | |
2829 | * does not count as idle. The caller must have disabled interrupts. | |
2830 | */ | |
2831 | static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, | |
2832 | unsigned long *maxj) | |
2833 | { | |
2834 | int cur; | |
2835 | unsigned long j; | |
2836 | struct rcu_dynticks *rdtp = rdp->dynticks; | |
2837 | ||
663e1310 PM |
2838 | /* If there are no nohz_full= CPUs, don't check system-wide idleness. */ |
2839 | if (!tick_nohz_full_enabled()) | |
2840 | return; | |
2841 | ||
0edd1b17 PM |
2842 | /* |
2843 | * If some other CPU has already reported non-idle, if this is | |
2844 | * not the flavor of RCU that tracks sysidle state, or if this | |
2845 | * is an offline or the timekeeping CPU, nothing to do. | |
2846 | */ | |
417e8d26 | 2847 | if (!*isidle || rdp->rsp != rcu_state_p || |
0edd1b17 PM |
2848 | cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) |
2849 | return; | |
eb75767b PM |
2850 | if (rcu_gp_in_progress(rdp->rsp)) |
2851 | WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); | |
0edd1b17 PM |
2852 | |
2853 | /* Pick up current idle and NMI-nesting counter and check. */ | |
2854 | cur = atomic_read(&rdtp->dynticks_idle); | |
2855 | if (cur & 0x1) { | |
2856 | *isidle = false; /* We are not idle! */ | |
2857 | return; | |
2858 | } | |
2859 | smp_mb(); /* Read counters before timestamps. */ | |
2860 | ||
2861 | /* Pick up timestamps. */ | |
2862 | j = ACCESS_ONCE(rdtp->dynticks_idle_jiffies); | |
2863 | /* If this CPU entered idle more recently, update maxj timestamp. */ | |
2864 | if (ULONG_CMP_LT(*maxj, j)) | |
2865 | *maxj = j; | |
2866 | } | |
2867 | ||
2868 | /* | |
2869 | * Is this the flavor of RCU that is handling full-system idle? | |
2870 | */ | |
2871 | static bool is_sysidle_rcu_state(struct rcu_state *rsp) | |
2872 | { | |
417e8d26 | 2873 | return rsp == rcu_state_p; |
0edd1b17 PM |
2874 | } |
2875 | ||
2876 | /* | |
2877 | * Return a delay in jiffies based on the number of CPUs, rcu_node | |
2878 | * leaf fanout, and jiffies tick rate. The idea is to allow larger | |
2879 | * systems more time to transition to full-idle state in order to | |
2880 | * avoid the cache thrashing that otherwise occur on the state variable. | |
2881 | * Really small systems (less than a couple of tens of CPUs) should | |
2882 | * instead use a single global atomically incremented counter, and later | |
2883 | * versions of this will automatically reconfigure themselves accordingly. | |
2884 | */ | |
2885 | static unsigned long rcu_sysidle_delay(void) | |
2886 | { | |
2887 | if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) | |
2888 | return 0; | |
2889 | return DIV_ROUND_UP(nr_cpu_ids * HZ, rcu_fanout_leaf * 1000); | |
2890 | } | |
2891 | ||
2892 | /* | |
2893 | * Advance the full-system-idle state. This is invoked when all of | |
2894 | * the non-timekeeping CPUs are idle. | |
2895 | */ | |
2896 | static void rcu_sysidle(unsigned long j) | |
2897 | { | |
2898 | /* Check the current state. */ | |
2899 | switch (ACCESS_ONCE(full_sysidle_state)) { | |
2900 | case RCU_SYSIDLE_NOT: | |
2901 | ||
2902 | /* First time all are idle, so note a short idle period. */ | |
2903 | ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_SHORT; | |
2904 | break; | |
2905 | ||
2906 | case RCU_SYSIDLE_SHORT: | |
2907 | ||
2908 | /* | |
2909 | * Idle for a bit, time to advance to next state? | |
2910 | * cmpxchg failure means race with non-idle, let them win. | |
2911 | */ | |
2912 | if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) | |
2913 | (void)cmpxchg(&full_sysidle_state, | |
2914 | RCU_SYSIDLE_SHORT, RCU_SYSIDLE_LONG); | |
2915 | break; | |
2916 | ||
2917 | case RCU_SYSIDLE_LONG: | |
2918 | ||
2919 | /* | |
2920 | * Do an additional check pass before advancing to full. | |
2921 | * cmpxchg failure means race with non-idle, let them win. | |
2922 | */ | |
2923 | if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) | |
2924 | (void)cmpxchg(&full_sysidle_state, | |
2925 | RCU_SYSIDLE_LONG, RCU_SYSIDLE_FULL); | |
2926 | break; | |
2927 | ||
2928 | default: | |
2929 | break; | |
2930 | } | |
2931 | } | |
2932 | ||
2933 | /* | |
2934 | * Found a non-idle non-timekeeping CPU, so kick the system-idle state | |
2935 | * back to the beginning. | |
2936 | */ | |
2937 | static void rcu_sysidle_cancel(void) | |
2938 | { | |
2939 | smp_mb(); | |
becb41bf PM |
2940 | if (full_sysidle_state > RCU_SYSIDLE_SHORT) |
2941 | ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT; | |
0edd1b17 PM |
2942 | } |
2943 | ||
2944 | /* | |
2945 | * Update the sysidle state based on the results of a force-quiescent-state | |
2946 | * scan of the CPUs' dyntick-idle state. | |
2947 | */ | |
2948 | static void rcu_sysidle_report(struct rcu_state *rsp, int isidle, | |
2949 | unsigned long maxj, bool gpkt) | |
2950 | { | |
417e8d26 | 2951 | if (rsp != rcu_state_p) |
0edd1b17 PM |
2952 | return; /* Wrong flavor, ignore. */ |
2953 | if (gpkt && nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) | |
2954 | return; /* Running state machine from timekeeping CPU. */ | |
2955 | if (isidle) | |
2956 | rcu_sysidle(maxj); /* More idle! */ | |
2957 | else | |
2958 | rcu_sysidle_cancel(); /* Idle is over. */ | |
2959 | } | |
2960 | ||
2961 | /* | |
2962 | * Wrapper for rcu_sysidle_report() when called from the grace-period | |
2963 | * kthread's context. | |
2964 | */ | |
2965 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, | |
2966 | unsigned long maxj) | |
2967 | { | |
663e1310 PM |
2968 | /* If there are no nohz_full= CPUs, no need to track this. */ |
2969 | if (!tick_nohz_full_enabled()) | |
2970 | return; | |
2971 | ||
0edd1b17 PM |
2972 | rcu_sysidle_report(rsp, isidle, maxj, true); |
2973 | } | |
2974 | ||
2975 | /* Callback and function for forcing an RCU grace period. */ | |
2976 | struct rcu_sysidle_head { | |
2977 | struct rcu_head rh; | |
2978 | int inuse; | |
2979 | }; | |
2980 | ||
2981 | static void rcu_sysidle_cb(struct rcu_head *rhp) | |
2982 | { | |
2983 | struct rcu_sysidle_head *rshp; | |
2984 | ||
2985 | /* | |
2986 | * The following memory barrier is needed to replace the | |
2987 | * memory barriers that would normally be in the memory | |
2988 | * allocator. | |
2989 | */ | |
2990 | smp_mb(); /* grace period precedes setting inuse. */ | |
2991 | ||
2992 | rshp = container_of(rhp, struct rcu_sysidle_head, rh); | |
2993 | ACCESS_ONCE(rshp->inuse) = 0; | |
2994 | } | |
2995 | ||
2996 | /* | |
2997 | * Check to see if the system is fully idle, other than the timekeeping CPU. | |
663e1310 PM |
2998 | * The caller must have disabled interrupts. This is not intended to be |
2999 | * called unless tick_nohz_full_enabled(). | |
0edd1b17 PM |
3000 | */ |
3001 | bool rcu_sys_is_idle(void) | |
3002 | { | |
3003 | static struct rcu_sysidle_head rsh; | |
3004 | int rss = ACCESS_ONCE(full_sysidle_state); | |
3005 | ||
3006 | if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu)) | |
3007 | return false; | |
3008 | ||
3009 | /* Handle small-system case by doing a full scan of CPUs. */ | |
3010 | if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) { | |
3011 | int oldrss = rss - 1; | |
3012 | ||
3013 | /* | |
3014 | * One pass to advance to each state up to _FULL. | |
3015 | * Give up if any pass fails to advance the state. | |
3016 | */ | |
3017 | while (rss < RCU_SYSIDLE_FULL && oldrss < rss) { | |
3018 | int cpu; | |
3019 | bool isidle = true; | |
3020 | unsigned long maxj = jiffies - ULONG_MAX / 4; | |
3021 | struct rcu_data *rdp; | |
3022 | ||
3023 | /* Scan all the CPUs looking for nonidle CPUs. */ | |
3024 | for_each_possible_cpu(cpu) { | |
417e8d26 | 3025 | rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
0edd1b17 PM |
3026 | rcu_sysidle_check_cpu(rdp, &isidle, &maxj); |
3027 | if (!isidle) | |
3028 | break; | |
3029 | } | |
417e8d26 | 3030 | rcu_sysidle_report(rcu_state_p, isidle, maxj, false); |
0edd1b17 PM |
3031 | oldrss = rss; |
3032 | rss = ACCESS_ONCE(full_sysidle_state); | |
3033 | } | |
3034 | } | |
3035 | ||
3036 | /* If this is the first observation of an idle period, record it. */ | |
3037 | if (rss == RCU_SYSIDLE_FULL) { | |
3038 | rss = cmpxchg(&full_sysidle_state, | |
3039 | RCU_SYSIDLE_FULL, RCU_SYSIDLE_FULL_NOTED); | |
3040 | return rss == RCU_SYSIDLE_FULL; | |
3041 | } | |
3042 | ||
3043 | smp_mb(); /* ensure rss load happens before later caller actions. */ | |
3044 | ||
3045 | /* If already fully idle, tell the caller (in case of races). */ | |
3046 | if (rss == RCU_SYSIDLE_FULL_NOTED) | |
3047 | return true; | |
3048 | ||
3049 | /* | |
3050 | * If we aren't there yet, and a grace period is not in flight, | |
3051 | * initiate a grace period. Either way, tell the caller that | |
3052 | * we are not there yet. We use an xchg() rather than an assignment | |
3053 | * to make up for the memory barriers that would otherwise be | |
3054 | * provided by the memory allocator. | |
3055 | */ | |
3056 | if (nr_cpu_ids > CONFIG_NO_HZ_FULL_SYSIDLE_SMALL && | |
417e8d26 | 3057 | !rcu_gp_in_progress(rcu_state_p) && |
0edd1b17 PM |
3058 | !rsh.inuse && xchg(&rsh.inuse, 1) == 0) |
3059 | call_rcu(&rsh.rh, rcu_sysidle_cb); | |
3060 | return false; | |
eb348b89 PM |
3061 | } |
3062 | ||
2333210b PM |
3063 | /* |
3064 | * Initialize dynticks sysidle state for CPUs coming online. | |
3065 | */ | |
3066 | static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) | |
3067 | { | |
3068 | rdtp->dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE; | |
3069 | } | |
3070 | ||
3071 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
3072 | ||
eb348b89 PM |
3073 | static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq) |
3074 | { | |
3075 | } | |
3076 | ||
3077 | static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq) | |
3078 | { | |
3079 | } | |
3080 | ||
0edd1b17 PM |
3081 | static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, |
3082 | unsigned long *maxj) | |
3083 | { | |
3084 | } | |
3085 | ||
3086 | static bool is_sysidle_rcu_state(struct rcu_state *rsp) | |
3087 | { | |
3088 | return false; | |
3089 | } | |
3090 | ||
3091 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, | |
3092 | unsigned long maxj) | |
3093 | { | |
3094 | } | |
3095 | ||
2333210b PM |
3096 | static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) |
3097 | { | |
3098 | } | |
3099 | ||
3100 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
a096932f PM |
3101 | |
3102 | /* | |
3103 | * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the | |
3104 | * grace-period kthread will do force_quiescent_state() processing? | |
3105 | * The idea is to avoid waking up RCU core processing on such a | |
3106 | * CPU unless the grace period has extended for too long. | |
3107 | * | |
3108 | * This code relies on the fact that all NO_HZ_FULL CPUs are also | |
52e2bb95 | 3109 | * CONFIG_RCU_NOCB_CPU CPUs. |
a096932f PM |
3110 | */ |
3111 | static bool rcu_nohz_full_cpu(struct rcu_state *rsp) | |
3112 | { | |
3113 | #ifdef CONFIG_NO_HZ_FULL | |
3114 | if (tick_nohz_full_cpu(smp_processor_id()) && | |
3115 | (!rcu_gp_in_progress(rsp) || | |
3116 | ULONG_CMP_LT(jiffies, ACCESS_ONCE(rsp->gp_start) + HZ))) | |
3117 | return 1; | |
3118 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ | |
3119 | return 0; | |
3120 | } | |
5057f55e PM |
3121 | |
3122 | /* | |
3123 | * Bind the grace-period kthread for the sysidle flavor of RCU to the | |
3124 | * timekeeping CPU. | |
3125 | */ | |
3126 | static void rcu_bind_gp_kthread(void) | |
3127 | { | |
c0f489d2 | 3128 | int __maybe_unused cpu; |
5057f55e | 3129 | |
c0f489d2 | 3130 | if (!tick_nohz_full_enabled()) |
5057f55e | 3131 | return; |
c0f489d2 PM |
3132 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
3133 | cpu = tick_do_timer_cpu; | |
3134 | if (cpu >= 0 && cpu < nr_cpu_ids && raw_smp_processor_id() != cpu) | |
5057f55e | 3135 | set_cpus_allowed_ptr(current, cpumask_of(cpu)); |
c0f489d2 PM |
3136 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
3137 | if (!is_housekeeping_cpu(raw_smp_processor_id())) | |
3138 | housekeeping_affine(current); | |
3139 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
5057f55e | 3140 | } |