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f41d911f PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion (tree-based version) | |
3 | * Internal non-public definitions that provide either classic | |
6cc68793 | 4 | * or preemptible semantics. |
f41d911f PM |
5 | * |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License as published by | |
8 | * the Free Software Foundation; either version 2 of the License, or | |
9 | * (at your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | * GNU General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
87de1cfd PM |
17 | * along with this program; if not, you can access it online at |
18 | * http://www.gnu.org/licenses/gpl-2.0.html. | |
f41d911f PM |
19 | * |
20 | * Copyright Red Hat, 2009 | |
21 | * Copyright IBM Corporation, 2009 | |
22 | * | |
23 | * Author: Ingo Molnar <mingo@elte.hu> | |
24 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> | |
25 | */ | |
26 | ||
d9a3da06 | 27 | #include <linux/delay.h> |
3fbfbf7a | 28 | #include <linux/gfp.h> |
b626c1b6 | 29 | #include <linux/oom.h> |
62ab7072 | 30 | #include <linux/smpboot.h> |
4102adab | 31 | #include "../time/tick-internal.h" |
f41d911f | 32 | |
5b61b0ba | 33 | #ifdef CONFIG_RCU_BOOST |
61cfd097 | 34 | |
abaa93d9 | 35 | #include "../locking/rtmutex_common.h" |
21871d7e CW |
36 | |
37 | /* rcuc/rcub kthread realtime priority */ | |
38 | static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO; | |
39 | module_param(kthread_prio, int, 0644); | |
61cfd097 PM |
40 | |
41 | /* | |
42 | * Control variables for per-CPU and per-rcu_node kthreads. These | |
43 | * handle all flavors of RCU. | |
44 | */ | |
45 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); | |
46 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); | |
47 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); | |
48 | DEFINE_PER_CPU(char, rcu_cpu_has_work); | |
49 | ||
21871d7e | 50 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
5b61b0ba | 51 | |
3fbfbf7a PM |
52 | #ifdef CONFIG_RCU_NOCB_CPU |
53 | static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ | |
54 | static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */ | |
1b0048a4 | 55 | static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ |
3fbfbf7a PM |
56 | static char __initdata nocb_buf[NR_CPUS * 5]; |
57 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ | |
58 | ||
26845c28 PM |
59 | /* |
60 | * Check the RCU kernel configuration parameters and print informative | |
61 | * messages about anything out of the ordinary. If you like #ifdef, you | |
62 | * will love this function. | |
63 | */ | |
64 | static void __init rcu_bootup_announce_oddness(void) | |
65 | { | |
66 | #ifdef CONFIG_RCU_TRACE | |
efc151c3 | 67 | pr_info("\tRCU debugfs-based tracing is enabled.\n"); |
26845c28 PM |
68 | #endif |
69 | #if (defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) || (!defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32) | |
efc151c3 | 70 | pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n", |
26845c28 PM |
71 | CONFIG_RCU_FANOUT); |
72 | #endif | |
73 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
efc151c3 | 74 | pr_info("\tHierarchical RCU autobalancing is disabled.\n"); |
26845c28 PM |
75 | #endif |
76 | #ifdef CONFIG_RCU_FAST_NO_HZ | |
efc151c3 | 77 | pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n"); |
26845c28 PM |
78 | #endif |
79 | #ifdef CONFIG_PROVE_RCU | |
efc151c3 | 80 | pr_info("\tRCU lockdep checking is enabled.\n"); |
26845c28 PM |
81 | #endif |
82 | #ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE | |
efc151c3 | 83 | pr_info("\tRCU torture testing starts during boot.\n"); |
26845c28 | 84 | #endif |
81a294c4 | 85 | #if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE) |
efc151c3 | 86 | pr_info("\tDump stacks of tasks blocking RCU-preempt GP.\n"); |
a858af28 PM |
87 | #endif |
88 | #if defined(CONFIG_RCU_CPU_STALL_INFO) | |
efc151c3 | 89 | pr_info("\tAdditional per-CPU info printed with stalls.\n"); |
26845c28 PM |
90 | #endif |
91 | #if NUM_RCU_LVL_4 != 0 | |
efc151c3 | 92 | pr_info("\tFour-level hierarchy is enabled.\n"); |
26845c28 | 93 | #endif |
f885b7f2 | 94 | if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF) |
9a5739d7 | 95 | pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf); |
cca6f393 | 96 | if (nr_cpu_ids != NR_CPUS) |
efc151c3 | 97 | pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); |
21871d7e CW |
98 | #ifdef CONFIG_RCU_BOOST |
99 | pr_info("\tRCU kthread priority: %d.\n", kthread_prio); | |
100 | #endif | |
26845c28 PM |
101 | } |
102 | ||
f41d911f PM |
103 | #ifdef CONFIG_TREE_PREEMPT_RCU |
104 | ||
a41bfeb2 | 105 | RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); |
e534165b | 106 | static struct rcu_state *rcu_state_p = &rcu_preempt_state; |
f41d911f | 107 | |
d9a3da06 PM |
108 | static int rcu_preempted_readers_exp(struct rcu_node *rnp); |
109 | ||
f41d911f PM |
110 | /* |
111 | * Tell them what RCU they are running. | |
112 | */ | |
0e0fc1c2 | 113 | static void __init rcu_bootup_announce(void) |
f41d911f | 114 | { |
efc151c3 | 115 | pr_info("Preemptible hierarchical RCU implementation.\n"); |
26845c28 | 116 | rcu_bootup_announce_oddness(); |
f41d911f PM |
117 | } |
118 | ||
119 | /* | |
120 | * Return the number of RCU-preempt batches processed thus far | |
121 | * for debug and statistics. | |
122 | */ | |
bf33eb1a | 123 | static long rcu_batches_completed_preempt(void) |
f41d911f PM |
124 | { |
125 | return rcu_preempt_state.completed; | |
126 | } | |
127 | EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt); | |
128 | ||
129 | /* | |
130 | * Return the number of RCU batches processed thus far for debug & stats. | |
131 | */ | |
132 | long rcu_batches_completed(void) | |
133 | { | |
134 | return rcu_batches_completed_preempt(); | |
135 | } | |
136 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
137 | ||
138 | /* | |
6cc68793 | 139 | * Record a preemptible-RCU quiescent state for the specified CPU. Note |
f41d911f PM |
140 | * that this just means that the task currently running on the CPU is |
141 | * not in a quiescent state. There might be any number of tasks blocked | |
142 | * while in an RCU read-side critical section. | |
25502a6c | 143 | * |
1d082fd0 PM |
144 | * As with the other rcu_*_qs() functions, callers to this function |
145 | * must disable preemption. | |
f41d911f | 146 | */ |
284a8c93 | 147 | static void rcu_preempt_qs(void) |
f41d911f | 148 | { |
284a8c93 PM |
149 | if (!__this_cpu_read(rcu_preempt_data.passed_quiesce)) { |
150 | trace_rcu_grace_period(TPS("rcu_preempt"), | |
151 | __this_cpu_read(rcu_preempt_data.gpnum), | |
152 | TPS("cpuqs")); | |
153 | __this_cpu_write(rcu_preempt_data.passed_quiesce, 1); | |
154 | barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */ | |
155 | current->rcu_read_unlock_special.b.need_qs = false; | |
156 | } | |
f41d911f PM |
157 | } |
158 | ||
159 | /* | |
c3422bea PM |
160 | * We have entered the scheduler, and the current task might soon be |
161 | * context-switched away from. If this task is in an RCU read-side | |
162 | * critical section, we will no longer be able to rely on the CPU to | |
12f5f524 PM |
163 | * record that fact, so we enqueue the task on the blkd_tasks list. |
164 | * The task will dequeue itself when it exits the outermost enclosing | |
165 | * RCU read-side critical section. Therefore, the current grace period | |
166 | * cannot be permitted to complete until the blkd_tasks list entries | |
167 | * predating the current grace period drain, in other words, until | |
168 | * rnp->gp_tasks becomes NULL. | |
c3422bea PM |
169 | * |
170 | * Caller must disable preemption. | |
f41d911f | 171 | */ |
cba6d0d6 | 172 | static void rcu_preempt_note_context_switch(int cpu) |
f41d911f PM |
173 | { |
174 | struct task_struct *t = current; | |
c3422bea | 175 | unsigned long flags; |
f41d911f PM |
176 | struct rcu_data *rdp; |
177 | struct rcu_node *rnp; | |
178 | ||
10f39bb1 | 179 | if (t->rcu_read_lock_nesting > 0 && |
1d082fd0 | 180 | !t->rcu_read_unlock_special.b.blocked) { |
f41d911f PM |
181 | |
182 | /* Possibly blocking in an RCU read-side critical section. */ | |
cba6d0d6 | 183 | rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu); |
f41d911f | 184 | rnp = rdp->mynode; |
1304afb2 | 185 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 186 | smp_mb__after_unlock_lock(); |
1d082fd0 | 187 | t->rcu_read_unlock_special.b.blocked = true; |
86848966 | 188 | t->rcu_blocked_node = rnp; |
f41d911f PM |
189 | |
190 | /* | |
191 | * If this CPU has already checked in, then this task | |
192 | * will hold up the next grace period rather than the | |
193 | * current grace period. Queue the task accordingly. | |
194 | * If the task is queued for the current grace period | |
195 | * (i.e., this CPU has not yet passed through a quiescent | |
196 | * state for the current grace period), then as long | |
197 | * as that task remains queued, the current grace period | |
12f5f524 PM |
198 | * cannot end. Note that there is some uncertainty as |
199 | * to exactly when the current grace period started. | |
200 | * We take a conservative approach, which can result | |
201 | * in unnecessarily waiting on tasks that started very | |
202 | * slightly after the current grace period began. C'est | |
203 | * la vie!!! | |
b0e165c0 PM |
204 | * |
205 | * But first, note that the current CPU must still be | |
206 | * on line! | |
f41d911f | 207 | */ |
b0e165c0 | 208 | WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0); |
e7d8842e | 209 | WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); |
12f5f524 PM |
210 | if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) { |
211 | list_add(&t->rcu_node_entry, rnp->gp_tasks->prev); | |
212 | rnp->gp_tasks = &t->rcu_node_entry; | |
27f4d280 PM |
213 | #ifdef CONFIG_RCU_BOOST |
214 | if (rnp->boost_tasks != NULL) | |
215 | rnp->boost_tasks = rnp->gp_tasks; | |
216 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
12f5f524 PM |
217 | } else { |
218 | list_add(&t->rcu_node_entry, &rnp->blkd_tasks); | |
219 | if (rnp->qsmask & rdp->grpmask) | |
220 | rnp->gp_tasks = &t->rcu_node_entry; | |
221 | } | |
d4c08f2a PM |
222 | trace_rcu_preempt_task(rdp->rsp->name, |
223 | t->pid, | |
224 | (rnp->qsmask & rdp->grpmask) | |
225 | ? rnp->gpnum | |
226 | : rnp->gpnum + 1); | |
1304afb2 | 227 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
10f39bb1 | 228 | } else if (t->rcu_read_lock_nesting < 0 && |
1d082fd0 | 229 | t->rcu_read_unlock_special.s) { |
10f39bb1 PM |
230 | |
231 | /* | |
232 | * Complete exit from RCU read-side critical section on | |
233 | * behalf of preempted instance of __rcu_read_unlock(). | |
234 | */ | |
235 | rcu_read_unlock_special(t); | |
f41d911f PM |
236 | } |
237 | ||
238 | /* | |
239 | * Either we were not in an RCU read-side critical section to | |
240 | * begin with, or we have now recorded that critical section | |
241 | * globally. Either way, we can now note a quiescent state | |
242 | * for this CPU. Again, if we were in an RCU read-side critical | |
243 | * section, and if that critical section was blocking the current | |
244 | * grace period, then the fact that the task has been enqueued | |
245 | * means that we continue to block the current grace period. | |
246 | */ | |
284a8c93 | 247 | rcu_preempt_qs(); |
f41d911f PM |
248 | } |
249 | ||
fc2219d4 PM |
250 | /* |
251 | * Check for preempted RCU readers blocking the current grace period | |
252 | * for the specified rcu_node structure. If the caller needs a reliable | |
253 | * answer, it must hold the rcu_node's ->lock. | |
254 | */ | |
27f4d280 | 255 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
fc2219d4 | 256 | { |
12f5f524 | 257 | return rnp->gp_tasks != NULL; |
fc2219d4 PM |
258 | } |
259 | ||
b668c9cf PM |
260 | /* |
261 | * Record a quiescent state for all tasks that were previously queued | |
262 | * on the specified rcu_node structure and that were blocking the current | |
263 | * RCU grace period. The caller must hold the specified rnp->lock with | |
264 | * irqs disabled, and this lock is released upon return, but irqs remain | |
265 | * disabled. | |
266 | */ | |
d3f6bad3 | 267 | static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
b668c9cf PM |
268 | __releases(rnp->lock) |
269 | { | |
270 | unsigned long mask; | |
271 | struct rcu_node *rnp_p; | |
272 | ||
27f4d280 | 273 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
1304afb2 | 274 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b668c9cf PM |
275 | return; /* Still need more quiescent states! */ |
276 | } | |
277 | ||
278 | rnp_p = rnp->parent; | |
279 | if (rnp_p == NULL) { | |
280 | /* | |
281 | * Either there is only one rcu_node in the tree, | |
282 | * or tasks were kicked up to root rcu_node due to | |
283 | * CPUs going offline. | |
284 | */ | |
d3f6bad3 | 285 | rcu_report_qs_rsp(&rcu_preempt_state, flags); |
b668c9cf PM |
286 | return; |
287 | } | |
288 | ||
289 | /* Report up the rest of the hierarchy. */ | |
290 | mask = rnp->grpmask; | |
1304afb2 PM |
291 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
292 | raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */ | |
6303b9c8 | 293 | smp_mb__after_unlock_lock(); |
d3f6bad3 | 294 | rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags); |
b668c9cf PM |
295 | } |
296 | ||
12f5f524 PM |
297 | /* |
298 | * Advance a ->blkd_tasks-list pointer to the next entry, instead | |
299 | * returning NULL if at the end of the list. | |
300 | */ | |
301 | static struct list_head *rcu_next_node_entry(struct task_struct *t, | |
302 | struct rcu_node *rnp) | |
303 | { | |
304 | struct list_head *np; | |
305 | ||
306 | np = t->rcu_node_entry.next; | |
307 | if (np == &rnp->blkd_tasks) | |
308 | np = NULL; | |
309 | return np; | |
310 | } | |
311 | ||
b668c9cf PM |
312 | /* |
313 | * Handle special cases during rcu_read_unlock(), such as needing to | |
314 | * notify RCU core processing or task having blocked during the RCU | |
315 | * read-side critical section. | |
316 | */ | |
2a3fa843 | 317 | void rcu_read_unlock_special(struct task_struct *t) |
f41d911f PM |
318 | { |
319 | int empty; | |
d9a3da06 | 320 | int empty_exp; |
389abd48 | 321 | int empty_exp_now; |
f41d911f | 322 | unsigned long flags; |
12f5f524 | 323 | struct list_head *np; |
82e78d80 | 324 | #ifdef CONFIG_RCU_BOOST |
abaa93d9 | 325 | bool drop_boost_mutex = false; |
82e78d80 | 326 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
f41d911f | 327 | struct rcu_node *rnp; |
1d082fd0 | 328 | union rcu_special special; |
f41d911f PM |
329 | |
330 | /* NMI handlers cannot block and cannot safely manipulate state. */ | |
331 | if (in_nmi()) | |
332 | return; | |
333 | ||
334 | local_irq_save(flags); | |
335 | ||
336 | /* | |
337 | * If RCU core is waiting for this CPU to exit critical section, | |
1d082fd0 PM |
338 | * let it know that we have done so. Because irqs are disabled, |
339 | * t->rcu_read_unlock_special cannot change. | |
f41d911f PM |
340 | */ |
341 | special = t->rcu_read_unlock_special; | |
1d082fd0 | 342 | if (special.b.need_qs) { |
284a8c93 | 343 | rcu_preempt_qs(); |
1d082fd0 | 344 | if (!t->rcu_read_unlock_special.s) { |
79a62f95 LJ |
345 | local_irq_restore(flags); |
346 | return; | |
347 | } | |
f41d911f PM |
348 | } |
349 | ||
79a62f95 LJ |
350 | /* Hardware IRQ handlers cannot block, complain if they get here. */ |
351 | if (WARN_ON_ONCE(in_irq() || in_serving_softirq())) { | |
f41d911f PM |
352 | local_irq_restore(flags); |
353 | return; | |
354 | } | |
355 | ||
356 | /* Clean up if blocked during RCU read-side critical section. */ | |
1d082fd0 PM |
357 | if (special.b.blocked) { |
358 | t->rcu_read_unlock_special.b.blocked = false; | |
f41d911f | 359 | |
dd5d19ba PM |
360 | /* |
361 | * Remove this task from the list it blocked on. The | |
362 | * task can migrate while we acquire the lock, but at | |
363 | * most one time. So at most two passes through loop. | |
364 | */ | |
365 | for (;;) { | |
86848966 | 366 | rnp = t->rcu_blocked_node; |
1304afb2 | 367 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
6303b9c8 | 368 | smp_mb__after_unlock_lock(); |
86848966 | 369 | if (rnp == t->rcu_blocked_node) |
dd5d19ba | 370 | break; |
1304afb2 | 371 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
dd5d19ba | 372 | } |
27f4d280 | 373 | empty = !rcu_preempt_blocked_readers_cgp(rnp); |
d9a3da06 PM |
374 | empty_exp = !rcu_preempted_readers_exp(rnp); |
375 | smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ | |
12f5f524 | 376 | np = rcu_next_node_entry(t, rnp); |
f41d911f | 377 | list_del_init(&t->rcu_node_entry); |
82e78d80 | 378 | t->rcu_blocked_node = NULL; |
f7f7bac9 | 379 | trace_rcu_unlock_preempted_task(TPS("rcu_preempt"), |
d4c08f2a | 380 | rnp->gpnum, t->pid); |
12f5f524 PM |
381 | if (&t->rcu_node_entry == rnp->gp_tasks) |
382 | rnp->gp_tasks = np; | |
383 | if (&t->rcu_node_entry == rnp->exp_tasks) | |
384 | rnp->exp_tasks = np; | |
27f4d280 PM |
385 | #ifdef CONFIG_RCU_BOOST |
386 | if (&t->rcu_node_entry == rnp->boost_tasks) | |
387 | rnp->boost_tasks = np; | |
abaa93d9 PM |
388 | /* Snapshot ->boost_mtx ownership with rcu_node lock held. */ |
389 | drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t; | |
27f4d280 | 390 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
f41d911f PM |
391 | |
392 | /* | |
393 | * If this was the last task on the current list, and if | |
394 | * we aren't waiting on any CPUs, report the quiescent state. | |
389abd48 PM |
395 | * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, |
396 | * so we must take a snapshot of the expedited state. | |
f41d911f | 397 | */ |
389abd48 | 398 | empty_exp_now = !rcu_preempted_readers_exp(rnp); |
d4c08f2a | 399 | if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) { |
f7f7bac9 | 400 | trace_rcu_quiescent_state_report(TPS("preempt_rcu"), |
d4c08f2a PM |
401 | rnp->gpnum, |
402 | 0, rnp->qsmask, | |
403 | rnp->level, | |
404 | rnp->grplo, | |
405 | rnp->grphi, | |
406 | !!rnp->gp_tasks); | |
d3f6bad3 | 407 | rcu_report_unblock_qs_rnp(rnp, flags); |
c701d5d9 | 408 | } else { |
d4c08f2a | 409 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c701d5d9 | 410 | } |
d9a3da06 | 411 | |
27f4d280 PM |
412 | #ifdef CONFIG_RCU_BOOST |
413 | /* Unboost if we were boosted. */ | |
abaa93d9 PM |
414 | if (drop_boost_mutex) { |
415 | rt_mutex_unlock(&rnp->boost_mtx); | |
dfeb9765 PM |
416 | complete(&rnp->boost_completion); |
417 | } | |
27f4d280 PM |
418 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
419 | ||
d9a3da06 PM |
420 | /* |
421 | * If this was the last task on the expedited lists, | |
422 | * then we need to report up the rcu_node hierarchy. | |
423 | */ | |
389abd48 | 424 | if (!empty_exp && empty_exp_now) |
b40d293e | 425 | rcu_report_exp_rnp(&rcu_preempt_state, rnp, true); |
b668c9cf PM |
426 | } else { |
427 | local_irq_restore(flags); | |
f41d911f | 428 | } |
f41d911f PM |
429 | } |
430 | ||
1ed509a2 PM |
431 | #ifdef CONFIG_RCU_CPU_STALL_VERBOSE |
432 | ||
433 | /* | |
434 | * Dump detailed information for all tasks blocking the current RCU | |
435 | * grace period on the specified rcu_node structure. | |
436 | */ | |
437 | static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) | |
438 | { | |
439 | unsigned long flags; | |
1ed509a2 PM |
440 | struct task_struct *t; |
441 | ||
12f5f524 | 442 | raw_spin_lock_irqsave(&rnp->lock, flags); |
5fd4dc06 PM |
443 | if (!rcu_preempt_blocked_readers_cgp(rnp)) { |
444 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
445 | return; | |
446 | } | |
12f5f524 PM |
447 | t = list_entry(rnp->gp_tasks, |
448 | struct task_struct, rcu_node_entry); | |
449 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) | |
450 | sched_show_task(t); | |
451 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1ed509a2 PM |
452 | } |
453 | ||
454 | /* | |
455 | * Dump detailed information for all tasks blocking the current RCU | |
456 | * grace period. | |
457 | */ | |
458 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) | |
459 | { | |
460 | struct rcu_node *rnp = rcu_get_root(rsp); | |
461 | ||
462 | rcu_print_detail_task_stall_rnp(rnp); | |
463 | rcu_for_each_leaf_node(rsp, rnp) | |
464 | rcu_print_detail_task_stall_rnp(rnp); | |
465 | } | |
466 | ||
467 | #else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ | |
468 | ||
469 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) | |
470 | { | |
471 | } | |
472 | ||
473 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ | |
474 | ||
a858af28 PM |
475 | #ifdef CONFIG_RCU_CPU_STALL_INFO |
476 | ||
477 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) | |
478 | { | |
efc151c3 | 479 | pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", |
a858af28 PM |
480 | rnp->level, rnp->grplo, rnp->grphi); |
481 | } | |
482 | ||
483 | static void rcu_print_task_stall_end(void) | |
484 | { | |
efc151c3 | 485 | pr_cont("\n"); |
a858af28 PM |
486 | } |
487 | ||
488 | #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
489 | ||
490 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) | |
491 | { | |
492 | } | |
493 | ||
494 | static void rcu_print_task_stall_end(void) | |
495 | { | |
496 | } | |
497 | ||
498 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
499 | ||
f41d911f PM |
500 | /* |
501 | * Scan the current list of tasks blocked within RCU read-side critical | |
502 | * sections, printing out the tid of each. | |
503 | */ | |
9bc8b558 | 504 | static int rcu_print_task_stall(struct rcu_node *rnp) |
f41d911f | 505 | { |
f41d911f | 506 | struct task_struct *t; |
9bc8b558 | 507 | int ndetected = 0; |
f41d911f | 508 | |
27f4d280 | 509 | if (!rcu_preempt_blocked_readers_cgp(rnp)) |
9bc8b558 | 510 | return 0; |
a858af28 | 511 | rcu_print_task_stall_begin(rnp); |
12f5f524 PM |
512 | t = list_entry(rnp->gp_tasks, |
513 | struct task_struct, rcu_node_entry); | |
9bc8b558 | 514 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
efc151c3 | 515 | pr_cont(" P%d", t->pid); |
9bc8b558 PM |
516 | ndetected++; |
517 | } | |
a858af28 | 518 | rcu_print_task_stall_end(); |
9bc8b558 | 519 | return ndetected; |
f41d911f PM |
520 | } |
521 | ||
b0e165c0 PM |
522 | /* |
523 | * Check that the list of blocked tasks for the newly completed grace | |
524 | * period is in fact empty. It is a serious bug to complete a grace | |
525 | * period that still has RCU readers blocked! This function must be | |
526 | * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock | |
527 | * must be held by the caller. | |
12f5f524 PM |
528 | * |
529 | * Also, if there are blocked tasks on the list, they automatically | |
530 | * block the newly created grace period, so set up ->gp_tasks accordingly. | |
b0e165c0 PM |
531 | */ |
532 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) | |
533 | { | |
27f4d280 | 534 | WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
12f5f524 PM |
535 | if (!list_empty(&rnp->blkd_tasks)) |
536 | rnp->gp_tasks = rnp->blkd_tasks.next; | |
28ecd580 | 537 | WARN_ON_ONCE(rnp->qsmask); |
b0e165c0 PM |
538 | } |
539 | ||
33f76148 PM |
540 | #ifdef CONFIG_HOTPLUG_CPU |
541 | ||
dd5d19ba PM |
542 | /* |
543 | * Handle tasklist migration for case in which all CPUs covered by the | |
544 | * specified rcu_node have gone offline. Move them up to the root | |
545 | * rcu_node. The reason for not just moving them to the immediate | |
546 | * parent is to remove the need for rcu_read_unlock_special() to | |
547 | * make more than two attempts to acquire the target rcu_node's lock. | |
b668c9cf PM |
548 | * Returns true if there were tasks blocking the current RCU grace |
549 | * period. | |
dd5d19ba | 550 | * |
237c80c5 PM |
551 | * Returns 1 if there was previously a task blocking the current grace |
552 | * period on the specified rcu_node structure. | |
553 | * | |
dd5d19ba PM |
554 | * The caller must hold rnp->lock with irqs disabled. |
555 | */ | |
237c80c5 PM |
556 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
557 | struct rcu_node *rnp, | |
558 | struct rcu_data *rdp) | |
dd5d19ba | 559 | { |
dd5d19ba PM |
560 | struct list_head *lp; |
561 | struct list_head *lp_root; | |
d9a3da06 | 562 | int retval = 0; |
dd5d19ba | 563 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
12f5f524 | 564 | struct task_struct *t; |
dd5d19ba | 565 | |
86848966 PM |
566 | if (rnp == rnp_root) { |
567 | WARN_ONCE(1, "Last CPU thought to be offlined?"); | |
237c80c5 | 568 | return 0; /* Shouldn't happen: at least one CPU online. */ |
86848966 | 569 | } |
12f5f524 PM |
570 | |
571 | /* If we are on an internal node, complain bitterly. */ | |
572 | WARN_ON_ONCE(rnp != rdp->mynode); | |
dd5d19ba PM |
573 | |
574 | /* | |
12f5f524 PM |
575 | * Move tasks up to root rcu_node. Don't try to get fancy for |
576 | * this corner-case operation -- just put this node's tasks | |
577 | * at the head of the root node's list, and update the root node's | |
578 | * ->gp_tasks and ->exp_tasks pointers to those of this node's, | |
579 | * if non-NULL. This might result in waiting for more tasks than | |
580 | * absolutely necessary, but this is a good performance/complexity | |
581 | * tradeoff. | |
dd5d19ba | 582 | */ |
2036d94a | 583 | if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0) |
d9a3da06 PM |
584 | retval |= RCU_OFL_TASKS_NORM_GP; |
585 | if (rcu_preempted_readers_exp(rnp)) | |
586 | retval |= RCU_OFL_TASKS_EXP_GP; | |
12f5f524 PM |
587 | lp = &rnp->blkd_tasks; |
588 | lp_root = &rnp_root->blkd_tasks; | |
589 | while (!list_empty(lp)) { | |
590 | t = list_entry(lp->next, typeof(*t), rcu_node_entry); | |
591 | raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ | |
6303b9c8 | 592 | smp_mb__after_unlock_lock(); |
12f5f524 PM |
593 | list_del(&t->rcu_node_entry); |
594 | t->rcu_blocked_node = rnp_root; | |
595 | list_add(&t->rcu_node_entry, lp_root); | |
596 | if (&t->rcu_node_entry == rnp->gp_tasks) | |
597 | rnp_root->gp_tasks = rnp->gp_tasks; | |
598 | if (&t->rcu_node_entry == rnp->exp_tasks) | |
599 | rnp_root->exp_tasks = rnp->exp_tasks; | |
27f4d280 PM |
600 | #ifdef CONFIG_RCU_BOOST |
601 | if (&t->rcu_node_entry == rnp->boost_tasks) | |
602 | rnp_root->boost_tasks = rnp->boost_tasks; | |
603 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
12f5f524 | 604 | raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ |
dd5d19ba | 605 | } |
27f4d280 | 606 | |
1e3fd2b3 PM |
607 | rnp->gp_tasks = NULL; |
608 | rnp->exp_tasks = NULL; | |
27f4d280 | 609 | #ifdef CONFIG_RCU_BOOST |
1e3fd2b3 | 610 | rnp->boost_tasks = NULL; |
5cc900cf PM |
611 | /* |
612 | * In case root is being boosted and leaf was not. Make sure | |
613 | * that we boost the tasks blocking the current grace period | |
614 | * in this case. | |
615 | */ | |
27f4d280 | 616 | raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ |
6303b9c8 | 617 | smp_mb__after_unlock_lock(); |
27f4d280 | 618 | if (rnp_root->boost_tasks != NULL && |
5cc900cf PM |
619 | rnp_root->boost_tasks != rnp_root->gp_tasks && |
620 | rnp_root->boost_tasks != rnp_root->exp_tasks) | |
27f4d280 PM |
621 | rnp_root->boost_tasks = rnp_root->gp_tasks; |
622 | raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ | |
623 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
624 | ||
237c80c5 | 625 | return retval; |
dd5d19ba PM |
626 | } |
627 | ||
e5601400 PM |
628 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
629 | ||
f41d911f PM |
630 | /* |
631 | * Check for a quiescent state from the current CPU. When a task blocks, | |
632 | * the task is recorded in the corresponding CPU's rcu_node structure, | |
633 | * which is checked elsewhere. | |
634 | * | |
635 | * Caller must disable hard irqs. | |
636 | */ | |
637 | static void rcu_preempt_check_callbacks(int cpu) | |
638 | { | |
639 | struct task_struct *t = current; | |
640 | ||
641 | if (t->rcu_read_lock_nesting == 0) { | |
284a8c93 | 642 | rcu_preempt_qs(); |
f41d911f PM |
643 | return; |
644 | } | |
10f39bb1 | 645 | if (t->rcu_read_lock_nesting > 0 && |
284a8c93 PM |
646 | per_cpu(rcu_preempt_data, cpu).qs_pending && |
647 | !per_cpu(rcu_preempt_data, cpu).passed_quiesce) | |
1d082fd0 | 648 | t->rcu_read_unlock_special.b.need_qs = true; |
f41d911f PM |
649 | } |
650 | ||
a46e0899 PM |
651 | #ifdef CONFIG_RCU_BOOST |
652 | ||
09223371 SL |
653 | static void rcu_preempt_do_callbacks(void) |
654 | { | |
c9d4b0af | 655 | rcu_do_batch(&rcu_preempt_state, this_cpu_ptr(&rcu_preempt_data)); |
09223371 SL |
656 | } |
657 | ||
a46e0899 PM |
658 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
659 | ||
f41d911f | 660 | /* |
6cc68793 | 661 | * Queue a preemptible-RCU callback for invocation after a grace period. |
f41d911f PM |
662 | */ |
663 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
664 | { | |
3fbfbf7a | 665 | __call_rcu(head, func, &rcu_preempt_state, -1, 0); |
f41d911f PM |
666 | } |
667 | EXPORT_SYMBOL_GPL(call_rcu); | |
668 | ||
6ebb237b PM |
669 | /** |
670 | * synchronize_rcu - wait until a grace period has elapsed. | |
671 | * | |
672 | * Control will return to the caller some time after a full grace | |
673 | * period has elapsed, in other words after all currently executing RCU | |
77d8485a PM |
674 | * read-side critical sections have completed. Note, however, that |
675 | * upon return from synchronize_rcu(), the caller might well be executing | |
676 | * concurrently with new RCU read-side critical sections that began while | |
677 | * synchronize_rcu() was waiting. RCU read-side critical sections are | |
678 | * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. | |
f0a0e6f2 PM |
679 | * |
680 | * See the description of synchronize_sched() for more detailed information | |
681 | * on memory ordering guarantees. | |
6ebb237b PM |
682 | */ |
683 | void synchronize_rcu(void) | |
684 | { | |
fe15d706 PM |
685 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
686 | !lock_is_held(&rcu_lock_map) && | |
687 | !lock_is_held(&rcu_sched_lock_map), | |
688 | "Illegal synchronize_rcu() in RCU read-side critical section"); | |
6ebb237b PM |
689 | if (!rcu_scheduler_active) |
690 | return; | |
3705b88d AM |
691 | if (rcu_expedited) |
692 | synchronize_rcu_expedited(); | |
693 | else | |
694 | wait_rcu_gp(call_rcu); | |
6ebb237b PM |
695 | } |
696 | EXPORT_SYMBOL_GPL(synchronize_rcu); | |
697 | ||
d9a3da06 | 698 | static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); |
bcfa57ce | 699 | static unsigned long sync_rcu_preempt_exp_count; |
d9a3da06 PM |
700 | static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); |
701 | ||
702 | /* | |
703 | * Return non-zero if there are any tasks in RCU read-side critical | |
704 | * sections blocking the current preemptible-RCU expedited grace period. | |
705 | * If there is no preemptible-RCU expedited grace period currently in | |
706 | * progress, returns zero unconditionally. | |
707 | */ | |
708 | static int rcu_preempted_readers_exp(struct rcu_node *rnp) | |
709 | { | |
12f5f524 | 710 | return rnp->exp_tasks != NULL; |
d9a3da06 PM |
711 | } |
712 | ||
713 | /* | |
714 | * return non-zero if there is no RCU expedited grace period in progress | |
715 | * for the specified rcu_node structure, in other words, if all CPUs and | |
716 | * tasks covered by the specified rcu_node structure have done their bit | |
717 | * for the current expedited grace period. Works only for preemptible | |
718 | * RCU -- other RCU implementation use other means. | |
719 | * | |
720 | * Caller must hold sync_rcu_preempt_exp_mutex. | |
721 | */ | |
722 | static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) | |
723 | { | |
724 | return !rcu_preempted_readers_exp(rnp) && | |
725 | ACCESS_ONCE(rnp->expmask) == 0; | |
726 | } | |
727 | ||
728 | /* | |
729 | * Report the exit from RCU read-side critical section for the last task | |
730 | * that queued itself during or before the current expedited preemptible-RCU | |
731 | * grace period. This event is reported either to the rcu_node structure on | |
732 | * which the task was queued or to one of that rcu_node structure's ancestors, | |
733 | * recursively up the tree. (Calm down, calm down, we do the recursion | |
734 | * iteratively!) | |
735 | * | |
b40d293e TG |
736 | * Most callers will set the "wake" flag, but the task initiating the |
737 | * expedited grace period need not wake itself. | |
738 | * | |
d9a3da06 PM |
739 | * Caller must hold sync_rcu_preempt_exp_mutex. |
740 | */ | |
b40d293e TG |
741 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
742 | bool wake) | |
d9a3da06 PM |
743 | { |
744 | unsigned long flags; | |
745 | unsigned long mask; | |
746 | ||
1304afb2 | 747 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 748 | smp_mb__after_unlock_lock(); |
d9a3da06 | 749 | for (;;) { |
131906b0 PM |
750 | if (!sync_rcu_preempt_exp_done(rnp)) { |
751 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
d9a3da06 | 752 | break; |
131906b0 | 753 | } |
d9a3da06 | 754 | if (rnp->parent == NULL) { |
131906b0 | 755 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
78e4bc34 PM |
756 | if (wake) { |
757 | smp_mb(); /* EGP done before wake_up(). */ | |
b40d293e | 758 | wake_up(&sync_rcu_preempt_exp_wq); |
78e4bc34 | 759 | } |
d9a3da06 PM |
760 | break; |
761 | } | |
762 | mask = rnp->grpmask; | |
1304afb2 | 763 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
d9a3da06 | 764 | rnp = rnp->parent; |
1304afb2 | 765 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
6303b9c8 | 766 | smp_mb__after_unlock_lock(); |
d9a3da06 PM |
767 | rnp->expmask &= ~mask; |
768 | } | |
d9a3da06 PM |
769 | } |
770 | ||
771 | /* | |
772 | * Snapshot the tasks blocking the newly started preemptible-RCU expedited | |
773 | * grace period for the specified rcu_node structure. If there are no such | |
774 | * tasks, report it up the rcu_node hierarchy. | |
775 | * | |
7b2e6011 PM |
776 | * Caller must hold sync_rcu_preempt_exp_mutex and must exclude |
777 | * CPU hotplug operations. | |
d9a3da06 PM |
778 | */ |
779 | static void | |
780 | sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp) | |
781 | { | |
1217ed1b | 782 | unsigned long flags; |
12f5f524 | 783 | int must_wait = 0; |
d9a3da06 | 784 | |
1217ed1b | 785 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 786 | smp_mb__after_unlock_lock(); |
c701d5d9 | 787 | if (list_empty(&rnp->blkd_tasks)) { |
1217ed1b | 788 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c701d5d9 | 789 | } else { |
12f5f524 | 790 | rnp->exp_tasks = rnp->blkd_tasks.next; |
1217ed1b | 791 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
12f5f524 PM |
792 | must_wait = 1; |
793 | } | |
d9a3da06 | 794 | if (!must_wait) |
b40d293e | 795 | rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */ |
d9a3da06 PM |
796 | } |
797 | ||
236fefaf PM |
798 | /** |
799 | * synchronize_rcu_expedited - Brute-force RCU grace period | |
800 | * | |
801 | * Wait for an RCU-preempt grace period, but expedite it. The basic | |
802 | * idea is to invoke synchronize_sched_expedited() to push all the tasks to | |
803 | * the ->blkd_tasks lists and wait for this list to drain. This consumes | |
804 | * significant time on all CPUs and is unfriendly to real-time workloads, | |
805 | * so is thus not recommended for any sort of common-case code. | |
806 | * In fact, if you are using synchronize_rcu_expedited() in a loop, | |
807 | * please restructure your code to batch your updates, and then Use a | |
808 | * single synchronize_rcu() instead. | |
019129d5 PM |
809 | */ |
810 | void synchronize_rcu_expedited(void) | |
811 | { | |
d9a3da06 PM |
812 | unsigned long flags; |
813 | struct rcu_node *rnp; | |
814 | struct rcu_state *rsp = &rcu_preempt_state; | |
bcfa57ce | 815 | unsigned long snap; |
d9a3da06 PM |
816 | int trycount = 0; |
817 | ||
818 | smp_mb(); /* Caller's modifications seen first by other CPUs. */ | |
819 | snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1; | |
820 | smp_mb(); /* Above access cannot bleed into critical section. */ | |
821 | ||
1943c89d PM |
822 | /* |
823 | * Block CPU-hotplug operations. This means that any CPU-hotplug | |
824 | * operation that finds an rcu_node structure with tasks in the | |
825 | * process of being boosted will know that all tasks blocking | |
826 | * this expedited grace period will already be in the process of | |
827 | * being boosted. This simplifies the process of moving tasks | |
828 | * from leaf to root rcu_node structures. | |
829 | */ | |
dd56af42 PM |
830 | if (!try_get_online_cpus()) { |
831 | /* CPU-hotplug operation in flight, fall back to normal GP. */ | |
832 | wait_rcu_gp(call_rcu); | |
833 | return; | |
834 | } | |
1943c89d | 835 | |
d9a3da06 PM |
836 | /* |
837 | * Acquire lock, falling back to synchronize_rcu() if too many | |
838 | * lock-acquisition failures. Of course, if someone does the | |
839 | * expedited grace period for us, just leave. | |
840 | */ | |
841 | while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) { | |
1943c89d PM |
842 | if (ULONG_CMP_LT(snap, |
843 | ACCESS_ONCE(sync_rcu_preempt_exp_count))) { | |
844 | put_online_cpus(); | |
845 | goto mb_ret; /* Others did our work for us. */ | |
846 | } | |
c701d5d9 | 847 | if (trycount++ < 10) { |
d9a3da06 | 848 | udelay(trycount * num_online_cpus()); |
c701d5d9 | 849 | } else { |
1943c89d | 850 | put_online_cpus(); |
3705b88d | 851 | wait_rcu_gp(call_rcu); |
d9a3da06 PM |
852 | return; |
853 | } | |
d9a3da06 | 854 | } |
1943c89d PM |
855 | if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) { |
856 | put_online_cpus(); | |
d9a3da06 | 857 | goto unlock_mb_ret; /* Others did our work for us. */ |
1943c89d | 858 | } |
d9a3da06 | 859 | |
12f5f524 | 860 | /* force all RCU readers onto ->blkd_tasks lists. */ |
d9a3da06 PM |
861 | synchronize_sched_expedited(); |
862 | ||
d9a3da06 PM |
863 | /* Initialize ->expmask for all non-leaf rcu_node structures. */ |
864 | rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) { | |
1943c89d | 865 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 866 | smp_mb__after_unlock_lock(); |
d9a3da06 | 867 | rnp->expmask = rnp->qsmaskinit; |
1943c89d | 868 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da06 PM |
869 | } |
870 | ||
12f5f524 | 871 | /* Snapshot current state of ->blkd_tasks lists. */ |
d9a3da06 PM |
872 | rcu_for_each_leaf_node(rsp, rnp) |
873 | sync_rcu_preempt_exp_init(rsp, rnp); | |
874 | if (NUM_RCU_NODES > 1) | |
875 | sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp)); | |
876 | ||
1943c89d | 877 | put_online_cpus(); |
d9a3da06 | 878 | |
12f5f524 | 879 | /* Wait for snapshotted ->blkd_tasks lists to drain. */ |
d9a3da06 PM |
880 | rnp = rcu_get_root(rsp); |
881 | wait_event(sync_rcu_preempt_exp_wq, | |
882 | sync_rcu_preempt_exp_done(rnp)); | |
883 | ||
884 | /* Clean up and exit. */ | |
885 | smp_mb(); /* ensure expedited GP seen before counter increment. */ | |
4de376a1 PK |
886 | ACCESS_ONCE(sync_rcu_preempt_exp_count) = |
887 | sync_rcu_preempt_exp_count + 1; | |
d9a3da06 PM |
888 | unlock_mb_ret: |
889 | mutex_unlock(&sync_rcu_preempt_exp_mutex); | |
890 | mb_ret: | |
891 | smp_mb(); /* ensure subsequent action seen after grace period. */ | |
019129d5 PM |
892 | } |
893 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
894 | ||
e74f4c45 PM |
895 | /** |
896 | * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. | |
f0a0e6f2 PM |
897 | * |
898 | * Note that this primitive does not necessarily wait for an RCU grace period | |
899 | * to complete. For example, if there are no RCU callbacks queued anywhere | |
900 | * in the system, then rcu_barrier() is within its rights to return | |
901 | * immediately, without waiting for anything, much less an RCU grace period. | |
e74f4c45 PM |
902 | */ |
903 | void rcu_barrier(void) | |
904 | { | |
037b64ed | 905 | _rcu_barrier(&rcu_preempt_state); |
e74f4c45 PM |
906 | } |
907 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
908 | ||
1eba8f84 | 909 | /* |
6cc68793 | 910 | * Initialize preemptible RCU's state structures. |
1eba8f84 PM |
911 | */ |
912 | static void __init __rcu_init_preempt(void) | |
913 | { | |
394f99a9 | 914 | rcu_init_one(&rcu_preempt_state, &rcu_preempt_data); |
1eba8f84 PM |
915 | } |
916 | ||
2439b696 PM |
917 | /* |
918 | * Check for a task exiting while in a preemptible-RCU read-side | |
919 | * critical section, clean up if so. No need to issue warnings, | |
920 | * as debug_check_no_locks_held() already does this if lockdep | |
921 | * is enabled. | |
922 | */ | |
923 | void exit_rcu(void) | |
924 | { | |
925 | struct task_struct *t = current; | |
926 | ||
927 | if (likely(list_empty(¤t->rcu_node_entry))) | |
928 | return; | |
929 | t->rcu_read_lock_nesting = 1; | |
930 | barrier(); | |
1d082fd0 | 931 | t->rcu_read_unlock_special.b.blocked = true; |
2439b696 PM |
932 | __rcu_read_unlock(); |
933 | } | |
934 | ||
f41d911f PM |
935 | #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
936 | ||
e534165b | 937 | static struct rcu_state *rcu_state_p = &rcu_sched_state; |
27f4d280 | 938 | |
f41d911f PM |
939 | /* |
940 | * Tell them what RCU they are running. | |
941 | */ | |
0e0fc1c2 | 942 | static void __init rcu_bootup_announce(void) |
f41d911f | 943 | { |
efc151c3 | 944 | pr_info("Hierarchical RCU implementation.\n"); |
26845c28 | 945 | rcu_bootup_announce_oddness(); |
f41d911f PM |
946 | } |
947 | ||
948 | /* | |
949 | * Return the number of RCU batches processed thus far for debug & stats. | |
950 | */ | |
951 | long rcu_batches_completed(void) | |
952 | { | |
953 | return rcu_batches_completed_sched(); | |
954 | } | |
955 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
956 | ||
cba6d0d6 PM |
957 | /* |
958 | * Because preemptible RCU does not exist, we never have to check for | |
959 | * CPUs being in quiescent states. | |
960 | */ | |
961 | static void rcu_preempt_note_context_switch(int cpu) | |
962 | { | |
963 | } | |
964 | ||
fc2219d4 | 965 | /* |
6cc68793 | 966 | * Because preemptible RCU does not exist, there are never any preempted |
fc2219d4 PM |
967 | * RCU readers. |
968 | */ | |
27f4d280 | 969 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
fc2219d4 PM |
970 | { |
971 | return 0; | |
972 | } | |
973 | ||
b668c9cf PM |
974 | #ifdef CONFIG_HOTPLUG_CPU |
975 | ||
976 | /* Because preemptible RCU does not exist, no quieting of tasks. */ | |
d3f6bad3 | 977 | static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
b41d1b92 | 978 | __releases(rnp->lock) |
b668c9cf | 979 | { |
1304afb2 | 980 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b668c9cf PM |
981 | } |
982 | ||
983 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ | |
984 | ||
1ed509a2 | 985 | /* |
6cc68793 | 986 | * Because preemptible RCU does not exist, we never have to check for |
1ed509a2 PM |
987 | * tasks blocked within RCU read-side critical sections. |
988 | */ | |
989 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) | |
990 | { | |
991 | } | |
992 | ||
f41d911f | 993 | /* |
6cc68793 | 994 | * Because preemptible RCU does not exist, we never have to check for |
f41d911f PM |
995 | * tasks blocked within RCU read-side critical sections. |
996 | */ | |
9bc8b558 | 997 | static int rcu_print_task_stall(struct rcu_node *rnp) |
f41d911f | 998 | { |
9bc8b558 | 999 | return 0; |
f41d911f PM |
1000 | } |
1001 | ||
b0e165c0 | 1002 | /* |
6cc68793 | 1003 | * Because there is no preemptible RCU, there can be no readers blocked, |
49e29126 PM |
1004 | * so there is no need to check for blocked tasks. So check only for |
1005 | * bogus qsmask values. | |
b0e165c0 PM |
1006 | */ |
1007 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) | |
1008 | { | |
49e29126 | 1009 | WARN_ON_ONCE(rnp->qsmask); |
b0e165c0 PM |
1010 | } |
1011 | ||
33f76148 PM |
1012 | #ifdef CONFIG_HOTPLUG_CPU |
1013 | ||
dd5d19ba | 1014 | /* |
6cc68793 | 1015 | * Because preemptible RCU does not exist, it never needs to migrate |
237c80c5 PM |
1016 | * tasks that were blocked within RCU read-side critical sections, and |
1017 | * such non-existent tasks cannot possibly have been blocking the current | |
1018 | * grace period. | |
dd5d19ba | 1019 | */ |
237c80c5 PM |
1020 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
1021 | struct rcu_node *rnp, | |
1022 | struct rcu_data *rdp) | |
dd5d19ba | 1023 | { |
237c80c5 | 1024 | return 0; |
dd5d19ba PM |
1025 | } |
1026 | ||
e5601400 PM |
1027 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
1028 | ||
f41d911f | 1029 | /* |
6cc68793 | 1030 | * Because preemptible RCU does not exist, it never has any callbacks |
f41d911f PM |
1031 | * to check. |
1032 | */ | |
1eba8f84 | 1033 | static void rcu_preempt_check_callbacks(int cpu) |
f41d911f PM |
1034 | { |
1035 | } | |
1036 | ||
019129d5 PM |
1037 | /* |
1038 | * Wait for an rcu-preempt grace period, but make it happen quickly. | |
6cc68793 | 1039 | * But because preemptible RCU does not exist, map to rcu-sched. |
019129d5 PM |
1040 | */ |
1041 | void synchronize_rcu_expedited(void) | |
1042 | { | |
1043 | synchronize_sched_expedited(); | |
1044 | } | |
1045 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
1046 | ||
d9a3da06 PM |
1047 | #ifdef CONFIG_HOTPLUG_CPU |
1048 | ||
1049 | /* | |
6cc68793 | 1050 | * Because preemptible RCU does not exist, there is never any need to |
d9a3da06 PM |
1051 | * report on tasks preempted in RCU read-side critical sections during |
1052 | * expedited RCU grace periods. | |
1053 | */ | |
b40d293e TG |
1054 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
1055 | bool wake) | |
d9a3da06 | 1056 | { |
d9a3da06 PM |
1057 | } |
1058 | ||
1059 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ | |
1060 | ||
e74f4c45 | 1061 | /* |
6cc68793 | 1062 | * Because preemptible RCU does not exist, rcu_barrier() is just |
e74f4c45 PM |
1063 | * another name for rcu_barrier_sched(). |
1064 | */ | |
1065 | void rcu_barrier(void) | |
1066 | { | |
1067 | rcu_barrier_sched(); | |
1068 | } | |
1069 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
1070 | ||
1eba8f84 | 1071 | /* |
6cc68793 | 1072 | * Because preemptible RCU does not exist, it need not be initialized. |
1eba8f84 PM |
1073 | */ |
1074 | static void __init __rcu_init_preempt(void) | |
1075 | { | |
1076 | } | |
1077 | ||
2439b696 PM |
1078 | /* |
1079 | * Because preemptible RCU does not exist, tasks cannot possibly exit | |
1080 | * while in preemptible RCU read-side critical sections. | |
1081 | */ | |
1082 | void exit_rcu(void) | |
1083 | { | |
1084 | } | |
1085 | ||
f41d911f | 1086 | #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ |
8bd93a2c | 1087 | |
27f4d280 PM |
1088 | #ifdef CONFIG_RCU_BOOST |
1089 | ||
1696a8be | 1090 | #include "../locking/rtmutex_common.h" |
27f4d280 | 1091 | |
0ea1f2eb PM |
1092 | #ifdef CONFIG_RCU_TRACE |
1093 | ||
1094 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) | |
1095 | { | |
1096 | if (list_empty(&rnp->blkd_tasks)) | |
1097 | rnp->n_balk_blkd_tasks++; | |
1098 | else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL) | |
1099 | rnp->n_balk_exp_gp_tasks++; | |
1100 | else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL) | |
1101 | rnp->n_balk_boost_tasks++; | |
1102 | else if (rnp->gp_tasks != NULL && rnp->qsmask != 0) | |
1103 | rnp->n_balk_notblocked++; | |
1104 | else if (rnp->gp_tasks != NULL && | |
a9f4793d | 1105 | ULONG_CMP_LT(jiffies, rnp->boost_time)) |
0ea1f2eb PM |
1106 | rnp->n_balk_notyet++; |
1107 | else | |
1108 | rnp->n_balk_nos++; | |
1109 | } | |
1110 | ||
1111 | #else /* #ifdef CONFIG_RCU_TRACE */ | |
1112 | ||
1113 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) | |
1114 | { | |
1115 | } | |
1116 | ||
1117 | #endif /* #else #ifdef CONFIG_RCU_TRACE */ | |
1118 | ||
5d01bbd1 TG |
1119 | static void rcu_wake_cond(struct task_struct *t, int status) |
1120 | { | |
1121 | /* | |
1122 | * If the thread is yielding, only wake it when this | |
1123 | * is invoked from idle | |
1124 | */ | |
1125 | if (status != RCU_KTHREAD_YIELDING || is_idle_task(current)) | |
1126 | wake_up_process(t); | |
1127 | } | |
1128 | ||
27f4d280 PM |
1129 | /* |
1130 | * Carry out RCU priority boosting on the task indicated by ->exp_tasks | |
1131 | * or ->boost_tasks, advancing the pointer to the next task in the | |
1132 | * ->blkd_tasks list. | |
1133 | * | |
1134 | * Note that irqs must be enabled: boosting the task can block. | |
1135 | * Returns 1 if there are more tasks needing to be boosted. | |
1136 | */ | |
1137 | static int rcu_boost(struct rcu_node *rnp) | |
1138 | { | |
1139 | unsigned long flags; | |
27f4d280 PM |
1140 | struct task_struct *t; |
1141 | struct list_head *tb; | |
1142 | ||
1143 | if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) | |
1144 | return 0; /* Nothing left to boost. */ | |
1145 | ||
1146 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 1147 | smp_mb__after_unlock_lock(); |
27f4d280 PM |
1148 | |
1149 | /* | |
1150 | * Recheck under the lock: all tasks in need of boosting | |
1151 | * might exit their RCU read-side critical sections on their own. | |
1152 | */ | |
1153 | if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { | |
1154 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1155 | return 0; | |
1156 | } | |
1157 | ||
1158 | /* | |
1159 | * Preferentially boost tasks blocking expedited grace periods. | |
1160 | * This cannot starve the normal grace periods because a second | |
1161 | * expedited grace period must boost all blocked tasks, including | |
1162 | * those blocking the pre-existing normal grace period. | |
1163 | */ | |
0ea1f2eb | 1164 | if (rnp->exp_tasks != NULL) { |
27f4d280 | 1165 | tb = rnp->exp_tasks; |
0ea1f2eb PM |
1166 | rnp->n_exp_boosts++; |
1167 | } else { | |
27f4d280 | 1168 | tb = rnp->boost_tasks; |
0ea1f2eb PM |
1169 | rnp->n_normal_boosts++; |
1170 | } | |
1171 | rnp->n_tasks_boosted++; | |
27f4d280 PM |
1172 | |
1173 | /* | |
1174 | * We boost task t by manufacturing an rt_mutex that appears to | |
1175 | * be held by task t. We leave a pointer to that rt_mutex where | |
1176 | * task t can find it, and task t will release the mutex when it | |
1177 | * exits its outermost RCU read-side critical section. Then | |
1178 | * simply acquiring this artificial rt_mutex will boost task | |
1179 | * t's priority. (Thanks to tglx for suggesting this approach!) | |
1180 | * | |
1181 | * Note that task t must acquire rnp->lock to remove itself from | |
1182 | * the ->blkd_tasks list, which it will do from exit() if from | |
1183 | * nowhere else. We therefore are guaranteed that task t will | |
1184 | * stay around at least until we drop rnp->lock. Note that | |
1185 | * rnp->lock also resolves races between our priority boosting | |
1186 | * and task t's exiting its outermost RCU read-side critical | |
1187 | * section. | |
1188 | */ | |
1189 | t = container_of(tb, struct task_struct, rcu_node_entry); | |
abaa93d9 | 1190 | rt_mutex_init_proxy_locked(&rnp->boost_mtx, t); |
dfeb9765 | 1191 | init_completion(&rnp->boost_completion); |
27f4d280 | 1192 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
abaa93d9 PM |
1193 | /* Lock only for side effect: boosts task t's priority. */ |
1194 | rt_mutex_lock(&rnp->boost_mtx); | |
1195 | rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ | |
27f4d280 | 1196 | |
abaa93d9 | 1197 | /* Wait for boostee to be done w/boost_mtx before reinitializing. */ |
dfeb9765 | 1198 | wait_for_completion(&rnp->boost_completion); |
27f4d280 | 1199 | |
4f89b336 PM |
1200 | return ACCESS_ONCE(rnp->exp_tasks) != NULL || |
1201 | ACCESS_ONCE(rnp->boost_tasks) != NULL; | |
27f4d280 PM |
1202 | } |
1203 | ||
27f4d280 PM |
1204 | /* |
1205 | * Priority-boosting kthread. One per leaf rcu_node and one for the | |
1206 | * root rcu_node. | |
1207 | */ | |
1208 | static int rcu_boost_kthread(void *arg) | |
1209 | { | |
1210 | struct rcu_node *rnp = (struct rcu_node *)arg; | |
1211 | int spincnt = 0; | |
1212 | int more2boost; | |
1213 | ||
f7f7bac9 | 1214 | trace_rcu_utilization(TPS("Start boost kthread@init")); |
27f4d280 | 1215 | for (;;) { |
d71df90e | 1216 | rnp->boost_kthread_status = RCU_KTHREAD_WAITING; |
f7f7bac9 | 1217 | trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); |
08bca60a | 1218 | rcu_wait(rnp->boost_tasks || rnp->exp_tasks); |
f7f7bac9 | 1219 | trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); |
d71df90e | 1220 | rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; |
27f4d280 PM |
1221 | more2boost = rcu_boost(rnp); |
1222 | if (more2boost) | |
1223 | spincnt++; | |
1224 | else | |
1225 | spincnt = 0; | |
1226 | if (spincnt > 10) { | |
5d01bbd1 | 1227 | rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; |
f7f7bac9 | 1228 | trace_rcu_utilization(TPS("End boost kthread@rcu_yield")); |
5d01bbd1 | 1229 | schedule_timeout_interruptible(2); |
f7f7bac9 | 1230 | trace_rcu_utilization(TPS("Start boost kthread@rcu_yield")); |
27f4d280 PM |
1231 | spincnt = 0; |
1232 | } | |
1233 | } | |
1217ed1b | 1234 | /* NOTREACHED */ |
f7f7bac9 | 1235 | trace_rcu_utilization(TPS("End boost kthread@notreached")); |
27f4d280 PM |
1236 | return 0; |
1237 | } | |
1238 | ||
1239 | /* | |
1240 | * Check to see if it is time to start boosting RCU readers that are | |
1241 | * blocking the current grace period, and, if so, tell the per-rcu_node | |
1242 | * kthread to start boosting them. If there is an expedited grace | |
1243 | * period in progress, it is always time to boost. | |
1244 | * | |
b065a853 PM |
1245 | * The caller must hold rnp->lock, which this function releases. |
1246 | * The ->boost_kthread_task is immortal, so we don't need to worry | |
1247 | * about it going away. | |
27f4d280 | 1248 | */ |
1217ed1b | 1249 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
615e41c6 | 1250 | __releases(rnp->lock) |
27f4d280 PM |
1251 | { |
1252 | struct task_struct *t; | |
1253 | ||
0ea1f2eb PM |
1254 | if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { |
1255 | rnp->n_balk_exp_gp_tasks++; | |
1217ed1b | 1256 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d280 | 1257 | return; |
0ea1f2eb | 1258 | } |
27f4d280 PM |
1259 | if (rnp->exp_tasks != NULL || |
1260 | (rnp->gp_tasks != NULL && | |
1261 | rnp->boost_tasks == NULL && | |
1262 | rnp->qsmask == 0 && | |
1263 | ULONG_CMP_GE(jiffies, rnp->boost_time))) { | |
1264 | if (rnp->exp_tasks == NULL) | |
1265 | rnp->boost_tasks = rnp->gp_tasks; | |
1217ed1b | 1266 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d280 | 1267 | t = rnp->boost_kthread_task; |
5d01bbd1 TG |
1268 | if (t) |
1269 | rcu_wake_cond(t, rnp->boost_kthread_status); | |
1217ed1b | 1270 | } else { |
0ea1f2eb | 1271 | rcu_initiate_boost_trace(rnp); |
1217ed1b PM |
1272 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1273 | } | |
27f4d280 PM |
1274 | } |
1275 | ||
a46e0899 PM |
1276 | /* |
1277 | * Wake up the per-CPU kthread to invoke RCU callbacks. | |
1278 | */ | |
1279 | static void invoke_rcu_callbacks_kthread(void) | |
1280 | { | |
1281 | unsigned long flags; | |
1282 | ||
1283 | local_irq_save(flags); | |
1284 | __this_cpu_write(rcu_cpu_has_work, 1); | |
1eb52121 | 1285 | if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && |
5d01bbd1 TG |
1286 | current != __this_cpu_read(rcu_cpu_kthread_task)) { |
1287 | rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), | |
1288 | __this_cpu_read(rcu_cpu_kthread_status)); | |
1289 | } | |
a46e0899 PM |
1290 | local_irq_restore(flags); |
1291 | } | |
1292 | ||
dff1672d PM |
1293 | /* |
1294 | * Is the current CPU running the RCU-callbacks kthread? | |
1295 | * Caller must have preemption disabled. | |
1296 | */ | |
1297 | static bool rcu_is_callbacks_kthread(void) | |
1298 | { | |
c9d4b0af | 1299 | return __this_cpu_read(rcu_cpu_kthread_task) == current; |
dff1672d PM |
1300 | } |
1301 | ||
27f4d280 PM |
1302 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
1303 | ||
1304 | /* | |
1305 | * Do priority-boost accounting for the start of a new grace period. | |
1306 | */ | |
1307 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) | |
1308 | { | |
1309 | rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; | |
1310 | } | |
1311 | ||
27f4d280 PM |
1312 | /* |
1313 | * Create an RCU-boost kthread for the specified node if one does not | |
1314 | * already exist. We only create this kthread for preemptible RCU. | |
1315 | * Returns zero if all is well, a negated errno otherwise. | |
1316 | */ | |
49fb4c62 | 1317 | static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, |
5d01bbd1 | 1318 | struct rcu_node *rnp) |
27f4d280 | 1319 | { |
5d01bbd1 | 1320 | int rnp_index = rnp - &rsp->node[0]; |
27f4d280 PM |
1321 | unsigned long flags; |
1322 | struct sched_param sp; | |
1323 | struct task_struct *t; | |
1324 | ||
1325 | if (&rcu_preempt_state != rsp) | |
1326 | return 0; | |
5d01bbd1 TG |
1327 | |
1328 | if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0) | |
1329 | return 0; | |
1330 | ||
a46e0899 | 1331 | rsp->boost = 1; |
27f4d280 PM |
1332 | if (rnp->boost_kthread_task != NULL) |
1333 | return 0; | |
1334 | t = kthread_create(rcu_boost_kthread, (void *)rnp, | |
5b61b0ba | 1335 | "rcub/%d", rnp_index); |
27f4d280 PM |
1336 | if (IS_ERR(t)) |
1337 | return PTR_ERR(t); | |
1338 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 1339 | smp_mb__after_unlock_lock(); |
27f4d280 PM |
1340 | rnp->boost_kthread_task = t; |
1341 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
21871d7e | 1342 | sp.sched_priority = kthread_prio; |
27f4d280 | 1343 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
9a432736 | 1344 | wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ |
27f4d280 PM |
1345 | return 0; |
1346 | } | |
1347 | ||
f8b7fc6b PM |
1348 | static void rcu_kthread_do_work(void) |
1349 | { | |
c9d4b0af CL |
1350 | rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data)); |
1351 | rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data)); | |
f8b7fc6b PM |
1352 | rcu_preempt_do_callbacks(); |
1353 | } | |
1354 | ||
62ab7072 | 1355 | static void rcu_cpu_kthread_setup(unsigned int cpu) |
f8b7fc6b | 1356 | { |
f8b7fc6b | 1357 | struct sched_param sp; |
f8b7fc6b | 1358 | |
21871d7e | 1359 | sp.sched_priority = kthread_prio; |
62ab7072 | 1360 | sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); |
f8b7fc6b PM |
1361 | } |
1362 | ||
62ab7072 | 1363 | static void rcu_cpu_kthread_park(unsigned int cpu) |
f8b7fc6b | 1364 | { |
62ab7072 | 1365 | per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; |
f8b7fc6b PM |
1366 | } |
1367 | ||
62ab7072 | 1368 | static int rcu_cpu_kthread_should_run(unsigned int cpu) |
f8b7fc6b | 1369 | { |
c9d4b0af | 1370 | return __this_cpu_read(rcu_cpu_has_work); |
f8b7fc6b PM |
1371 | } |
1372 | ||
1373 | /* | |
1374 | * Per-CPU kernel thread that invokes RCU callbacks. This replaces the | |
e0f23060 PM |
1375 | * RCU softirq used in flavors and configurations of RCU that do not |
1376 | * support RCU priority boosting. | |
f8b7fc6b | 1377 | */ |
62ab7072 | 1378 | static void rcu_cpu_kthread(unsigned int cpu) |
f8b7fc6b | 1379 | { |
c9d4b0af CL |
1380 | unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status); |
1381 | char work, *workp = this_cpu_ptr(&rcu_cpu_has_work); | |
62ab7072 | 1382 | int spincnt; |
f8b7fc6b | 1383 | |
62ab7072 | 1384 | for (spincnt = 0; spincnt < 10; spincnt++) { |
f7f7bac9 | 1385 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); |
f8b7fc6b | 1386 | local_bh_disable(); |
f8b7fc6b | 1387 | *statusp = RCU_KTHREAD_RUNNING; |
62ab7072 PM |
1388 | this_cpu_inc(rcu_cpu_kthread_loops); |
1389 | local_irq_disable(); | |
f8b7fc6b PM |
1390 | work = *workp; |
1391 | *workp = 0; | |
62ab7072 | 1392 | local_irq_enable(); |
f8b7fc6b PM |
1393 | if (work) |
1394 | rcu_kthread_do_work(); | |
1395 | local_bh_enable(); | |
62ab7072 | 1396 | if (*workp == 0) { |
f7f7bac9 | 1397 | trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); |
62ab7072 PM |
1398 | *statusp = RCU_KTHREAD_WAITING; |
1399 | return; | |
f8b7fc6b PM |
1400 | } |
1401 | } | |
62ab7072 | 1402 | *statusp = RCU_KTHREAD_YIELDING; |
f7f7bac9 | 1403 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield")); |
62ab7072 | 1404 | schedule_timeout_interruptible(2); |
f7f7bac9 | 1405 | trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); |
62ab7072 | 1406 | *statusp = RCU_KTHREAD_WAITING; |
f8b7fc6b PM |
1407 | } |
1408 | ||
1409 | /* | |
1410 | * Set the per-rcu_node kthread's affinity to cover all CPUs that are | |
1411 | * served by the rcu_node in question. The CPU hotplug lock is still | |
1412 | * held, so the value of rnp->qsmaskinit will be stable. | |
1413 | * | |
1414 | * We don't include outgoingcpu in the affinity set, use -1 if there is | |
1415 | * no outgoing CPU. If there are no CPUs left in the affinity set, | |
1416 | * this function allows the kthread to execute on any CPU. | |
1417 | */ | |
5d01bbd1 | 1418 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
f8b7fc6b | 1419 | { |
5d01bbd1 TG |
1420 | struct task_struct *t = rnp->boost_kthread_task; |
1421 | unsigned long mask = rnp->qsmaskinit; | |
f8b7fc6b PM |
1422 | cpumask_var_t cm; |
1423 | int cpu; | |
f8b7fc6b | 1424 | |
5d01bbd1 | 1425 | if (!t) |
f8b7fc6b | 1426 | return; |
5d01bbd1 | 1427 | if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) |
f8b7fc6b | 1428 | return; |
f8b7fc6b PM |
1429 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) |
1430 | if ((mask & 0x1) && cpu != outgoingcpu) | |
1431 | cpumask_set_cpu(cpu, cm); | |
1432 | if (cpumask_weight(cm) == 0) { | |
1433 | cpumask_setall(cm); | |
1434 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) | |
1435 | cpumask_clear_cpu(cpu, cm); | |
1436 | WARN_ON_ONCE(cpumask_weight(cm) == 0); | |
1437 | } | |
5d01bbd1 | 1438 | set_cpus_allowed_ptr(t, cm); |
f8b7fc6b PM |
1439 | free_cpumask_var(cm); |
1440 | } | |
1441 | ||
62ab7072 PM |
1442 | static struct smp_hotplug_thread rcu_cpu_thread_spec = { |
1443 | .store = &rcu_cpu_kthread_task, | |
1444 | .thread_should_run = rcu_cpu_kthread_should_run, | |
1445 | .thread_fn = rcu_cpu_kthread, | |
1446 | .thread_comm = "rcuc/%u", | |
1447 | .setup = rcu_cpu_kthread_setup, | |
1448 | .park = rcu_cpu_kthread_park, | |
1449 | }; | |
f8b7fc6b PM |
1450 | |
1451 | /* | |
9386c0b7 | 1452 | * Spawn boost kthreads -- called as soon as the scheduler is running. |
f8b7fc6b | 1453 | */ |
9386c0b7 | 1454 | static void __init rcu_spawn_boost_kthreads(void) |
f8b7fc6b | 1455 | { |
f8b7fc6b | 1456 | struct rcu_node *rnp; |
5d01bbd1 | 1457 | int cpu; |
f8b7fc6b | 1458 | |
62ab7072 | 1459 | for_each_possible_cpu(cpu) |
f8b7fc6b | 1460 | per_cpu(rcu_cpu_has_work, cpu) = 0; |
62ab7072 | 1461 | BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); |
e534165b US |
1462 | rnp = rcu_get_root(rcu_state_p); |
1463 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); | |
f8b7fc6b | 1464 | if (NUM_RCU_NODES > 1) { |
e534165b US |
1465 | rcu_for_each_leaf_node(rcu_state_p, rnp) |
1466 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); | |
f8b7fc6b | 1467 | } |
f8b7fc6b | 1468 | } |
f8b7fc6b | 1469 | |
49fb4c62 | 1470 | static void rcu_prepare_kthreads(int cpu) |
f8b7fc6b | 1471 | { |
e534165b | 1472 | struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
f8b7fc6b PM |
1473 | struct rcu_node *rnp = rdp->mynode; |
1474 | ||
1475 | /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ | |
62ab7072 | 1476 | if (rcu_scheduler_fully_active) |
e534165b | 1477 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); |
f8b7fc6b PM |
1478 | } |
1479 | ||
27f4d280 PM |
1480 | #else /* #ifdef CONFIG_RCU_BOOST */ |
1481 | ||
1217ed1b | 1482 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
615e41c6 | 1483 | __releases(rnp->lock) |
27f4d280 | 1484 | { |
1217ed1b | 1485 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d280 PM |
1486 | } |
1487 | ||
a46e0899 | 1488 | static void invoke_rcu_callbacks_kthread(void) |
27f4d280 | 1489 | { |
a46e0899 | 1490 | WARN_ON_ONCE(1); |
27f4d280 PM |
1491 | } |
1492 | ||
dff1672d PM |
1493 | static bool rcu_is_callbacks_kthread(void) |
1494 | { | |
1495 | return false; | |
1496 | } | |
1497 | ||
27f4d280 PM |
1498 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) |
1499 | { | |
1500 | } | |
1501 | ||
5d01bbd1 | 1502 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
f8b7fc6b PM |
1503 | { |
1504 | } | |
1505 | ||
9386c0b7 | 1506 | static void __init rcu_spawn_boost_kthreads(void) |
b0d30417 | 1507 | { |
b0d30417 | 1508 | } |
b0d30417 | 1509 | |
49fb4c62 | 1510 | static void rcu_prepare_kthreads(int cpu) |
f8b7fc6b PM |
1511 | { |
1512 | } | |
1513 | ||
27f4d280 PM |
1514 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ |
1515 | ||
8bd93a2c PM |
1516 | #if !defined(CONFIG_RCU_FAST_NO_HZ) |
1517 | ||
1518 | /* | |
1519 | * Check to see if any future RCU-related work will need to be done | |
1520 | * by the current CPU, even if none need be done immediately, returning | |
1521 | * 1 if so. This function is part of the RCU implementation; it is -not- | |
1522 | * an exported member of the RCU API. | |
1523 | * | |
7cb92499 PM |
1524 | * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs |
1525 | * any flavor of RCU. | |
8bd93a2c | 1526 | */ |
ffa83fb5 | 1527 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
aa9b1630 | 1528 | int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) |
8bd93a2c | 1529 | { |
aa9b1630 | 1530 | *delta_jiffies = ULONG_MAX; |
c0f4dfd4 | 1531 | return rcu_cpu_has_callbacks(cpu, NULL); |
7cb92499 | 1532 | } |
ffa83fb5 | 1533 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
7cb92499 PM |
1534 | |
1535 | /* | |
1536 | * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up | |
1537 | * after it. | |
1538 | */ | |
1539 | static void rcu_cleanup_after_idle(int cpu) | |
1540 | { | |
1541 | } | |
1542 | ||
aea1b35e | 1543 | /* |
a858af28 | 1544 | * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, |
aea1b35e PM |
1545 | * is nothing. |
1546 | */ | |
1547 | static void rcu_prepare_for_idle(int cpu) | |
1548 | { | |
1549 | } | |
1550 | ||
c57afe80 PM |
1551 | /* |
1552 | * Don't bother keeping a running count of the number of RCU callbacks | |
1553 | * posted because CONFIG_RCU_FAST_NO_HZ=n. | |
1554 | */ | |
1555 | static void rcu_idle_count_callbacks_posted(void) | |
1556 | { | |
1557 | } | |
1558 | ||
8bd93a2c PM |
1559 | #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
1560 | ||
f23f7fa1 PM |
1561 | /* |
1562 | * This code is invoked when a CPU goes idle, at which point we want | |
1563 | * to have the CPU do everything required for RCU so that it can enter | |
1564 | * the energy-efficient dyntick-idle mode. This is handled by a | |
1565 | * state machine implemented by rcu_prepare_for_idle() below. | |
1566 | * | |
1567 | * The following three proprocessor symbols control this state machine: | |
1568 | * | |
f23f7fa1 PM |
1569 | * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted |
1570 | * to sleep in dyntick-idle mode with RCU callbacks pending. This | |
1571 | * is sized to be roughly one RCU grace period. Those energy-efficiency | |
1572 | * benchmarkers who might otherwise be tempted to set this to a large | |
1573 | * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your | |
1574 | * system. And if you are -that- concerned about energy efficiency, | |
1575 | * just power the system down and be done with it! | |
778d250a PM |
1576 | * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is |
1577 | * permitted to sleep in dyntick-idle mode with only lazy RCU | |
1578 | * callbacks pending. Setting this too high can OOM your system. | |
f23f7fa1 PM |
1579 | * |
1580 | * The values below work well in practice. If future workloads require | |
1581 | * adjustment, they can be converted into kernel config parameters, though | |
1582 | * making the state machine smarter might be a better option. | |
1583 | */ | |
e84c48ae | 1584 | #define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ |
778d250a | 1585 | #define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ |
f23f7fa1 | 1586 | |
5e44ce35 PM |
1587 | static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY; |
1588 | module_param(rcu_idle_gp_delay, int, 0644); | |
1589 | static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY; | |
1590 | module_param(rcu_idle_lazy_gp_delay, int, 0644); | |
486e2593 | 1591 | |
d689fe22 | 1592 | extern int tick_nohz_active; |
486e2593 PM |
1593 | |
1594 | /* | |
c229828c PM |
1595 | * Try to advance callbacks for all flavors of RCU on the current CPU, but |
1596 | * only if it has been awhile since the last time we did so. Afterwards, | |
1597 | * if there are any callbacks ready for immediate invocation, return true. | |
486e2593 | 1598 | */ |
f1f399d1 | 1599 | static bool __maybe_unused rcu_try_advance_all_cbs(void) |
486e2593 | 1600 | { |
c0f4dfd4 PM |
1601 | bool cbs_ready = false; |
1602 | struct rcu_data *rdp; | |
c229828c | 1603 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
c0f4dfd4 PM |
1604 | struct rcu_node *rnp; |
1605 | struct rcu_state *rsp; | |
486e2593 | 1606 | |
c229828c PM |
1607 | /* Exit early if we advanced recently. */ |
1608 | if (jiffies == rdtp->last_advance_all) | |
d0bc90fd | 1609 | return false; |
c229828c PM |
1610 | rdtp->last_advance_all = jiffies; |
1611 | ||
c0f4dfd4 PM |
1612 | for_each_rcu_flavor(rsp) { |
1613 | rdp = this_cpu_ptr(rsp->rda); | |
1614 | rnp = rdp->mynode; | |
486e2593 | 1615 | |
c0f4dfd4 PM |
1616 | /* |
1617 | * Don't bother checking unless a grace period has | |
1618 | * completed since we last checked and there are | |
1619 | * callbacks not yet ready to invoke. | |
1620 | */ | |
1621 | if (rdp->completed != rnp->completed && | |
1622 | rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL]) | |
470716fc | 1623 | note_gp_changes(rsp, rdp); |
486e2593 | 1624 | |
c0f4dfd4 PM |
1625 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
1626 | cbs_ready = true; | |
1627 | } | |
1628 | return cbs_ready; | |
486e2593 PM |
1629 | } |
1630 | ||
aa9b1630 | 1631 | /* |
c0f4dfd4 PM |
1632 | * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready |
1633 | * to invoke. If the CPU has callbacks, try to advance them. Tell the | |
1634 | * caller to set the timeout based on whether or not there are non-lazy | |
1635 | * callbacks. | |
aa9b1630 | 1636 | * |
c0f4dfd4 | 1637 | * The caller must have disabled interrupts. |
aa9b1630 | 1638 | */ |
ffa83fb5 | 1639 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
c0f4dfd4 | 1640 | int rcu_needs_cpu(int cpu, unsigned long *dj) |
aa9b1630 PM |
1641 | { |
1642 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); | |
1643 | ||
c0f4dfd4 PM |
1644 | /* Snapshot to detect later posting of non-lazy callback. */ |
1645 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; | |
1646 | ||
aa9b1630 | 1647 | /* If no callbacks, RCU doesn't need the CPU. */ |
c0f4dfd4 PM |
1648 | if (!rcu_cpu_has_callbacks(cpu, &rdtp->all_lazy)) { |
1649 | *dj = ULONG_MAX; | |
aa9b1630 PM |
1650 | return 0; |
1651 | } | |
c0f4dfd4 PM |
1652 | |
1653 | /* Attempt to advance callbacks. */ | |
1654 | if (rcu_try_advance_all_cbs()) { | |
1655 | /* Some ready to invoke, so initiate later invocation. */ | |
1656 | invoke_rcu_core(); | |
aa9b1630 PM |
1657 | return 1; |
1658 | } | |
c0f4dfd4 PM |
1659 | rdtp->last_accelerate = jiffies; |
1660 | ||
1661 | /* Request timer delay depending on laziness, and round. */ | |
6faf7283 | 1662 | if (!rdtp->all_lazy) { |
c0f4dfd4 PM |
1663 | *dj = round_up(rcu_idle_gp_delay + jiffies, |
1664 | rcu_idle_gp_delay) - jiffies; | |
e84c48ae | 1665 | } else { |
c0f4dfd4 | 1666 | *dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; |
e84c48ae | 1667 | } |
aa9b1630 PM |
1668 | return 0; |
1669 | } | |
ffa83fb5 | 1670 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
aa9b1630 | 1671 | |
21e52e15 | 1672 | /* |
c0f4dfd4 PM |
1673 | * Prepare a CPU for idle from an RCU perspective. The first major task |
1674 | * is to sense whether nohz mode has been enabled or disabled via sysfs. | |
1675 | * The second major task is to check to see if a non-lazy callback has | |
1676 | * arrived at a CPU that previously had only lazy callbacks. The third | |
1677 | * major task is to accelerate (that is, assign grace-period numbers to) | |
1678 | * any recently arrived callbacks. | |
aea1b35e PM |
1679 | * |
1680 | * The caller must have disabled interrupts. | |
8bd93a2c | 1681 | */ |
aea1b35e | 1682 | static void rcu_prepare_for_idle(int cpu) |
8bd93a2c | 1683 | { |
f1f399d1 | 1684 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
48a7639c | 1685 | bool needwake; |
c0f4dfd4 | 1686 | struct rcu_data *rdp; |
5955f7ee | 1687 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
c0f4dfd4 PM |
1688 | struct rcu_node *rnp; |
1689 | struct rcu_state *rsp; | |
9d2ad243 PM |
1690 | int tne; |
1691 | ||
1692 | /* Handle nohz enablement switches conservatively. */ | |
d689fe22 | 1693 | tne = ACCESS_ONCE(tick_nohz_active); |
9d2ad243 | 1694 | if (tne != rdtp->tick_nohz_enabled_snap) { |
c0f4dfd4 | 1695 | if (rcu_cpu_has_callbacks(cpu, NULL)) |
9d2ad243 PM |
1696 | invoke_rcu_core(); /* force nohz to see update. */ |
1697 | rdtp->tick_nohz_enabled_snap = tne; | |
1698 | return; | |
1699 | } | |
1700 | if (!tne) | |
1701 | return; | |
f511fc62 | 1702 | |
c0f4dfd4 | 1703 | /* If this is a no-CBs CPU, no callbacks, just return. */ |
534c97b0 | 1704 | if (rcu_is_nocb_cpu(cpu)) |
9a0c6fef | 1705 | return; |
9a0c6fef | 1706 | |
c57afe80 | 1707 | /* |
c0f4dfd4 PM |
1708 | * If a non-lazy callback arrived at a CPU having only lazy |
1709 | * callbacks, invoke RCU core for the side-effect of recalculating | |
1710 | * idle duration on re-entry to idle. | |
c57afe80 | 1711 | */ |
c0f4dfd4 PM |
1712 | if (rdtp->all_lazy && |
1713 | rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) { | |
c337f8f5 PM |
1714 | rdtp->all_lazy = false; |
1715 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; | |
c0f4dfd4 | 1716 | invoke_rcu_core(); |
c57afe80 PM |
1717 | return; |
1718 | } | |
c57afe80 | 1719 | |
3084f2f8 | 1720 | /* |
c0f4dfd4 PM |
1721 | * If we have not yet accelerated this jiffy, accelerate all |
1722 | * callbacks on this CPU. | |
3084f2f8 | 1723 | */ |
c0f4dfd4 | 1724 | if (rdtp->last_accelerate == jiffies) |
aea1b35e | 1725 | return; |
c0f4dfd4 PM |
1726 | rdtp->last_accelerate = jiffies; |
1727 | for_each_rcu_flavor(rsp) { | |
1728 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
1729 | if (!*rdp->nxttail[RCU_DONE_TAIL]) | |
1730 | continue; | |
1731 | rnp = rdp->mynode; | |
1732 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
6303b9c8 | 1733 | smp_mb__after_unlock_lock(); |
48a7639c | 1734 | needwake = rcu_accelerate_cbs(rsp, rnp, rdp); |
c0f4dfd4 | 1735 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
48a7639c PM |
1736 | if (needwake) |
1737 | rcu_gp_kthread_wake(rsp); | |
77e38ed3 | 1738 | } |
f1f399d1 | 1739 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
c0f4dfd4 | 1740 | } |
3084f2f8 | 1741 | |
c0f4dfd4 PM |
1742 | /* |
1743 | * Clean up for exit from idle. Attempt to advance callbacks based on | |
1744 | * any grace periods that elapsed while the CPU was idle, and if any | |
1745 | * callbacks are now ready to invoke, initiate invocation. | |
1746 | */ | |
1747 | static void rcu_cleanup_after_idle(int cpu) | |
1748 | { | |
f1f399d1 | 1749 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
534c97b0 | 1750 | if (rcu_is_nocb_cpu(cpu)) |
aea1b35e | 1751 | return; |
7a497c96 PM |
1752 | if (rcu_try_advance_all_cbs()) |
1753 | invoke_rcu_core(); | |
f1f399d1 | 1754 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
8bd93a2c PM |
1755 | } |
1756 | ||
c57afe80 | 1757 | /* |
98248a0e PM |
1758 | * Keep a running count of the number of non-lazy callbacks posted |
1759 | * on this CPU. This running counter (which is never decremented) allows | |
1760 | * rcu_prepare_for_idle() to detect when something out of the idle loop | |
1761 | * posts a callback, even if an equal number of callbacks are invoked. | |
1762 | * Of course, callbacks should only be posted from within a trace event | |
1763 | * designed to be called from idle or from within RCU_NONIDLE(). | |
c57afe80 PM |
1764 | */ |
1765 | static void rcu_idle_count_callbacks_posted(void) | |
1766 | { | |
5955f7ee | 1767 | __this_cpu_add(rcu_dynticks.nonlazy_posted, 1); |
c57afe80 PM |
1768 | } |
1769 | ||
b626c1b6 PM |
1770 | /* |
1771 | * Data for flushing lazy RCU callbacks at OOM time. | |
1772 | */ | |
1773 | static atomic_t oom_callback_count; | |
1774 | static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq); | |
1775 | ||
1776 | /* | |
1777 | * RCU OOM callback -- decrement the outstanding count and deliver the | |
1778 | * wake-up if we are the last one. | |
1779 | */ | |
1780 | static void rcu_oom_callback(struct rcu_head *rhp) | |
1781 | { | |
1782 | if (atomic_dec_and_test(&oom_callback_count)) | |
1783 | wake_up(&oom_callback_wq); | |
1784 | } | |
1785 | ||
1786 | /* | |
1787 | * Post an rcu_oom_notify callback on the current CPU if it has at | |
1788 | * least one lazy callback. This will unnecessarily post callbacks | |
1789 | * to CPUs that already have a non-lazy callback at the end of their | |
1790 | * callback list, but this is an infrequent operation, so accept some | |
1791 | * extra overhead to keep things simple. | |
1792 | */ | |
1793 | static void rcu_oom_notify_cpu(void *unused) | |
1794 | { | |
1795 | struct rcu_state *rsp; | |
1796 | struct rcu_data *rdp; | |
1797 | ||
1798 | for_each_rcu_flavor(rsp) { | |
fa07a58f | 1799 | rdp = raw_cpu_ptr(rsp->rda); |
b626c1b6 PM |
1800 | if (rdp->qlen_lazy != 0) { |
1801 | atomic_inc(&oom_callback_count); | |
1802 | rsp->call(&rdp->oom_head, rcu_oom_callback); | |
1803 | } | |
1804 | } | |
1805 | } | |
1806 | ||
1807 | /* | |
1808 | * If low on memory, ensure that each CPU has a non-lazy callback. | |
1809 | * This will wake up CPUs that have only lazy callbacks, in turn | |
1810 | * ensuring that they free up the corresponding memory in a timely manner. | |
1811 | * Because an uncertain amount of memory will be freed in some uncertain | |
1812 | * timeframe, we do not claim to have freed anything. | |
1813 | */ | |
1814 | static int rcu_oom_notify(struct notifier_block *self, | |
1815 | unsigned long notused, void *nfreed) | |
1816 | { | |
1817 | int cpu; | |
1818 | ||
1819 | /* Wait for callbacks from earlier instance to complete. */ | |
1820 | wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0); | |
78e4bc34 | 1821 | smp_mb(); /* Ensure callback reuse happens after callback invocation. */ |
b626c1b6 PM |
1822 | |
1823 | /* | |
1824 | * Prevent premature wakeup: ensure that all increments happen | |
1825 | * before there is a chance of the counter reaching zero. | |
1826 | */ | |
1827 | atomic_set(&oom_callback_count, 1); | |
1828 | ||
1829 | get_online_cpus(); | |
1830 | for_each_online_cpu(cpu) { | |
1831 | smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); | |
bde6c3aa | 1832 | cond_resched_rcu_qs(); |
b626c1b6 PM |
1833 | } |
1834 | put_online_cpus(); | |
1835 | ||
1836 | /* Unconditionally decrement: no need to wake ourselves up. */ | |
1837 | atomic_dec(&oom_callback_count); | |
1838 | ||
1839 | return NOTIFY_OK; | |
1840 | } | |
1841 | ||
1842 | static struct notifier_block rcu_oom_nb = { | |
1843 | .notifier_call = rcu_oom_notify | |
1844 | }; | |
1845 | ||
1846 | static int __init rcu_register_oom_notifier(void) | |
1847 | { | |
1848 | register_oom_notifier(&rcu_oom_nb); | |
1849 | return 0; | |
1850 | } | |
1851 | early_initcall(rcu_register_oom_notifier); | |
1852 | ||
8bd93a2c | 1853 | #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
a858af28 PM |
1854 | |
1855 | #ifdef CONFIG_RCU_CPU_STALL_INFO | |
1856 | ||
1857 | #ifdef CONFIG_RCU_FAST_NO_HZ | |
1858 | ||
1859 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) | |
1860 | { | |
5955f7ee | 1861 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
c0f4dfd4 | 1862 | unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap; |
a858af28 | 1863 | |
c0f4dfd4 PM |
1864 | sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", |
1865 | rdtp->last_accelerate & 0xffff, jiffies & 0xffff, | |
1866 | ulong2long(nlpd), | |
1867 | rdtp->all_lazy ? 'L' : '.', | |
1868 | rdtp->tick_nohz_enabled_snap ? '.' : 'D'); | |
a858af28 PM |
1869 | } |
1870 | ||
1871 | #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ | |
1872 | ||
1873 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) | |
1874 | { | |
1c17e4d4 | 1875 | *cp = '\0'; |
a858af28 PM |
1876 | } |
1877 | ||
1878 | #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ | |
1879 | ||
1880 | /* Initiate the stall-info list. */ | |
1881 | static void print_cpu_stall_info_begin(void) | |
1882 | { | |
efc151c3 | 1883 | pr_cont("\n"); |
a858af28 PM |
1884 | } |
1885 | ||
1886 | /* | |
1887 | * Print out diagnostic information for the specified stalled CPU. | |
1888 | * | |
1889 | * If the specified CPU is aware of the current RCU grace period | |
1890 | * (flavor specified by rsp), then print the number of scheduling | |
1891 | * clock interrupts the CPU has taken during the time that it has | |
1892 | * been aware. Otherwise, print the number of RCU grace periods | |
1893 | * that this CPU is ignorant of, for example, "1" if the CPU was | |
1894 | * aware of the previous grace period. | |
1895 | * | |
1896 | * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. | |
1897 | */ | |
1898 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) | |
1899 | { | |
1900 | char fast_no_hz[72]; | |
1901 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
1902 | struct rcu_dynticks *rdtp = rdp->dynticks; | |
1903 | char *ticks_title; | |
1904 | unsigned long ticks_value; | |
1905 | ||
1906 | if (rsp->gpnum == rdp->gpnum) { | |
1907 | ticks_title = "ticks this GP"; | |
1908 | ticks_value = rdp->ticks_this_gp; | |
1909 | } else { | |
1910 | ticks_title = "GPs behind"; | |
1911 | ticks_value = rsp->gpnum - rdp->gpnum; | |
1912 | } | |
1913 | print_cpu_stall_fast_no_hz(fast_no_hz, cpu); | |
efc151c3 | 1914 | pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u %s\n", |
a858af28 PM |
1915 | cpu, ticks_value, ticks_title, |
1916 | atomic_read(&rdtp->dynticks) & 0xfff, | |
1917 | rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, | |
6231069b | 1918 | rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), |
a858af28 PM |
1919 | fast_no_hz); |
1920 | } | |
1921 | ||
1922 | /* Terminate the stall-info list. */ | |
1923 | static void print_cpu_stall_info_end(void) | |
1924 | { | |
efc151c3 | 1925 | pr_err("\t"); |
a858af28 PM |
1926 | } |
1927 | ||
1928 | /* Zero ->ticks_this_gp for all flavors of RCU. */ | |
1929 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) | |
1930 | { | |
1931 | rdp->ticks_this_gp = 0; | |
6231069b | 1932 | rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); |
a858af28 PM |
1933 | } |
1934 | ||
1935 | /* Increment ->ticks_this_gp for all flavors of RCU. */ | |
1936 | static void increment_cpu_stall_ticks(void) | |
1937 | { | |
115f7a7c PM |
1938 | struct rcu_state *rsp; |
1939 | ||
1940 | for_each_rcu_flavor(rsp) | |
fa07a58f | 1941 | raw_cpu_inc(rsp->rda->ticks_this_gp); |
a858af28 PM |
1942 | } |
1943 | ||
1944 | #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
1945 | ||
1946 | static void print_cpu_stall_info_begin(void) | |
1947 | { | |
efc151c3 | 1948 | pr_cont(" {"); |
a858af28 PM |
1949 | } |
1950 | ||
1951 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) | |
1952 | { | |
efc151c3 | 1953 | pr_cont(" %d", cpu); |
a858af28 PM |
1954 | } |
1955 | ||
1956 | static void print_cpu_stall_info_end(void) | |
1957 | { | |
efc151c3 | 1958 | pr_cont("} "); |
a858af28 PM |
1959 | } |
1960 | ||
1961 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) | |
1962 | { | |
1963 | } | |
1964 | ||
1965 | static void increment_cpu_stall_ticks(void) | |
1966 | { | |
1967 | } | |
1968 | ||
1969 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ | |
3fbfbf7a PM |
1970 | |
1971 | #ifdef CONFIG_RCU_NOCB_CPU | |
1972 | ||
1973 | /* | |
1974 | * Offload callback processing from the boot-time-specified set of CPUs | |
1975 | * specified by rcu_nocb_mask. For each CPU in the set, there is a | |
1976 | * kthread created that pulls the callbacks from the corresponding CPU, | |
1977 | * waits for a grace period to elapse, and invokes the callbacks. | |
1978 | * The no-CBs CPUs do a wake_up() on their kthread when they insert | |
1979 | * a callback into any empty list, unless the rcu_nocb_poll boot parameter | |
1980 | * has been specified, in which case each kthread actively polls its | |
1981 | * CPU. (Which isn't so great for energy efficiency, but which does | |
1982 | * reduce RCU's overhead on that CPU.) | |
1983 | * | |
1984 | * This is intended to be used in conjunction with Frederic Weisbecker's | |
1985 | * adaptive-idle work, which would seriously reduce OS jitter on CPUs | |
1986 | * running CPU-bound user-mode computations. | |
1987 | * | |
1988 | * Offloading of callback processing could also in theory be used as | |
1989 | * an energy-efficiency measure because CPUs with no RCU callbacks | |
1990 | * queued are more aggressive about entering dyntick-idle mode. | |
1991 | */ | |
1992 | ||
1993 | ||
1994 | /* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */ | |
1995 | static int __init rcu_nocb_setup(char *str) | |
1996 | { | |
1997 | alloc_bootmem_cpumask_var(&rcu_nocb_mask); | |
1998 | have_rcu_nocb_mask = true; | |
1999 | cpulist_parse(str, rcu_nocb_mask); | |
2000 | return 1; | |
2001 | } | |
2002 | __setup("rcu_nocbs=", rcu_nocb_setup); | |
2003 | ||
1b0048a4 PG |
2004 | static int __init parse_rcu_nocb_poll(char *arg) |
2005 | { | |
2006 | rcu_nocb_poll = 1; | |
2007 | return 0; | |
2008 | } | |
2009 | early_param("rcu_nocb_poll", parse_rcu_nocb_poll); | |
2010 | ||
dae6e64d | 2011 | /* |
0446be48 PM |
2012 | * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended |
2013 | * grace period. | |
dae6e64d | 2014 | */ |
0446be48 | 2015 | static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
dae6e64d | 2016 | { |
0446be48 | 2017 | wake_up_all(&rnp->nocb_gp_wq[rnp->completed & 0x1]); |
dae6e64d PM |
2018 | } |
2019 | ||
2020 | /* | |
8b425aa8 | 2021 | * Set the root rcu_node structure's ->need_future_gp field |
dae6e64d PM |
2022 | * based on the sum of those of all rcu_node structures. This does |
2023 | * double-count the root rcu_node structure's requests, but this | |
2024 | * is necessary to handle the possibility of a rcu_nocb_kthread() | |
2025 | * having awakened during the time that the rcu_node structures | |
2026 | * were being updated for the end of the previous grace period. | |
34ed6246 | 2027 | */ |
dae6e64d PM |
2028 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
2029 | { | |
8b425aa8 | 2030 | rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq; |
dae6e64d PM |
2031 | } |
2032 | ||
2033 | static void rcu_init_one_nocb(struct rcu_node *rnp) | |
34ed6246 | 2034 | { |
dae6e64d PM |
2035 | init_waitqueue_head(&rnp->nocb_gp_wq[0]); |
2036 | init_waitqueue_head(&rnp->nocb_gp_wq[1]); | |
34ed6246 PM |
2037 | } |
2038 | ||
2f33b512 | 2039 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
24342c96 | 2040 | /* Is the specified CPU a no-CBs CPU? */ |
d1e43fa5 | 2041 | bool rcu_is_nocb_cpu(int cpu) |
3fbfbf7a PM |
2042 | { |
2043 | if (have_rcu_nocb_mask) | |
2044 | return cpumask_test_cpu(cpu, rcu_nocb_mask); | |
2045 | return false; | |
2046 | } | |
2f33b512 | 2047 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
3fbfbf7a | 2048 | |
fbce7497 PM |
2049 | /* |
2050 | * Kick the leader kthread for this NOCB group. | |
2051 | */ | |
2052 | static void wake_nocb_leader(struct rcu_data *rdp, bool force) | |
2053 | { | |
2054 | struct rcu_data *rdp_leader = rdp->nocb_leader; | |
2055 | ||
2056 | if (!ACCESS_ONCE(rdp_leader->nocb_kthread)) | |
2057 | return; | |
11ed7f93 | 2058 | if (ACCESS_ONCE(rdp_leader->nocb_leader_sleep) || force) { |
39953dfd | 2059 | /* Prior smp_mb__after_atomic() orders against prior enqueue. */ |
11ed7f93 | 2060 | ACCESS_ONCE(rdp_leader->nocb_leader_sleep) = false; |
fbce7497 PM |
2061 | wake_up(&rdp_leader->nocb_wq); |
2062 | } | |
2063 | } | |
2064 | ||
d7e29933 PM |
2065 | /* |
2066 | * Does the specified CPU need an RCU callback for the specified flavor | |
2067 | * of rcu_barrier()? | |
2068 | */ | |
2069 | static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) | |
2070 | { | |
2071 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
2072 | struct rcu_head *rhp; | |
2073 | ||
2074 | /* No-CBs CPUs might have callbacks on any of three lists. */ | |
2075 | rhp = ACCESS_ONCE(rdp->nocb_head); | |
2076 | if (!rhp) | |
2077 | rhp = ACCESS_ONCE(rdp->nocb_gp_head); | |
2078 | if (!rhp) | |
2079 | rhp = ACCESS_ONCE(rdp->nocb_follower_head); | |
2080 | ||
2081 | /* Having no rcuo kthread but CBs after scheduler starts is bad! */ | |
2082 | if (!ACCESS_ONCE(rdp->nocb_kthread) && rhp) { | |
2083 | /* RCU callback enqueued before CPU first came online??? */ | |
2084 | pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n", | |
2085 | cpu, rhp->func); | |
2086 | WARN_ON_ONCE(1); | |
2087 | } | |
2088 | ||
2089 | return !!rhp; | |
2090 | } | |
2091 | ||
3fbfbf7a PM |
2092 | /* |
2093 | * Enqueue the specified string of rcu_head structures onto the specified | |
2094 | * CPU's no-CBs lists. The CPU is specified by rdp, the head of the | |
2095 | * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy | |
2096 | * counts are supplied by rhcount and rhcount_lazy. | |
2097 | * | |
2098 | * If warranted, also wake up the kthread servicing this CPUs queues. | |
2099 | */ | |
2100 | static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, | |
2101 | struct rcu_head *rhp, | |
2102 | struct rcu_head **rhtp, | |
96d3fd0d PM |
2103 | int rhcount, int rhcount_lazy, |
2104 | unsigned long flags) | |
3fbfbf7a PM |
2105 | { |
2106 | int len; | |
2107 | struct rcu_head **old_rhpp; | |
2108 | struct task_struct *t; | |
2109 | ||
2110 | /* Enqueue the callback on the nocb list and update counts. */ | |
2111 | old_rhpp = xchg(&rdp->nocb_tail, rhtp); | |
2112 | ACCESS_ONCE(*old_rhpp) = rhp; | |
2113 | atomic_long_add(rhcount, &rdp->nocb_q_count); | |
2114 | atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy); | |
39953dfd | 2115 | smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */ |
3fbfbf7a PM |
2116 | |
2117 | /* If we are not being polled and there is a kthread, awaken it ... */ | |
2118 | t = ACCESS_ONCE(rdp->nocb_kthread); | |
25e03a74 | 2119 | if (rcu_nocb_poll || !t) { |
9261dd0d PM |
2120 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2121 | TPS("WakeNotPoll")); | |
3fbfbf7a | 2122 | return; |
9261dd0d | 2123 | } |
3fbfbf7a PM |
2124 | len = atomic_long_read(&rdp->nocb_q_count); |
2125 | if (old_rhpp == &rdp->nocb_head) { | |
96d3fd0d | 2126 | if (!irqs_disabled_flags(flags)) { |
fbce7497 PM |
2127 | /* ... if queue was empty ... */ |
2128 | wake_nocb_leader(rdp, false); | |
96d3fd0d PM |
2129 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2130 | TPS("WakeEmpty")); | |
2131 | } else { | |
9fdd3bc9 | 2132 | rdp->nocb_defer_wakeup = RCU_NOGP_WAKE; |
96d3fd0d PM |
2133 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2134 | TPS("WakeEmptyIsDeferred")); | |
2135 | } | |
3fbfbf7a PM |
2136 | rdp->qlen_last_fqs_check = 0; |
2137 | } else if (len > rdp->qlen_last_fqs_check + qhimark) { | |
fbce7497 | 2138 | /* ... or if many callbacks queued. */ |
9fdd3bc9 PM |
2139 | if (!irqs_disabled_flags(flags)) { |
2140 | wake_nocb_leader(rdp, true); | |
2141 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2142 | TPS("WakeOvf")); | |
2143 | } else { | |
2144 | rdp->nocb_defer_wakeup = RCU_NOGP_WAKE_FORCE; | |
2145 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2146 | TPS("WakeOvfIsDeferred")); | |
2147 | } | |
3fbfbf7a | 2148 | rdp->qlen_last_fqs_check = LONG_MAX / 2; |
9261dd0d PM |
2149 | } else { |
2150 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot")); | |
3fbfbf7a PM |
2151 | } |
2152 | return; | |
2153 | } | |
2154 | ||
2155 | /* | |
2156 | * This is a helper for __call_rcu(), which invokes this when the normal | |
2157 | * callback queue is inoperable. If this is not a no-CBs CPU, this | |
2158 | * function returns failure back to __call_rcu(), which can complain | |
2159 | * appropriately. | |
2160 | * | |
2161 | * Otherwise, this function queues the callback where the corresponding | |
2162 | * "rcuo" kthread can find it. | |
2163 | */ | |
2164 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, | |
96d3fd0d | 2165 | bool lazy, unsigned long flags) |
3fbfbf7a PM |
2166 | { |
2167 | ||
d1e43fa5 | 2168 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
c271d3a9 | 2169 | return false; |
96d3fd0d | 2170 | __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy, flags); |
21e7a608 PM |
2171 | if (__is_kfree_rcu_offset((unsigned long)rhp->func)) |
2172 | trace_rcu_kfree_callback(rdp->rsp->name, rhp, | |
2173 | (unsigned long)rhp->func, | |
756cbf6b PM |
2174 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
2175 | -atomic_long_read(&rdp->nocb_q_count)); | |
21e7a608 PM |
2176 | else |
2177 | trace_rcu_callback(rdp->rsp->name, rhp, | |
756cbf6b PM |
2178 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
2179 | -atomic_long_read(&rdp->nocb_q_count)); | |
1772947b PM |
2180 | |
2181 | /* | |
2182 | * If called from an extended quiescent state with interrupts | |
2183 | * disabled, invoke the RCU core in order to allow the idle-entry | |
2184 | * deferred-wakeup check to function. | |
2185 | */ | |
2186 | if (irqs_disabled_flags(flags) && | |
2187 | !rcu_is_watching() && | |
2188 | cpu_online(smp_processor_id())) | |
2189 | invoke_rcu_core(); | |
2190 | ||
c271d3a9 | 2191 | return true; |
3fbfbf7a PM |
2192 | } |
2193 | ||
2194 | /* | |
2195 | * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is | |
2196 | * not a no-CBs CPU. | |
2197 | */ | |
2198 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, | |
96d3fd0d PM |
2199 | struct rcu_data *rdp, |
2200 | unsigned long flags) | |
3fbfbf7a PM |
2201 | { |
2202 | long ql = rsp->qlen; | |
2203 | long qll = rsp->qlen_lazy; | |
2204 | ||
2205 | /* If this is not a no-CBs CPU, tell the caller to do it the old way. */ | |
d1e43fa5 | 2206 | if (!rcu_is_nocb_cpu(smp_processor_id())) |
0a9e1e11 | 2207 | return false; |
3fbfbf7a PM |
2208 | rsp->qlen = 0; |
2209 | rsp->qlen_lazy = 0; | |
2210 | ||
2211 | /* First, enqueue the donelist, if any. This preserves CB ordering. */ | |
2212 | if (rsp->orphan_donelist != NULL) { | |
2213 | __call_rcu_nocb_enqueue(rdp, rsp->orphan_donelist, | |
96d3fd0d | 2214 | rsp->orphan_donetail, ql, qll, flags); |
3fbfbf7a PM |
2215 | ql = qll = 0; |
2216 | rsp->orphan_donelist = NULL; | |
2217 | rsp->orphan_donetail = &rsp->orphan_donelist; | |
2218 | } | |
2219 | if (rsp->orphan_nxtlist != NULL) { | |
2220 | __call_rcu_nocb_enqueue(rdp, rsp->orphan_nxtlist, | |
96d3fd0d | 2221 | rsp->orphan_nxttail, ql, qll, flags); |
3fbfbf7a PM |
2222 | ql = qll = 0; |
2223 | rsp->orphan_nxtlist = NULL; | |
2224 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; | |
2225 | } | |
0a9e1e11 | 2226 | return true; |
3fbfbf7a PM |
2227 | } |
2228 | ||
2229 | /* | |
34ed6246 PM |
2230 | * If necessary, kick off a new grace period, and either way wait |
2231 | * for a subsequent grace period to complete. | |
3fbfbf7a | 2232 | */ |
34ed6246 | 2233 | static void rcu_nocb_wait_gp(struct rcu_data *rdp) |
3fbfbf7a | 2234 | { |
34ed6246 | 2235 | unsigned long c; |
dae6e64d | 2236 | bool d; |
34ed6246 | 2237 | unsigned long flags; |
48a7639c | 2238 | bool needwake; |
34ed6246 PM |
2239 | struct rcu_node *rnp = rdp->mynode; |
2240 | ||
2241 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 2242 | smp_mb__after_unlock_lock(); |
48a7639c | 2243 | needwake = rcu_start_future_gp(rnp, rdp, &c); |
0446be48 | 2244 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
48a7639c PM |
2245 | if (needwake) |
2246 | rcu_gp_kthread_wake(rdp->rsp); | |
3fbfbf7a PM |
2247 | |
2248 | /* | |
34ed6246 PM |
2249 | * Wait for the grace period. Do so interruptibly to avoid messing |
2250 | * up the load average. | |
3fbfbf7a | 2251 | */ |
f7f7bac9 | 2252 | trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait")); |
34ed6246 | 2253 | for (;;) { |
dae6e64d PM |
2254 | wait_event_interruptible( |
2255 | rnp->nocb_gp_wq[c & 0x1], | |
2256 | (d = ULONG_CMP_GE(ACCESS_ONCE(rnp->completed), c))); | |
2257 | if (likely(d)) | |
34ed6246 | 2258 | break; |
73a860cd | 2259 | WARN_ON(signal_pending(current)); |
f7f7bac9 | 2260 | trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait")); |
34ed6246 | 2261 | } |
f7f7bac9 | 2262 | trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait")); |
34ed6246 | 2263 | smp_mb(); /* Ensure that CB invocation happens after GP end. */ |
3fbfbf7a PM |
2264 | } |
2265 | ||
fbce7497 PM |
2266 | /* |
2267 | * Leaders come here to wait for additional callbacks to show up. | |
2268 | * This function does not return until callbacks appear. | |
2269 | */ | |
2270 | static void nocb_leader_wait(struct rcu_data *my_rdp) | |
2271 | { | |
2272 | bool firsttime = true; | |
2273 | bool gotcbs; | |
2274 | struct rcu_data *rdp; | |
2275 | struct rcu_head **tail; | |
2276 | ||
2277 | wait_again: | |
2278 | ||
2279 | /* Wait for callbacks to appear. */ | |
2280 | if (!rcu_nocb_poll) { | |
2281 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep"); | |
2282 | wait_event_interruptible(my_rdp->nocb_wq, | |
11ed7f93 | 2283 | !ACCESS_ONCE(my_rdp->nocb_leader_sleep)); |
fbce7497 PM |
2284 | /* Memory barrier handled by smp_mb() calls below and repoll. */ |
2285 | } else if (firsttime) { | |
2286 | firsttime = false; /* Don't drown trace log with "Poll"! */ | |
2287 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Poll"); | |
2288 | } | |
2289 | ||
2290 | /* | |
2291 | * Each pass through the following loop checks a follower for CBs. | |
2292 | * We are our own first follower. Any CBs found are moved to | |
2293 | * nocb_gp_head, where they await a grace period. | |
2294 | */ | |
2295 | gotcbs = false; | |
2296 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { | |
2297 | rdp->nocb_gp_head = ACCESS_ONCE(rdp->nocb_head); | |
2298 | if (!rdp->nocb_gp_head) | |
2299 | continue; /* No CBs here, try next follower. */ | |
2300 | ||
2301 | /* Move callbacks to wait-for-GP list, which is empty. */ | |
2302 | ACCESS_ONCE(rdp->nocb_head) = NULL; | |
2303 | rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head); | |
2304 | rdp->nocb_gp_count = atomic_long_xchg(&rdp->nocb_q_count, 0); | |
2305 | rdp->nocb_gp_count_lazy = | |
2306 | atomic_long_xchg(&rdp->nocb_q_count_lazy, 0); | |
2307 | gotcbs = true; | |
2308 | } | |
2309 | ||
2310 | /* | |
2311 | * If there were no callbacks, sleep a bit, rescan after a | |
2312 | * memory barrier, and go retry. | |
2313 | */ | |
2314 | if (unlikely(!gotcbs)) { | |
2315 | if (!rcu_nocb_poll) | |
2316 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, | |
2317 | "WokeEmpty"); | |
73a860cd | 2318 | WARN_ON(signal_pending(current)); |
fbce7497 PM |
2319 | schedule_timeout_interruptible(1); |
2320 | ||
2321 | /* Rescan in case we were a victim of memory ordering. */ | |
11ed7f93 PK |
2322 | my_rdp->nocb_leader_sleep = true; |
2323 | smp_mb(); /* Ensure _sleep true before scan. */ | |
fbce7497 PM |
2324 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) |
2325 | if (ACCESS_ONCE(rdp->nocb_head)) { | |
2326 | /* Found CB, so short-circuit next wait. */ | |
11ed7f93 | 2327 | my_rdp->nocb_leader_sleep = false; |
fbce7497 PM |
2328 | break; |
2329 | } | |
2330 | goto wait_again; | |
2331 | } | |
2332 | ||
2333 | /* Wait for one grace period. */ | |
2334 | rcu_nocb_wait_gp(my_rdp); | |
2335 | ||
2336 | /* | |
11ed7f93 PK |
2337 | * We left ->nocb_leader_sleep unset to reduce cache thrashing. |
2338 | * We set it now, but recheck for new callbacks while | |
fbce7497 PM |
2339 | * traversing our follower list. |
2340 | */ | |
11ed7f93 PK |
2341 | my_rdp->nocb_leader_sleep = true; |
2342 | smp_mb(); /* Ensure _sleep true before scan of ->nocb_head. */ | |
fbce7497 PM |
2343 | |
2344 | /* Each pass through the following loop wakes a follower, if needed. */ | |
2345 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { | |
2346 | if (ACCESS_ONCE(rdp->nocb_head)) | |
11ed7f93 | 2347 | my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/ |
fbce7497 PM |
2348 | if (!rdp->nocb_gp_head) |
2349 | continue; /* No CBs, so no need to wake follower. */ | |
2350 | ||
2351 | /* Append callbacks to follower's "done" list. */ | |
2352 | tail = xchg(&rdp->nocb_follower_tail, rdp->nocb_gp_tail); | |
2353 | *tail = rdp->nocb_gp_head; | |
2354 | atomic_long_add(rdp->nocb_gp_count, &rdp->nocb_follower_count); | |
2355 | atomic_long_add(rdp->nocb_gp_count_lazy, | |
2356 | &rdp->nocb_follower_count_lazy); | |
c847f142 | 2357 | smp_mb__after_atomic(); /* Store *tail before wakeup. */ |
fbce7497 PM |
2358 | if (rdp != my_rdp && tail == &rdp->nocb_follower_head) { |
2359 | /* | |
2360 | * List was empty, wake up the follower. | |
2361 | * Memory barriers supplied by atomic_long_add(). | |
2362 | */ | |
2363 | wake_up(&rdp->nocb_wq); | |
2364 | } | |
2365 | } | |
2366 | ||
2367 | /* If we (the leader) don't have CBs, go wait some more. */ | |
2368 | if (!my_rdp->nocb_follower_head) | |
2369 | goto wait_again; | |
2370 | } | |
2371 | ||
2372 | /* | |
2373 | * Followers come here to wait for additional callbacks to show up. | |
2374 | * This function does not return until callbacks appear. | |
2375 | */ | |
2376 | static void nocb_follower_wait(struct rcu_data *rdp) | |
2377 | { | |
2378 | bool firsttime = true; | |
2379 | ||
2380 | for (;;) { | |
2381 | if (!rcu_nocb_poll) { | |
2382 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2383 | "FollowerSleep"); | |
2384 | wait_event_interruptible(rdp->nocb_wq, | |
2385 | ACCESS_ONCE(rdp->nocb_follower_head)); | |
2386 | } else if (firsttime) { | |
2387 | /* Don't drown trace log with "Poll"! */ | |
2388 | firsttime = false; | |
2389 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "Poll"); | |
2390 | } | |
2391 | if (smp_load_acquire(&rdp->nocb_follower_head)) { | |
2392 | /* ^^^ Ensure CB invocation follows _head test. */ | |
2393 | return; | |
2394 | } | |
2395 | if (!rcu_nocb_poll) | |
2396 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, | |
2397 | "WokeEmpty"); | |
73a860cd | 2398 | WARN_ON(signal_pending(current)); |
fbce7497 PM |
2399 | schedule_timeout_interruptible(1); |
2400 | } | |
2401 | } | |
2402 | ||
3fbfbf7a PM |
2403 | /* |
2404 | * Per-rcu_data kthread, but only for no-CBs CPUs. Each kthread invokes | |
fbce7497 PM |
2405 | * callbacks queued by the corresponding no-CBs CPU, however, there is |
2406 | * an optional leader-follower relationship so that the grace-period | |
2407 | * kthreads don't have to do quite so many wakeups. | |
3fbfbf7a PM |
2408 | */ |
2409 | static int rcu_nocb_kthread(void *arg) | |
2410 | { | |
2411 | int c, cl; | |
2412 | struct rcu_head *list; | |
2413 | struct rcu_head *next; | |
2414 | struct rcu_head **tail; | |
2415 | struct rcu_data *rdp = arg; | |
2416 | ||
2417 | /* Each pass through this loop invokes one batch of callbacks */ | |
2418 | for (;;) { | |
fbce7497 PM |
2419 | /* Wait for callbacks. */ |
2420 | if (rdp->nocb_leader == rdp) | |
2421 | nocb_leader_wait(rdp); | |
2422 | else | |
2423 | nocb_follower_wait(rdp); | |
2424 | ||
2425 | /* Pull the ready-to-invoke callbacks onto local list. */ | |
2426 | list = ACCESS_ONCE(rdp->nocb_follower_head); | |
2427 | BUG_ON(!list); | |
2428 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty"); | |
2429 | ACCESS_ONCE(rdp->nocb_follower_head) = NULL; | |
2430 | tail = xchg(&rdp->nocb_follower_tail, &rdp->nocb_follower_head); | |
2431 | c = atomic_long_xchg(&rdp->nocb_follower_count, 0); | |
2432 | cl = atomic_long_xchg(&rdp->nocb_follower_count_lazy, 0); | |
2433 | rdp->nocb_p_count += c; | |
2434 | rdp->nocb_p_count_lazy += cl; | |
3fbfbf7a PM |
2435 | |
2436 | /* Each pass through the following loop invokes a callback. */ | |
2437 | trace_rcu_batch_start(rdp->rsp->name, cl, c, -1); | |
2438 | c = cl = 0; | |
2439 | while (list) { | |
2440 | next = list->next; | |
2441 | /* Wait for enqueuing to complete, if needed. */ | |
2442 | while (next == NULL && &list->next != tail) { | |
69a79bb1 PM |
2443 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2444 | TPS("WaitQueue")); | |
3fbfbf7a | 2445 | schedule_timeout_interruptible(1); |
69a79bb1 PM |
2446 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
2447 | TPS("WokeQueue")); | |
3fbfbf7a PM |
2448 | next = list->next; |
2449 | } | |
2450 | debug_rcu_head_unqueue(list); | |
2451 | local_bh_disable(); | |
2452 | if (__rcu_reclaim(rdp->rsp->name, list)) | |
2453 | cl++; | |
2454 | c++; | |
2455 | local_bh_enable(); | |
2456 | list = next; | |
2457 | } | |
2458 | trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); | |
4de376a1 PK |
2459 | ACCESS_ONCE(rdp->nocb_p_count) = rdp->nocb_p_count - c; |
2460 | ACCESS_ONCE(rdp->nocb_p_count_lazy) = | |
2461 | rdp->nocb_p_count_lazy - cl; | |
c635a4e1 | 2462 | rdp->n_nocbs_invoked += c; |
3fbfbf7a PM |
2463 | } |
2464 | return 0; | |
2465 | } | |
2466 | ||
96d3fd0d | 2467 | /* Is a deferred wakeup of rcu_nocb_kthread() required? */ |
9fdd3bc9 | 2468 | static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) |
96d3fd0d PM |
2469 | { |
2470 | return ACCESS_ONCE(rdp->nocb_defer_wakeup); | |
2471 | } | |
2472 | ||
2473 | /* Do a deferred wakeup of rcu_nocb_kthread(). */ | |
2474 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) | |
2475 | { | |
9fdd3bc9 PM |
2476 | int ndw; |
2477 | ||
96d3fd0d PM |
2478 | if (!rcu_nocb_need_deferred_wakeup(rdp)) |
2479 | return; | |
9fdd3bc9 PM |
2480 | ndw = ACCESS_ONCE(rdp->nocb_defer_wakeup); |
2481 | ACCESS_ONCE(rdp->nocb_defer_wakeup) = RCU_NOGP_WAKE_NOT; | |
2482 | wake_nocb_leader(rdp, ndw == RCU_NOGP_WAKE_FORCE); | |
2483 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("DeferredWake")); | |
96d3fd0d PM |
2484 | } |
2485 | ||
f4579fc5 PM |
2486 | void __init rcu_init_nohz(void) |
2487 | { | |
2488 | int cpu; | |
2489 | bool need_rcu_nocb_mask = true; | |
2490 | struct rcu_state *rsp; | |
2491 | ||
2492 | #ifdef CONFIG_RCU_NOCB_CPU_NONE | |
2493 | need_rcu_nocb_mask = false; | |
2494 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */ | |
2495 | ||
2496 | #if defined(CONFIG_NO_HZ_FULL) | |
2497 | if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask)) | |
2498 | need_rcu_nocb_mask = true; | |
2499 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ | |
2500 | ||
2501 | if (!have_rcu_nocb_mask && need_rcu_nocb_mask) { | |
949cccdb PK |
2502 | if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { |
2503 | pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); | |
2504 | return; | |
2505 | } | |
f4579fc5 PM |
2506 | have_rcu_nocb_mask = true; |
2507 | } | |
2508 | if (!have_rcu_nocb_mask) | |
2509 | return; | |
2510 | ||
2511 | #ifdef CONFIG_RCU_NOCB_CPU_ZERO | |
2512 | pr_info("\tOffload RCU callbacks from CPU 0\n"); | |
2513 | cpumask_set_cpu(0, rcu_nocb_mask); | |
2514 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */ | |
2515 | #ifdef CONFIG_RCU_NOCB_CPU_ALL | |
2516 | pr_info("\tOffload RCU callbacks from all CPUs\n"); | |
2517 | cpumask_copy(rcu_nocb_mask, cpu_possible_mask); | |
2518 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ | |
2519 | #if defined(CONFIG_NO_HZ_FULL) | |
2520 | if (tick_nohz_full_running) | |
2521 | cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); | |
2522 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ | |
2523 | ||
2524 | if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { | |
2525 | pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n"); | |
2526 | cpumask_and(rcu_nocb_mask, cpu_possible_mask, | |
2527 | rcu_nocb_mask); | |
2528 | } | |
2529 | cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask); | |
2530 | pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf); | |
2531 | if (rcu_nocb_poll) | |
2532 | pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); | |
2533 | ||
2534 | for_each_rcu_flavor(rsp) { | |
2535 | for_each_cpu(cpu, rcu_nocb_mask) { | |
2536 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
2537 | ||
2538 | /* | |
2539 | * If there are early callbacks, they will need | |
2540 | * to be moved to the nocb lists. | |
2541 | */ | |
2542 | WARN_ON_ONCE(rdp->nxttail[RCU_NEXT_TAIL] != | |
2543 | &rdp->nxtlist && | |
2544 | rdp->nxttail[RCU_NEXT_TAIL] != NULL); | |
2545 | init_nocb_callback_list(rdp); | |
2546 | } | |
35ce7f29 | 2547 | rcu_organize_nocb_kthreads(rsp); |
f4579fc5 | 2548 | } |
96d3fd0d PM |
2549 | } |
2550 | ||
3fbfbf7a PM |
2551 | /* Initialize per-rcu_data variables for no-CBs CPUs. */ |
2552 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) | |
2553 | { | |
2554 | rdp->nocb_tail = &rdp->nocb_head; | |
2555 | init_waitqueue_head(&rdp->nocb_wq); | |
fbce7497 | 2556 | rdp->nocb_follower_tail = &rdp->nocb_follower_head; |
3fbfbf7a PM |
2557 | } |
2558 | ||
35ce7f29 PM |
2559 | /* |
2560 | * If the specified CPU is a no-CBs CPU that does not already have its | |
2561 | * rcuo kthread for the specified RCU flavor, spawn it. If the CPUs are | |
2562 | * brought online out of order, this can require re-organizing the | |
2563 | * leader-follower relationships. | |
2564 | */ | |
2565 | static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu) | |
2566 | { | |
2567 | struct rcu_data *rdp; | |
2568 | struct rcu_data *rdp_last; | |
2569 | struct rcu_data *rdp_old_leader; | |
2570 | struct rcu_data *rdp_spawn = per_cpu_ptr(rsp->rda, cpu); | |
2571 | struct task_struct *t; | |
2572 | ||
2573 | /* | |
2574 | * If this isn't a no-CBs CPU or if it already has an rcuo kthread, | |
2575 | * then nothing to do. | |
2576 | */ | |
2577 | if (!rcu_is_nocb_cpu(cpu) || rdp_spawn->nocb_kthread) | |
2578 | return; | |
2579 | ||
2580 | /* If we didn't spawn the leader first, reorganize! */ | |
2581 | rdp_old_leader = rdp_spawn->nocb_leader; | |
2582 | if (rdp_old_leader != rdp_spawn && !rdp_old_leader->nocb_kthread) { | |
2583 | rdp_last = NULL; | |
2584 | rdp = rdp_old_leader; | |
2585 | do { | |
2586 | rdp->nocb_leader = rdp_spawn; | |
2587 | if (rdp_last && rdp != rdp_spawn) | |
2588 | rdp_last->nocb_next_follower = rdp; | |
2589 | rdp_last = rdp; | |
2590 | rdp = rdp->nocb_next_follower; | |
2591 | rdp_last->nocb_next_follower = NULL; | |
2592 | } while (rdp); | |
2593 | rdp_spawn->nocb_next_follower = rdp_old_leader; | |
2594 | } | |
2595 | ||
2596 | /* Spawn the kthread for this CPU and RCU flavor. */ | |
2597 | t = kthread_run(rcu_nocb_kthread, rdp_spawn, | |
2598 | "rcuo%c/%d", rsp->abbr, cpu); | |
2599 | BUG_ON(IS_ERR(t)); | |
2600 | ACCESS_ONCE(rdp_spawn->nocb_kthread) = t; | |
2601 | } | |
2602 | ||
2603 | /* | |
2604 | * If the specified CPU is a no-CBs CPU that does not already have its | |
2605 | * rcuo kthreads, spawn them. | |
2606 | */ | |
2607 | static void rcu_spawn_all_nocb_kthreads(int cpu) | |
2608 | { | |
2609 | struct rcu_state *rsp; | |
2610 | ||
2611 | if (rcu_scheduler_fully_active) | |
2612 | for_each_rcu_flavor(rsp) | |
2613 | rcu_spawn_one_nocb_kthread(rsp, cpu); | |
2614 | } | |
2615 | ||
2616 | /* | |
2617 | * Once the scheduler is running, spawn rcuo kthreads for all online | |
2618 | * no-CBs CPUs. This assumes that the early_initcall()s happen before | |
2619 | * non-boot CPUs come online -- if this changes, we will need to add | |
2620 | * some mutual exclusion. | |
2621 | */ | |
2622 | static void __init rcu_spawn_nocb_kthreads(void) | |
2623 | { | |
2624 | int cpu; | |
2625 | ||
2626 | for_each_online_cpu(cpu) | |
2627 | rcu_spawn_all_nocb_kthreads(cpu); | |
2628 | } | |
2629 | ||
fbce7497 PM |
2630 | /* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids). */ |
2631 | static int rcu_nocb_leader_stride = -1; | |
2632 | module_param(rcu_nocb_leader_stride, int, 0444); | |
2633 | ||
2634 | /* | |
35ce7f29 | 2635 | * Initialize leader-follower relationships for all no-CBs CPU. |
fbce7497 | 2636 | */ |
35ce7f29 | 2637 | static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) |
3fbfbf7a PM |
2638 | { |
2639 | int cpu; | |
fbce7497 PM |
2640 | int ls = rcu_nocb_leader_stride; |
2641 | int nl = 0; /* Next leader. */ | |
3fbfbf7a | 2642 | struct rcu_data *rdp; |
fbce7497 PM |
2643 | struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ |
2644 | struct rcu_data *rdp_prev = NULL; | |
3fbfbf7a | 2645 | |
22c2f669 | 2646 | if (!have_rcu_nocb_mask) |
3fbfbf7a | 2647 | return; |
fbce7497 PM |
2648 | if (ls == -1) { |
2649 | ls = int_sqrt(nr_cpu_ids); | |
2650 | rcu_nocb_leader_stride = ls; | |
2651 | } | |
2652 | ||
2653 | /* | |
2654 | * Each pass through this loop sets up one rcu_data structure and | |
2655 | * spawns one rcu_nocb_kthread(). | |
2656 | */ | |
3fbfbf7a PM |
2657 | for_each_cpu(cpu, rcu_nocb_mask) { |
2658 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
fbce7497 PM |
2659 | if (rdp->cpu >= nl) { |
2660 | /* New leader, set up for followers & next leader. */ | |
2661 | nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls; | |
2662 | rdp->nocb_leader = rdp; | |
2663 | rdp_leader = rdp; | |
2664 | } else { | |
2665 | /* Another follower, link to previous leader. */ | |
2666 | rdp->nocb_leader = rdp_leader; | |
2667 | rdp_prev->nocb_next_follower = rdp; | |
2668 | } | |
2669 | rdp_prev = rdp; | |
3fbfbf7a PM |
2670 | } |
2671 | } | |
2672 | ||
2673 | /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ | |
34ed6246 | 2674 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
3fbfbf7a | 2675 | { |
22c2f669 | 2676 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
34ed6246 | 2677 | return false; |
22c2f669 | 2678 | |
3fbfbf7a | 2679 | rdp->nxttail[RCU_NEXT_TAIL] = NULL; |
34ed6246 | 2680 | return true; |
3fbfbf7a PM |
2681 | } |
2682 | ||
34ed6246 PM |
2683 | #else /* #ifdef CONFIG_RCU_NOCB_CPU */ |
2684 | ||
d7e29933 PM |
2685 | static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) |
2686 | { | |
2687 | WARN_ON_ONCE(1); /* Should be dead code. */ | |
2688 | return false; | |
2689 | } | |
2690 | ||
0446be48 | 2691 | static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
3fbfbf7a | 2692 | { |
3fbfbf7a PM |
2693 | } |
2694 | ||
dae6e64d PM |
2695 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
2696 | { | |
2697 | } | |
2698 | ||
2699 | static void rcu_init_one_nocb(struct rcu_node *rnp) | |
2700 | { | |
2701 | } | |
3fbfbf7a | 2702 | |
3fbfbf7a | 2703 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, |
96d3fd0d | 2704 | bool lazy, unsigned long flags) |
3fbfbf7a | 2705 | { |
4afc7e26 | 2706 | return false; |
3fbfbf7a PM |
2707 | } |
2708 | ||
2709 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, | |
96d3fd0d PM |
2710 | struct rcu_data *rdp, |
2711 | unsigned long flags) | |
3fbfbf7a | 2712 | { |
f4aa84ba | 2713 | return false; |
3fbfbf7a PM |
2714 | } |
2715 | ||
3fbfbf7a PM |
2716 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) |
2717 | { | |
2718 | } | |
2719 | ||
9fdd3bc9 | 2720 | static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) |
96d3fd0d PM |
2721 | { |
2722 | return false; | |
2723 | } | |
2724 | ||
2725 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) | |
2726 | { | |
2727 | } | |
2728 | ||
35ce7f29 PM |
2729 | static void rcu_spawn_all_nocb_kthreads(int cpu) |
2730 | { | |
2731 | } | |
2732 | ||
2733 | static void __init rcu_spawn_nocb_kthreads(void) | |
3fbfbf7a PM |
2734 | { |
2735 | } | |
2736 | ||
34ed6246 | 2737 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
3fbfbf7a | 2738 | { |
34ed6246 | 2739 | return false; |
3fbfbf7a PM |
2740 | } |
2741 | ||
2742 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ | |
65d798f0 PM |
2743 | |
2744 | /* | |
2745 | * An adaptive-ticks CPU can potentially execute in kernel mode for an | |
2746 | * arbitrarily long period of time with the scheduling-clock tick turned | |
2747 | * off. RCU will be paying attention to this CPU because it is in the | |
2748 | * kernel, but the CPU cannot be guaranteed to be executing the RCU state | |
2749 | * machine because the scheduling-clock tick has been disabled. Therefore, | |
2750 | * if an adaptive-ticks CPU is failing to respond to the current grace | |
2751 | * period and has not be idle from an RCU perspective, kick it. | |
2752 | */ | |
4a81e832 | 2753 | static void __maybe_unused rcu_kick_nohz_cpu(int cpu) |
65d798f0 PM |
2754 | { |
2755 | #ifdef CONFIG_NO_HZ_FULL | |
2756 | if (tick_nohz_full_cpu(cpu)) | |
2757 | smp_send_reschedule(cpu); | |
2758 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ | |
2759 | } | |
2333210b PM |
2760 | |
2761 | ||
2762 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE | |
2763 | ||
0edd1b17 | 2764 | static int full_sysidle_state; /* Current system-idle state. */ |
d4bd54fb PM |
2765 | #define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ |
2766 | #define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ | |
2767 | #define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ | |
2768 | #define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ | |
2769 | #define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ | |
2770 | ||
eb348b89 PM |
2771 | /* |
2772 | * Invoked to note exit from irq or task transition to idle. Note that | |
2773 | * usermode execution does -not- count as idle here! After all, we want | |
2774 | * to detect full-system idle states, not RCU quiescent states and grace | |
2775 | * periods. The caller must have disabled interrupts. | |
2776 | */ | |
2777 | static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq) | |
2778 | { | |
2779 | unsigned long j; | |
2780 | ||
663e1310 PM |
2781 | /* If there are no nohz_full= CPUs, no need to track this. */ |
2782 | if (!tick_nohz_full_enabled()) | |
2783 | return; | |
2784 | ||
eb348b89 PM |
2785 | /* Adjust nesting, check for fully idle. */ |
2786 | if (irq) { | |
2787 | rdtp->dynticks_idle_nesting--; | |
2788 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); | |
2789 | if (rdtp->dynticks_idle_nesting != 0) | |
2790 | return; /* Still not fully idle. */ | |
2791 | } else { | |
2792 | if ((rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) == | |
2793 | DYNTICK_TASK_NEST_VALUE) { | |
2794 | rdtp->dynticks_idle_nesting = 0; | |
2795 | } else { | |
2796 | rdtp->dynticks_idle_nesting -= DYNTICK_TASK_NEST_VALUE; | |
2797 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); | |
2798 | return; /* Still not fully idle. */ | |
2799 | } | |
2800 | } | |
2801 | ||
2802 | /* Record start of fully idle period. */ | |
2803 | j = jiffies; | |
2804 | ACCESS_ONCE(rdtp->dynticks_idle_jiffies) = j; | |
4e857c58 | 2805 | smp_mb__before_atomic(); |
eb348b89 | 2806 | atomic_inc(&rdtp->dynticks_idle); |
4e857c58 | 2807 | smp_mb__after_atomic(); |
eb348b89 PM |
2808 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks_idle) & 0x1); |
2809 | } | |
2810 | ||
0edd1b17 PM |
2811 | /* |
2812 | * Unconditionally force exit from full system-idle state. This is | |
2813 | * invoked when a normal CPU exits idle, but must be called separately | |
2814 | * for the timekeeping CPU (tick_do_timer_cpu). The reason for this | |
2815 | * is that the timekeeping CPU is permitted to take scheduling-clock | |
2816 | * interrupts while the system is in system-idle state, and of course | |
2817 | * rcu_sysidle_exit() has no way of distinguishing a scheduling-clock | |
2818 | * interrupt from any other type of interrupt. | |
2819 | */ | |
2820 | void rcu_sysidle_force_exit(void) | |
2821 | { | |
2822 | int oldstate = ACCESS_ONCE(full_sysidle_state); | |
2823 | int newoldstate; | |
2824 | ||
2825 | /* | |
2826 | * Each pass through the following loop attempts to exit full | |
2827 | * system-idle state. If contention proves to be a problem, | |
2828 | * a trylock-based contention tree could be used here. | |
2829 | */ | |
2830 | while (oldstate > RCU_SYSIDLE_SHORT) { | |
2831 | newoldstate = cmpxchg(&full_sysidle_state, | |
2832 | oldstate, RCU_SYSIDLE_NOT); | |
2833 | if (oldstate == newoldstate && | |
2834 | oldstate == RCU_SYSIDLE_FULL_NOTED) { | |
2835 | rcu_kick_nohz_cpu(tick_do_timer_cpu); | |
2836 | return; /* We cleared it, done! */ | |
2837 | } | |
2838 | oldstate = newoldstate; | |
2839 | } | |
2840 | smp_mb(); /* Order initial oldstate fetch vs. later non-idle work. */ | |
2841 | } | |
2842 | ||
eb348b89 PM |
2843 | /* |
2844 | * Invoked to note entry to irq or task transition from idle. Note that | |
2845 | * usermode execution does -not- count as idle here! The caller must | |
2846 | * have disabled interrupts. | |
2847 | */ | |
2848 | static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq) | |
2849 | { | |
663e1310 PM |
2850 | /* If there are no nohz_full= CPUs, no need to track this. */ |
2851 | if (!tick_nohz_full_enabled()) | |
2852 | return; | |
2853 | ||
eb348b89 PM |
2854 | /* Adjust nesting, check for already non-idle. */ |
2855 | if (irq) { | |
2856 | rdtp->dynticks_idle_nesting++; | |
2857 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); | |
2858 | if (rdtp->dynticks_idle_nesting != 1) | |
2859 | return; /* Already non-idle. */ | |
2860 | } else { | |
2861 | /* | |
2862 | * Allow for irq misnesting. Yes, it really is possible | |
2863 | * to enter an irq handler then never leave it, and maybe | |
2864 | * also vice versa. Handle both possibilities. | |
2865 | */ | |
2866 | if (rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) { | |
2867 | rdtp->dynticks_idle_nesting += DYNTICK_TASK_NEST_VALUE; | |
2868 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); | |
2869 | return; /* Already non-idle. */ | |
2870 | } else { | |
2871 | rdtp->dynticks_idle_nesting = DYNTICK_TASK_EXIT_IDLE; | |
2872 | } | |
2873 | } | |
2874 | ||
2875 | /* Record end of idle period. */ | |
4e857c58 | 2876 | smp_mb__before_atomic(); |
eb348b89 | 2877 | atomic_inc(&rdtp->dynticks_idle); |
4e857c58 | 2878 | smp_mb__after_atomic(); |
eb348b89 | 2879 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks_idle) & 0x1)); |
0edd1b17 PM |
2880 | |
2881 | /* | |
2882 | * If we are the timekeeping CPU, we are permitted to be non-idle | |
2883 | * during a system-idle state. This must be the case, because | |
2884 | * the timekeeping CPU has to take scheduling-clock interrupts | |
2885 | * during the time that the system is transitioning to full | |
2886 | * system-idle state. This means that the timekeeping CPU must | |
2887 | * invoke rcu_sysidle_force_exit() directly if it does anything | |
2888 | * more than take a scheduling-clock interrupt. | |
2889 | */ | |
2890 | if (smp_processor_id() == tick_do_timer_cpu) | |
2891 | return; | |
2892 | ||
2893 | /* Update system-idle state: We are clearly no longer fully idle! */ | |
2894 | rcu_sysidle_force_exit(); | |
2895 | } | |
2896 | ||
2897 | /* | |
2898 | * Check to see if the current CPU is idle. Note that usermode execution | |
2899 | * does not count as idle. The caller must have disabled interrupts. | |
2900 | */ | |
2901 | static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, | |
2902 | unsigned long *maxj) | |
2903 | { | |
2904 | int cur; | |
2905 | unsigned long j; | |
2906 | struct rcu_dynticks *rdtp = rdp->dynticks; | |
2907 | ||
663e1310 PM |
2908 | /* If there are no nohz_full= CPUs, don't check system-wide idleness. */ |
2909 | if (!tick_nohz_full_enabled()) | |
2910 | return; | |
2911 | ||
0edd1b17 PM |
2912 | /* |
2913 | * If some other CPU has already reported non-idle, if this is | |
2914 | * not the flavor of RCU that tracks sysidle state, or if this | |
2915 | * is an offline or the timekeeping CPU, nothing to do. | |
2916 | */ | |
417e8d26 | 2917 | if (!*isidle || rdp->rsp != rcu_state_p || |
0edd1b17 PM |
2918 | cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) |
2919 | return; | |
eb75767b PM |
2920 | if (rcu_gp_in_progress(rdp->rsp)) |
2921 | WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); | |
0edd1b17 PM |
2922 | |
2923 | /* Pick up current idle and NMI-nesting counter and check. */ | |
2924 | cur = atomic_read(&rdtp->dynticks_idle); | |
2925 | if (cur & 0x1) { | |
2926 | *isidle = false; /* We are not idle! */ | |
2927 | return; | |
2928 | } | |
2929 | smp_mb(); /* Read counters before timestamps. */ | |
2930 | ||
2931 | /* Pick up timestamps. */ | |
2932 | j = ACCESS_ONCE(rdtp->dynticks_idle_jiffies); | |
2933 | /* If this CPU entered idle more recently, update maxj timestamp. */ | |
2934 | if (ULONG_CMP_LT(*maxj, j)) | |
2935 | *maxj = j; | |
2936 | } | |
2937 | ||
2938 | /* | |
2939 | * Is this the flavor of RCU that is handling full-system idle? | |
2940 | */ | |
2941 | static bool is_sysidle_rcu_state(struct rcu_state *rsp) | |
2942 | { | |
417e8d26 | 2943 | return rsp == rcu_state_p; |
0edd1b17 PM |
2944 | } |
2945 | ||
2946 | /* | |
2947 | * Return a delay in jiffies based on the number of CPUs, rcu_node | |
2948 | * leaf fanout, and jiffies tick rate. The idea is to allow larger | |
2949 | * systems more time to transition to full-idle state in order to | |
2950 | * avoid the cache thrashing that otherwise occur on the state variable. | |
2951 | * Really small systems (less than a couple of tens of CPUs) should | |
2952 | * instead use a single global atomically incremented counter, and later | |
2953 | * versions of this will automatically reconfigure themselves accordingly. | |
2954 | */ | |
2955 | static unsigned long rcu_sysidle_delay(void) | |
2956 | { | |
2957 | if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) | |
2958 | return 0; | |
2959 | return DIV_ROUND_UP(nr_cpu_ids * HZ, rcu_fanout_leaf * 1000); | |
2960 | } | |
2961 | ||
2962 | /* | |
2963 | * Advance the full-system-idle state. This is invoked when all of | |
2964 | * the non-timekeeping CPUs are idle. | |
2965 | */ | |
2966 | static void rcu_sysidle(unsigned long j) | |
2967 | { | |
2968 | /* Check the current state. */ | |
2969 | switch (ACCESS_ONCE(full_sysidle_state)) { | |
2970 | case RCU_SYSIDLE_NOT: | |
2971 | ||
2972 | /* First time all are idle, so note a short idle period. */ | |
2973 | ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_SHORT; | |
2974 | break; | |
2975 | ||
2976 | case RCU_SYSIDLE_SHORT: | |
2977 | ||
2978 | /* | |
2979 | * Idle for a bit, time to advance to next state? | |
2980 | * cmpxchg failure means race with non-idle, let them win. | |
2981 | */ | |
2982 | if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) | |
2983 | (void)cmpxchg(&full_sysidle_state, | |
2984 | RCU_SYSIDLE_SHORT, RCU_SYSIDLE_LONG); | |
2985 | break; | |
2986 | ||
2987 | case RCU_SYSIDLE_LONG: | |
2988 | ||
2989 | /* | |
2990 | * Do an additional check pass before advancing to full. | |
2991 | * cmpxchg failure means race with non-idle, let them win. | |
2992 | */ | |
2993 | if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) | |
2994 | (void)cmpxchg(&full_sysidle_state, | |
2995 | RCU_SYSIDLE_LONG, RCU_SYSIDLE_FULL); | |
2996 | break; | |
2997 | ||
2998 | default: | |
2999 | break; | |
3000 | } | |
3001 | } | |
3002 | ||
3003 | /* | |
3004 | * Found a non-idle non-timekeeping CPU, so kick the system-idle state | |
3005 | * back to the beginning. | |
3006 | */ | |
3007 | static void rcu_sysidle_cancel(void) | |
3008 | { | |
3009 | smp_mb(); | |
becb41bf PM |
3010 | if (full_sysidle_state > RCU_SYSIDLE_SHORT) |
3011 | ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT; | |
0edd1b17 PM |
3012 | } |
3013 | ||
3014 | /* | |
3015 | * Update the sysidle state based on the results of a force-quiescent-state | |
3016 | * scan of the CPUs' dyntick-idle state. | |
3017 | */ | |
3018 | static void rcu_sysidle_report(struct rcu_state *rsp, int isidle, | |
3019 | unsigned long maxj, bool gpkt) | |
3020 | { | |
417e8d26 | 3021 | if (rsp != rcu_state_p) |
0edd1b17 PM |
3022 | return; /* Wrong flavor, ignore. */ |
3023 | if (gpkt && nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) | |
3024 | return; /* Running state machine from timekeeping CPU. */ | |
3025 | if (isidle) | |
3026 | rcu_sysidle(maxj); /* More idle! */ | |
3027 | else | |
3028 | rcu_sysidle_cancel(); /* Idle is over. */ | |
3029 | } | |
3030 | ||
3031 | /* | |
3032 | * Wrapper for rcu_sysidle_report() when called from the grace-period | |
3033 | * kthread's context. | |
3034 | */ | |
3035 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, | |
3036 | unsigned long maxj) | |
3037 | { | |
663e1310 PM |
3038 | /* If there are no nohz_full= CPUs, no need to track this. */ |
3039 | if (!tick_nohz_full_enabled()) | |
3040 | return; | |
3041 | ||
0edd1b17 PM |
3042 | rcu_sysidle_report(rsp, isidle, maxj, true); |
3043 | } | |
3044 | ||
3045 | /* Callback and function for forcing an RCU grace period. */ | |
3046 | struct rcu_sysidle_head { | |
3047 | struct rcu_head rh; | |
3048 | int inuse; | |
3049 | }; | |
3050 | ||
3051 | static void rcu_sysidle_cb(struct rcu_head *rhp) | |
3052 | { | |
3053 | struct rcu_sysidle_head *rshp; | |
3054 | ||
3055 | /* | |
3056 | * The following memory barrier is needed to replace the | |
3057 | * memory barriers that would normally be in the memory | |
3058 | * allocator. | |
3059 | */ | |
3060 | smp_mb(); /* grace period precedes setting inuse. */ | |
3061 | ||
3062 | rshp = container_of(rhp, struct rcu_sysidle_head, rh); | |
3063 | ACCESS_ONCE(rshp->inuse) = 0; | |
3064 | } | |
3065 | ||
3066 | /* | |
3067 | * Check to see if the system is fully idle, other than the timekeeping CPU. | |
663e1310 PM |
3068 | * The caller must have disabled interrupts. This is not intended to be |
3069 | * called unless tick_nohz_full_enabled(). | |
0edd1b17 PM |
3070 | */ |
3071 | bool rcu_sys_is_idle(void) | |
3072 | { | |
3073 | static struct rcu_sysidle_head rsh; | |
3074 | int rss = ACCESS_ONCE(full_sysidle_state); | |
3075 | ||
3076 | if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu)) | |
3077 | return false; | |
3078 | ||
3079 | /* Handle small-system case by doing a full scan of CPUs. */ | |
3080 | if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) { | |
3081 | int oldrss = rss - 1; | |
3082 | ||
3083 | /* | |
3084 | * One pass to advance to each state up to _FULL. | |
3085 | * Give up if any pass fails to advance the state. | |
3086 | */ | |
3087 | while (rss < RCU_SYSIDLE_FULL && oldrss < rss) { | |
3088 | int cpu; | |
3089 | bool isidle = true; | |
3090 | unsigned long maxj = jiffies - ULONG_MAX / 4; | |
3091 | struct rcu_data *rdp; | |
3092 | ||
3093 | /* Scan all the CPUs looking for nonidle CPUs. */ | |
3094 | for_each_possible_cpu(cpu) { | |
417e8d26 | 3095 | rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
0edd1b17 PM |
3096 | rcu_sysidle_check_cpu(rdp, &isidle, &maxj); |
3097 | if (!isidle) | |
3098 | break; | |
3099 | } | |
417e8d26 | 3100 | rcu_sysidle_report(rcu_state_p, isidle, maxj, false); |
0edd1b17 PM |
3101 | oldrss = rss; |
3102 | rss = ACCESS_ONCE(full_sysidle_state); | |
3103 | } | |
3104 | } | |
3105 | ||
3106 | /* If this is the first observation of an idle period, record it. */ | |
3107 | if (rss == RCU_SYSIDLE_FULL) { | |
3108 | rss = cmpxchg(&full_sysidle_state, | |
3109 | RCU_SYSIDLE_FULL, RCU_SYSIDLE_FULL_NOTED); | |
3110 | return rss == RCU_SYSIDLE_FULL; | |
3111 | } | |
3112 | ||
3113 | smp_mb(); /* ensure rss load happens before later caller actions. */ | |
3114 | ||
3115 | /* If already fully idle, tell the caller (in case of races). */ | |
3116 | if (rss == RCU_SYSIDLE_FULL_NOTED) | |
3117 | return true; | |
3118 | ||
3119 | /* | |
3120 | * If we aren't there yet, and a grace period is not in flight, | |
3121 | * initiate a grace period. Either way, tell the caller that | |
3122 | * we are not there yet. We use an xchg() rather than an assignment | |
3123 | * to make up for the memory barriers that would otherwise be | |
3124 | * provided by the memory allocator. | |
3125 | */ | |
3126 | if (nr_cpu_ids > CONFIG_NO_HZ_FULL_SYSIDLE_SMALL && | |
417e8d26 | 3127 | !rcu_gp_in_progress(rcu_state_p) && |
0edd1b17 PM |
3128 | !rsh.inuse && xchg(&rsh.inuse, 1) == 0) |
3129 | call_rcu(&rsh.rh, rcu_sysidle_cb); | |
3130 | return false; | |
eb348b89 PM |
3131 | } |
3132 | ||
2333210b PM |
3133 | /* |
3134 | * Initialize dynticks sysidle state for CPUs coming online. | |
3135 | */ | |
3136 | static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) | |
3137 | { | |
3138 | rdtp->dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE; | |
3139 | } | |
3140 | ||
3141 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
3142 | ||
eb348b89 PM |
3143 | static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq) |
3144 | { | |
3145 | } | |
3146 | ||
3147 | static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq) | |
3148 | { | |
3149 | } | |
3150 | ||
0edd1b17 PM |
3151 | static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, |
3152 | unsigned long *maxj) | |
3153 | { | |
3154 | } | |
3155 | ||
3156 | static bool is_sysidle_rcu_state(struct rcu_state *rsp) | |
3157 | { | |
3158 | return false; | |
3159 | } | |
3160 | ||
3161 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, | |
3162 | unsigned long maxj) | |
3163 | { | |
3164 | } | |
3165 | ||
2333210b PM |
3166 | static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) |
3167 | { | |
3168 | } | |
3169 | ||
3170 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
a096932f PM |
3171 | |
3172 | /* | |
3173 | * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the | |
3174 | * grace-period kthread will do force_quiescent_state() processing? | |
3175 | * The idea is to avoid waking up RCU core processing on such a | |
3176 | * CPU unless the grace period has extended for too long. | |
3177 | * | |
3178 | * This code relies on the fact that all NO_HZ_FULL CPUs are also | |
52e2bb95 | 3179 | * CONFIG_RCU_NOCB_CPU CPUs. |
a096932f PM |
3180 | */ |
3181 | static bool rcu_nohz_full_cpu(struct rcu_state *rsp) | |
3182 | { | |
3183 | #ifdef CONFIG_NO_HZ_FULL | |
3184 | if (tick_nohz_full_cpu(smp_processor_id()) && | |
3185 | (!rcu_gp_in_progress(rsp) || | |
3186 | ULONG_CMP_LT(jiffies, ACCESS_ONCE(rsp->gp_start) + HZ))) | |
3187 | return 1; | |
3188 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ | |
3189 | return 0; | |
3190 | } | |
5057f55e PM |
3191 | |
3192 | /* | |
3193 | * Bind the grace-period kthread for the sysidle flavor of RCU to the | |
3194 | * timekeeping CPU. | |
3195 | */ | |
3196 | static void rcu_bind_gp_kthread(void) | |
3197 | { | |
c0f489d2 | 3198 | int __maybe_unused cpu; |
5057f55e | 3199 | |
c0f489d2 | 3200 | if (!tick_nohz_full_enabled()) |
5057f55e | 3201 | return; |
c0f489d2 PM |
3202 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
3203 | cpu = tick_do_timer_cpu; | |
3204 | if (cpu >= 0 && cpu < nr_cpu_ids && raw_smp_processor_id() != cpu) | |
5057f55e | 3205 | set_cpus_allowed_ptr(current, cpumask_of(cpu)); |
c0f489d2 PM |
3206 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
3207 | if (!is_housekeeping_cpu(raw_smp_processor_id())) | |
3208 | housekeeping_affine(current); | |
3209 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
5057f55e | 3210 | } |
176f8f7a PM |
3211 | |
3212 | /* Record the current task on dyntick-idle entry. */ | |
3213 | static void rcu_dynticks_task_enter(void) | |
3214 | { | |
3215 | #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) | |
3216 | ACCESS_ONCE(current->rcu_tasks_idle_cpu) = smp_processor_id(); | |
3217 | #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ | |
3218 | } | |
3219 | ||
3220 | /* Record no current task on dyntick-idle exit. */ | |
3221 | static void rcu_dynticks_task_exit(void) | |
3222 | { | |
3223 | #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) | |
3224 | ACCESS_ONCE(current->rcu_tasks_idle_cpu) = -1; | |
3225 | #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ | |
3226 | } |