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64db4cff PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | * | |
18 | * Copyright IBM Corporation, 2008 | |
19 | * | |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> | |
21 | * Manfred Spraul <manfred@colorfullife.com> | |
22 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version | |
23 | * | |
24 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> | |
25 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. | |
26 | * | |
27 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 28 | * Documentation/RCU |
64db4cff PM |
29 | */ |
30 | #include <linux/types.h> | |
31 | #include <linux/kernel.h> | |
32 | #include <linux/init.h> | |
33 | #include <linux/spinlock.h> | |
34 | #include <linux/smp.h> | |
35 | #include <linux/rcupdate.h> | |
36 | #include <linux/interrupt.h> | |
37 | #include <linux/sched.h> | |
c1dc0b9c | 38 | #include <linux/nmi.h> |
64db4cff PM |
39 | #include <asm/atomic.h> |
40 | #include <linux/bitops.h> | |
41 | #include <linux/module.h> | |
42 | #include <linux/completion.h> | |
43 | #include <linux/moduleparam.h> | |
44 | #include <linux/percpu.h> | |
45 | #include <linux/notifier.h> | |
46 | #include <linux/cpu.h> | |
47 | #include <linux/mutex.h> | |
48 | #include <linux/time.h> | |
bbad9379 | 49 | #include <linux/kernel_stat.h> |
a26ac245 PM |
50 | #include <linux/wait.h> |
51 | #include <linux/kthread.h> | |
64db4cff | 52 | |
9f77da9f PM |
53 | #include "rcutree.h" |
54 | ||
64db4cff PM |
55 | /* Data structures. */ |
56 | ||
b668c9cf | 57 | static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; |
88b91c7c | 58 | |
4300aa64 PM |
59 | #define RCU_STATE_INITIALIZER(structname) { \ |
60 | .level = { &structname.node[0] }, \ | |
64db4cff PM |
61 | .levelcnt = { \ |
62 | NUM_RCU_LVL_0, /* root of hierarchy. */ \ | |
63 | NUM_RCU_LVL_1, \ | |
64 | NUM_RCU_LVL_2, \ | |
cf244dc0 PM |
65 | NUM_RCU_LVL_3, \ |
66 | NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ | |
64db4cff | 67 | }, \ |
83f5b01f | 68 | .signaled = RCU_GP_IDLE, \ |
64db4cff PM |
69 | .gpnum = -300, \ |
70 | .completed = -300, \ | |
4300aa64 | 71 | .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \ |
4300aa64 | 72 | .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \ |
64db4cff PM |
73 | .n_force_qs = 0, \ |
74 | .n_force_qs_ngp = 0, \ | |
4300aa64 | 75 | .name = #structname, \ |
64db4cff PM |
76 | } |
77 | ||
d6714c22 PM |
78 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
79 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); | |
64db4cff | 80 | |
6258c4fb IM |
81 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
82 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); | |
b1f77b05 | 83 | |
27f4d280 PM |
84 | static struct rcu_state *rcu_state; |
85 | ||
bbad9379 PM |
86 | int rcu_scheduler_active __read_mostly; |
87 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
88 | ||
a26ac245 PM |
89 | /* |
90 | * Control variables for per-CPU and per-rcu_node kthreads. These | |
91 | * handle all flavors of RCU. | |
92 | */ | |
93 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); | |
d71df90e | 94 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
a26ac245 | 95 | static DEFINE_PER_CPU(wait_queue_head_t, rcu_cpu_wq); |
d71df90e | 96 | DEFINE_PER_CPU(char, rcu_cpu_has_work); |
a26ac245 PM |
97 | static char rcu_kthreads_spawnable; |
98 | ||
0f962a5e | 99 | static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
27f4d280 | 100 | static void invoke_rcu_cpu_kthread(void); |
a26ac245 PM |
101 | |
102 | #define RCU_KTHREAD_PRIO 1 /* RT priority for per-CPU kthreads. */ | |
103 | ||
4a298656 PM |
104 | /* |
105 | * Track the rcutorture test sequence number and the update version | |
106 | * number within a given test. The rcutorture_testseq is incremented | |
107 | * on every rcutorture module load and unload, so has an odd value | |
108 | * when a test is running. The rcutorture_vernum is set to zero | |
109 | * when rcutorture starts and is incremented on each rcutorture update. | |
110 | * These variables enable correlating rcutorture output with the | |
111 | * RCU tracing information. | |
112 | */ | |
113 | unsigned long rcutorture_testseq; | |
114 | unsigned long rcutorture_vernum; | |
115 | ||
fc2219d4 PM |
116 | /* |
117 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
118 | * permit this function to be invoked without holding the root rcu_node | |
119 | * structure's ->lock, but of course results can be subject to change. | |
120 | */ | |
121 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
122 | { | |
123 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
124 | } | |
125 | ||
b1f77b05 | 126 | /* |
d6714c22 | 127 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 128 | * how many quiescent states passed, just if there was at least |
d6714c22 | 129 | * one since the start of the grace period, this just sets a flag. |
b1f77b05 | 130 | */ |
d6714c22 | 131 | void rcu_sched_qs(int cpu) |
b1f77b05 | 132 | { |
25502a6c | 133 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
f41d911f | 134 | |
c64ac3ce | 135 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
c3422bea PM |
136 | barrier(); |
137 | rdp->passed_quiesc = 1; | |
b1f77b05 IM |
138 | } |
139 | ||
d6714c22 | 140 | void rcu_bh_qs(int cpu) |
b1f77b05 | 141 | { |
25502a6c | 142 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
f41d911f | 143 | |
c64ac3ce | 144 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
c3422bea PM |
145 | barrier(); |
146 | rdp->passed_quiesc = 1; | |
b1f77b05 | 147 | } |
64db4cff | 148 | |
25502a6c PM |
149 | /* |
150 | * Note a context switch. This is a quiescent state for RCU-sched, | |
151 | * and requires special handling for preemptible RCU. | |
152 | */ | |
153 | void rcu_note_context_switch(int cpu) | |
154 | { | |
155 | rcu_sched_qs(cpu); | |
156 | rcu_preempt_note_context_switch(cpu); | |
157 | } | |
158 | ||
64db4cff | 159 | #ifdef CONFIG_NO_HZ |
90a4d2c0 PM |
160 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
161 | .dynticks_nesting = 1, | |
e59fb312 | 162 | .dynticks = ATOMIC_INIT(1), |
90a4d2c0 | 163 | }; |
64db4cff PM |
164 | #endif /* #ifdef CONFIG_NO_HZ */ |
165 | ||
166 | static int blimit = 10; /* Maximum callbacks per softirq. */ | |
167 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ | |
168 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ | |
169 | ||
3d76c082 PM |
170 | module_param(blimit, int, 0); |
171 | module_param(qhimark, int, 0); | |
172 | module_param(qlowmark, int, 0); | |
173 | ||
a00e0d71 | 174 | int rcu_cpu_stall_suppress __read_mostly; |
f2e0dd70 | 175 | module_param(rcu_cpu_stall_suppress, int, 0644); |
742734ee | 176 | |
64db4cff | 177 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
a157229c | 178 | static int rcu_pending(int cpu); |
64db4cff PM |
179 | |
180 | /* | |
d6714c22 | 181 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 182 | */ |
d6714c22 | 183 | long rcu_batches_completed_sched(void) |
64db4cff | 184 | { |
d6714c22 | 185 | return rcu_sched_state.completed; |
64db4cff | 186 | } |
d6714c22 | 187 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
188 | |
189 | /* | |
190 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
191 | */ | |
192 | long rcu_batches_completed_bh(void) | |
193 | { | |
194 | return rcu_bh_state.completed; | |
195 | } | |
196 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
197 | ||
bf66f18e PM |
198 | /* |
199 | * Force a quiescent state for RCU BH. | |
200 | */ | |
201 | void rcu_bh_force_quiescent_state(void) | |
202 | { | |
203 | force_quiescent_state(&rcu_bh_state, 0); | |
204 | } | |
205 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
206 | ||
4a298656 PM |
207 | /* |
208 | * Record the number of times rcutorture tests have been initiated and | |
209 | * terminated. This information allows the debugfs tracing stats to be | |
210 | * correlated to the rcutorture messages, even when the rcutorture module | |
211 | * is being repeatedly loaded and unloaded. In other words, we cannot | |
212 | * store this state in rcutorture itself. | |
213 | */ | |
214 | void rcutorture_record_test_transition(void) | |
215 | { | |
216 | rcutorture_testseq++; | |
217 | rcutorture_vernum = 0; | |
218 | } | |
219 | EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); | |
220 | ||
221 | /* | |
222 | * Record the number of writer passes through the current rcutorture test. | |
223 | * This is also used to correlate debugfs tracing stats with the rcutorture | |
224 | * messages. | |
225 | */ | |
226 | void rcutorture_record_progress(unsigned long vernum) | |
227 | { | |
228 | rcutorture_vernum++; | |
229 | } | |
230 | EXPORT_SYMBOL_GPL(rcutorture_record_progress); | |
231 | ||
bf66f18e PM |
232 | /* |
233 | * Force a quiescent state for RCU-sched. | |
234 | */ | |
235 | void rcu_sched_force_quiescent_state(void) | |
236 | { | |
237 | force_quiescent_state(&rcu_sched_state, 0); | |
238 | } | |
239 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
240 | ||
64db4cff PM |
241 | /* |
242 | * Does the CPU have callbacks ready to be invoked? | |
243 | */ | |
244 | static int | |
245 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
246 | { | |
247 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; | |
248 | } | |
249 | ||
250 | /* | |
251 | * Does the current CPU require a yet-as-unscheduled grace period? | |
252 | */ | |
253 | static int | |
254 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
255 | { | |
fc2219d4 | 256 | return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
64db4cff PM |
257 | } |
258 | ||
259 | /* | |
260 | * Return the root node of the specified rcu_state structure. | |
261 | */ | |
262 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
263 | { | |
264 | return &rsp->node[0]; | |
265 | } | |
266 | ||
267 | #ifdef CONFIG_SMP | |
268 | ||
269 | /* | |
270 | * If the specified CPU is offline, tell the caller that it is in | |
271 | * a quiescent state. Otherwise, whack it with a reschedule IPI. | |
272 | * Grace periods can end up waiting on an offline CPU when that | |
273 | * CPU is in the process of coming online -- it will be added to the | |
274 | * rcu_node bitmasks before it actually makes it online. The same thing | |
275 | * can happen while a CPU is in the process of coming online. Because this | |
276 | * race is quite rare, we check for it after detecting that the grace | |
277 | * period has been delayed rather than checking each and every CPU | |
278 | * each and every time we start a new grace period. | |
279 | */ | |
280 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) | |
281 | { | |
282 | /* | |
283 | * If the CPU is offline, it is in a quiescent state. We can | |
284 | * trust its state not to change because interrupts are disabled. | |
285 | */ | |
286 | if (cpu_is_offline(rdp->cpu)) { | |
287 | rdp->offline_fqs++; | |
288 | return 1; | |
289 | } | |
290 | ||
f41d911f PM |
291 | /* If preemptable RCU, no point in sending reschedule IPI. */ |
292 | if (rdp->preemptable) | |
293 | return 0; | |
294 | ||
64db4cff PM |
295 | /* The CPU is online, so send it a reschedule IPI. */ |
296 | if (rdp->cpu != smp_processor_id()) | |
297 | smp_send_reschedule(rdp->cpu); | |
298 | else | |
299 | set_need_resched(); | |
300 | rdp->resched_ipi++; | |
301 | return 0; | |
302 | } | |
303 | ||
304 | #endif /* #ifdef CONFIG_SMP */ | |
305 | ||
306 | #ifdef CONFIG_NO_HZ | |
64db4cff PM |
307 | |
308 | /** | |
309 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz | |
310 | * | |
311 | * Enter nohz mode, in other words, -leave- the mode in which RCU | |
312 | * read-side critical sections can occur. (Though RCU read-side | |
313 | * critical sections can occur in irq handlers in nohz mode, a possibility | |
314 | * handled by rcu_irq_enter() and rcu_irq_exit()). | |
315 | */ | |
316 | void rcu_enter_nohz(void) | |
317 | { | |
318 | unsigned long flags; | |
319 | struct rcu_dynticks *rdtp; | |
320 | ||
64db4cff PM |
321 | local_irq_save(flags); |
322 | rdtp = &__get_cpu_var(rcu_dynticks); | |
e59fb312 PM |
323 | if (--rdtp->dynticks_nesting) { |
324 | local_irq_restore(flags); | |
325 | return; | |
326 | } | |
327 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ | |
328 | smp_mb__before_atomic_inc(); /* See above. */ | |
329 | atomic_inc(&rdtp->dynticks); | |
330 | smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ | |
331 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
64db4cff | 332 | local_irq_restore(flags); |
e59fb312 PM |
333 | |
334 | /* If the interrupt queued a callback, get out of dyntick mode. */ | |
335 | if (in_irq() && | |
336 | (__get_cpu_var(rcu_sched_data).nxtlist || | |
337 | __get_cpu_var(rcu_bh_data).nxtlist || | |
338 | rcu_preempt_needs_cpu(smp_processor_id()))) | |
339 | set_need_resched(); | |
64db4cff PM |
340 | } |
341 | ||
342 | /* | |
343 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz | |
344 | * | |
345 | * Exit nohz mode, in other words, -enter- the mode in which RCU | |
346 | * read-side critical sections normally occur. | |
347 | */ | |
348 | void rcu_exit_nohz(void) | |
349 | { | |
350 | unsigned long flags; | |
351 | struct rcu_dynticks *rdtp; | |
352 | ||
353 | local_irq_save(flags); | |
354 | rdtp = &__get_cpu_var(rcu_dynticks); | |
e59fb312 PM |
355 | if (rdtp->dynticks_nesting++) { |
356 | local_irq_restore(flags); | |
357 | return; | |
358 | } | |
359 | smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ | |
360 | atomic_inc(&rdtp->dynticks); | |
361 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
362 | smp_mb__after_atomic_inc(); /* See above. */ | |
363 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
64db4cff | 364 | local_irq_restore(flags); |
64db4cff PM |
365 | } |
366 | ||
367 | /** | |
368 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
369 | * | |
370 | * If the CPU was idle with dynamic ticks active, and there is no | |
371 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
372 | * RCU grace-period handling know that the CPU is active. | |
373 | */ | |
374 | void rcu_nmi_enter(void) | |
375 | { | |
376 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
377 | ||
e59fb312 PM |
378 | if (rdtp->dynticks_nmi_nesting == 0 && |
379 | (atomic_read(&rdtp->dynticks) & 0x1)) | |
64db4cff | 380 | return; |
e59fb312 PM |
381 | rdtp->dynticks_nmi_nesting++; |
382 | smp_mb__before_atomic_inc(); /* Force delay from prior write. */ | |
383 | atomic_inc(&rdtp->dynticks); | |
384 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
385 | smp_mb__after_atomic_inc(); /* See above. */ | |
386 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
64db4cff PM |
387 | } |
388 | ||
389 | /** | |
390 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
391 | * | |
392 | * If the CPU was idle with dynamic ticks active, and there is no | |
393 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
394 | * RCU grace-period handling know that the CPU is no longer active. | |
395 | */ | |
396 | void rcu_nmi_exit(void) | |
397 | { | |
398 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
399 | ||
e59fb312 PM |
400 | if (rdtp->dynticks_nmi_nesting == 0 || |
401 | --rdtp->dynticks_nmi_nesting != 0) | |
64db4cff | 402 | return; |
e59fb312 PM |
403 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
404 | smp_mb__before_atomic_inc(); /* See above. */ | |
405 | atomic_inc(&rdtp->dynticks); | |
406 | smp_mb__after_atomic_inc(); /* Force delay to next write. */ | |
407 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
64db4cff PM |
408 | } |
409 | ||
410 | /** | |
411 | * rcu_irq_enter - inform RCU of entry to hard irq context | |
412 | * | |
413 | * If the CPU was idle with dynamic ticks active, this updates the | |
414 | * rdtp->dynticks to let the RCU handling know that the CPU is active. | |
415 | */ | |
416 | void rcu_irq_enter(void) | |
417 | { | |
e59fb312 | 418 | rcu_exit_nohz(); |
64db4cff PM |
419 | } |
420 | ||
421 | /** | |
422 | * rcu_irq_exit - inform RCU of exit from hard irq context | |
423 | * | |
424 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks | |
425 | * to put let the RCU handling be aware that the CPU is going back to idle | |
426 | * with no ticks. | |
427 | */ | |
428 | void rcu_irq_exit(void) | |
429 | { | |
e59fb312 | 430 | rcu_enter_nohz(); |
64db4cff PM |
431 | } |
432 | ||
64db4cff PM |
433 | #ifdef CONFIG_SMP |
434 | ||
64db4cff PM |
435 | /* |
436 | * Snapshot the specified CPU's dynticks counter so that we can later | |
437 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 438 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff PM |
439 | */ |
440 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
441 | { | |
e59fb312 PM |
442 | rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
443 | return 0; | |
64db4cff PM |
444 | } |
445 | ||
446 | /* | |
447 | * Return true if the specified CPU has passed through a quiescent | |
448 | * state by virtue of being in or having passed through an dynticks | |
449 | * idle state since the last call to dyntick_save_progress_counter() | |
450 | * for this same CPU. | |
451 | */ | |
452 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
453 | { | |
e59fb312 PM |
454 | unsigned long curr; |
455 | unsigned long snap; | |
64db4cff | 456 | |
e59fb312 PM |
457 | curr = (unsigned long)atomic_add_return(0, &rdp->dynticks->dynticks); |
458 | snap = (unsigned long)rdp->dynticks_snap; | |
64db4cff PM |
459 | |
460 | /* | |
461 | * If the CPU passed through or entered a dynticks idle phase with | |
462 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
463 | * already acknowledged the request to pass through a quiescent | |
464 | * state. Either way, that CPU cannot possibly be in an RCU | |
465 | * read-side critical section that started before the beginning | |
466 | * of the current RCU grace period. | |
467 | */ | |
e59fb312 | 468 | if ((curr & 0x1) == 0 || ULONG_CMP_GE(curr, snap + 2)) { |
64db4cff PM |
469 | rdp->dynticks_fqs++; |
470 | return 1; | |
471 | } | |
472 | ||
473 | /* Go check for the CPU being offline. */ | |
474 | return rcu_implicit_offline_qs(rdp); | |
475 | } | |
476 | ||
477 | #endif /* #ifdef CONFIG_SMP */ | |
478 | ||
479 | #else /* #ifdef CONFIG_NO_HZ */ | |
480 | ||
64db4cff PM |
481 | #ifdef CONFIG_SMP |
482 | ||
64db4cff PM |
483 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
484 | { | |
485 | return 0; | |
486 | } | |
487 | ||
488 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
489 | { | |
490 | return rcu_implicit_offline_qs(rdp); | |
491 | } | |
492 | ||
493 | #endif /* #ifdef CONFIG_SMP */ | |
494 | ||
495 | #endif /* #else #ifdef CONFIG_NO_HZ */ | |
496 | ||
742734ee | 497 | int rcu_cpu_stall_suppress __read_mostly; |
c68de209 | 498 | |
64db4cff PM |
499 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
500 | { | |
501 | rsp->gp_start = jiffies; | |
502 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; | |
503 | } | |
504 | ||
505 | static void print_other_cpu_stall(struct rcu_state *rsp) | |
506 | { | |
507 | int cpu; | |
508 | long delta; | |
509 | unsigned long flags; | |
510 | struct rcu_node *rnp = rcu_get_root(rsp); | |
64db4cff PM |
511 | |
512 | /* Only let one CPU complain about others per time interval. */ | |
513 | ||
1304afb2 | 514 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 515 | delta = jiffies - rsp->jiffies_stall; |
fc2219d4 | 516 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
1304afb2 | 517 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
518 | return; |
519 | } | |
520 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
a0b6c9a7 PM |
521 | |
522 | /* | |
523 | * Now rat on any tasks that got kicked up to the root rcu_node | |
524 | * due to CPU offlining. | |
525 | */ | |
526 | rcu_print_task_stall(rnp); | |
1304afb2 | 527 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 528 | |
8cdd32a9 PM |
529 | /* |
530 | * OK, time to rat on our buddy... | |
531 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
532 | * RCU CPU stall warnings. | |
533 | */ | |
4300aa64 PM |
534 | printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {", |
535 | rsp->name); | |
a0b6c9a7 | 536 | rcu_for_each_leaf_node(rsp, rnp) { |
3acd9eb3 | 537 | raw_spin_lock_irqsave(&rnp->lock, flags); |
f41d911f | 538 | rcu_print_task_stall(rnp); |
3acd9eb3 | 539 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
a0b6c9a7 | 540 | if (rnp->qsmask == 0) |
64db4cff | 541 | continue; |
a0b6c9a7 PM |
542 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
543 | if (rnp->qsmask & (1UL << cpu)) | |
544 | printk(" %d", rnp->grplo + cpu); | |
64db4cff | 545 | } |
4300aa64 | 546 | printk("} (detected by %d, t=%ld jiffies)\n", |
64db4cff | 547 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
c1dc0b9c IM |
548 | trigger_all_cpu_backtrace(); |
549 | ||
1ed509a2 PM |
550 | /* If so configured, complain about tasks blocking the grace period. */ |
551 | ||
552 | rcu_print_detail_task_stall(rsp); | |
553 | ||
64db4cff PM |
554 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
555 | } | |
556 | ||
557 | static void print_cpu_stall(struct rcu_state *rsp) | |
558 | { | |
559 | unsigned long flags; | |
560 | struct rcu_node *rnp = rcu_get_root(rsp); | |
561 | ||
8cdd32a9 PM |
562 | /* |
563 | * OK, time to rat on ourselves... | |
564 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
565 | * RCU CPU stall warnings. | |
566 | */ | |
4300aa64 PM |
567 | printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n", |
568 | rsp->name, smp_processor_id(), jiffies - rsp->gp_start); | |
c1dc0b9c IM |
569 | trigger_all_cpu_backtrace(); |
570 | ||
1304afb2 | 571 | raw_spin_lock_irqsave(&rnp->lock, flags); |
20133cfc | 572 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
64db4cff PM |
573 | rsp->jiffies_stall = |
574 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
1304afb2 | 575 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c1dc0b9c | 576 | |
64db4cff PM |
577 | set_need_resched(); /* kick ourselves to get things going. */ |
578 | } | |
579 | ||
580 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
581 | { | |
582 | long delta; | |
583 | struct rcu_node *rnp; | |
584 | ||
742734ee | 585 | if (rcu_cpu_stall_suppress) |
c68de209 | 586 | return; |
4ee0a603 | 587 | delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall); |
64db4cff | 588 | rnp = rdp->mynode; |
4ee0a603 | 589 | if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && delta >= 0) { |
64db4cff PM |
590 | |
591 | /* We haven't checked in, so go dump stack. */ | |
592 | print_cpu_stall(rsp); | |
593 | ||
fc2219d4 | 594 | } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) { |
64db4cff PM |
595 | |
596 | /* They had two time units to dump stack, so complain. */ | |
597 | print_other_cpu_stall(rsp); | |
598 | } | |
599 | } | |
600 | ||
c68de209 PM |
601 | static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
602 | { | |
742734ee | 603 | rcu_cpu_stall_suppress = 1; |
c68de209 PM |
604 | return NOTIFY_DONE; |
605 | } | |
606 | ||
53d84e00 PM |
607 | /** |
608 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
609 | * | |
610 | * Set the stall-warning timeout way off into the future, thus preventing | |
611 | * any RCU CPU stall-warning messages from appearing in the current set of | |
612 | * RCU grace periods. | |
613 | * | |
614 | * The caller must disable hard irqs. | |
615 | */ | |
616 | void rcu_cpu_stall_reset(void) | |
617 | { | |
618 | rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2; | |
619 | rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2; | |
620 | rcu_preempt_stall_reset(); | |
621 | } | |
622 | ||
c68de209 PM |
623 | static struct notifier_block rcu_panic_block = { |
624 | .notifier_call = rcu_panic, | |
625 | }; | |
626 | ||
627 | static void __init check_cpu_stall_init(void) | |
628 | { | |
629 | atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); | |
630 | } | |
631 | ||
64db4cff PM |
632 | /* |
633 | * Update CPU-local rcu_data state to record the newly noticed grace period. | |
634 | * This is used both when we started the grace period and when we notice | |
9160306e PM |
635 | * that someone else started the grace period. The caller must hold the |
636 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, | |
637 | * and must have irqs disabled. | |
64db4cff | 638 | */ |
9160306e PM |
639 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
640 | { | |
641 | if (rdp->gpnum != rnp->gpnum) { | |
121dfc4b PM |
642 | /* |
643 | * If the current grace period is waiting for this CPU, | |
644 | * set up to detect a quiescent state, otherwise don't | |
645 | * go looking for one. | |
646 | */ | |
9160306e | 647 | rdp->gpnum = rnp->gpnum; |
121dfc4b PM |
648 | if (rnp->qsmask & rdp->grpmask) { |
649 | rdp->qs_pending = 1; | |
650 | rdp->passed_quiesc = 0; | |
651 | } else | |
652 | rdp->qs_pending = 0; | |
9160306e PM |
653 | } |
654 | } | |
655 | ||
64db4cff PM |
656 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
657 | { | |
9160306e PM |
658 | unsigned long flags; |
659 | struct rcu_node *rnp; | |
660 | ||
661 | local_irq_save(flags); | |
662 | rnp = rdp->mynode; | |
663 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ | |
1304afb2 | 664 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
9160306e PM |
665 | local_irq_restore(flags); |
666 | return; | |
667 | } | |
668 | __note_new_gpnum(rsp, rnp, rdp); | |
1304afb2 | 669 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
670 | } |
671 | ||
672 | /* | |
673 | * Did someone else start a new RCU grace period start since we last | |
674 | * checked? Update local state appropriately if so. Must be called | |
675 | * on the CPU corresponding to rdp. | |
676 | */ | |
677 | static int | |
678 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) | |
679 | { | |
680 | unsigned long flags; | |
681 | int ret = 0; | |
682 | ||
683 | local_irq_save(flags); | |
684 | if (rdp->gpnum != rsp->gpnum) { | |
685 | note_new_gpnum(rsp, rdp); | |
686 | ret = 1; | |
687 | } | |
688 | local_irq_restore(flags); | |
689 | return ret; | |
690 | } | |
691 | ||
d09b62df PM |
692 | /* |
693 | * Advance this CPU's callbacks, but only if the current grace period | |
694 | * has ended. This may be called only from the CPU to whom the rdp | |
695 | * belongs. In addition, the corresponding leaf rcu_node structure's | |
696 | * ->lock must be held by the caller, with irqs disabled. | |
697 | */ | |
698 | static void | |
699 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
700 | { | |
701 | /* Did another grace period end? */ | |
702 | if (rdp->completed != rnp->completed) { | |
703 | ||
704 | /* Advance callbacks. No harm if list empty. */ | |
705 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; | |
706 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; | |
707 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
708 | ||
709 | /* Remember that we saw this grace-period completion. */ | |
710 | rdp->completed = rnp->completed; | |
20377f32 | 711 | |
5ff8e6f0 FW |
712 | /* |
713 | * If we were in an extended quiescent state, we may have | |
121dfc4b | 714 | * missed some grace periods that others CPUs handled on |
5ff8e6f0 | 715 | * our behalf. Catch up with this state to avoid noting |
121dfc4b PM |
716 | * spurious new grace periods. If another grace period |
717 | * has started, then rnp->gpnum will have advanced, so | |
718 | * we will detect this later on. | |
5ff8e6f0 | 719 | */ |
121dfc4b | 720 | if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) |
5ff8e6f0 FW |
721 | rdp->gpnum = rdp->completed; |
722 | ||
20377f32 | 723 | /* |
121dfc4b PM |
724 | * If RCU does not need a quiescent state from this CPU, |
725 | * then make sure that this CPU doesn't go looking for one. | |
20377f32 | 726 | */ |
121dfc4b | 727 | if ((rnp->qsmask & rdp->grpmask) == 0) |
20377f32 | 728 | rdp->qs_pending = 0; |
d09b62df PM |
729 | } |
730 | } | |
731 | ||
732 | /* | |
733 | * Advance this CPU's callbacks, but only if the current grace period | |
734 | * has ended. This may be called only from the CPU to whom the rdp | |
735 | * belongs. | |
736 | */ | |
737 | static void | |
738 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) | |
739 | { | |
740 | unsigned long flags; | |
741 | struct rcu_node *rnp; | |
742 | ||
743 | local_irq_save(flags); | |
744 | rnp = rdp->mynode; | |
745 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ | |
1304afb2 | 746 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
d09b62df PM |
747 | local_irq_restore(flags); |
748 | return; | |
749 | } | |
750 | __rcu_process_gp_end(rsp, rnp, rdp); | |
1304afb2 | 751 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d09b62df PM |
752 | } |
753 | ||
754 | /* | |
755 | * Do per-CPU grace-period initialization for running CPU. The caller | |
756 | * must hold the lock of the leaf rcu_node structure corresponding to | |
757 | * this CPU. | |
758 | */ | |
759 | static void | |
760 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
761 | { | |
762 | /* Prior grace period ended, so advance callbacks for current CPU. */ | |
763 | __rcu_process_gp_end(rsp, rnp, rdp); | |
764 | ||
765 | /* | |
766 | * Because this CPU just now started the new grace period, we know | |
767 | * that all of its callbacks will be covered by this upcoming grace | |
768 | * period, even the ones that were registered arbitrarily recently. | |
769 | * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. | |
770 | * | |
771 | * Other CPUs cannot be sure exactly when the grace period started. | |
772 | * Therefore, their recently registered callbacks must pass through | |
773 | * an additional RCU_NEXT_READY stage, so that they will be handled | |
774 | * by the next RCU grace period. | |
775 | */ | |
776 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
777 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
9160306e PM |
778 | |
779 | /* Set state so that this CPU will detect the next quiescent state. */ | |
780 | __note_new_gpnum(rsp, rnp, rdp); | |
d09b62df PM |
781 | } |
782 | ||
64db4cff PM |
783 | /* |
784 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
785 | * in preparation for detecting the next grace period. The caller must hold | |
786 | * the root node's ->lock, which is released before return. Hard irqs must | |
787 | * be disabled. | |
788 | */ | |
789 | static void | |
790 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) | |
791 | __releases(rcu_get_root(rsp)->lock) | |
792 | { | |
394f99a9 | 793 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
64db4cff | 794 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 795 | |
07079d53 | 796 | if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) { |
46a1e34e PM |
797 | if (cpu_needs_another_gp(rsp, rdp)) |
798 | rsp->fqs_need_gp = 1; | |
b32e9eb6 | 799 | if (rnp->completed == rsp->completed) { |
1304afb2 | 800 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b32e9eb6 PM |
801 | return; |
802 | } | |
1304afb2 | 803 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
b32e9eb6 PM |
804 | |
805 | /* | |
806 | * Propagate new ->completed value to rcu_node structures | |
807 | * so that other CPUs don't have to wait until the start | |
808 | * of the next grace period to process their callbacks. | |
809 | */ | |
810 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
1304afb2 | 811 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
b32e9eb6 | 812 | rnp->completed = rsp->completed; |
1304afb2 | 813 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
b32e9eb6 PM |
814 | } |
815 | local_irq_restore(flags); | |
64db4cff PM |
816 | return; |
817 | } | |
818 | ||
819 | /* Advance to a new grace period and initialize state. */ | |
820 | rsp->gpnum++; | |
c3422bea | 821 | WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
64db4cff PM |
822 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
823 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; | |
64db4cff | 824 | record_gp_stall_check_time(rsp); |
64db4cff | 825 | |
64db4cff PM |
826 | /* Special-case the common single-level case. */ |
827 | if (NUM_RCU_NODES == 1) { | |
b0e165c0 | 828 | rcu_preempt_check_blocked_tasks(rnp); |
28ecd580 | 829 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 830 | rnp->gpnum = rsp->gpnum; |
d09b62df | 831 | rnp->completed = rsp->completed; |
c12172c0 | 832 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
d09b62df | 833 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
27f4d280 | 834 | rcu_preempt_boost_start_gp(rnp); |
1304afb2 | 835 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
836 | return; |
837 | } | |
838 | ||
1304afb2 | 839 | raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
64db4cff PM |
840 | |
841 | ||
842 | /* Exclude any concurrent CPU-hotplug operations. */ | |
1304afb2 | 843 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
844 | |
845 | /* | |
b835db1f PM |
846 | * Set the quiescent-state-needed bits in all the rcu_node |
847 | * structures for all currently online CPUs in breadth-first | |
848 | * order, starting from the root rcu_node structure. This | |
849 | * operation relies on the layout of the hierarchy within the | |
850 | * rsp->node[] array. Note that other CPUs will access only | |
851 | * the leaves of the hierarchy, which still indicate that no | |
852 | * grace period is in progress, at least until the corresponding | |
853 | * leaf node has been initialized. In addition, we have excluded | |
854 | * CPU-hotplug operations. | |
64db4cff PM |
855 | * |
856 | * Note that the grace period cannot complete until we finish | |
857 | * the initialization process, as there will be at least one | |
858 | * qsmask bit set in the root node until that time, namely the | |
b835db1f PM |
859 | * one corresponding to this CPU, due to the fact that we have |
860 | * irqs disabled. | |
64db4cff | 861 | */ |
a0b6c9a7 | 862 | rcu_for_each_node_breadth_first(rsp, rnp) { |
1304afb2 | 863 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
b0e165c0 | 864 | rcu_preempt_check_blocked_tasks(rnp); |
49e29126 | 865 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 866 | rnp->gpnum = rsp->gpnum; |
d09b62df PM |
867 | rnp->completed = rsp->completed; |
868 | if (rnp == rdp->mynode) | |
869 | rcu_start_gp_per_cpu(rsp, rnp, rdp); | |
27f4d280 | 870 | rcu_preempt_boost_start_gp(rnp); |
1304afb2 | 871 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
872 | } |
873 | ||
83f5b01f | 874 | rnp = rcu_get_root(rsp); |
1304afb2 | 875 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff | 876 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
1304afb2 PM |
877 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
878 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); | |
64db4cff PM |
879 | } |
880 | ||
f41d911f | 881 | /* |
d3f6bad3 PM |
882 | * Report a full set of quiescent states to the specified rcu_state |
883 | * data structure. This involves cleaning up after the prior grace | |
884 | * period and letting rcu_start_gp() start up the next grace period | |
885 | * if one is needed. Note that the caller must hold rnp->lock, as | |
886 | * required by rcu_start_gp(), which will release it. | |
f41d911f | 887 | */ |
d3f6bad3 | 888 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 889 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 890 | { |
fc2219d4 | 891 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
e59fb312 PM |
892 | |
893 | /* | |
894 | * Ensure that all grace-period and pre-grace-period activity | |
895 | * is seen before the assignment to rsp->completed. | |
896 | */ | |
897 | smp_mb(); /* See above block comment. */ | |
f41d911f | 898 | rsp->completed = rsp->gpnum; |
83f5b01f | 899 | rsp->signaled = RCU_GP_IDLE; |
f41d911f PM |
900 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
901 | } | |
902 | ||
64db4cff | 903 | /* |
d3f6bad3 PM |
904 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
905 | * Allows quiescent states for a group of CPUs to be reported at one go | |
906 | * to the specified rcu_node structure, though all the CPUs in the group | |
907 | * must be represented by the same rcu_node structure (which need not be | |
908 | * a leaf rcu_node structure, though it often will be). That structure's | |
909 | * lock must be held upon entry, and it is released before return. | |
64db4cff PM |
910 | */ |
911 | static void | |
d3f6bad3 PM |
912 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
913 | struct rcu_node *rnp, unsigned long flags) | |
64db4cff PM |
914 | __releases(rnp->lock) |
915 | { | |
28ecd580 PM |
916 | struct rcu_node *rnp_c; |
917 | ||
64db4cff PM |
918 | /* Walk up the rcu_node hierarchy. */ |
919 | for (;;) { | |
920 | if (!(rnp->qsmask & mask)) { | |
921 | ||
922 | /* Our bit has already been cleared, so done. */ | |
1304afb2 | 923 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
924 | return; |
925 | } | |
926 | rnp->qsmask &= ~mask; | |
27f4d280 | 927 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
64db4cff PM |
928 | |
929 | /* Other bits still set at this level, so done. */ | |
1304afb2 | 930 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
931 | return; |
932 | } | |
933 | mask = rnp->grpmask; | |
934 | if (rnp->parent == NULL) { | |
935 | ||
936 | /* No more levels. Exit loop holding root lock. */ | |
937 | ||
938 | break; | |
939 | } | |
1304afb2 | 940 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
28ecd580 | 941 | rnp_c = rnp; |
64db4cff | 942 | rnp = rnp->parent; |
1304afb2 | 943 | raw_spin_lock_irqsave(&rnp->lock, flags); |
28ecd580 | 944 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
945 | } |
946 | ||
947 | /* | |
948 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 949 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 950 | * to clean up and start the next grace period if one is needed. |
64db4cff | 951 | */ |
d3f6bad3 | 952 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
953 | } |
954 | ||
955 | /* | |
d3f6bad3 PM |
956 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
957 | * structure. This must be either called from the specified CPU, or | |
958 | * called when the specified CPU is known to be offline (and when it is | |
959 | * also known that no other CPU is concurrently trying to help the offline | |
960 | * CPU). The lastcomp argument is used to make sure we are still in the | |
961 | * grace period of interest. We don't want to end the current grace period | |
962 | * based on quiescent states detected in an earlier grace period! | |
64db4cff PM |
963 | */ |
964 | static void | |
d3f6bad3 | 965 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) |
64db4cff PM |
966 | { |
967 | unsigned long flags; | |
968 | unsigned long mask; | |
969 | struct rcu_node *rnp; | |
970 | ||
971 | rnp = rdp->mynode; | |
1304afb2 | 972 | raw_spin_lock_irqsave(&rnp->lock, flags); |
560d4bc0 | 973 | if (lastcomp != rnp->completed) { |
64db4cff PM |
974 | |
975 | /* | |
976 | * Someone beat us to it for this grace period, so leave. | |
977 | * The race with GP start is resolved by the fact that we | |
978 | * hold the leaf rcu_node lock, so that the per-CPU bits | |
979 | * cannot yet be initialized -- so we would simply find our | |
d3f6bad3 PM |
980 | * CPU's bit already cleared in rcu_report_qs_rnp() if this |
981 | * race occurred. | |
64db4cff PM |
982 | */ |
983 | rdp->passed_quiesc = 0; /* try again later! */ | |
1304afb2 | 984 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
985 | return; |
986 | } | |
987 | mask = rdp->grpmask; | |
988 | if ((rnp->qsmask & mask) == 0) { | |
1304afb2 | 989 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
990 | } else { |
991 | rdp->qs_pending = 0; | |
992 | ||
993 | /* | |
994 | * This GP can't end until cpu checks in, so all of our | |
995 | * callbacks can be processed during the next GP. | |
996 | */ | |
64db4cff PM |
997 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
998 | ||
d3f6bad3 | 999 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
64db4cff PM |
1000 | } |
1001 | } | |
1002 | ||
1003 | /* | |
1004 | * Check to see if there is a new grace period of which this CPU | |
1005 | * is not yet aware, and if so, set up local rcu_data state for it. | |
1006 | * Otherwise, see if this CPU has just passed through its first | |
1007 | * quiescent state for this grace period, and record that fact if so. | |
1008 | */ | |
1009 | static void | |
1010 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
1011 | { | |
1012 | /* If there is now a new grace period, record and return. */ | |
1013 | if (check_for_new_grace_period(rsp, rdp)) | |
1014 | return; | |
1015 | ||
1016 | /* | |
1017 | * Does this CPU still need to do its part for current grace period? | |
1018 | * If no, return and let the other CPUs do their part as well. | |
1019 | */ | |
1020 | if (!rdp->qs_pending) | |
1021 | return; | |
1022 | ||
1023 | /* | |
1024 | * Was there a quiescent state since the beginning of the grace | |
1025 | * period? If no, then exit and wait for the next call. | |
1026 | */ | |
1027 | if (!rdp->passed_quiesc) | |
1028 | return; | |
1029 | ||
d3f6bad3 PM |
1030 | /* |
1031 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
1032 | * judge of that). | |
1033 | */ | |
1034 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); | |
64db4cff PM |
1035 | } |
1036 | ||
1037 | #ifdef CONFIG_HOTPLUG_CPU | |
1038 | ||
e74f4c45 | 1039 | /* |
29494be7 LJ |
1040 | * Move a dying CPU's RCU callbacks to online CPU's callback list. |
1041 | * Synchronization is not required because this function executes | |
1042 | * in stop_machine() context. | |
e74f4c45 | 1043 | */ |
29494be7 | 1044 | static void rcu_send_cbs_to_online(struct rcu_state *rsp) |
e74f4c45 PM |
1045 | { |
1046 | int i; | |
29494be7 LJ |
1047 | /* current DYING CPU is cleared in the cpu_online_mask */ |
1048 | int receive_cpu = cpumask_any(cpu_online_mask); | |
394f99a9 | 1049 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
29494be7 | 1050 | struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu); |
e74f4c45 PM |
1051 | |
1052 | if (rdp->nxtlist == NULL) | |
1053 | return; /* irqs disabled, so comparison is stable. */ | |
29494be7 LJ |
1054 | |
1055 | *receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist; | |
1056 | receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
1057 | receive_rdp->qlen += rdp->qlen; | |
1058 | receive_rdp->n_cbs_adopted += rdp->qlen; | |
1059 | rdp->n_cbs_orphaned += rdp->qlen; | |
1060 | ||
e74f4c45 PM |
1061 | rdp->nxtlist = NULL; |
1062 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1063 | rdp->nxttail[i] = &rdp->nxtlist; | |
e74f4c45 | 1064 | rdp->qlen = 0; |
e74f4c45 PM |
1065 | } |
1066 | ||
64db4cff PM |
1067 | /* |
1068 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy | |
1069 | * and move all callbacks from the outgoing CPU to the current one. | |
a26ac245 PM |
1070 | * There can only be one CPU hotplug operation at a time, so no other |
1071 | * CPU can be attempting to update rcu_cpu_kthread_task. | |
64db4cff PM |
1072 | */ |
1073 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) | |
1074 | { | |
64db4cff | 1075 | unsigned long flags; |
64db4cff | 1076 | unsigned long mask; |
d9a3da06 | 1077 | int need_report = 0; |
394f99a9 | 1078 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff | 1079 | struct rcu_node *rnp; |
a26ac245 PM |
1080 | struct task_struct *t; |
1081 | ||
1082 | /* Stop the CPU's kthread. */ | |
1083 | t = per_cpu(rcu_cpu_kthread_task, cpu); | |
1084 | if (t != NULL) { | |
1085 | per_cpu(rcu_cpu_kthread_task, cpu) = NULL; | |
1086 | kthread_stop(t); | |
1087 | } | |
64db4cff PM |
1088 | |
1089 | /* Exclude any attempts to start a new grace period. */ | |
1304afb2 | 1090 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
64db4cff PM |
1091 | |
1092 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ | |
28ecd580 | 1093 | rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
64db4cff PM |
1094 | mask = rdp->grpmask; /* rnp->grplo is constant. */ |
1095 | do { | |
1304afb2 | 1096 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
1097 | rnp->qsmaskinit &= ~mask; |
1098 | if (rnp->qsmaskinit != 0) { | |
b668c9cf | 1099 | if (rnp != rdp->mynode) |
1304afb2 | 1100 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
1101 | break; |
1102 | } | |
b668c9cf | 1103 | if (rnp == rdp->mynode) |
d9a3da06 | 1104 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); |
b668c9cf | 1105 | else |
1304afb2 | 1106 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff | 1107 | mask = rnp->grpmask; |
64db4cff PM |
1108 | rnp = rnp->parent; |
1109 | } while (rnp != NULL); | |
64db4cff | 1110 | |
b668c9cf PM |
1111 | /* |
1112 | * We still hold the leaf rcu_node structure lock here, and | |
1113 | * irqs are still disabled. The reason for this subterfuge is | |
d3f6bad3 PM |
1114 | * because invoking rcu_report_unblock_qs_rnp() with ->onofflock |
1115 | * held leads to deadlock. | |
b668c9cf | 1116 | */ |
1304afb2 | 1117 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
b668c9cf | 1118 | rnp = rdp->mynode; |
d9a3da06 | 1119 | if (need_report & RCU_OFL_TASKS_NORM_GP) |
d3f6bad3 | 1120 | rcu_report_unblock_qs_rnp(rnp, flags); |
b668c9cf | 1121 | else |
1304afb2 | 1122 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da06 PM |
1123 | if (need_report & RCU_OFL_TASKS_EXP_GP) |
1124 | rcu_report_exp_rnp(rsp, rnp); | |
a26ac245 PM |
1125 | |
1126 | /* | |
1127 | * If there are no more online CPUs for this rcu_node structure, | |
1128 | * kill the rcu_node structure's kthread. Otherwise, adjust its | |
1129 | * affinity. | |
1130 | */ | |
1131 | t = rnp->node_kthread_task; | |
1132 | if (t != NULL && | |
1133 | rnp->qsmaskinit == 0) { | |
27f4d280 | 1134 | raw_spin_lock_irqsave(&rnp->lock, flags); |
a26ac245 | 1135 | rnp->node_kthread_task = NULL; |
27f4d280 PM |
1136 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1137 | kthread_stop(t); | |
1138 | rcu_stop_boost_kthread(rnp); | |
a26ac245 | 1139 | } else |
0f962a5e | 1140 | rcu_node_kthread_setaffinity(rnp, -1); |
64db4cff PM |
1141 | } |
1142 | ||
1143 | /* | |
1144 | * Remove the specified CPU from the RCU hierarchy and move any pending | |
1145 | * callbacks that it might have to the current CPU. This code assumes | |
1146 | * that at least one CPU in the system will remain running at all times. | |
1147 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. | |
1148 | */ | |
1149 | static void rcu_offline_cpu(int cpu) | |
1150 | { | |
d6714c22 | 1151 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
64db4cff | 1152 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
33f76148 | 1153 | rcu_preempt_offline_cpu(cpu); |
64db4cff PM |
1154 | } |
1155 | ||
1156 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
1157 | ||
29494be7 | 1158 | static void rcu_send_cbs_to_online(struct rcu_state *rsp) |
e74f4c45 PM |
1159 | { |
1160 | } | |
1161 | ||
64db4cff PM |
1162 | static void rcu_offline_cpu(int cpu) |
1163 | { | |
1164 | } | |
1165 | ||
1166 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
1167 | ||
1168 | /* | |
1169 | * Invoke any RCU callbacks that have made it to the end of their grace | |
1170 | * period. Thottle as specified by rdp->blimit. | |
1171 | */ | |
37c72e56 | 1172 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1173 | { |
1174 | unsigned long flags; | |
1175 | struct rcu_head *next, *list, **tail; | |
1176 | int count; | |
1177 | ||
1178 | /* If no callbacks are ready, just return.*/ | |
1179 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) | |
1180 | return; | |
1181 | ||
1182 | /* | |
1183 | * Extract the list of ready callbacks, disabling to prevent | |
1184 | * races with call_rcu() from interrupt handlers. | |
1185 | */ | |
1186 | local_irq_save(flags); | |
1187 | list = rdp->nxtlist; | |
1188 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
1189 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
1190 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
1191 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) | |
1192 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) | |
1193 | rdp->nxttail[count] = &rdp->nxtlist; | |
1194 | local_irq_restore(flags); | |
1195 | ||
1196 | /* Invoke callbacks. */ | |
1197 | count = 0; | |
1198 | while (list) { | |
1199 | next = list->next; | |
1200 | prefetch(next); | |
551d55a9 | 1201 | debug_rcu_head_unqueue(list); |
64db4cff PM |
1202 | list->func(list); |
1203 | list = next; | |
1204 | if (++count >= rdp->blimit) | |
1205 | break; | |
1206 | } | |
1207 | ||
1208 | local_irq_save(flags); | |
1209 | ||
1210 | /* Update count, and requeue any remaining callbacks. */ | |
1211 | rdp->qlen -= count; | |
269dcc1c | 1212 | rdp->n_cbs_invoked += count; |
64db4cff PM |
1213 | if (list != NULL) { |
1214 | *tail = rdp->nxtlist; | |
1215 | rdp->nxtlist = list; | |
1216 | for (count = 0; count < RCU_NEXT_SIZE; count++) | |
1217 | if (&rdp->nxtlist == rdp->nxttail[count]) | |
1218 | rdp->nxttail[count] = tail; | |
1219 | else | |
1220 | break; | |
1221 | } | |
1222 | ||
1223 | /* Reinstate batch limit if we have worked down the excess. */ | |
1224 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
1225 | rdp->blimit = blimit; | |
1226 | ||
37c72e56 PM |
1227 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
1228 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
1229 | rdp->qlen_last_fqs_check = 0; | |
1230 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1231 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
1232 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1233 | ||
64db4cff PM |
1234 | local_irq_restore(flags); |
1235 | ||
1236 | /* Re-raise the RCU softirq if there are callbacks remaining. */ | |
1237 | if (cpu_has_callbacks_ready_to_invoke(rdp)) | |
27f4d280 | 1238 | invoke_rcu_cpu_kthread(); |
64db4cff PM |
1239 | } |
1240 | ||
1241 | /* | |
1242 | * Check to see if this CPU is in a non-context-switch quiescent state | |
1243 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
1244 | * Also schedule the RCU softirq handler. | |
1245 | * | |
1246 | * This function must be called with hardirqs disabled. It is normally | |
1247 | * invoked from the scheduling-clock interrupt. If rcu_pending returns | |
1248 | * false, there is no point in invoking rcu_check_callbacks(). | |
1249 | */ | |
1250 | void rcu_check_callbacks(int cpu, int user) | |
1251 | { | |
1252 | if (user || | |
a6826048 PM |
1253 | (idle_cpu(cpu) && rcu_scheduler_active && |
1254 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { | |
64db4cff PM |
1255 | |
1256 | /* | |
1257 | * Get here if this CPU took its interrupt from user | |
1258 | * mode or from the idle loop, and if this is not a | |
1259 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 1260 | * a quiescent state, so note it. |
64db4cff PM |
1261 | * |
1262 | * No memory barrier is required here because both | |
d6714c22 PM |
1263 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1264 | * variables that other CPUs neither access nor modify, | |
1265 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
1266 | */ |
1267 | ||
d6714c22 PM |
1268 | rcu_sched_qs(cpu); |
1269 | rcu_bh_qs(cpu); | |
64db4cff PM |
1270 | |
1271 | } else if (!in_softirq()) { | |
1272 | ||
1273 | /* | |
1274 | * Get here if this CPU did not take its interrupt from | |
1275 | * softirq, in other words, if it is not interrupting | |
1276 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 1277 | * critical section, so note it. |
64db4cff PM |
1278 | */ |
1279 | ||
d6714c22 | 1280 | rcu_bh_qs(cpu); |
64db4cff | 1281 | } |
f41d911f | 1282 | rcu_preempt_check_callbacks(cpu); |
d21670ac | 1283 | if (rcu_pending(cpu)) |
27f4d280 | 1284 | invoke_rcu_cpu_kthread(); |
64db4cff PM |
1285 | } |
1286 | ||
1287 | #ifdef CONFIG_SMP | |
1288 | ||
1289 | /* | |
1290 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
1291 | * have not yet encountered a quiescent state, using the function specified. | |
27f4d280 PM |
1292 | * Also initiate boosting for any threads blocked on the root rcu_node. |
1293 | * | |
ee47eb9f | 1294 | * The caller must have suppressed start of new grace periods. |
64db4cff | 1295 | */ |
45f014c5 | 1296 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
64db4cff PM |
1297 | { |
1298 | unsigned long bit; | |
1299 | int cpu; | |
1300 | unsigned long flags; | |
1301 | unsigned long mask; | |
a0b6c9a7 | 1302 | struct rcu_node *rnp; |
64db4cff | 1303 | |
a0b6c9a7 | 1304 | rcu_for_each_leaf_node(rsp, rnp) { |
64db4cff | 1305 | mask = 0; |
1304afb2 | 1306 | raw_spin_lock_irqsave(&rnp->lock, flags); |
ee47eb9f | 1307 | if (!rcu_gp_in_progress(rsp)) { |
1304afb2 | 1308 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
0f10dc82 | 1309 | return; |
64db4cff | 1310 | } |
a0b6c9a7 | 1311 | if (rnp->qsmask == 0) { |
27f4d280 | 1312 | rcu_initiate_boost(rnp); |
1304afb2 | 1313 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1314 | continue; |
1315 | } | |
a0b6c9a7 | 1316 | cpu = rnp->grplo; |
64db4cff | 1317 | bit = 1; |
a0b6c9a7 | 1318 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
394f99a9 LJ |
1319 | if ((rnp->qsmask & bit) != 0 && |
1320 | f(per_cpu_ptr(rsp->rda, cpu))) | |
64db4cff PM |
1321 | mask |= bit; |
1322 | } | |
45f014c5 | 1323 | if (mask != 0) { |
64db4cff | 1324 | |
d3f6bad3 PM |
1325 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
1326 | rcu_report_qs_rnp(mask, rsp, rnp, flags); | |
64db4cff PM |
1327 | continue; |
1328 | } | |
1304afb2 | 1329 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 1330 | } |
27f4d280 PM |
1331 | rnp = rcu_get_root(rsp); |
1332 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
1333 | if (rnp->qsmask == 0) | |
1334 | rcu_initiate_boost(rnp); | |
1335 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
64db4cff PM |
1336 | } |
1337 | ||
1338 | /* | |
1339 | * Force quiescent states on reluctant CPUs, and also detect which | |
1340 | * CPUs are in dyntick-idle mode. | |
1341 | */ | |
1342 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1343 | { | |
1344 | unsigned long flags; | |
64db4cff | 1345 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 1346 | |
fc2219d4 | 1347 | if (!rcu_gp_in_progress(rsp)) |
64db4cff | 1348 | return; /* No grace period in progress, nothing to force. */ |
1304afb2 | 1349 | if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) { |
64db4cff PM |
1350 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
1351 | return; /* Someone else is already on the job. */ | |
1352 | } | |
20133cfc | 1353 | if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies)) |
f96e9232 | 1354 | goto unlock_fqs_ret; /* no emergency and done recently. */ |
64db4cff | 1355 | rsp->n_force_qs++; |
1304afb2 | 1356 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
64db4cff | 1357 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
560d4bc0 | 1358 | if(!rcu_gp_in_progress(rsp)) { |
64db4cff | 1359 | rsp->n_force_qs_ngp++; |
1304afb2 | 1360 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
f96e9232 | 1361 | goto unlock_fqs_ret; /* no GP in progress, time updated. */ |
64db4cff | 1362 | } |
07079d53 | 1363 | rsp->fqs_active = 1; |
f3a8b5c6 | 1364 | switch (rsp->signaled) { |
83f5b01f | 1365 | case RCU_GP_IDLE: |
64db4cff PM |
1366 | case RCU_GP_INIT: |
1367 | ||
83f5b01f | 1368 | break; /* grace period idle or initializing, ignore. */ |
64db4cff PM |
1369 | |
1370 | case RCU_SAVE_DYNTICK: | |
64db4cff PM |
1371 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
1372 | break; /* So gcc recognizes the dead code. */ | |
1373 | ||
f261414f LJ |
1374 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1375 | ||
64db4cff | 1376 | /* Record dyntick-idle state. */ |
45f014c5 | 1377 | force_qs_rnp(rsp, dyntick_save_progress_counter); |
1304afb2 | 1378 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
ee47eb9f | 1379 | if (rcu_gp_in_progress(rsp)) |
64db4cff | 1380 | rsp->signaled = RCU_FORCE_QS; |
ee47eb9f | 1381 | break; |
64db4cff PM |
1382 | |
1383 | case RCU_FORCE_QS: | |
1384 | ||
1385 | /* Check dyntick-idle state, send IPI to laggarts. */ | |
1304afb2 | 1386 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
45f014c5 | 1387 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
64db4cff PM |
1388 | |
1389 | /* Leave state in case more forcing is required. */ | |
1390 | ||
1304afb2 | 1391 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
f96e9232 | 1392 | break; |
64db4cff | 1393 | } |
07079d53 | 1394 | rsp->fqs_active = 0; |
46a1e34e | 1395 | if (rsp->fqs_need_gp) { |
1304afb2 | 1396 | raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */ |
46a1e34e PM |
1397 | rsp->fqs_need_gp = 0; |
1398 | rcu_start_gp(rsp, flags); /* releases rnp->lock */ | |
1399 | return; | |
1400 | } | |
1304afb2 | 1401 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
f96e9232 | 1402 | unlock_fqs_ret: |
1304afb2 | 1403 | raw_spin_unlock_irqrestore(&rsp->fqslock, flags); |
64db4cff PM |
1404 | } |
1405 | ||
1406 | #else /* #ifdef CONFIG_SMP */ | |
1407 | ||
1408 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1409 | { | |
1410 | set_need_resched(); | |
1411 | } | |
1412 | ||
1413 | #endif /* #else #ifdef CONFIG_SMP */ | |
1414 | ||
1415 | /* | |
1416 | * This does the RCU processing work from softirq context for the | |
1417 | * specified rcu_state and rcu_data structures. This may be called | |
1418 | * only from the CPU to whom the rdp belongs. | |
1419 | */ | |
1420 | static void | |
1421 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) | |
1422 | { | |
1423 | unsigned long flags; | |
1424 | ||
2e597558 PM |
1425 | WARN_ON_ONCE(rdp->beenonline == 0); |
1426 | ||
64db4cff PM |
1427 | /* |
1428 | * If an RCU GP has gone long enough, go check for dyntick | |
1429 | * idle CPUs and, if needed, send resched IPIs. | |
1430 | */ | |
20133cfc | 1431 | if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
64db4cff PM |
1432 | force_quiescent_state(rsp, 1); |
1433 | ||
1434 | /* | |
1435 | * Advance callbacks in response to end of earlier grace | |
1436 | * period that some other CPU ended. | |
1437 | */ | |
1438 | rcu_process_gp_end(rsp, rdp); | |
1439 | ||
1440 | /* Update RCU state based on any recent quiescent states. */ | |
1441 | rcu_check_quiescent_state(rsp, rdp); | |
1442 | ||
1443 | /* Does this CPU require a not-yet-started grace period? */ | |
1444 | if (cpu_needs_another_gp(rsp, rdp)) { | |
1304afb2 | 1445 | raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
64db4cff PM |
1446 | rcu_start_gp(rsp, flags); /* releases above lock */ |
1447 | } | |
1448 | ||
1449 | /* If there are callbacks ready, invoke them. */ | |
37c72e56 | 1450 | rcu_do_batch(rsp, rdp); |
64db4cff PM |
1451 | } |
1452 | ||
1453 | /* | |
1454 | * Do softirq processing for the current CPU. | |
1455 | */ | |
a26ac245 | 1456 | static void rcu_process_callbacks(void) |
64db4cff | 1457 | { |
d6714c22 PM |
1458 | __rcu_process_callbacks(&rcu_sched_state, |
1459 | &__get_cpu_var(rcu_sched_data)); | |
64db4cff | 1460 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
f41d911f | 1461 | rcu_preempt_process_callbacks(); |
a47cd880 PM |
1462 | |
1463 | /* If we are last CPU on way to dyntick-idle mode, accelerate it. */ | |
1464 | rcu_needs_cpu_flush(); | |
64db4cff PM |
1465 | } |
1466 | ||
a26ac245 PM |
1467 | /* |
1468 | * Wake up the current CPU's kthread. This replaces raise_softirq() | |
1469 | * in earlier versions of RCU. Note that because we are running on | |
1470 | * the current CPU with interrupts disabled, the rcu_cpu_kthread_task | |
1471 | * cannot disappear out from under us. | |
1472 | */ | |
27f4d280 | 1473 | static void invoke_rcu_cpu_kthread(void) |
a26ac245 PM |
1474 | { |
1475 | unsigned long flags; | |
1476 | wait_queue_head_t *q; | |
1477 | int cpu; | |
1478 | ||
1479 | local_irq_save(flags); | |
1480 | cpu = smp_processor_id(); | |
1481 | per_cpu(rcu_cpu_has_work, cpu) = 1; | |
1482 | if (per_cpu(rcu_cpu_kthread_task, cpu) == NULL) { | |
1483 | local_irq_restore(flags); | |
1484 | return; | |
1485 | } | |
1486 | q = &per_cpu(rcu_cpu_wq, cpu); | |
1487 | wake_up(q); | |
1488 | local_irq_restore(flags); | |
1489 | } | |
1490 | ||
27f4d280 PM |
1491 | /* |
1492 | * Wake up the specified per-rcu_node-structure kthread. | |
1493 | * The caller must hold ->lock. | |
1494 | */ | |
1495 | static void invoke_rcu_node_kthread(struct rcu_node *rnp) | |
1496 | { | |
1497 | struct task_struct *t; | |
1498 | ||
1499 | t = rnp->node_kthread_task; | |
1500 | if (t != NULL) | |
1501 | wake_up_process(t); | |
1502 | } | |
1503 | ||
e3995a25 PM |
1504 | /* |
1505 | * Set the specified CPU's kthread to run RT or not, as specified by | |
1506 | * the to_rt argument. The CPU-hotplug locks are held, so the task | |
1507 | * is not going away. | |
1508 | */ | |
1509 | static void rcu_cpu_kthread_setrt(int cpu, int to_rt) | |
1510 | { | |
1511 | int policy; | |
1512 | struct sched_param sp; | |
1513 | struct task_struct *t; | |
1514 | ||
1515 | t = per_cpu(rcu_cpu_kthread_task, cpu); | |
1516 | if (t == NULL) | |
1517 | return; | |
1518 | if (to_rt) { | |
1519 | policy = SCHED_FIFO; | |
1520 | sp.sched_priority = RCU_KTHREAD_PRIO; | |
1521 | } else { | |
1522 | policy = SCHED_NORMAL; | |
1523 | sp.sched_priority = 0; | |
1524 | } | |
1525 | sched_setscheduler_nocheck(t, policy, &sp); | |
1526 | } | |
1527 | ||
a26ac245 PM |
1528 | /* |
1529 | * Timer handler to initiate the waking up of per-CPU kthreads that | |
1530 | * have yielded the CPU due to excess numbers of RCU callbacks. | |
27f4d280 PM |
1531 | * We wake up the per-rcu_node kthread, which in turn will wake up |
1532 | * the booster kthread. | |
a26ac245 PM |
1533 | */ |
1534 | static void rcu_cpu_kthread_timer(unsigned long arg) | |
1535 | { | |
1536 | unsigned long flags; | |
27f4d280 | 1537 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg); |
a26ac245 | 1538 | struct rcu_node *rnp = rdp->mynode; |
a26ac245 PM |
1539 | |
1540 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
1541 | rnp->wakemask |= rdp->grpmask; | |
27f4d280 | 1542 | invoke_rcu_node_kthread(rnp); |
a26ac245 PM |
1543 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1544 | } | |
1545 | ||
1546 | /* | |
1547 | * Drop to non-real-time priority and yield, but only after posting a | |
1548 | * timer that will cause us to regain our real-time priority if we | |
1549 | * remain preempted. Either way, we restore our real-time priority | |
1550 | * before returning. | |
1551 | */ | |
27f4d280 | 1552 | static void rcu_yield(void (*f)(unsigned long), unsigned long arg) |
a26ac245 | 1553 | { |
a26ac245 PM |
1554 | struct sched_param sp; |
1555 | struct timer_list yield_timer; | |
1556 | ||
27f4d280 | 1557 | setup_timer_on_stack(&yield_timer, f, arg); |
a26ac245 PM |
1558 | mod_timer(&yield_timer, jiffies + 2); |
1559 | sp.sched_priority = 0; | |
1560 | sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp); | |
1561 | schedule(); | |
1562 | sp.sched_priority = RCU_KTHREAD_PRIO; | |
1563 | sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); | |
1564 | del_timer(&yield_timer); | |
1565 | } | |
1566 | ||
1567 | /* | |
1568 | * Handle cases where the rcu_cpu_kthread() ends up on the wrong CPU. | |
1569 | * This can happen while the corresponding CPU is either coming online | |
1570 | * or going offline. We cannot wait until the CPU is fully online | |
1571 | * before starting the kthread, because the various notifier functions | |
1572 | * can wait for RCU grace periods. So we park rcu_cpu_kthread() until | |
1573 | * the corresponding CPU is online. | |
1574 | * | |
1575 | * Return 1 if the kthread needs to stop, 0 otherwise. | |
1576 | * | |
1577 | * Caller must disable bh. This function can momentarily enable it. | |
1578 | */ | |
1579 | static int rcu_cpu_kthread_should_stop(int cpu) | |
1580 | { | |
1581 | while (cpu_is_offline(cpu) || | |
1582 | !cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)) || | |
1583 | smp_processor_id() != cpu) { | |
1584 | if (kthread_should_stop()) | |
1585 | return 1; | |
1586 | local_bh_enable(); | |
1587 | schedule_timeout_uninterruptible(1); | |
1588 | if (!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu))) | |
1589 | set_cpus_allowed_ptr(current, cpumask_of(cpu)); | |
1590 | local_bh_disable(); | |
1591 | } | |
1592 | return 0; | |
1593 | } | |
1594 | ||
1595 | /* | |
1596 | * Per-CPU kernel thread that invokes RCU callbacks. This replaces the | |
1597 | * earlier RCU softirq. | |
1598 | */ | |
1599 | static int rcu_cpu_kthread(void *arg) | |
1600 | { | |
1601 | int cpu = (int)(long)arg; | |
1602 | unsigned long flags; | |
1603 | int spincnt = 0; | |
d71df90e | 1604 | unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu); |
a26ac245 PM |
1605 | wait_queue_head_t *wqp = &per_cpu(rcu_cpu_wq, cpu); |
1606 | char work; | |
1607 | char *workp = &per_cpu(rcu_cpu_has_work, cpu); | |
1608 | ||
1609 | for (;;) { | |
d71df90e | 1610 | *statusp = RCU_KTHREAD_WAITING; |
a26ac245 PM |
1611 | wait_event_interruptible(*wqp, |
1612 | *workp != 0 || kthread_should_stop()); | |
1613 | local_bh_disable(); | |
1614 | if (rcu_cpu_kthread_should_stop(cpu)) { | |
1615 | local_bh_enable(); | |
1616 | break; | |
1617 | } | |
d71df90e | 1618 | *statusp = RCU_KTHREAD_RUNNING; |
a26ac245 PM |
1619 | local_irq_save(flags); |
1620 | work = *workp; | |
1621 | *workp = 0; | |
1622 | local_irq_restore(flags); | |
1623 | if (work) | |
1624 | rcu_process_callbacks(); | |
1625 | local_bh_enable(); | |
1626 | if (*workp != 0) | |
1627 | spincnt++; | |
1628 | else | |
1629 | spincnt = 0; | |
1630 | if (spincnt > 10) { | |
d71df90e | 1631 | *statusp = RCU_KTHREAD_YIELDING; |
27f4d280 | 1632 | rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu); |
a26ac245 PM |
1633 | spincnt = 0; |
1634 | } | |
1635 | } | |
d71df90e | 1636 | *statusp = RCU_KTHREAD_STOPPED; |
a26ac245 PM |
1637 | return 0; |
1638 | } | |
1639 | ||
1640 | /* | |
1641 | * Spawn a per-CPU kthread, setting up affinity and priority. | |
1642 | * Because the CPU hotplug lock is held, no other CPU will be attempting | |
1643 | * to manipulate rcu_cpu_kthread_task. There might be another CPU | |
1644 | * attempting to access it during boot, but the locking in kthread_bind() | |
1645 | * will enforce sufficient ordering. | |
1646 | */ | |
1647 | static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu) | |
1648 | { | |
1649 | struct sched_param sp; | |
1650 | struct task_struct *t; | |
1651 | ||
1652 | if (!rcu_kthreads_spawnable || | |
1653 | per_cpu(rcu_cpu_kthread_task, cpu) != NULL) | |
1654 | return 0; | |
1655 | t = kthread_create(rcu_cpu_kthread, (void *)(long)cpu, "rcuc%d", cpu); | |
1656 | if (IS_ERR(t)) | |
1657 | return PTR_ERR(t); | |
1658 | kthread_bind(t, cpu); | |
1659 | WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL); | |
1660 | per_cpu(rcu_cpu_kthread_task, cpu) = t; | |
1661 | wake_up_process(t); | |
1662 | sp.sched_priority = RCU_KTHREAD_PRIO; | |
1663 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); | |
1664 | return 0; | |
1665 | } | |
1666 | ||
1667 | /* | |
1668 | * Per-rcu_node kthread, which is in charge of waking up the per-CPU | |
1669 | * kthreads when needed. We ignore requests to wake up kthreads | |
1670 | * for offline CPUs, which is OK because force_quiescent_state() | |
1671 | * takes care of this case. | |
1672 | */ | |
1673 | static int rcu_node_kthread(void *arg) | |
1674 | { | |
1675 | int cpu; | |
1676 | unsigned long flags; | |
1677 | unsigned long mask; | |
1678 | struct rcu_node *rnp = (struct rcu_node *)arg; | |
1679 | struct sched_param sp; | |
1680 | struct task_struct *t; | |
1681 | ||
1682 | for (;;) { | |
d71df90e | 1683 | rnp->node_kthread_status = RCU_KTHREAD_WAITING; |
a26ac245 PM |
1684 | wait_event_interruptible(rnp->node_wq, rnp->wakemask != 0 || |
1685 | kthread_should_stop()); | |
1686 | if (kthread_should_stop()) | |
1687 | break; | |
d71df90e | 1688 | rnp->node_kthread_status = RCU_KTHREAD_RUNNING; |
a26ac245 PM |
1689 | raw_spin_lock_irqsave(&rnp->lock, flags); |
1690 | mask = rnp->wakemask; | |
1691 | rnp->wakemask = 0; | |
27f4d280 | 1692 | rcu_initiate_boost(rnp); |
a26ac245 PM |
1693 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1694 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) { | |
1695 | if ((mask & 0x1) == 0) | |
1696 | continue; | |
1697 | preempt_disable(); | |
1698 | t = per_cpu(rcu_cpu_kthread_task, cpu); | |
1699 | if (!cpu_online(cpu) || t == NULL) { | |
1700 | preempt_enable(); | |
1701 | continue; | |
1702 | } | |
1703 | per_cpu(rcu_cpu_has_work, cpu) = 1; | |
1704 | sp.sched_priority = RCU_KTHREAD_PRIO; | |
1705 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); | |
1706 | preempt_enable(); | |
1707 | } | |
1708 | } | |
d71df90e | 1709 | rnp->node_kthread_status = RCU_KTHREAD_STOPPED; |
a26ac245 PM |
1710 | return 0; |
1711 | } | |
1712 | ||
1713 | /* | |
1714 | * Set the per-rcu_node kthread's affinity to cover all CPUs that are | |
27f4d280 PM |
1715 | * served by the rcu_node in question. The CPU hotplug lock is still |
1716 | * held, so the value of rnp->qsmaskinit will be stable. | |
0f962a5e PM |
1717 | * |
1718 | * We don't include outgoingcpu in the affinity set, use -1 if there is | |
1719 | * no outgoing CPU. If there are no CPUs left in the affinity set, | |
1720 | * this function allows the kthread to execute on any CPU. | |
a26ac245 | 1721 | */ |
0f962a5e | 1722 | static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
a26ac245 PM |
1723 | { |
1724 | cpumask_var_t cm; | |
1725 | int cpu; | |
1726 | unsigned long mask = rnp->qsmaskinit; | |
1727 | ||
27f4d280 | 1728 | if (rnp->node_kthread_task == NULL || mask == 0) |
a26ac245 PM |
1729 | return; |
1730 | if (!alloc_cpumask_var(&cm, GFP_KERNEL)) | |
1731 | return; | |
1732 | cpumask_clear(cm); | |
1733 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) | |
0f962a5e | 1734 | if ((mask & 0x1) && cpu != outgoingcpu) |
a26ac245 | 1735 | cpumask_set_cpu(cpu, cm); |
0f962a5e PM |
1736 | if (cpumask_weight(cm) == 0) { |
1737 | cpumask_setall(cm); | |
1738 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) | |
1739 | cpumask_clear_cpu(cpu, cm); | |
1740 | WARN_ON_ONCE(cpumask_weight(cm) == 0); | |
1741 | } | |
a26ac245 | 1742 | set_cpus_allowed_ptr(rnp->node_kthread_task, cm); |
27f4d280 | 1743 | rcu_boost_kthread_setaffinity(rnp, cm); |
a26ac245 PM |
1744 | free_cpumask_var(cm); |
1745 | } | |
1746 | ||
1747 | /* | |
1748 | * Spawn a per-rcu_node kthread, setting priority and affinity. | |
27f4d280 PM |
1749 | * Called during boot before online/offline can happen, or, if |
1750 | * during runtime, with the main CPU-hotplug locks held. So only | |
1751 | * one of these can be executing at a time. | |
a26ac245 PM |
1752 | */ |
1753 | static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp, | |
1754 | struct rcu_node *rnp) | |
1755 | { | |
27f4d280 | 1756 | unsigned long flags; |
a26ac245 PM |
1757 | int rnp_index = rnp - &rsp->node[0]; |
1758 | struct sched_param sp; | |
1759 | struct task_struct *t; | |
1760 | ||
1761 | if (!rcu_kthreads_spawnable || | |
27f4d280 | 1762 | rnp->qsmaskinit == 0) |
a26ac245 | 1763 | return 0; |
27f4d280 PM |
1764 | if (rnp->node_kthread_task == NULL) { |
1765 | t = kthread_create(rcu_node_kthread, (void *)rnp, | |
1766 | "rcun%d", rnp_index); | |
1767 | if (IS_ERR(t)) | |
1768 | return PTR_ERR(t); | |
1769 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
1770 | rnp->node_kthread_task = t; | |
1771 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1772 | wake_up_process(t); | |
1773 | sp.sched_priority = 99; | |
1774 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); | |
1775 | } | |
1776 | return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index); | |
a26ac245 PM |
1777 | } |
1778 | ||
1779 | /* | |
1780 | * Spawn all kthreads -- called as soon as the scheduler is running. | |
1781 | */ | |
1782 | static int __init rcu_spawn_kthreads(void) | |
1783 | { | |
1784 | int cpu; | |
1785 | struct rcu_node *rnp; | |
1786 | ||
1787 | rcu_kthreads_spawnable = 1; | |
1788 | for_each_possible_cpu(cpu) { | |
1789 | init_waitqueue_head(&per_cpu(rcu_cpu_wq, cpu)); | |
1790 | per_cpu(rcu_cpu_has_work, cpu) = 0; | |
1791 | if (cpu_online(cpu)) | |
1792 | (void)rcu_spawn_one_cpu_kthread(cpu); | |
1793 | } | |
27f4d280 PM |
1794 | rnp = rcu_get_root(rcu_state); |
1795 | init_waitqueue_head(&rnp->node_wq); | |
1796 | rcu_init_boost_waitqueue(rnp); | |
1797 | (void)rcu_spawn_one_node_kthread(rcu_state, rnp); | |
1798 | if (NUM_RCU_NODES > 1) | |
1799 | rcu_for_each_leaf_node(rcu_state, rnp) { | |
1800 | init_waitqueue_head(&rnp->node_wq); | |
1801 | rcu_init_boost_waitqueue(rnp); | |
1802 | (void)rcu_spawn_one_node_kthread(rcu_state, rnp); | |
1803 | } | |
a26ac245 PM |
1804 | return 0; |
1805 | } | |
1806 | early_initcall(rcu_spawn_kthreads); | |
1807 | ||
64db4cff PM |
1808 | static void |
1809 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
1810 | struct rcu_state *rsp) | |
1811 | { | |
1812 | unsigned long flags; | |
1813 | struct rcu_data *rdp; | |
1814 | ||
551d55a9 | 1815 | debug_rcu_head_queue(head); |
64db4cff PM |
1816 | head->func = func; |
1817 | head->next = NULL; | |
1818 | ||
1819 | smp_mb(); /* Ensure RCU update seen before callback registry. */ | |
1820 | ||
1821 | /* | |
1822 | * Opportunistically note grace-period endings and beginnings. | |
1823 | * Note that we might see a beginning right after we see an | |
1824 | * end, but never vice versa, since this CPU has to pass through | |
1825 | * a quiescent state betweentimes. | |
1826 | */ | |
1827 | local_irq_save(flags); | |
394f99a9 | 1828 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
1829 | |
1830 | /* Add the callback to our list. */ | |
1831 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
1832 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
1833 | ||
37c72e56 PM |
1834 | /* |
1835 | * Force the grace period if too many callbacks or too long waiting. | |
1836 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
1837 | * if some other CPU has recently done so. Also, don't bother | |
1838 | * invoking force_quiescent_state() if the newly enqueued callback | |
1839 | * is the only one waiting for a grace period to complete. | |
1840 | */ | |
1841 | if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { | |
b52573d2 PM |
1842 | |
1843 | /* Are we ignoring a completed grace period? */ | |
1844 | rcu_process_gp_end(rsp, rdp); | |
1845 | check_for_new_grace_period(rsp, rdp); | |
1846 | ||
1847 | /* Start a new grace period if one not already started. */ | |
1848 | if (!rcu_gp_in_progress(rsp)) { | |
1849 | unsigned long nestflag; | |
1850 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
1851 | ||
1852 | raw_spin_lock_irqsave(&rnp_root->lock, nestflag); | |
1853 | rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */ | |
1854 | } else { | |
1855 | /* Give the grace period a kick. */ | |
1856 | rdp->blimit = LONG_MAX; | |
1857 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
1858 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
1859 | force_quiescent_state(rsp, 0); | |
1860 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1861 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1862 | } | |
20133cfc | 1863 | } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
64db4cff PM |
1864 | force_quiescent_state(rsp, 1); |
1865 | local_irq_restore(flags); | |
1866 | } | |
1867 | ||
1868 | /* | |
d6714c22 | 1869 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 1870 | */ |
d6714c22 | 1871 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 1872 | { |
d6714c22 | 1873 | __call_rcu(head, func, &rcu_sched_state); |
64db4cff | 1874 | } |
d6714c22 | 1875 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
1876 | |
1877 | /* | |
1878 | * Queue an RCU for invocation after a quicker grace period. | |
1879 | */ | |
1880 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
1881 | { | |
1882 | __call_rcu(head, func, &rcu_bh_state); | |
1883 | } | |
1884 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
1885 | ||
6ebb237b PM |
1886 | /** |
1887 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
1888 | * | |
1889 | * Control will return to the caller some time after a full rcu-sched | |
1890 | * grace period has elapsed, in other words after all currently executing | |
1891 | * rcu-sched read-side critical sections have completed. These read-side | |
1892 | * critical sections are delimited by rcu_read_lock_sched() and | |
1893 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
1894 | * local_irq_disable(), and so on may be used in place of | |
1895 | * rcu_read_lock_sched(). | |
1896 | * | |
1897 | * This means that all preempt_disable code sequences, including NMI and | |
1898 | * hardware-interrupt handlers, in progress on entry will have completed | |
1899 | * before this primitive returns. However, this does not guarantee that | |
1900 | * softirq handlers will have completed, since in some kernels, these | |
1901 | * handlers can run in process context, and can block. | |
1902 | * | |
1903 | * This primitive provides the guarantees made by the (now removed) | |
1904 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
1905 | * guarantees that rcu_read_lock() sections will have completed. | |
1906 | * In "classic RCU", these two guarantees happen to be one and | |
1907 | * the same, but can differ in realtime RCU implementations. | |
1908 | */ | |
1909 | void synchronize_sched(void) | |
1910 | { | |
1911 | struct rcu_synchronize rcu; | |
1912 | ||
1913 | if (rcu_blocking_is_gp()) | |
1914 | return; | |
1915 | ||
72d5a9f7 | 1916 | init_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1917 | init_completion(&rcu.completion); |
1918 | /* Will wake me after RCU finished. */ | |
1919 | call_rcu_sched(&rcu.head, wakeme_after_rcu); | |
1920 | /* Wait for it. */ | |
1921 | wait_for_completion(&rcu.completion); | |
72d5a9f7 | 1922 | destroy_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1923 | } |
1924 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
1925 | ||
1926 | /** | |
1927 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
1928 | * | |
1929 | * Control will return to the caller some time after a full rcu_bh grace | |
1930 | * period has elapsed, in other words after all currently executing rcu_bh | |
1931 | * read-side critical sections have completed. RCU read-side critical | |
1932 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
1933 | * and may be nested. | |
1934 | */ | |
1935 | void synchronize_rcu_bh(void) | |
1936 | { | |
1937 | struct rcu_synchronize rcu; | |
1938 | ||
1939 | if (rcu_blocking_is_gp()) | |
1940 | return; | |
1941 | ||
72d5a9f7 | 1942 | init_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1943 | init_completion(&rcu.completion); |
1944 | /* Will wake me after RCU finished. */ | |
1945 | call_rcu_bh(&rcu.head, wakeme_after_rcu); | |
1946 | /* Wait for it. */ | |
1947 | wait_for_completion(&rcu.completion); | |
72d5a9f7 | 1948 | destroy_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1949 | } |
1950 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
1951 | ||
64db4cff PM |
1952 | /* |
1953 | * Check to see if there is any immediate RCU-related work to be done | |
1954 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
1955 | * The checks are in order of increasing expense: checks that can be | |
1956 | * carried out against CPU-local state are performed first. However, | |
1957 | * we must check for CPU stalls first, else we might not get a chance. | |
1958 | */ | |
1959 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
1960 | { | |
2f51f988 PM |
1961 | struct rcu_node *rnp = rdp->mynode; |
1962 | ||
64db4cff PM |
1963 | rdp->n_rcu_pending++; |
1964 | ||
1965 | /* Check for CPU stalls, if enabled. */ | |
1966 | check_cpu_stall(rsp, rdp); | |
1967 | ||
1968 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
d21670ac | 1969 | if (rdp->qs_pending && !rdp->passed_quiesc) { |
d25eb944 PM |
1970 | |
1971 | /* | |
1972 | * If force_quiescent_state() coming soon and this CPU | |
1973 | * needs a quiescent state, and this is either RCU-sched | |
1974 | * or RCU-bh, force a local reschedule. | |
1975 | */ | |
d21670ac | 1976 | rdp->n_rp_qs_pending++; |
d25eb944 PM |
1977 | if (!rdp->preemptable && |
1978 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1, | |
1979 | jiffies)) | |
1980 | set_need_resched(); | |
d21670ac PM |
1981 | } else if (rdp->qs_pending && rdp->passed_quiesc) { |
1982 | rdp->n_rp_report_qs++; | |
64db4cff | 1983 | return 1; |
7ba5c840 | 1984 | } |
64db4cff PM |
1985 | |
1986 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
1987 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
1988 | rdp->n_rp_cb_ready++; | |
64db4cff | 1989 | return 1; |
7ba5c840 | 1990 | } |
64db4cff PM |
1991 | |
1992 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
1993 | if (cpu_needs_another_gp(rsp, rdp)) { |
1994 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 1995 | return 1; |
7ba5c840 | 1996 | } |
64db4cff PM |
1997 | |
1998 | /* Has another RCU grace period completed? */ | |
2f51f988 | 1999 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 2000 | rdp->n_rp_gp_completed++; |
64db4cff | 2001 | return 1; |
7ba5c840 | 2002 | } |
64db4cff PM |
2003 | |
2004 | /* Has a new RCU grace period started? */ | |
2f51f988 | 2005 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
7ba5c840 | 2006 | rdp->n_rp_gp_started++; |
64db4cff | 2007 | return 1; |
7ba5c840 | 2008 | } |
64db4cff PM |
2009 | |
2010 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ | |
fc2219d4 | 2011 | if (rcu_gp_in_progress(rsp) && |
20133cfc | 2012 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) { |
7ba5c840 | 2013 | rdp->n_rp_need_fqs++; |
64db4cff | 2014 | return 1; |
7ba5c840 | 2015 | } |
64db4cff PM |
2016 | |
2017 | /* nothing to do */ | |
7ba5c840 | 2018 | rdp->n_rp_need_nothing++; |
64db4cff PM |
2019 | return 0; |
2020 | } | |
2021 | ||
2022 | /* | |
2023 | * Check to see if there is any immediate RCU-related work to be done | |
2024 | * by the current CPU, returning 1 if so. This function is part of the | |
2025 | * RCU implementation; it is -not- an exported member of the RCU API. | |
2026 | */ | |
a157229c | 2027 | static int rcu_pending(int cpu) |
64db4cff | 2028 | { |
d6714c22 | 2029 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
f41d911f PM |
2030 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
2031 | rcu_preempt_pending(cpu); | |
64db4cff PM |
2032 | } |
2033 | ||
2034 | /* | |
2035 | * Check to see if any future RCU-related work will need to be done | |
2036 | * by the current CPU, even if none need be done immediately, returning | |
8bd93a2c | 2037 | * 1 if so. |
64db4cff | 2038 | */ |
8bd93a2c | 2039 | static int rcu_needs_cpu_quick_check(int cpu) |
64db4cff PM |
2040 | { |
2041 | /* RCU callbacks either ready or pending? */ | |
d6714c22 | 2042 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
f41d911f PM |
2043 | per_cpu(rcu_bh_data, cpu).nxtlist || |
2044 | rcu_preempt_needs_cpu(cpu); | |
64db4cff PM |
2045 | } |
2046 | ||
d0ec774c PM |
2047 | static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
2048 | static atomic_t rcu_barrier_cpu_count; | |
2049 | static DEFINE_MUTEX(rcu_barrier_mutex); | |
2050 | static struct completion rcu_barrier_completion; | |
d0ec774c PM |
2051 | |
2052 | static void rcu_barrier_callback(struct rcu_head *notused) | |
2053 | { | |
2054 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
2055 | complete(&rcu_barrier_completion); | |
2056 | } | |
2057 | ||
2058 | /* | |
2059 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
2060 | */ | |
2061 | static void rcu_barrier_func(void *type) | |
2062 | { | |
2063 | int cpu = smp_processor_id(); | |
2064 | struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); | |
2065 | void (*call_rcu_func)(struct rcu_head *head, | |
2066 | void (*func)(struct rcu_head *head)); | |
2067 | ||
2068 | atomic_inc(&rcu_barrier_cpu_count); | |
2069 | call_rcu_func = type; | |
2070 | call_rcu_func(head, rcu_barrier_callback); | |
2071 | } | |
2072 | ||
d0ec774c PM |
2073 | /* |
2074 | * Orchestrate the specified type of RCU barrier, waiting for all | |
2075 | * RCU callbacks of the specified type to complete. | |
2076 | */ | |
e74f4c45 PM |
2077 | static void _rcu_barrier(struct rcu_state *rsp, |
2078 | void (*call_rcu_func)(struct rcu_head *head, | |
d0ec774c PM |
2079 | void (*func)(struct rcu_head *head))) |
2080 | { | |
2081 | BUG_ON(in_interrupt()); | |
e74f4c45 | 2082 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
d0ec774c PM |
2083 | mutex_lock(&rcu_barrier_mutex); |
2084 | init_completion(&rcu_barrier_completion); | |
2085 | /* | |
2086 | * Initialize rcu_barrier_cpu_count to 1, then invoke | |
2087 | * rcu_barrier_func() on each CPU, so that each CPU also has | |
2088 | * incremented rcu_barrier_cpu_count. Only then is it safe to | |
2089 | * decrement rcu_barrier_cpu_count -- otherwise the first CPU | |
2090 | * might complete its grace period before all of the other CPUs | |
2091 | * did their increment, causing this function to return too | |
2d999e03 PM |
2092 | * early. Note that on_each_cpu() disables irqs, which prevents |
2093 | * any CPUs from coming online or going offline until each online | |
2094 | * CPU has queued its RCU-barrier callback. | |
d0ec774c PM |
2095 | */ |
2096 | atomic_set(&rcu_barrier_cpu_count, 1); | |
2097 | on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1); | |
2098 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
2099 | complete(&rcu_barrier_completion); | |
2100 | wait_for_completion(&rcu_barrier_completion); | |
2101 | mutex_unlock(&rcu_barrier_mutex); | |
d0ec774c | 2102 | } |
d0ec774c PM |
2103 | |
2104 | /** | |
2105 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
2106 | */ | |
2107 | void rcu_barrier_bh(void) | |
2108 | { | |
e74f4c45 | 2109 | _rcu_barrier(&rcu_bh_state, call_rcu_bh); |
d0ec774c PM |
2110 | } |
2111 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
2112 | ||
2113 | /** | |
2114 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
2115 | */ | |
2116 | void rcu_barrier_sched(void) | |
2117 | { | |
e74f4c45 | 2118 | _rcu_barrier(&rcu_sched_state, call_rcu_sched); |
d0ec774c PM |
2119 | } |
2120 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
2121 | ||
64db4cff | 2122 | /* |
27569620 | 2123 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 2124 | */ |
27569620 PM |
2125 | static void __init |
2126 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
2127 | { |
2128 | unsigned long flags; | |
2129 | int i; | |
394f99a9 | 2130 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
2131 | struct rcu_node *rnp = rcu_get_root(rsp); |
2132 | ||
2133 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 2134 | raw_spin_lock_irqsave(&rnp->lock, flags); |
27569620 PM |
2135 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
2136 | rdp->nxtlist = NULL; | |
2137 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
2138 | rdp->nxttail[i] = &rdp->nxtlist; | |
2139 | rdp->qlen = 0; | |
2140 | #ifdef CONFIG_NO_HZ | |
2141 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); | |
2142 | #endif /* #ifdef CONFIG_NO_HZ */ | |
2143 | rdp->cpu = cpu; | |
1304afb2 | 2144 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27569620 PM |
2145 | } |
2146 | ||
2147 | /* | |
2148 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
2149 | * offline event can be happening at a given time. Note also that we | |
2150 | * can accept some slop in the rsp->completed access due to the fact | |
2151 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 2152 | */ |
e4fa4c97 | 2153 | static void __cpuinit |
f41d911f | 2154 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) |
64db4cff PM |
2155 | { |
2156 | unsigned long flags; | |
64db4cff | 2157 | unsigned long mask; |
394f99a9 | 2158 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
2159 | struct rcu_node *rnp = rcu_get_root(rsp); |
2160 | ||
2161 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 2162 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff PM |
2163 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
2164 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ | |
2165 | rdp->beenonline = 1; /* We have now been online. */ | |
f41d911f | 2166 | rdp->preemptable = preemptable; |
37c72e56 PM |
2167 | rdp->qlen_last_fqs_check = 0; |
2168 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 2169 | rdp->blimit = blimit; |
1304afb2 | 2170 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
2171 | |
2172 | /* | |
2173 | * A new grace period might start here. If so, we won't be part | |
2174 | * of it, but that is OK, as we are currently in a quiescent state. | |
2175 | */ | |
2176 | ||
2177 | /* Exclude any attempts to start a new GP on large systems. */ | |
1304afb2 | 2178 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
2179 | |
2180 | /* Add CPU to rcu_node bitmasks. */ | |
2181 | rnp = rdp->mynode; | |
2182 | mask = rdp->grpmask; | |
2183 | do { | |
2184 | /* Exclude any attempts to start a new GP on small systems. */ | |
1304afb2 | 2185 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2186 | rnp->qsmaskinit |= mask; |
2187 | mask = rnp->grpmask; | |
d09b62df PM |
2188 | if (rnp == rdp->mynode) { |
2189 | rdp->gpnum = rnp->completed; /* if GP in progress... */ | |
2190 | rdp->completed = rnp->completed; | |
2191 | rdp->passed_quiesc_completed = rnp->completed - 1; | |
2192 | } | |
1304afb2 | 2193 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2194 | rnp = rnp->parent; |
2195 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
2196 | ||
1304afb2 | 2197 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
64db4cff PM |
2198 | } |
2199 | ||
2200 | static void __cpuinit rcu_online_cpu(int cpu) | |
2201 | { | |
f41d911f PM |
2202 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
2203 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); | |
2204 | rcu_preempt_init_percpu_data(cpu); | |
64db4cff PM |
2205 | } |
2206 | ||
a26ac245 PM |
2207 | static void __cpuinit rcu_online_kthreads(int cpu) |
2208 | { | |
27f4d280 | 2209 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
a26ac245 PM |
2210 | struct rcu_node *rnp = rdp->mynode; |
2211 | ||
2212 | /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ | |
2213 | if (rcu_kthreads_spawnable) { | |
2214 | (void)rcu_spawn_one_cpu_kthread(cpu); | |
2215 | if (rnp->node_kthread_task == NULL) | |
27f4d280 | 2216 | (void)rcu_spawn_one_node_kthread(rcu_state, rnp); |
a26ac245 PM |
2217 | } |
2218 | } | |
2219 | ||
64db4cff | 2220 | /* |
f41d911f | 2221 | * Handle CPU online/offline notification events. |
64db4cff | 2222 | */ |
9f680ab4 PM |
2223 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
2224 | unsigned long action, void *hcpu) | |
64db4cff PM |
2225 | { |
2226 | long cpu = (long)hcpu; | |
27f4d280 | 2227 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
a26ac245 | 2228 | struct rcu_node *rnp = rdp->mynode; |
64db4cff PM |
2229 | |
2230 | switch (action) { | |
2231 | case CPU_UP_PREPARE: | |
2232 | case CPU_UP_PREPARE_FROZEN: | |
2233 | rcu_online_cpu(cpu); | |
a26ac245 PM |
2234 | rcu_online_kthreads(cpu); |
2235 | break; | |
2236 | case CPU_ONLINE: | |
0f962a5e PM |
2237 | case CPU_DOWN_FAILED: |
2238 | rcu_node_kthread_setaffinity(rnp, -1); | |
e3995a25 | 2239 | rcu_cpu_kthread_setrt(cpu, 1); |
0f962a5e PM |
2240 | break; |
2241 | case CPU_DOWN_PREPARE: | |
2242 | rcu_node_kthread_setaffinity(rnp, cpu); | |
e3995a25 | 2243 | rcu_cpu_kthread_setrt(cpu, 0); |
64db4cff | 2244 | break; |
d0ec774c PM |
2245 | case CPU_DYING: |
2246 | case CPU_DYING_FROZEN: | |
2247 | /* | |
2d999e03 PM |
2248 | * The whole machine is "stopped" except this CPU, so we can |
2249 | * touch any data without introducing corruption. We send the | |
2250 | * dying CPU's callbacks to an arbitrarily chosen online CPU. | |
d0ec774c | 2251 | */ |
29494be7 LJ |
2252 | rcu_send_cbs_to_online(&rcu_bh_state); |
2253 | rcu_send_cbs_to_online(&rcu_sched_state); | |
2254 | rcu_preempt_send_cbs_to_online(); | |
d0ec774c | 2255 | break; |
64db4cff PM |
2256 | case CPU_DEAD: |
2257 | case CPU_DEAD_FROZEN: | |
2258 | case CPU_UP_CANCELED: | |
2259 | case CPU_UP_CANCELED_FROZEN: | |
2260 | rcu_offline_cpu(cpu); | |
2261 | break; | |
2262 | default: | |
2263 | break; | |
2264 | } | |
2265 | return NOTIFY_OK; | |
2266 | } | |
2267 | ||
bbad9379 PM |
2268 | /* |
2269 | * This function is invoked towards the end of the scheduler's initialization | |
2270 | * process. Before this is called, the idle task might contain | |
2271 | * RCU read-side critical sections (during which time, this idle | |
2272 | * task is booting the system). After this function is called, the | |
2273 | * idle tasks are prohibited from containing RCU read-side critical | |
2274 | * sections. This function also enables RCU lockdep checking. | |
2275 | */ | |
2276 | void rcu_scheduler_starting(void) | |
2277 | { | |
2278 | WARN_ON(num_online_cpus() != 1); | |
2279 | WARN_ON(nr_context_switches() > 0); | |
2280 | rcu_scheduler_active = 1; | |
2281 | } | |
2282 | ||
64db4cff PM |
2283 | /* |
2284 | * Compute the per-level fanout, either using the exact fanout specified | |
2285 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
2286 | */ | |
2287 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
2288 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
2289 | { | |
2290 | int i; | |
2291 | ||
0209f649 | 2292 | for (i = NUM_RCU_LVLS - 1; i > 0; i--) |
64db4cff | 2293 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
0209f649 | 2294 | rsp->levelspread[0] = RCU_FANOUT_LEAF; |
64db4cff PM |
2295 | } |
2296 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
2297 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
2298 | { | |
2299 | int ccur; | |
2300 | int cprv; | |
2301 | int i; | |
2302 | ||
2303 | cprv = NR_CPUS; | |
2304 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
2305 | ccur = rsp->levelcnt[i]; | |
2306 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
2307 | cprv = ccur; | |
2308 | } | |
2309 | } | |
2310 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
2311 | ||
2312 | /* | |
2313 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
2314 | */ | |
394f99a9 LJ |
2315 | static void __init rcu_init_one(struct rcu_state *rsp, |
2316 | struct rcu_data __percpu *rda) | |
64db4cff | 2317 | { |
b6407e86 PM |
2318 | static char *buf[] = { "rcu_node_level_0", |
2319 | "rcu_node_level_1", | |
2320 | "rcu_node_level_2", | |
2321 | "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ | |
64db4cff PM |
2322 | int cpustride = 1; |
2323 | int i; | |
2324 | int j; | |
2325 | struct rcu_node *rnp; | |
2326 | ||
b6407e86 PM |
2327 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
2328 | ||
64db4cff PM |
2329 | /* Initialize the level-tracking arrays. */ |
2330 | ||
2331 | for (i = 1; i < NUM_RCU_LVLS; i++) | |
2332 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; | |
2333 | rcu_init_levelspread(rsp); | |
2334 | ||
2335 | /* Initialize the elements themselves, starting from the leaves. */ | |
2336 | ||
2337 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
2338 | cpustride *= rsp->levelspread[i]; | |
2339 | rnp = rsp->level[i]; | |
2340 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1304afb2 | 2341 | raw_spin_lock_init(&rnp->lock); |
b6407e86 PM |
2342 | lockdep_set_class_and_name(&rnp->lock, |
2343 | &rcu_node_class[i], buf[i]); | |
f41d911f | 2344 | rnp->gpnum = 0; |
64db4cff PM |
2345 | rnp->qsmask = 0; |
2346 | rnp->qsmaskinit = 0; | |
2347 | rnp->grplo = j * cpustride; | |
2348 | rnp->grphi = (j + 1) * cpustride - 1; | |
2349 | if (rnp->grphi >= NR_CPUS) | |
2350 | rnp->grphi = NR_CPUS - 1; | |
2351 | if (i == 0) { | |
2352 | rnp->grpnum = 0; | |
2353 | rnp->grpmask = 0; | |
2354 | rnp->parent = NULL; | |
2355 | } else { | |
2356 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
2357 | rnp->grpmask = 1UL << rnp->grpnum; | |
2358 | rnp->parent = rsp->level[i - 1] + | |
2359 | j / rsp->levelspread[i - 1]; | |
2360 | } | |
2361 | rnp->level = i; | |
12f5f524 | 2362 | INIT_LIST_HEAD(&rnp->blkd_tasks); |
64db4cff PM |
2363 | } |
2364 | } | |
0c34029a | 2365 | |
394f99a9 | 2366 | rsp->rda = rda; |
0c34029a LJ |
2367 | rnp = rsp->level[NUM_RCU_LVLS - 1]; |
2368 | for_each_possible_cpu(i) { | |
4a90a068 | 2369 | while (i > rnp->grphi) |
0c34029a | 2370 | rnp++; |
394f99a9 | 2371 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
2372 | rcu_boot_init_percpu_data(i, rsp); |
2373 | } | |
64db4cff PM |
2374 | } |
2375 | ||
9f680ab4 | 2376 | void __init rcu_init(void) |
64db4cff | 2377 | { |
017c4261 | 2378 | int cpu; |
9f680ab4 | 2379 | |
f41d911f | 2380 | rcu_bootup_announce(); |
394f99a9 LJ |
2381 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
2382 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); | |
f41d911f | 2383 | __rcu_init_preempt(); |
9f680ab4 PM |
2384 | |
2385 | /* | |
2386 | * We don't need protection against CPU-hotplug here because | |
2387 | * this is called early in boot, before either interrupts | |
2388 | * or the scheduler are operational. | |
2389 | */ | |
2390 | cpu_notifier(rcu_cpu_notify, 0); | |
017c4261 PM |
2391 | for_each_online_cpu(cpu) |
2392 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); | |
c68de209 | 2393 | check_cpu_stall_init(); |
64db4cff PM |
2394 | } |
2395 | ||
1eba8f84 | 2396 | #include "rcutree_plugin.h" |