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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> |
8826f3b0 | 39 | #include <linux/atomic.h> |
64db4cff PM |
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> | |
268bb0ce | 52 | #include <linux/prefetch.h> |
64db4cff | 53 | |
9f77da9f PM |
54 | #include "rcutree.h" |
55 | ||
64db4cff PM |
56 | /* Data structures. */ |
57 | ||
b668c9cf | 58 | static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; |
88b91c7c | 59 | |
4300aa64 PM |
60 | #define RCU_STATE_INITIALIZER(structname) { \ |
61 | .level = { &structname.node[0] }, \ | |
64db4cff PM |
62 | .levelcnt = { \ |
63 | NUM_RCU_LVL_0, /* root of hierarchy. */ \ | |
64 | NUM_RCU_LVL_1, \ | |
65 | NUM_RCU_LVL_2, \ | |
cf244dc0 PM |
66 | NUM_RCU_LVL_3, \ |
67 | NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ | |
64db4cff | 68 | }, \ |
83f5b01f | 69 | .signaled = RCU_GP_IDLE, \ |
64db4cff PM |
70 | .gpnum = -300, \ |
71 | .completed = -300, \ | |
4300aa64 | 72 | .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \ |
4300aa64 | 73 | .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \ |
64db4cff PM |
74 | .n_force_qs = 0, \ |
75 | .n_force_qs_ngp = 0, \ | |
4300aa64 | 76 | .name = #structname, \ |
64db4cff PM |
77 | } |
78 | ||
d6714c22 PM |
79 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
80 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); | |
64db4cff | 81 | |
6258c4fb IM |
82 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
83 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); | |
b1f77b05 | 84 | |
27f4d280 PM |
85 | static struct rcu_state *rcu_state; |
86 | ||
b0d30417 PM |
87 | /* |
88 | * The rcu_scheduler_active variable transitions from zero to one just | |
89 | * before the first task is spawned. So when this variable is zero, RCU | |
90 | * can assume that there is but one task, allowing RCU to (for example) | |
91 | * optimized synchronize_sched() to a simple barrier(). When this variable | |
92 | * is one, RCU must actually do all the hard work required to detect real | |
93 | * grace periods. This variable is also used to suppress boot-time false | |
94 | * positives from lockdep-RCU error checking. | |
95 | */ | |
bbad9379 PM |
96 | int rcu_scheduler_active __read_mostly; |
97 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
98 | ||
b0d30417 PM |
99 | /* |
100 | * The rcu_scheduler_fully_active variable transitions from zero to one | |
101 | * during the early_initcall() processing, which is after the scheduler | |
102 | * is capable of creating new tasks. So RCU processing (for example, | |
103 | * creating tasks for RCU priority boosting) must be delayed until after | |
104 | * rcu_scheduler_fully_active transitions from zero to one. We also | |
105 | * currently delay invocation of any RCU callbacks until after this point. | |
106 | * | |
107 | * It might later prove better for people registering RCU callbacks during | |
108 | * early boot to take responsibility for these callbacks, but one step at | |
109 | * a time. | |
110 | */ | |
111 | static int rcu_scheduler_fully_active __read_mostly; | |
112 | ||
a46e0899 PM |
113 | #ifdef CONFIG_RCU_BOOST |
114 | ||
a26ac245 PM |
115 | /* |
116 | * Control variables for per-CPU and per-rcu_node kthreads. These | |
117 | * handle all flavors of RCU. | |
118 | */ | |
119 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); | |
d71df90e | 120 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
15ba0ba8 | 121 | DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu); |
5ece5bab | 122 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
d71df90e | 123 | DEFINE_PER_CPU(char, rcu_cpu_has_work); |
a26ac245 | 124 | |
a46e0899 PM |
125 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
126 | ||
0f962a5e | 127 | static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
a46e0899 PM |
128 | static void invoke_rcu_core(void); |
129 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); | |
a26ac245 PM |
130 | |
131 | #define RCU_KTHREAD_PRIO 1 /* RT priority for per-CPU kthreads. */ | |
132 | ||
4a298656 PM |
133 | /* |
134 | * Track the rcutorture test sequence number and the update version | |
135 | * number within a given test. The rcutorture_testseq is incremented | |
136 | * on every rcutorture module load and unload, so has an odd value | |
137 | * when a test is running. The rcutorture_vernum is set to zero | |
138 | * when rcutorture starts and is incremented on each rcutorture update. | |
139 | * These variables enable correlating rcutorture output with the | |
140 | * RCU tracing information. | |
141 | */ | |
142 | unsigned long rcutorture_testseq; | |
143 | unsigned long rcutorture_vernum; | |
144 | ||
fc2219d4 PM |
145 | /* |
146 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
147 | * permit this function to be invoked without holding the root rcu_node | |
148 | * structure's ->lock, but of course results can be subject to change. | |
149 | */ | |
150 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
151 | { | |
152 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
153 | } | |
154 | ||
b1f77b05 | 155 | /* |
d6714c22 | 156 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 157 | * how many quiescent states passed, just if there was at least |
d6714c22 | 158 | * one since the start of the grace period, this just sets a flag. |
b1f77b05 | 159 | */ |
d6714c22 | 160 | void rcu_sched_qs(int cpu) |
b1f77b05 | 161 | { |
25502a6c | 162 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
f41d911f | 163 | |
c64ac3ce | 164 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
c3422bea PM |
165 | barrier(); |
166 | rdp->passed_quiesc = 1; | |
b1f77b05 IM |
167 | } |
168 | ||
d6714c22 | 169 | void rcu_bh_qs(int cpu) |
b1f77b05 | 170 | { |
25502a6c | 171 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
f41d911f | 172 | |
c64ac3ce | 173 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
c3422bea PM |
174 | barrier(); |
175 | rdp->passed_quiesc = 1; | |
b1f77b05 | 176 | } |
64db4cff | 177 | |
25502a6c PM |
178 | /* |
179 | * Note a context switch. This is a quiescent state for RCU-sched, | |
180 | * and requires special handling for preemptible RCU. | |
181 | */ | |
182 | void rcu_note_context_switch(int cpu) | |
183 | { | |
184 | rcu_sched_qs(cpu); | |
185 | rcu_preempt_note_context_switch(cpu); | |
186 | } | |
29ce8310 | 187 | EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
25502a6c | 188 | |
64db4cff | 189 | #ifdef CONFIG_NO_HZ |
90a4d2c0 PM |
190 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
191 | .dynticks_nesting = 1, | |
23b5c8fa | 192 | .dynticks = ATOMIC_INIT(1), |
90a4d2c0 | 193 | }; |
64db4cff PM |
194 | #endif /* #ifdef CONFIG_NO_HZ */ |
195 | ||
196 | static int blimit = 10; /* Maximum callbacks per softirq. */ | |
197 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ | |
198 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ | |
199 | ||
3d76c082 PM |
200 | module_param(blimit, int, 0); |
201 | module_param(qhimark, int, 0); | |
202 | module_param(qlowmark, int, 0); | |
203 | ||
a00e0d71 | 204 | int rcu_cpu_stall_suppress __read_mostly; |
f2e0dd70 | 205 | module_param(rcu_cpu_stall_suppress, int, 0644); |
742734ee | 206 | |
64db4cff | 207 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
a157229c | 208 | static int rcu_pending(int cpu); |
64db4cff PM |
209 | |
210 | /* | |
d6714c22 | 211 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 212 | */ |
d6714c22 | 213 | long rcu_batches_completed_sched(void) |
64db4cff | 214 | { |
d6714c22 | 215 | return rcu_sched_state.completed; |
64db4cff | 216 | } |
d6714c22 | 217 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
218 | |
219 | /* | |
220 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
221 | */ | |
222 | long rcu_batches_completed_bh(void) | |
223 | { | |
224 | return rcu_bh_state.completed; | |
225 | } | |
226 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
227 | ||
bf66f18e PM |
228 | /* |
229 | * Force a quiescent state for RCU BH. | |
230 | */ | |
231 | void rcu_bh_force_quiescent_state(void) | |
232 | { | |
233 | force_quiescent_state(&rcu_bh_state, 0); | |
234 | } | |
235 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
236 | ||
4a298656 PM |
237 | /* |
238 | * Record the number of times rcutorture tests have been initiated and | |
239 | * terminated. This information allows the debugfs tracing stats to be | |
240 | * correlated to the rcutorture messages, even when the rcutorture module | |
241 | * is being repeatedly loaded and unloaded. In other words, we cannot | |
242 | * store this state in rcutorture itself. | |
243 | */ | |
244 | void rcutorture_record_test_transition(void) | |
245 | { | |
246 | rcutorture_testseq++; | |
247 | rcutorture_vernum = 0; | |
248 | } | |
249 | EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); | |
250 | ||
251 | /* | |
252 | * Record the number of writer passes through the current rcutorture test. | |
253 | * This is also used to correlate debugfs tracing stats with the rcutorture | |
254 | * messages. | |
255 | */ | |
256 | void rcutorture_record_progress(unsigned long vernum) | |
257 | { | |
258 | rcutorture_vernum++; | |
259 | } | |
260 | EXPORT_SYMBOL_GPL(rcutorture_record_progress); | |
261 | ||
bf66f18e PM |
262 | /* |
263 | * Force a quiescent state for RCU-sched. | |
264 | */ | |
265 | void rcu_sched_force_quiescent_state(void) | |
266 | { | |
267 | force_quiescent_state(&rcu_sched_state, 0); | |
268 | } | |
269 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
270 | ||
64db4cff PM |
271 | /* |
272 | * Does the CPU have callbacks ready to be invoked? | |
273 | */ | |
274 | static int | |
275 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
276 | { | |
277 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; | |
278 | } | |
279 | ||
280 | /* | |
281 | * Does the current CPU require a yet-as-unscheduled grace period? | |
282 | */ | |
283 | static int | |
284 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
285 | { | |
fc2219d4 | 286 | return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
64db4cff PM |
287 | } |
288 | ||
289 | /* | |
290 | * Return the root node of the specified rcu_state structure. | |
291 | */ | |
292 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
293 | { | |
294 | return &rsp->node[0]; | |
295 | } | |
296 | ||
297 | #ifdef CONFIG_SMP | |
298 | ||
299 | /* | |
300 | * If the specified CPU is offline, tell the caller that it is in | |
301 | * a quiescent state. Otherwise, whack it with a reschedule IPI. | |
302 | * Grace periods can end up waiting on an offline CPU when that | |
303 | * CPU is in the process of coming online -- it will be added to the | |
304 | * rcu_node bitmasks before it actually makes it online. The same thing | |
305 | * can happen while a CPU is in the process of coming online. Because this | |
306 | * race is quite rare, we check for it after detecting that the grace | |
307 | * period has been delayed rather than checking each and every CPU | |
308 | * each and every time we start a new grace period. | |
309 | */ | |
310 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) | |
311 | { | |
312 | /* | |
313 | * If the CPU is offline, it is in a quiescent state. We can | |
314 | * trust its state not to change because interrupts are disabled. | |
315 | */ | |
316 | if (cpu_is_offline(rdp->cpu)) { | |
317 | rdp->offline_fqs++; | |
318 | return 1; | |
319 | } | |
320 | ||
6cc68793 PM |
321 | /* If preemptible RCU, no point in sending reschedule IPI. */ |
322 | if (rdp->preemptible) | |
f41d911f PM |
323 | return 0; |
324 | ||
64db4cff PM |
325 | /* The CPU is online, so send it a reschedule IPI. */ |
326 | if (rdp->cpu != smp_processor_id()) | |
327 | smp_send_reschedule(rdp->cpu); | |
328 | else | |
329 | set_need_resched(); | |
330 | rdp->resched_ipi++; | |
331 | return 0; | |
332 | } | |
333 | ||
334 | #endif /* #ifdef CONFIG_SMP */ | |
335 | ||
336 | #ifdef CONFIG_NO_HZ | |
64db4cff PM |
337 | |
338 | /** | |
339 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz | |
340 | * | |
341 | * Enter nohz mode, in other words, -leave- the mode in which RCU | |
342 | * read-side critical sections can occur. (Though RCU read-side | |
343 | * critical sections can occur in irq handlers in nohz mode, a possibility | |
344 | * handled by rcu_irq_enter() and rcu_irq_exit()). | |
345 | */ | |
346 | void rcu_enter_nohz(void) | |
347 | { | |
348 | unsigned long flags; | |
349 | struct rcu_dynticks *rdtp; | |
350 | ||
64db4cff PM |
351 | local_irq_save(flags); |
352 | rdtp = &__get_cpu_var(rcu_dynticks); | |
23b5c8fa PM |
353 | if (--rdtp->dynticks_nesting) { |
354 | local_irq_restore(flags); | |
355 | return; | |
356 | } | |
357 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ | |
358 | smp_mb__before_atomic_inc(); /* See above. */ | |
359 | atomic_inc(&rdtp->dynticks); | |
360 | smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ | |
361 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
64db4cff | 362 | local_irq_restore(flags); |
23b5c8fa PM |
363 | |
364 | /* If the interrupt queued a callback, get out of dyntick mode. */ | |
365 | if (in_irq() && | |
366 | (__get_cpu_var(rcu_sched_data).nxtlist || | |
367 | __get_cpu_var(rcu_bh_data).nxtlist || | |
368 | rcu_preempt_needs_cpu(smp_processor_id()))) | |
369 | set_need_resched(); | |
64db4cff PM |
370 | } |
371 | ||
372 | /* | |
373 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz | |
374 | * | |
375 | * Exit nohz mode, in other words, -enter- the mode in which RCU | |
376 | * read-side critical sections normally occur. | |
377 | */ | |
378 | void rcu_exit_nohz(void) | |
379 | { | |
380 | unsigned long flags; | |
381 | struct rcu_dynticks *rdtp; | |
382 | ||
383 | local_irq_save(flags); | |
384 | rdtp = &__get_cpu_var(rcu_dynticks); | |
23b5c8fa PM |
385 | if (rdtp->dynticks_nesting++) { |
386 | local_irq_restore(flags); | |
387 | return; | |
388 | } | |
389 | smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ | |
390 | atomic_inc(&rdtp->dynticks); | |
391 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
392 | smp_mb__after_atomic_inc(); /* See above. */ | |
393 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
64db4cff | 394 | local_irq_restore(flags); |
64db4cff PM |
395 | } |
396 | ||
397 | /** | |
398 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
399 | * | |
400 | * If the CPU was idle with dynamic ticks active, and there is no | |
401 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
402 | * RCU grace-period handling know that the CPU is active. | |
403 | */ | |
404 | void rcu_nmi_enter(void) | |
405 | { | |
406 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
407 | ||
23b5c8fa PM |
408 | if (rdtp->dynticks_nmi_nesting == 0 && |
409 | (atomic_read(&rdtp->dynticks) & 0x1)) | |
64db4cff | 410 | return; |
23b5c8fa PM |
411 | rdtp->dynticks_nmi_nesting++; |
412 | smp_mb__before_atomic_inc(); /* Force delay from prior write. */ | |
413 | atomic_inc(&rdtp->dynticks); | |
414 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
415 | smp_mb__after_atomic_inc(); /* See above. */ | |
416 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
64db4cff PM |
417 | } |
418 | ||
419 | /** | |
420 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
421 | * | |
422 | * If the CPU was idle with dynamic ticks active, and there is no | |
423 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
424 | * RCU grace-period handling know that the CPU is no longer active. | |
425 | */ | |
426 | void rcu_nmi_exit(void) | |
427 | { | |
428 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
429 | ||
23b5c8fa PM |
430 | if (rdtp->dynticks_nmi_nesting == 0 || |
431 | --rdtp->dynticks_nmi_nesting != 0) | |
64db4cff | 432 | return; |
23b5c8fa PM |
433 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
434 | smp_mb__before_atomic_inc(); /* See above. */ | |
435 | atomic_inc(&rdtp->dynticks); | |
436 | smp_mb__after_atomic_inc(); /* Force delay to next write. */ | |
437 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
64db4cff PM |
438 | } |
439 | ||
440 | /** | |
441 | * rcu_irq_enter - inform RCU of entry to hard irq context | |
442 | * | |
443 | * If the CPU was idle with dynamic ticks active, this updates the | |
444 | * rdtp->dynticks to let the RCU handling know that the CPU is active. | |
445 | */ | |
446 | void rcu_irq_enter(void) | |
447 | { | |
23b5c8fa | 448 | rcu_exit_nohz(); |
64db4cff PM |
449 | } |
450 | ||
451 | /** | |
452 | * rcu_irq_exit - inform RCU of exit from hard irq context | |
453 | * | |
454 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks | |
455 | * to put let the RCU handling be aware that the CPU is going back to idle | |
456 | * with no ticks. | |
457 | */ | |
458 | void rcu_irq_exit(void) | |
459 | { | |
23b5c8fa | 460 | rcu_enter_nohz(); |
64db4cff PM |
461 | } |
462 | ||
64db4cff PM |
463 | #ifdef CONFIG_SMP |
464 | ||
64db4cff PM |
465 | /* |
466 | * Snapshot the specified CPU's dynticks counter so that we can later | |
467 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 468 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff PM |
469 | */ |
470 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
471 | { | |
23b5c8fa PM |
472 | rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
473 | return 0; | |
64db4cff PM |
474 | } |
475 | ||
476 | /* | |
477 | * Return true if the specified CPU has passed through a quiescent | |
478 | * state by virtue of being in or having passed through an dynticks | |
479 | * idle state since the last call to dyntick_save_progress_counter() | |
480 | * for this same CPU. | |
481 | */ | |
482 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
483 | { | |
23b5c8fa PM |
484 | unsigned long curr; |
485 | unsigned long snap; | |
64db4cff | 486 | |
23b5c8fa PM |
487 | curr = (unsigned long)atomic_add_return(0, &rdp->dynticks->dynticks); |
488 | snap = (unsigned long)rdp->dynticks_snap; | |
64db4cff PM |
489 | |
490 | /* | |
491 | * If the CPU passed through or entered a dynticks idle phase with | |
492 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
493 | * already acknowledged the request to pass through a quiescent | |
494 | * state. Either way, that CPU cannot possibly be in an RCU | |
495 | * read-side critical section that started before the beginning | |
496 | * of the current RCU grace period. | |
497 | */ | |
23b5c8fa | 498 | if ((curr & 0x1) == 0 || ULONG_CMP_GE(curr, snap + 2)) { |
64db4cff PM |
499 | rdp->dynticks_fqs++; |
500 | return 1; | |
501 | } | |
502 | ||
503 | /* Go check for the CPU being offline. */ | |
504 | return rcu_implicit_offline_qs(rdp); | |
505 | } | |
506 | ||
507 | #endif /* #ifdef CONFIG_SMP */ | |
508 | ||
509 | #else /* #ifdef CONFIG_NO_HZ */ | |
510 | ||
64db4cff PM |
511 | #ifdef CONFIG_SMP |
512 | ||
64db4cff PM |
513 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
514 | { | |
515 | return 0; | |
516 | } | |
517 | ||
518 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
519 | { | |
520 | return rcu_implicit_offline_qs(rdp); | |
521 | } | |
522 | ||
523 | #endif /* #ifdef CONFIG_SMP */ | |
524 | ||
525 | #endif /* #else #ifdef CONFIG_NO_HZ */ | |
526 | ||
742734ee | 527 | int rcu_cpu_stall_suppress __read_mostly; |
c68de209 | 528 | |
64db4cff PM |
529 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
530 | { | |
531 | rsp->gp_start = jiffies; | |
532 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; | |
533 | } | |
534 | ||
535 | static void print_other_cpu_stall(struct rcu_state *rsp) | |
536 | { | |
537 | int cpu; | |
538 | long delta; | |
539 | unsigned long flags; | |
540 | struct rcu_node *rnp = rcu_get_root(rsp); | |
64db4cff PM |
541 | |
542 | /* Only let one CPU complain about others per time interval. */ | |
543 | ||
1304afb2 | 544 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 545 | delta = jiffies - rsp->jiffies_stall; |
fc2219d4 | 546 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
1304afb2 | 547 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
548 | return; |
549 | } | |
550 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
a0b6c9a7 PM |
551 | |
552 | /* | |
553 | * Now rat on any tasks that got kicked up to the root rcu_node | |
554 | * due to CPU offlining. | |
555 | */ | |
556 | rcu_print_task_stall(rnp); | |
1304afb2 | 557 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 558 | |
8cdd32a9 PM |
559 | /* |
560 | * OK, time to rat on our buddy... | |
561 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
562 | * RCU CPU stall warnings. | |
563 | */ | |
4300aa64 PM |
564 | printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {", |
565 | rsp->name); | |
a0b6c9a7 | 566 | rcu_for_each_leaf_node(rsp, rnp) { |
3acd9eb3 | 567 | raw_spin_lock_irqsave(&rnp->lock, flags); |
f41d911f | 568 | rcu_print_task_stall(rnp); |
3acd9eb3 | 569 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
a0b6c9a7 | 570 | if (rnp->qsmask == 0) |
64db4cff | 571 | continue; |
a0b6c9a7 PM |
572 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
573 | if (rnp->qsmask & (1UL << cpu)) | |
574 | printk(" %d", rnp->grplo + cpu); | |
64db4cff | 575 | } |
4300aa64 | 576 | printk("} (detected by %d, t=%ld jiffies)\n", |
64db4cff | 577 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
c1dc0b9c IM |
578 | trigger_all_cpu_backtrace(); |
579 | ||
1ed509a2 PM |
580 | /* If so configured, complain about tasks blocking the grace period. */ |
581 | ||
582 | rcu_print_detail_task_stall(rsp); | |
583 | ||
64db4cff PM |
584 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
585 | } | |
586 | ||
587 | static void print_cpu_stall(struct rcu_state *rsp) | |
588 | { | |
589 | unsigned long flags; | |
590 | struct rcu_node *rnp = rcu_get_root(rsp); | |
591 | ||
8cdd32a9 PM |
592 | /* |
593 | * OK, time to rat on ourselves... | |
594 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
595 | * RCU CPU stall warnings. | |
596 | */ | |
4300aa64 PM |
597 | printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n", |
598 | rsp->name, smp_processor_id(), jiffies - rsp->gp_start); | |
c1dc0b9c IM |
599 | trigger_all_cpu_backtrace(); |
600 | ||
1304afb2 | 601 | raw_spin_lock_irqsave(&rnp->lock, flags); |
20133cfc | 602 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
64db4cff PM |
603 | rsp->jiffies_stall = |
604 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
1304afb2 | 605 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c1dc0b9c | 606 | |
64db4cff PM |
607 | set_need_resched(); /* kick ourselves to get things going. */ |
608 | } | |
609 | ||
610 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
611 | { | |
bad6e139 PM |
612 | unsigned long j; |
613 | unsigned long js; | |
64db4cff PM |
614 | struct rcu_node *rnp; |
615 | ||
742734ee | 616 | if (rcu_cpu_stall_suppress) |
c68de209 | 617 | return; |
bad6e139 PM |
618 | j = ACCESS_ONCE(jiffies); |
619 | js = ACCESS_ONCE(rsp->jiffies_stall); | |
64db4cff | 620 | rnp = rdp->mynode; |
bad6e139 | 621 | if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { |
64db4cff PM |
622 | |
623 | /* We haven't checked in, so go dump stack. */ | |
624 | print_cpu_stall(rsp); | |
625 | ||
bad6e139 PM |
626 | } else if (rcu_gp_in_progress(rsp) && |
627 | ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { | |
64db4cff | 628 | |
bad6e139 | 629 | /* They had a few time units to dump stack, so complain. */ |
64db4cff PM |
630 | print_other_cpu_stall(rsp); |
631 | } | |
632 | } | |
633 | ||
c68de209 PM |
634 | static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
635 | { | |
742734ee | 636 | rcu_cpu_stall_suppress = 1; |
c68de209 PM |
637 | return NOTIFY_DONE; |
638 | } | |
639 | ||
53d84e00 PM |
640 | /** |
641 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
642 | * | |
643 | * Set the stall-warning timeout way off into the future, thus preventing | |
644 | * any RCU CPU stall-warning messages from appearing in the current set of | |
645 | * RCU grace periods. | |
646 | * | |
647 | * The caller must disable hard irqs. | |
648 | */ | |
649 | void rcu_cpu_stall_reset(void) | |
650 | { | |
651 | rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2; | |
652 | rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2; | |
653 | rcu_preempt_stall_reset(); | |
654 | } | |
655 | ||
c68de209 PM |
656 | static struct notifier_block rcu_panic_block = { |
657 | .notifier_call = rcu_panic, | |
658 | }; | |
659 | ||
660 | static void __init check_cpu_stall_init(void) | |
661 | { | |
662 | atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); | |
663 | } | |
664 | ||
64db4cff PM |
665 | /* |
666 | * Update CPU-local rcu_data state to record the newly noticed grace period. | |
667 | * This is used both when we started the grace period and when we notice | |
9160306e PM |
668 | * that someone else started the grace period. The caller must hold the |
669 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, | |
670 | * and must have irqs disabled. | |
64db4cff | 671 | */ |
9160306e PM |
672 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
673 | { | |
674 | if (rdp->gpnum != rnp->gpnum) { | |
121dfc4b PM |
675 | /* |
676 | * If the current grace period is waiting for this CPU, | |
677 | * set up to detect a quiescent state, otherwise don't | |
678 | * go looking for one. | |
679 | */ | |
9160306e | 680 | rdp->gpnum = rnp->gpnum; |
121dfc4b PM |
681 | if (rnp->qsmask & rdp->grpmask) { |
682 | rdp->qs_pending = 1; | |
683 | rdp->passed_quiesc = 0; | |
684 | } else | |
685 | rdp->qs_pending = 0; | |
9160306e PM |
686 | } |
687 | } | |
688 | ||
64db4cff PM |
689 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
690 | { | |
9160306e PM |
691 | unsigned long flags; |
692 | struct rcu_node *rnp; | |
693 | ||
694 | local_irq_save(flags); | |
695 | rnp = rdp->mynode; | |
696 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ | |
1304afb2 | 697 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
9160306e PM |
698 | local_irq_restore(flags); |
699 | return; | |
700 | } | |
701 | __note_new_gpnum(rsp, rnp, rdp); | |
1304afb2 | 702 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
703 | } |
704 | ||
705 | /* | |
706 | * Did someone else start a new RCU grace period start since we last | |
707 | * checked? Update local state appropriately if so. Must be called | |
708 | * on the CPU corresponding to rdp. | |
709 | */ | |
710 | static int | |
711 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) | |
712 | { | |
713 | unsigned long flags; | |
714 | int ret = 0; | |
715 | ||
716 | local_irq_save(flags); | |
717 | if (rdp->gpnum != rsp->gpnum) { | |
718 | note_new_gpnum(rsp, rdp); | |
719 | ret = 1; | |
720 | } | |
721 | local_irq_restore(flags); | |
722 | return ret; | |
723 | } | |
724 | ||
d09b62df PM |
725 | /* |
726 | * Advance this CPU's callbacks, but only if the current grace period | |
727 | * has ended. This may be called only from the CPU to whom the rdp | |
728 | * belongs. In addition, the corresponding leaf rcu_node structure's | |
729 | * ->lock must be held by the caller, with irqs disabled. | |
730 | */ | |
731 | static void | |
732 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
733 | { | |
734 | /* Did another grace period end? */ | |
735 | if (rdp->completed != rnp->completed) { | |
736 | ||
737 | /* Advance callbacks. No harm if list empty. */ | |
738 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; | |
739 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; | |
740 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
741 | ||
742 | /* Remember that we saw this grace-period completion. */ | |
743 | rdp->completed = rnp->completed; | |
20377f32 | 744 | |
5ff8e6f0 FW |
745 | /* |
746 | * If we were in an extended quiescent state, we may have | |
121dfc4b | 747 | * missed some grace periods that others CPUs handled on |
5ff8e6f0 | 748 | * our behalf. Catch up with this state to avoid noting |
121dfc4b PM |
749 | * spurious new grace periods. If another grace period |
750 | * has started, then rnp->gpnum will have advanced, so | |
751 | * we will detect this later on. | |
5ff8e6f0 | 752 | */ |
121dfc4b | 753 | if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) |
5ff8e6f0 FW |
754 | rdp->gpnum = rdp->completed; |
755 | ||
20377f32 | 756 | /* |
121dfc4b PM |
757 | * If RCU does not need a quiescent state from this CPU, |
758 | * then make sure that this CPU doesn't go looking for one. | |
20377f32 | 759 | */ |
121dfc4b | 760 | if ((rnp->qsmask & rdp->grpmask) == 0) |
20377f32 | 761 | rdp->qs_pending = 0; |
d09b62df PM |
762 | } |
763 | } | |
764 | ||
765 | /* | |
766 | * Advance this CPU's callbacks, but only if the current grace period | |
767 | * has ended. This may be called only from the CPU to whom the rdp | |
768 | * belongs. | |
769 | */ | |
770 | static void | |
771 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) | |
772 | { | |
773 | unsigned long flags; | |
774 | struct rcu_node *rnp; | |
775 | ||
776 | local_irq_save(flags); | |
777 | rnp = rdp->mynode; | |
778 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ | |
1304afb2 | 779 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
d09b62df PM |
780 | local_irq_restore(flags); |
781 | return; | |
782 | } | |
783 | __rcu_process_gp_end(rsp, rnp, rdp); | |
1304afb2 | 784 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d09b62df PM |
785 | } |
786 | ||
787 | /* | |
788 | * Do per-CPU grace-period initialization for running CPU. The caller | |
789 | * must hold the lock of the leaf rcu_node structure corresponding to | |
790 | * this CPU. | |
791 | */ | |
792 | static void | |
793 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
794 | { | |
795 | /* Prior grace period ended, so advance callbacks for current CPU. */ | |
796 | __rcu_process_gp_end(rsp, rnp, rdp); | |
797 | ||
798 | /* | |
799 | * Because this CPU just now started the new grace period, we know | |
800 | * that all of its callbacks will be covered by this upcoming grace | |
801 | * period, even the ones that were registered arbitrarily recently. | |
802 | * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. | |
803 | * | |
804 | * Other CPUs cannot be sure exactly when the grace period started. | |
805 | * Therefore, their recently registered callbacks must pass through | |
806 | * an additional RCU_NEXT_READY stage, so that they will be handled | |
807 | * by the next RCU grace period. | |
808 | */ | |
809 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
810 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
9160306e PM |
811 | |
812 | /* Set state so that this CPU will detect the next quiescent state. */ | |
813 | __note_new_gpnum(rsp, rnp, rdp); | |
d09b62df PM |
814 | } |
815 | ||
64db4cff PM |
816 | /* |
817 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
818 | * in preparation for detecting the next grace period. The caller must hold | |
819 | * the root node's ->lock, which is released before return. Hard irqs must | |
820 | * be disabled. | |
821 | */ | |
822 | static void | |
823 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) | |
824 | __releases(rcu_get_root(rsp)->lock) | |
825 | { | |
394f99a9 | 826 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
64db4cff | 827 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 828 | |
07079d53 | 829 | if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) { |
46a1e34e PM |
830 | if (cpu_needs_another_gp(rsp, rdp)) |
831 | rsp->fqs_need_gp = 1; | |
b32e9eb6 | 832 | if (rnp->completed == rsp->completed) { |
1304afb2 | 833 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b32e9eb6 PM |
834 | return; |
835 | } | |
1304afb2 | 836 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
b32e9eb6 PM |
837 | |
838 | /* | |
839 | * Propagate new ->completed value to rcu_node structures | |
840 | * so that other CPUs don't have to wait until the start | |
841 | * of the next grace period to process their callbacks. | |
842 | */ | |
843 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
1304afb2 | 844 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
b32e9eb6 | 845 | rnp->completed = rsp->completed; |
1304afb2 | 846 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
b32e9eb6 PM |
847 | } |
848 | local_irq_restore(flags); | |
64db4cff PM |
849 | return; |
850 | } | |
851 | ||
852 | /* Advance to a new grace period and initialize state. */ | |
853 | rsp->gpnum++; | |
c3422bea | 854 | WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
64db4cff PM |
855 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
856 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; | |
64db4cff | 857 | record_gp_stall_check_time(rsp); |
64db4cff | 858 | |
64db4cff PM |
859 | /* Special-case the common single-level case. */ |
860 | if (NUM_RCU_NODES == 1) { | |
b0e165c0 | 861 | rcu_preempt_check_blocked_tasks(rnp); |
28ecd580 | 862 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 863 | rnp->gpnum = rsp->gpnum; |
d09b62df | 864 | rnp->completed = rsp->completed; |
c12172c0 | 865 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
d09b62df | 866 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
27f4d280 | 867 | rcu_preempt_boost_start_gp(rnp); |
1304afb2 | 868 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
869 | return; |
870 | } | |
871 | ||
1304afb2 | 872 | raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
64db4cff PM |
873 | |
874 | ||
875 | /* Exclude any concurrent CPU-hotplug operations. */ | |
1304afb2 | 876 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
877 | |
878 | /* | |
b835db1f PM |
879 | * Set the quiescent-state-needed bits in all the rcu_node |
880 | * structures for all currently online CPUs in breadth-first | |
881 | * order, starting from the root rcu_node structure. This | |
882 | * operation relies on the layout of the hierarchy within the | |
883 | * rsp->node[] array. Note that other CPUs will access only | |
884 | * the leaves of the hierarchy, which still indicate that no | |
885 | * grace period is in progress, at least until the corresponding | |
886 | * leaf node has been initialized. In addition, we have excluded | |
887 | * CPU-hotplug operations. | |
64db4cff PM |
888 | * |
889 | * Note that the grace period cannot complete until we finish | |
890 | * the initialization process, as there will be at least one | |
891 | * qsmask bit set in the root node until that time, namely the | |
b835db1f PM |
892 | * one corresponding to this CPU, due to the fact that we have |
893 | * irqs disabled. | |
64db4cff | 894 | */ |
a0b6c9a7 | 895 | rcu_for_each_node_breadth_first(rsp, rnp) { |
1304afb2 | 896 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
b0e165c0 | 897 | rcu_preempt_check_blocked_tasks(rnp); |
49e29126 | 898 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 899 | rnp->gpnum = rsp->gpnum; |
d09b62df PM |
900 | rnp->completed = rsp->completed; |
901 | if (rnp == rdp->mynode) | |
902 | rcu_start_gp_per_cpu(rsp, rnp, rdp); | |
27f4d280 | 903 | rcu_preempt_boost_start_gp(rnp); |
1304afb2 | 904 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
905 | } |
906 | ||
83f5b01f | 907 | rnp = rcu_get_root(rsp); |
1304afb2 | 908 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff | 909 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
1304afb2 PM |
910 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
911 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); | |
64db4cff PM |
912 | } |
913 | ||
f41d911f | 914 | /* |
d3f6bad3 PM |
915 | * Report a full set of quiescent states to the specified rcu_state |
916 | * data structure. This involves cleaning up after the prior grace | |
917 | * period and letting rcu_start_gp() start up the next grace period | |
918 | * if one is needed. Note that the caller must hold rnp->lock, as | |
919 | * required by rcu_start_gp(), which will release it. | |
f41d911f | 920 | */ |
d3f6bad3 | 921 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 922 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 923 | { |
15ba0ba8 PM |
924 | unsigned long gp_duration; |
925 | ||
fc2219d4 | 926 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
0bbcc529 PM |
927 | |
928 | /* | |
929 | * Ensure that all grace-period and pre-grace-period activity | |
930 | * is seen before the assignment to rsp->completed. | |
931 | */ | |
932 | smp_mb(); /* See above block comment. */ | |
15ba0ba8 PM |
933 | gp_duration = jiffies - rsp->gp_start; |
934 | if (gp_duration > rsp->gp_max) | |
935 | rsp->gp_max = gp_duration; | |
f41d911f | 936 | rsp->completed = rsp->gpnum; |
83f5b01f | 937 | rsp->signaled = RCU_GP_IDLE; |
f41d911f PM |
938 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
939 | } | |
940 | ||
64db4cff | 941 | /* |
d3f6bad3 PM |
942 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
943 | * Allows quiescent states for a group of CPUs to be reported at one go | |
944 | * to the specified rcu_node structure, though all the CPUs in the group | |
945 | * must be represented by the same rcu_node structure (which need not be | |
946 | * a leaf rcu_node structure, though it often will be). That structure's | |
947 | * lock must be held upon entry, and it is released before return. | |
64db4cff PM |
948 | */ |
949 | static void | |
d3f6bad3 PM |
950 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
951 | struct rcu_node *rnp, unsigned long flags) | |
64db4cff PM |
952 | __releases(rnp->lock) |
953 | { | |
28ecd580 PM |
954 | struct rcu_node *rnp_c; |
955 | ||
64db4cff PM |
956 | /* Walk up the rcu_node hierarchy. */ |
957 | for (;;) { | |
958 | if (!(rnp->qsmask & mask)) { | |
959 | ||
960 | /* Our bit has already been cleared, so done. */ | |
1304afb2 | 961 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
962 | return; |
963 | } | |
964 | rnp->qsmask &= ~mask; | |
27f4d280 | 965 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
64db4cff PM |
966 | |
967 | /* Other bits still set at this level, so done. */ | |
1304afb2 | 968 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
969 | return; |
970 | } | |
971 | mask = rnp->grpmask; | |
972 | if (rnp->parent == NULL) { | |
973 | ||
974 | /* No more levels. Exit loop holding root lock. */ | |
975 | ||
976 | break; | |
977 | } | |
1304afb2 | 978 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
28ecd580 | 979 | rnp_c = rnp; |
64db4cff | 980 | rnp = rnp->parent; |
1304afb2 | 981 | raw_spin_lock_irqsave(&rnp->lock, flags); |
28ecd580 | 982 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
983 | } |
984 | ||
985 | /* | |
986 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 987 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 988 | * to clean up and start the next grace period if one is needed. |
64db4cff | 989 | */ |
d3f6bad3 | 990 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
991 | } |
992 | ||
993 | /* | |
d3f6bad3 PM |
994 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
995 | * structure. This must be either called from the specified CPU, or | |
996 | * called when the specified CPU is known to be offline (and when it is | |
997 | * also known that no other CPU is concurrently trying to help the offline | |
998 | * CPU). The lastcomp argument is used to make sure we are still in the | |
999 | * grace period of interest. We don't want to end the current grace period | |
1000 | * based on quiescent states detected in an earlier grace period! | |
64db4cff PM |
1001 | */ |
1002 | static void | |
d3f6bad3 | 1003 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) |
64db4cff PM |
1004 | { |
1005 | unsigned long flags; | |
1006 | unsigned long mask; | |
1007 | struct rcu_node *rnp; | |
1008 | ||
1009 | rnp = rdp->mynode; | |
1304afb2 | 1010 | raw_spin_lock_irqsave(&rnp->lock, flags); |
560d4bc0 | 1011 | if (lastcomp != rnp->completed) { |
64db4cff PM |
1012 | |
1013 | /* | |
1014 | * Someone beat us to it for this grace period, so leave. | |
1015 | * The race with GP start is resolved by the fact that we | |
1016 | * hold the leaf rcu_node lock, so that the per-CPU bits | |
1017 | * cannot yet be initialized -- so we would simply find our | |
d3f6bad3 PM |
1018 | * CPU's bit already cleared in rcu_report_qs_rnp() if this |
1019 | * race occurred. | |
64db4cff PM |
1020 | */ |
1021 | rdp->passed_quiesc = 0; /* try again later! */ | |
1304afb2 | 1022 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1023 | return; |
1024 | } | |
1025 | mask = rdp->grpmask; | |
1026 | if ((rnp->qsmask & mask) == 0) { | |
1304afb2 | 1027 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1028 | } else { |
1029 | rdp->qs_pending = 0; | |
1030 | ||
1031 | /* | |
1032 | * This GP can't end until cpu checks in, so all of our | |
1033 | * callbacks can be processed during the next GP. | |
1034 | */ | |
64db4cff PM |
1035 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
1036 | ||
d3f6bad3 | 1037 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
64db4cff PM |
1038 | } |
1039 | } | |
1040 | ||
1041 | /* | |
1042 | * Check to see if there is a new grace period of which this CPU | |
1043 | * is not yet aware, and if so, set up local rcu_data state for it. | |
1044 | * Otherwise, see if this CPU has just passed through its first | |
1045 | * quiescent state for this grace period, and record that fact if so. | |
1046 | */ | |
1047 | static void | |
1048 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
1049 | { | |
1050 | /* If there is now a new grace period, record and return. */ | |
1051 | if (check_for_new_grace_period(rsp, rdp)) | |
1052 | return; | |
1053 | ||
1054 | /* | |
1055 | * Does this CPU still need to do its part for current grace period? | |
1056 | * If no, return and let the other CPUs do their part as well. | |
1057 | */ | |
1058 | if (!rdp->qs_pending) | |
1059 | return; | |
1060 | ||
1061 | /* | |
1062 | * Was there a quiescent state since the beginning of the grace | |
1063 | * period? If no, then exit and wait for the next call. | |
1064 | */ | |
1065 | if (!rdp->passed_quiesc) | |
1066 | return; | |
1067 | ||
d3f6bad3 PM |
1068 | /* |
1069 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
1070 | * judge of that). | |
1071 | */ | |
1072 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); | |
64db4cff PM |
1073 | } |
1074 | ||
1075 | #ifdef CONFIG_HOTPLUG_CPU | |
1076 | ||
e74f4c45 | 1077 | /* |
29494be7 LJ |
1078 | * Move a dying CPU's RCU callbacks to online CPU's callback list. |
1079 | * Synchronization is not required because this function executes | |
1080 | * in stop_machine() context. | |
e74f4c45 | 1081 | */ |
29494be7 | 1082 | static void rcu_send_cbs_to_online(struct rcu_state *rsp) |
e74f4c45 PM |
1083 | { |
1084 | int i; | |
29494be7 LJ |
1085 | /* current DYING CPU is cleared in the cpu_online_mask */ |
1086 | int receive_cpu = cpumask_any(cpu_online_mask); | |
394f99a9 | 1087 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
29494be7 | 1088 | struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu); |
e74f4c45 PM |
1089 | |
1090 | if (rdp->nxtlist == NULL) | |
1091 | return; /* irqs disabled, so comparison is stable. */ | |
29494be7 LJ |
1092 | |
1093 | *receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist; | |
1094 | receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
1095 | receive_rdp->qlen += rdp->qlen; | |
1096 | receive_rdp->n_cbs_adopted += rdp->qlen; | |
1097 | rdp->n_cbs_orphaned += rdp->qlen; | |
1098 | ||
e74f4c45 PM |
1099 | rdp->nxtlist = NULL; |
1100 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1101 | rdp->nxttail[i] = &rdp->nxtlist; | |
e74f4c45 | 1102 | rdp->qlen = 0; |
e74f4c45 PM |
1103 | } |
1104 | ||
64db4cff PM |
1105 | /* |
1106 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy | |
1107 | * and move all callbacks from the outgoing CPU to the current one. | |
a26ac245 PM |
1108 | * There can only be one CPU hotplug operation at a time, so no other |
1109 | * CPU can be attempting to update rcu_cpu_kthread_task. | |
64db4cff PM |
1110 | */ |
1111 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) | |
1112 | { | |
64db4cff | 1113 | unsigned long flags; |
64db4cff | 1114 | unsigned long mask; |
d9a3da06 | 1115 | int need_report = 0; |
394f99a9 | 1116 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff | 1117 | struct rcu_node *rnp; |
a26ac245 | 1118 | |
f8b7fc6b | 1119 | rcu_stop_cpu_kthread(cpu); |
64db4cff PM |
1120 | |
1121 | /* Exclude any attempts to start a new grace period. */ | |
1304afb2 | 1122 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
64db4cff PM |
1123 | |
1124 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ | |
28ecd580 | 1125 | rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
64db4cff PM |
1126 | mask = rdp->grpmask; /* rnp->grplo is constant. */ |
1127 | do { | |
1304afb2 | 1128 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
1129 | rnp->qsmaskinit &= ~mask; |
1130 | if (rnp->qsmaskinit != 0) { | |
b668c9cf | 1131 | if (rnp != rdp->mynode) |
1304afb2 | 1132 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
1133 | break; |
1134 | } | |
b668c9cf | 1135 | if (rnp == rdp->mynode) |
d9a3da06 | 1136 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); |
b668c9cf | 1137 | else |
1304afb2 | 1138 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff | 1139 | mask = rnp->grpmask; |
64db4cff PM |
1140 | rnp = rnp->parent; |
1141 | } while (rnp != NULL); | |
64db4cff | 1142 | |
b668c9cf PM |
1143 | /* |
1144 | * We still hold the leaf rcu_node structure lock here, and | |
1145 | * irqs are still disabled. The reason for this subterfuge is | |
d3f6bad3 PM |
1146 | * because invoking rcu_report_unblock_qs_rnp() with ->onofflock |
1147 | * held leads to deadlock. | |
b668c9cf | 1148 | */ |
1304afb2 | 1149 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
b668c9cf | 1150 | rnp = rdp->mynode; |
d9a3da06 | 1151 | if (need_report & RCU_OFL_TASKS_NORM_GP) |
d3f6bad3 | 1152 | rcu_report_unblock_qs_rnp(rnp, flags); |
b668c9cf | 1153 | else |
1304afb2 | 1154 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da06 PM |
1155 | if (need_report & RCU_OFL_TASKS_EXP_GP) |
1156 | rcu_report_exp_rnp(rsp, rnp); | |
1217ed1b | 1157 | rcu_node_kthread_setaffinity(rnp, -1); |
64db4cff PM |
1158 | } |
1159 | ||
1160 | /* | |
1161 | * Remove the specified CPU from the RCU hierarchy and move any pending | |
1162 | * callbacks that it might have to the current CPU. This code assumes | |
1163 | * that at least one CPU in the system will remain running at all times. | |
1164 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. | |
1165 | */ | |
1166 | static void rcu_offline_cpu(int cpu) | |
1167 | { | |
d6714c22 | 1168 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
64db4cff | 1169 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
33f76148 | 1170 | rcu_preempt_offline_cpu(cpu); |
64db4cff PM |
1171 | } |
1172 | ||
1173 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
1174 | ||
29494be7 | 1175 | static void rcu_send_cbs_to_online(struct rcu_state *rsp) |
e74f4c45 PM |
1176 | { |
1177 | } | |
1178 | ||
64db4cff PM |
1179 | static void rcu_offline_cpu(int cpu) |
1180 | { | |
1181 | } | |
1182 | ||
1183 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
1184 | ||
1185 | /* | |
1186 | * Invoke any RCU callbacks that have made it to the end of their grace | |
1187 | * period. Thottle as specified by rdp->blimit. | |
1188 | */ | |
37c72e56 | 1189 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1190 | { |
1191 | unsigned long flags; | |
1192 | struct rcu_head *next, *list, **tail; | |
1193 | int count; | |
1194 | ||
1195 | /* If no callbacks are ready, just return.*/ | |
1196 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) | |
1197 | return; | |
1198 | ||
1199 | /* | |
1200 | * Extract the list of ready callbacks, disabling to prevent | |
1201 | * races with call_rcu() from interrupt handlers. | |
1202 | */ | |
1203 | local_irq_save(flags); | |
1204 | list = rdp->nxtlist; | |
1205 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
1206 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
1207 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
1208 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) | |
1209 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) | |
1210 | rdp->nxttail[count] = &rdp->nxtlist; | |
1211 | local_irq_restore(flags); | |
1212 | ||
1213 | /* Invoke callbacks. */ | |
1214 | count = 0; | |
1215 | while (list) { | |
1216 | next = list->next; | |
1217 | prefetch(next); | |
551d55a9 | 1218 | debug_rcu_head_unqueue(list); |
9ab1544e | 1219 | __rcu_reclaim(list); |
64db4cff PM |
1220 | list = next; |
1221 | if (++count >= rdp->blimit) | |
1222 | break; | |
1223 | } | |
1224 | ||
1225 | local_irq_save(flags); | |
1226 | ||
1227 | /* Update count, and requeue any remaining callbacks. */ | |
1228 | rdp->qlen -= count; | |
269dcc1c | 1229 | rdp->n_cbs_invoked += count; |
64db4cff PM |
1230 | if (list != NULL) { |
1231 | *tail = rdp->nxtlist; | |
1232 | rdp->nxtlist = list; | |
1233 | for (count = 0; count < RCU_NEXT_SIZE; count++) | |
1234 | if (&rdp->nxtlist == rdp->nxttail[count]) | |
1235 | rdp->nxttail[count] = tail; | |
1236 | else | |
1237 | break; | |
1238 | } | |
1239 | ||
1240 | /* Reinstate batch limit if we have worked down the excess. */ | |
1241 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
1242 | rdp->blimit = blimit; | |
1243 | ||
37c72e56 PM |
1244 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
1245 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
1246 | rdp->qlen_last_fqs_check = 0; | |
1247 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1248 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
1249 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1250 | ||
64db4cff PM |
1251 | local_irq_restore(flags); |
1252 | ||
1253 | /* Re-raise the RCU softirq if there are callbacks remaining. */ | |
1254 | if (cpu_has_callbacks_ready_to_invoke(rdp)) | |
a46e0899 | 1255 | invoke_rcu_core(); |
64db4cff PM |
1256 | } |
1257 | ||
1258 | /* | |
1259 | * Check to see if this CPU is in a non-context-switch quiescent state | |
1260 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
1261 | * Also schedule the RCU softirq handler. | |
1262 | * | |
1263 | * This function must be called with hardirqs disabled. It is normally | |
1264 | * invoked from the scheduling-clock interrupt. If rcu_pending returns | |
1265 | * false, there is no point in invoking rcu_check_callbacks(). | |
1266 | */ | |
1267 | void rcu_check_callbacks(int cpu, int user) | |
1268 | { | |
1269 | if (user || | |
a6826048 PM |
1270 | (idle_cpu(cpu) && rcu_scheduler_active && |
1271 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { | |
64db4cff PM |
1272 | |
1273 | /* | |
1274 | * Get here if this CPU took its interrupt from user | |
1275 | * mode or from the idle loop, and if this is not a | |
1276 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 1277 | * a quiescent state, so note it. |
64db4cff PM |
1278 | * |
1279 | * No memory barrier is required here because both | |
d6714c22 PM |
1280 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1281 | * variables that other CPUs neither access nor modify, | |
1282 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
1283 | */ |
1284 | ||
d6714c22 PM |
1285 | rcu_sched_qs(cpu); |
1286 | rcu_bh_qs(cpu); | |
64db4cff PM |
1287 | |
1288 | } else if (!in_softirq()) { | |
1289 | ||
1290 | /* | |
1291 | * Get here if this CPU did not take its interrupt from | |
1292 | * softirq, in other words, if it is not interrupting | |
1293 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 1294 | * critical section, so note it. |
64db4cff PM |
1295 | */ |
1296 | ||
d6714c22 | 1297 | rcu_bh_qs(cpu); |
64db4cff | 1298 | } |
f41d911f | 1299 | rcu_preempt_check_callbacks(cpu); |
d21670ac | 1300 | if (rcu_pending(cpu)) |
a46e0899 | 1301 | invoke_rcu_core(); |
64db4cff PM |
1302 | } |
1303 | ||
1304 | #ifdef CONFIG_SMP | |
1305 | ||
1306 | /* | |
1307 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
1308 | * have not yet encountered a quiescent state, using the function specified. | |
27f4d280 PM |
1309 | * Also initiate boosting for any threads blocked on the root rcu_node. |
1310 | * | |
ee47eb9f | 1311 | * The caller must have suppressed start of new grace periods. |
64db4cff | 1312 | */ |
45f014c5 | 1313 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
64db4cff PM |
1314 | { |
1315 | unsigned long bit; | |
1316 | int cpu; | |
1317 | unsigned long flags; | |
1318 | unsigned long mask; | |
a0b6c9a7 | 1319 | struct rcu_node *rnp; |
64db4cff | 1320 | |
a0b6c9a7 | 1321 | rcu_for_each_leaf_node(rsp, rnp) { |
64db4cff | 1322 | mask = 0; |
1304afb2 | 1323 | raw_spin_lock_irqsave(&rnp->lock, flags); |
ee47eb9f | 1324 | if (!rcu_gp_in_progress(rsp)) { |
1304afb2 | 1325 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
0f10dc82 | 1326 | return; |
64db4cff | 1327 | } |
a0b6c9a7 | 1328 | if (rnp->qsmask == 0) { |
1217ed1b | 1329 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
64db4cff PM |
1330 | continue; |
1331 | } | |
a0b6c9a7 | 1332 | cpu = rnp->grplo; |
64db4cff | 1333 | bit = 1; |
a0b6c9a7 | 1334 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
394f99a9 LJ |
1335 | if ((rnp->qsmask & bit) != 0 && |
1336 | f(per_cpu_ptr(rsp->rda, cpu))) | |
64db4cff PM |
1337 | mask |= bit; |
1338 | } | |
45f014c5 | 1339 | if (mask != 0) { |
64db4cff | 1340 | |
d3f6bad3 PM |
1341 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
1342 | rcu_report_qs_rnp(mask, rsp, rnp, flags); | |
64db4cff PM |
1343 | continue; |
1344 | } | |
1304afb2 | 1345 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 1346 | } |
27f4d280 | 1347 | rnp = rcu_get_root(rsp); |
1217ed1b PM |
1348 | if (rnp->qsmask == 0) { |
1349 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
1350 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ | |
1351 | } | |
64db4cff PM |
1352 | } |
1353 | ||
1354 | /* | |
1355 | * Force quiescent states on reluctant CPUs, and also detect which | |
1356 | * CPUs are in dyntick-idle mode. | |
1357 | */ | |
1358 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1359 | { | |
1360 | unsigned long flags; | |
64db4cff | 1361 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 1362 | |
fc2219d4 | 1363 | if (!rcu_gp_in_progress(rsp)) |
64db4cff | 1364 | return; /* No grace period in progress, nothing to force. */ |
1304afb2 | 1365 | if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) { |
64db4cff PM |
1366 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
1367 | return; /* Someone else is already on the job. */ | |
1368 | } | |
20133cfc | 1369 | if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies)) |
f96e9232 | 1370 | goto unlock_fqs_ret; /* no emergency and done recently. */ |
64db4cff | 1371 | rsp->n_force_qs++; |
1304afb2 | 1372 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
64db4cff | 1373 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
560d4bc0 | 1374 | if(!rcu_gp_in_progress(rsp)) { |
64db4cff | 1375 | rsp->n_force_qs_ngp++; |
1304afb2 | 1376 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
f96e9232 | 1377 | goto unlock_fqs_ret; /* no GP in progress, time updated. */ |
64db4cff | 1378 | } |
07079d53 | 1379 | rsp->fqs_active = 1; |
f3a8b5c6 | 1380 | switch (rsp->signaled) { |
83f5b01f | 1381 | case RCU_GP_IDLE: |
64db4cff PM |
1382 | case RCU_GP_INIT: |
1383 | ||
83f5b01f | 1384 | break; /* grace period idle or initializing, ignore. */ |
64db4cff PM |
1385 | |
1386 | case RCU_SAVE_DYNTICK: | |
64db4cff PM |
1387 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
1388 | break; /* So gcc recognizes the dead code. */ | |
1389 | ||
f261414f LJ |
1390 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1391 | ||
64db4cff | 1392 | /* Record dyntick-idle state. */ |
45f014c5 | 1393 | force_qs_rnp(rsp, dyntick_save_progress_counter); |
1304afb2 | 1394 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
ee47eb9f | 1395 | if (rcu_gp_in_progress(rsp)) |
64db4cff | 1396 | rsp->signaled = RCU_FORCE_QS; |
ee47eb9f | 1397 | break; |
64db4cff PM |
1398 | |
1399 | case RCU_FORCE_QS: | |
1400 | ||
1401 | /* Check dyntick-idle state, send IPI to laggarts. */ | |
1304afb2 | 1402 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
45f014c5 | 1403 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
64db4cff PM |
1404 | |
1405 | /* Leave state in case more forcing is required. */ | |
1406 | ||
1304afb2 | 1407 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
f96e9232 | 1408 | break; |
64db4cff | 1409 | } |
07079d53 | 1410 | rsp->fqs_active = 0; |
46a1e34e | 1411 | if (rsp->fqs_need_gp) { |
1304afb2 | 1412 | raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */ |
46a1e34e PM |
1413 | rsp->fqs_need_gp = 0; |
1414 | rcu_start_gp(rsp, flags); /* releases rnp->lock */ | |
1415 | return; | |
1416 | } | |
1304afb2 | 1417 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
f96e9232 | 1418 | unlock_fqs_ret: |
1304afb2 | 1419 | raw_spin_unlock_irqrestore(&rsp->fqslock, flags); |
64db4cff PM |
1420 | } |
1421 | ||
1422 | #else /* #ifdef CONFIG_SMP */ | |
1423 | ||
1424 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1425 | { | |
1426 | set_need_resched(); | |
1427 | } | |
1428 | ||
1429 | #endif /* #else #ifdef CONFIG_SMP */ | |
1430 | ||
1431 | /* | |
1432 | * This does the RCU processing work from softirq context for the | |
1433 | * specified rcu_state and rcu_data structures. This may be called | |
1434 | * only from the CPU to whom the rdp belongs. | |
1435 | */ | |
1436 | static void | |
1437 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) | |
1438 | { | |
1439 | unsigned long flags; | |
1440 | ||
2e597558 PM |
1441 | WARN_ON_ONCE(rdp->beenonline == 0); |
1442 | ||
64db4cff PM |
1443 | /* |
1444 | * If an RCU GP has gone long enough, go check for dyntick | |
1445 | * idle CPUs and, if needed, send resched IPIs. | |
1446 | */ | |
20133cfc | 1447 | if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
64db4cff PM |
1448 | force_quiescent_state(rsp, 1); |
1449 | ||
1450 | /* | |
1451 | * Advance callbacks in response to end of earlier grace | |
1452 | * period that some other CPU ended. | |
1453 | */ | |
1454 | rcu_process_gp_end(rsp, rdp); | |
1455 | ||
1456 | /* Update RCU state based on any recent quiescent states. */ | |
1457 | rcu_check_quiescent_state(rsp, rdp); | |
1458 | ||
1459 | /* Does this CPU require a not-yet-started grace period? */ | |
1460 | if (cpu_needs_another_gp(rsp, rdp)) { | |
1304afb2 | 1461 | raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
64db4cff PM |
1462 | rcu_start_gp(rsp, flags); /* releases above lock */ |
1463 | } | |
1464 | ||
1465 | /* If there are callbacks ready, invoke them. */ | |
09223371 | 1466 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 1467 | invoke_rcu_callbacks(rsp, rdp); |
09223371 SL |
1468 | } |
1469 | ||
64db4cff PM |
1470 | /* |
1471 | * Do softirq processing for the current CPU. | |
1472 | */ | |
09223371 | 1473 | static void rcu_process_callbacks(struct softirq_action *unused) |
64db4cff | 1474 | { |
d6714c22 PM |
1475 | __rcu_process_callbacks(&rcu_sched_state, |
1476 | &__get_cpu_var(rcu_sched_data)); | |
64db4cff | 1477 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
f41d911f | 1478 | rcu_preempt_process_callbacks(); |
a47cd880 PM |
1479 | |
1480 | /* If we are last CPU on way to dyntick-idle mode, accelerate it. */ | |
1481 | rcu_needs_cpu_flush(); | |
64db4cff PM |
1482 | } |
1483 | ||
a26ac245 PM |
1484 | /* |
1485 | * Wake up the current CPU's kthread. This replaces raise_softirq() | |
1486 | * in earlier versions of RCU. Note that because we are running on | |
1487 | * the current CPU with interrupts disabled, the rcu_cpu_kthread_task | |
1488 | * cannot disappear out from under us. | |
1489 | */ | |
a46e0899 | 1490 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
a26ac245 | 1491 | { |
b0d30417 PM |
1492 | if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) |
1493 | return; | |
a46e0899 PM |
1494 | if (likely(!rsp->boost)) { |
1495 | rcu_do_batch(rsp, rdp); | |
a26ac245 PM |
1496 | return; |
1497 | } | |
a46e0899 | 1498 | invoke_rcu_callbacks_kthread(); |
a26ac245 PM |
1499 | } |
1500 | ||
a46e0899 | 1501 | static void invoke_rcu_core(void) |
09223371 SL |
1502 | { |
1503 | raise_softirq(RCU_SOFTIRQ); | |
1504 | } | |
1505 | ||
64db4cff PM |
1506 | static void |
1507 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
1508 | struct rcu_state *rsp) | |
1509 | { | |
1510 | unsigned long flags; | |
1511 | struct rcu_data *rdp; | |
1512 | ||
551d55a9 | 1513 | debug_rcu_head_queue(head); |
64db4cff PM |
1514 | head->func = func; |
1515 | head->next = NULL; | |
1516 | ||
1517 | smp_mb(); /* Ensure RCU update seen before callback registry. */ | |
1518 | ||
1519 | /* | |
1520 | * Opportunistically note grace-period endings and beginnings. | |
1521 | * Note that we might see a beginning right after we see an | |
1522 | * end, but never vice versa, since this CPU has to pass through | |
1523 | * a quiescent state betweentimes. | |
1524 | */ | |
1525 | local_irq_save(flags); | |
394f99a9 | 1526 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
1527 | |
1528 | /* Add the callback to our list. */ | |
1529 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
1530 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
2655d57e PM |
1531 | rdp->qlen++; |
1532 | ||
1533 | /* If interrupts were disabled, don't dive into RCU core. */ | |
1534 | if (irqs_disabled_flags(flags)) { | |
1535 | local_irq_restore(flags); | |
1536 | return; | |
1537 | } | |
64db4cff | 1538 | |
37c72e56 PM |
1539 | /* |
1540 | * Force the grace period if too many callbacks or too long waiting. | |
1541 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
1542 | * if some other CPU has recently done so. Also, don't bother | |
1543 | * invoking force_quiescent_state() if the newly enqueued callback | |
1544 | * is the only one waiting for a grace period to complete. | |
1545 | */ | |
2655d57e | 1546 | if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
b52573d2 PM |
1547 | |
1548 | /* Are we ignoring a completed grace period? */ | |
1549 | rcu_process_gp_end(rsp, rdp); | |
1550 | check_for_new_grace_period(rsp, rdp); | |
1551 | ||
1552 | /* Start a new grace period if one not already started. */ | |
1553 | if (!rcu_gp_in_progress(rsp)) { | |
1554 | unsigned long nestflag; | |
1555 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
1556 | ||
1557 | raw_spin_lock_irqsave(&rnp_root->lock, nestflag); | |
1558 | rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */ | |
1559 | } else { | |
1560 | /* Give the grace period a kick. */ | |
1561 | rdp->blimit = LONG_MAX; | |
1562 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
1563 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
1564 | force_quiescent_state(rsp, 0); | |
1565 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1566 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1567 | } | |
20133cfc | 1568 | } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
64db4cff PM |
1569 | force_quiescent_state(rsp, 1); |
1570 | local_irq_restore(flags); | |
1571 | } | |
1572 | ||
1573 | /* | |
d6714c22 | 1574 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 1575 | */ |
d6714c22 | 1576 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 1577 | { |
d6714c22 | 1578 | __call_rcu(head, func, &rcu_sched_state); |
64db4cff | 1579 | } |
d6714c22 | 1580 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
1581 | |
1582 | /* | |
1583 | * Queue an RCU for invocation after a quicker grace period. | |
1584 | */ | |
1585 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
1586 | { | |
1587 | __call_rcu(head, func, &rcu_bh_state); | |
1588 | } | |
1589 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
1590 | ||
6ebb237b PM |
1591 | /** |
1592 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
1593 | * | |
1594 | * Control will return to the caller some time after a full rcu-sched | |
1595 | * grace period has elapsed, in other words after all currently executing | |
1596 | * rcu-sched read-side critical sections have completed. These read-side | |
1597 | * critical sections are delimited by rcu_read_lock_sched() and | |
1598 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
1599 | * local_irq_disable(), and so on may be used in place of | |
1600 | * rcu_read_lock_sched(). | |
1601 | * | |
1602 | * This means that all preempt_disable code sequences, including NMI and | |
1603 | * hardware-interrupt handlers, in progress on entry will have completed | |
1604 | * before this primitive returns. However, this does not guarantee that | |
1605 | * softirq handlers will have completed, since in some kernels, these | |
1606 | * handlers can run in process context, and can block. | |
1607 | * | |
1608 | * This primitive provides the guarantees made by the (now removed) | |
1609 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
1610 | * guarantees that rcu_read_lock() sections will have completed. | |
1611 | * In "classic RCU", these two guarantees happen to be one and | |
1612 | * the same, but can differ in realtime RCU implementations. | |
1613 | */ | |
1614 | void synchronize_sched(void) | |
1615 | { | |
1616 | struct rcu_synchronize rcu; | |
1617 | ||
1618 | if (rcu_blocking_is_gp()) | |
1619 | return; | |
1620 | ||
72d5a9f7 | 1621 | init_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1622 | init_completion(&rcu.completion); |
1623 | /* Will wake me after RCU finished. */ | |
1624 | call_rcu_sched(&rcu.head, wakeme_after_rcu); | |
1625 | /* Wait for it. */ | |
1626 | wait_for_completion(&rcu.completion); | |
72d5a9f7 | 1627 | destroy_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1628 | } |
1629 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
1630 | ||
1631 | /** | |
1632 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
1633 | * | |
1634 | * Control will return to the caller some time after a full rcu_bh grace | |
1635 | * period has elapsed, in other words after all currently executing rcu_bh | |
1636 | * read-side critical sections have completed. RCU read-side critical | |
1637 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
1638 | * and may be nested. | |
1639 | */ | |
1640 | void synchronize_rcu_bh(void) | |
1641 | { | |
1642 | struct rcu_synchronize rcu; | |
1643 | ||
1644 | if (rcu_blocking_is_gp()) | |
1645 | return; | |
1646 | ||
72d5a9f7 | 1647 | init_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1648 | init_completion(&rcu.completion); |
1649 | /* Will wake me after RCU finished. */ | |
1650 | call_rcu_bh(&rcu.head, wakeme_after_rcu); | |
1651 | /* Wait for it. */ | |
1652 | wait_for_completion(&rcu.completion); | |
72d5a9f7 | 1653 | destroy_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1654 | } |
1655 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
1656 | ||
64db4cff PM |
1657 | /* |
1658 | * Check to see if there is any immediate RCU-related work to be done | |
1659 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
1660 | * The checks are in order of increasing expense: checks that can be | |
1661 | * carried out against CPU-local state are performed first. However, | |
1662 | * we must check for CPU stalls first, else we might not get a chance. | |
1663 | */ | |
1664 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
1665 | { | |
2f51f988 PM |
1666 | struct rcu_node *rnp = rdp->mynode; |
1667 | ||
64db4cff PM |
1668 | rdp->n_rcu_pending++; |
1669 | ||
1670 | /* Check for CPU stalls, if enabled. */ | |
1671 | check_cpu_stall(rsp, rdp); | |
1672 | ||
1673 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
d21670ac | 1674 | if (rdp->qs_pending && !rdp->passed_quiesc) { |
d25eb944 PM |
1675 | |
1676 | /* | |
1677 | * If force_quiescent_state() coming soon and this CPU | |
1678 | * needs a quiescent state, and this is either RCU-sched | |
1679 | * or RCU-bh, force a local reschedule. | |
1680 | */ | |
d21670ac | 1681 | rdp->n_rp_qs_pending++; |
6cc68793 | 1682 | if (!rdp->preemptible && |
d25eb944 PM |
1683 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1, |
1684 | jiffies)) | |
1685 | set_need_resched(); | |
d21670ac PM |
1686 | } else if (rdp->qs_pending && rdp->passed_quiesc) { |
1687 | rdp->n_rp_report_qs++; | |
64db4cff | 1688 | return 1; |
7ba5c840 | 1689 | } |
64db4cff PM |
1690 | |
1691 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
1692 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
1693 | rdp->n_rp_cb_ready++; | |
64db4cff | 1694 | return 1; |
7ba5c840 | 1695 | } |
64db4cff PM |
1696 | |
1697 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
1698 | if (cpu_needs_another_gp(rsp, rdp)) { |
1699 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 1700 | return 1; |
7ba5c840 | 1701 | } |
64db4cff PM |
1702 | |
1703 | /* Has another RCU grace period completed? */ | |
2f51f988 | 1704 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 1705 | rdp->n_rp_gp_completed++; |
64db4cff | 1706 | return 1; |
7ba5c840 | 1707 | } |
64db4cff PM |
1708 | |
1709 | /* Has a new RCU grace period started? */ | |
2f51f988 | 1710 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
7ba5c840 | 1711 | rdp->n_rp_gp_started++; |
64db4cff | 1712 | return 1; |
7ba5c840 | 1713 | } |
64db4cff PM |
1714 | |
1715 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ | |
fc2219d4 | 1716 | if (rcu_gp_in_progress(rsp) && |
20133cfc | 1717 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) { |
7ba5c840 | 1718 | rdp->n_rp_need_fqs++; |
64db4cff | 1719 | return 1; |
7ba5c840 | 1720 | } |
64db4cff PM |
1721 | |
1722 | /* nothing to do */ | |
7ba5c840 | 1723 | rdp->n_rp_need_nothing++; |
64db4cff PM |
1724 | return 0; |
1725 | } | |
1726 | ||
1727 | /* | |
1728 | * Check to see if there is any immediate RCU-related work to be done | |
1729 | * by the current CPU, returning 1 if so. This function is part of the | |
1730 | * RCU implementation; it is -not- an exported member of the RCU API. | |
1731 | */ | |
a157229c | 1732 | static int rcu_pending(int cpu) |
64db4cff | 1733 | { |
d6714c22 | 1734 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
f41d911f PM |
1735 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
1736 | rcu_preempt_pending(cpu); | |
64db4cff PM |
1737 | } |
1738 | ||
1739 | /* | |
1740 | * Check to see if any future RCU-related work will need to be done | |
1741 | * by the current CPU, even if none need be done immediately, returning | |
8bd93a2c | 1742 | * 1 if so. |
64db4cff | 1743 | */ |
8bd93a2c | 1744 | static int rcu_needs_cpu_quick_check(int cpu) |
64db4cff PM |
1745 | { |
1746 | /* RCU callbacks either ready or pending? */ | |
d6714c22 | 1747 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
f41d911f PM |
1748 | per_cpu(rcu_bh_data, cpu).nxtlist || |
1749 | rcu_preempt_needs_cpu(cpu); | |
64db4cff PM |
1750 | } |
1751 | ||
d0ec774c PM |
1752 | static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
1753 | static atomic_t rcu_barrier_cpu_count; | |
1754 | static DEFINE_MUTEX(rcu_barrier_mutex); | |
1755 | static struct completion rcu_barrier_completion; | |
d0ec774c PM |
1756 | |
1757 | static void rcu_barrier_callback(struct rcu_head *notused) | |
1758 | { | |
1759 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
1760 | complete(&rcu_barrier_completion); | |
1761 | } | |
1762 | ||
1763 | /* | |
1764 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
1765 | */ | |
1766 | static void rcu_barrier_func(void *type) | |
1767 | { | |
1768 | int cpu = smp_processor_id(); | |
1769 | struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); | |
1770 | void (*call_rcu_func)(struct rcu_head *head, | |
1771 | void (*func)(struct rcu_head *head)); | |
1772 | ||
1773 | atomic_inc(&rcu_barrier_cpu_count); | |
1774 | call_rcu_func = type; | |
1775 | call_rcu_func(head, rcu_barrier_callback); | |
1776 | } | |
1777 | ||
d0ec774c PM |
1778 | /* |
1779 | * Orchestrate the specified type of RCU barrier, waiting for all | |
1780 | * RCU callbacks of the specified type to complete. | |
1781 | */ | |
e74f4c45 PM |
1782 | static void _rcu_barrier(struct rcu_state *rsp, |
1783 | void (*call_rcu_func)(struct rcu_head *head, | |
d0ec774c PM |
1784 | void (*func)(struct rcu_head *head))) |
1785 | { | |
1786 | BUG_ON(in_interrupt()); | |
e74f4c45 | 1787 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
d0ec774c PM |
1788 | mutex_lock(&rcu_barrier_mutex); |
1789 | init_completion(&rcu_barrier_completion); | |
1790 | /* | |
1791 | * Initialize rcu_barrier_cpu_count to 1, then invoke | |
1792 | * rcu_barrier_func() on each CPU, so that each CPU also has | |
1793 | * incremented rcu_barrier_cpu_count. Only then is it safe to | |
1794 | * decrement rcu_barrier_cpu_count -- otherwise the first CPU | |
1795 | * might complete its grace period before all of the other CPUs | |
1796 | * did their increment, causing this function to return too | |
2d999e03 PM |
1797 | * early. Note that on_each_cpu() disables irqs, which prevents |
1798 | * any CPUs from coming online or going offline until each online | |
1799 | * CPU has queued its RCU-barrier callback. | |
d0ec774c PM |
1800 | */ |
1801 | atomic_set(&rcu_barrier_cpu_count, 1); | |
1802 | on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1); | |
1803 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
1804 | complete(&rcu_barrier_completion); | |
1805 | wait_for_completion(&rcu_barrier_completion); | |
1806 | mutex_unlock(&rcu_barrier_mutex); | |
d0ec774c | 1807 | } |
d0ec774c PM |
1808 | |
1809 | /** | |
1810 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
1811 | */ | |
1812 | void rcu_barrier_bh(void) | |
1813 | { | |
e74f4c45 | 1814 | _rcu_barrier(&rcu_bh_state, call_rcu_bh); |
d0ec774c PM |
1815 | } |
1816 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
1817 | ||
1818 | /** | |
1819 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
1820 | */ | |
1821 | void rcu_barrier_sched(void) | |
1822 | { | |
e74f4c45 | 1823 | _rcu_barrier(&rcu_sched_state, call_rcu_sched); |
d0ec774c PM |
1824 | } |
1825 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
1826 | ||
64db4cff | 1827 | /* |
27569620 | 1828 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 1829 | */ |
27569620 PM |
1830 | static void __init |
1831 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
1832 | { |
1833 | unsigned long flags; | |
1834 | int i; | |
394f99a9 | 1835 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
1836 | struct rcu_node *rnp = rcu_get_root(rsp); |
1837 | ||
1838 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 1839 | raw_spin_lock_irqsave(&rnp->lock, flags); |
27569620 PM |
1840 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
1841 | rdp->nxtlist = NULL; | |
1842 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1843 | rdp->nxttail[i] = &rdp->nxtlist; | |
1844 | rdp->qlen = 0; | |
1845 | #ifdef CONFIG_NO_HZ | |
1846 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); | |
1847 | #endif /* #ifdef CONFIG_NO_HZ */ | |
1848 | rdp->cpu = cpu; | |
1304afb2 | 1849 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27569620 PM |
1850 | } |
1851 | ||
1852 | /* | |
1853 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
1854 | * offline event can be happening at a given time. Note also that we | |
1855 | * can accept some slop in the rsp->completed access due to the fact | |
1856 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 1857 | */ |
e4fa4c97 | 1858 | static void __cpuinit |
6cc68793 | 1859 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) |
64db4cff PM |
1860 | { |
1861 | unsigned long flags; | |
64db4cff | 1862 | unsigned long mask; |
394f99a9 | 1863 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
1864 | struct rcu_node *rnp = rcu_get_root(rsp); |
1865 | ||
1866 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 1867 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff PM |
1868 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
1869 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ | |
1870 | rdp->beenonline = 1; /* We have now been online. */ | |
6cc68793 | 1871 | rdp->preemptible = preemptible; |
37c72e56 PM |
1872 | rdp->qlen_last_fqs_check = 0; |
1873 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 1874 | rdp->blimit = blimit; |
1304afb2 | 1875 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
1876 | |
1877 | /* | |
1878 | * A new grace period might start here. If so, we won't be part | |
1879 | * of it, but that is OK, as we are currently in a quiescent state. | |
1880 | */ | |
1881 | ||
1882 | /* Exclude any attempts to start a new GP on large systems. */ | |
1304afb2 | 1883 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
1884 | |
1885 | /* Add CPU to rcu_node bitmasks. */ | |
1886 | rnp = rdp->mynode; | |
1887 | mask = rdp->grpmask; | |
1888 | do { | |
1889 | /* Exclude any attempts to start a new GP on small systems. */ | |
1304afb2 | 1890 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
1891 | rnp->qsmaskinit |= mask; |
1892 | mask = rnp->grpmask; | |
d09b62df PM |
1893 | if (rnp == rdp->mynode) { |
1894 | rdp->gpnum = rnp->completed; /* if GP in progress... */ | |
1895 | rdp->completed = rnp->completed; | |
1896 | rdp->passed_quiesc_completed = rnp->completed - 1; | |
1897 | } | |
1304afb2 | 1898 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
1899 | rnp = rnp->parent; |
1900 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
1901 | ||
1304afb2 | 1902 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
64db4cff PM |
1903 | } |
1904 | ||
d72bce0e | 1905 | static void __cpuinit rcu_prepare_cpu(int cpu) |
64db4cff | 1906 | { |
f41d911f PM |
1907 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
1908 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); | |
1909 | rcu_preempt_init_percpu_data(cpu); | |
64db4cff PM |
1910 | } |
1911 | ||
1912 | /* | |
f41d911f | 1913 | * Handle CPU online/offline notification events. |
64db4cff | 1914 | */ |
9f680ab4 PM |
1915 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
1916 | unsigned long action, void *hcpu) | |
64db4cff PM |
1917 | { |
1918 | long cpu = (long)hcpu; | |
27f4d280 | 1919 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
a26ac245 | 1920 | struct rcu_node *rnp = rdp->mynode; |
64db4cff PM |
1921 | |
1922 | switch (action) { | |
1923 | case CPU_UP_PREPARE: | |
1924 | case CPU_UP_PREPARE_FROZEN: | |
d72bce0e PZ |
1925 | rcu_prepare_cpu(cpu); |
1926 | rcu_prepare_kthreads(cpu); | |
a26ac245 PM |
1927 | break; |
1928 | case CPU_ONLINE: | |
0f962a5e PM |
1929 | case CPU_DOWN_FAILED: |
1930 | rcu_node_kthread_setaffinity(rnp, -1); | |
e3995a25 | 1931 | rcu_cpu_kthread_setrt(cpu, 1); |
0f962a5e PM |
1932 | break; |
1933 | case CPU_DOWN_PREPARE: | |
1934 | rcu_node_kthread_setaffinity(rnp, cpu); | |
e3995a25 | 1935 | rcu_cpu_kthread_setrt(cpu, 0); |
64db4cff | 1936 | break; |
d0ec774c PM |
1937 | case CPU_DYING: |
1938 | case CPU_DYING_FROZEN: | |
1939 | /* | |
2d999e03 PM |
1940 | * The whole machine is "stopped" except this CPU, so we can |
1941 | * touch any data without introducing corruption. We send the | |
1942 | * dying CPU's callbacks to an arbitrarily chosen online CPU. | |
d0ec774c | 1943 | */ |
29494be7 LJ |
1944 | rcu_send_cbs_to_online(&rcu_bh_state); |
1945 | rcu_send_cbs_to_online(&rcu_sched_state); | |
1946 | rcu_preempt_send_cbs_to_online(); | |
d0ec774c | 1947 | break; |
64db4cff PM |
1948 | case CPU_DEAD: |
1949 | case CPU_DEAD_FROZEN: | |
1950 | case CPU_UP_CANCELED: | |
1951 | case CPU_UP_CANCELED_FROZEN: | |
1952 | rcu_offline_cpu(cpu); | |
1953 | break; | |
1954 | default: | |
1955 | break; | |
1956 | } | |
1957 | return NOTIFY_OK; | |
1958 | } | |
1959 | ||
bbad9379 PM |
1960 | /* |
1961 | * This function is invoked towards the end of the scheduler's initialization | |
1962 | * process. Before this is called, the idle task might contain | |
1963 | * RCU read-side critical sections (during which time, this idle | |
1964 | * task is booting the system). After this function is called, the | |
1965 | * idle tasks are prohibited from containing RCU read-side critical | |
1966 | * sections. This function also enables RCU lockdep checking. | |
1967 | */ | |
1968 | void rcu_scheduler_starting(void) | |
1969 | { | |
1970 | WARN_ON(num_online_cpus() != 1); | |
1971 | WARN_ON(nr_context_switches() > 0); | |
1972 | rcu_scheduler_active = 1; | |
1973 | } | |
1974 | ||
64db4cff PM |
1975 | /* |
1976 | * Compute the per-level fanout, either using the exact fanout specified | |
1977 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
1978 | */ | |
1979 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
1980 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1981 | { | |
1982 | int i; | |
1983 | ||
0209f649 | 1984 | for (i = NUM_RCU_LVLS - 1; i > 0; i--) |
64db4cff | 1985 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
0209f649 | 1986 | rsp->levelspread[0] = RCU_FANOUT_LEAF; |
64db4cff PM |
1987 | } |
1988 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
1989 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1990 | { | |
1991 | int ccur; | |
1992 | int cprv; | |
1993 | int i; | |
1994 | ||
1995 | cprv = NR_CPUS; | |
1996 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
1997 | ccur = rsp->levelcnt[i]; | |
1998 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
1999 | cprv = ccur; | |
2000 | } | |
2001 | } | |
2002 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
2003 | ||
2004 | /* | |
2005 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
2006 | */ | |
394f99a9 LJ |
2007 | static void __init rcu_init_one(struct rcu_state *rsp, |
2008 | struct rcu_data __percpu *rda) | |
64db4cff | 2009 | { |
b6407e86 PM |
2010 | static char *buf[] = { "rcu_node_level_0", |
2011 | "rcu_node_level_1", | |
2012 | "rcu_node_level_2", | |
2013 | "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ | |
64db4cff PM |
2014 | int cpustride = 1; |
2015 | int i; | |
2016 | int j; | |
2017 | struct rcu_node *rnp; | |
2018 | ||
b6407e86 PM |
2019 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
2020 | ||
64db4cff PM |
2021 | /* Initialize the level-tracking arrays. */ |
2022 | ||
2023 | for (i = 1; i < NUM_RCU_LVLS; i++) | |
2024 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; | |
2025 | rcu_init_levelspread(rsp); | |
2026 | ||
2027 | /* Initialize the elements themselves, starting from the leaves. */ | |
2028 | ||
2029 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
2030 | cpustride *= rsp->levelspread[i]; | |
2031 | rnp = rsp->level[i]; | |
2032 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1304afb2 | 2033 | raw_spin_lock_init(&rnp->lock); |
b6407e86 PM |
2034 | lockdep_set_class_and_name(&rnp->lock, |
2035 | &rcu_node_class[i], buf[i]); | |
f41d911f | 2036 | rnp->gpnum = 0; |
64db4cff PM |
2037 | rnp->qsmask = 0; |
2038 | rnp->qsmaskinit = 0; | |
2039 | rnp->grplo = j * cpustride; | |
2040 | rnp->grphi = (j + 1) * cpustride - 1; | |
2041 | if (rnp->grphi >= NR_CPUS) | |
2042 | rnp->grphi = NR_CPUS - 1; | |
2043 | if (i == 0) { | |
2044 | rnp->grpnum = 0; | |
2045 | rnp->grpmask = 0; | |
2046 | rnp->parent = NULL; | |
2047 | } else { | |
2048 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
2049 | rnp->grpmask = 1UL << rnp->grpnum; | |
2050 | rnp->parent = rsp->level[i - 1] + | |
2051 | j / rsp->levelspread[i - 1]; | |
2052 | } | |
2053 | rnp->level = i; | |
12f5f524 | 2054 | INIT_LIST_HEAD(&rnp->blkd_tasks); |
64db4cff PM |
2055 | } |
2056 | } | |
0c34029a | 2057 | |
394f99a9 | 2058 | rsp->rda = rda; |
0c34029a LJ |
2059 | rnp = rsp->level[NUM_RCU_LVLS - 1]; |
2060 | for_each_possible_cpu(i) { | |
4a90a068 | 2061 | while (i > rnp->grphi) |
0c34029a | 2062 | rnp++; |
394f99a9 | 2063 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
2064 | rcu_boot_init_percpu_data(i, rsp); |
2065 | } | |
64db4cff PM |
2066 | } |
2067 | ||
9f680ab4 | 2068 | void __init rcu_init(void) |
64db4cff | 2069 | { |
017c4261 | 2070 | int cpu; |
9f680ab4 | 2071 | |
f41d911f | 2072 | rcu_bootup_announce(); |
394f99a9 LJ |
2073 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
2074 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); | |
f41d911f | 2075 | __rcu_init_preempt(); |
09223371 | 2076 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
2077 | |
2078 | /* | |
2079 | * We don't need protection against CPU-hotplug here because | |
2080 | * this is called early in boot, before either interrupts | |
2081 | * or the scheduler are operational. | |
2082 | */ | |
2083 | cpu_notifier(rcu_cpu_notify, 0); | |
017c4261 PM |
2084 | for_each_online_cpu(cpu) |
2085 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); | |
c68de209 | 2086 | check_cpu_stall_init(); |
64db4cff PM |
2087 | } |
2088 | ||
1eba8f84 | 2089 | #include "rcutree_plugin.h" |