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621934e [PATCH] srcu-3: RCU variant permitting read-side blocking
Paul E. McKenney authored
1 /*
2 * Sleepable 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 (C) IBM Corporation, 2006
19 *
20 * Author: Paul McKenney <paulmck@us.ibm.com>
21 *
22 * For detailed explanation of Read-Copy Update mechanism see -
23 * Documentation/RCU/ *.txt
24 *
25 */
26
9984de1 kernel: Map most files to use export.h instead of module.h
Paul Gortmaker authored
27 #include <linux/export.h>
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28 #include <linux/mutex.h>
29 #include <linux/percpu.h>
30 #include <linux/preempt.h>
31 #include <linux/rcupdate.h>
32 #include <linux/sched.h>
33 #include <linux/smp.h>
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34 #include <linux/delay.h>
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35 #include <linux/srcu.h>
36
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37 /*
38 * Initialize an rcu_batch structure to empty.
39 */
40 static inline void rcu_batch_init(struct rcu_batch *b)
41 {
42 b->head = NULL;
43 b->tail = &b->head;
44 }
45
46 /*
47 * Enqueue a callback onto the tail of the specified rcu_batch structure.
48 */
49 static inline void rcu_batch_queue(struct rcu_batch *b, struct rcu_head *head)
50 {
51 *b->tail = head;
52 b->tail = &head->next;
53 }
54
55 /*
56 * Is the specified rcu_batch structure empty?
57 */
58 static inline bool rcu_batch_empty(struct rcu_batch *b)
59 {
60 return b->tail == &b->head;
61 }
62
63 /*
64 * Remove the callback at the head of the specified rcu_batch structure
65 * and return a pointer to it, or return NULL if the structure is empty.
66 */
67 static inline struct rcu_head *rcu_batch_dequeue(struct rcu_batch *b)
68 {
69 struct rcu_head *head;
70
71 if (rcu_batch_empty(b))
72 return NULL;
73
74 head = b->head;
75 b->head = head->next;
76 if (b->tail == &head->next)
77 rcu_batch_init(b);
78
79 return head;
80 }
81
82 /*
83 * Move all callbacks from the rcu_batch structure specified by "from" to
84 * the structure specified by "to".
85 */
86 static inline void rcu_batch_move(struct rcu_batch *to, struct rcu_batch *from)
87 {
88 if (!rcu_batch_empty(from)) {
89 *to->tail = from->head;
90 to->tail = from->tail;
91 rcu_batch_init(from);
92 }
93 }
94
95 /* single-thread state-machine */
96 static void process_srcu(struct work_struct *work);
97
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98 static int init_srcu_struct_fields(struct srcu_struct *sp)
99 {
100 sp->completed = 0;
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101 spin_lock_init(&sp->queue_lock);
102 sp->running = false;
103 rcu_batch_init(&sp->batch_queue);
104 rcu_batch_init(&sp->batch_check0);
105 rcu_batch_init(&sp->batch_check1);
106 rcu_batch_init(&sp->batch_done);
107 INIT_DELAYED_WORK(&sp->work, process_srcu);
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108 sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
109 return sp->per_cpu_ref ? 0 : -ENOMEM;
110 }
111
112 #ifdef CONFIG_DEBUG_LOCK_ALLOC
113
114 int __init_srcu_struct(struct srcu_struct *sp, const char *name,
115 struct lock_class_key *key)
116 {
117 /* Don't re-initialize a lock while it is held. */
118 debug_check_no_locks_freed((void *)sp, sizeof(*sp));
119 lockdep_init_map(&sp->dep_map, name, key, 0);
120 return init_srcu_struct_fields(sp);
121 }
122 EXPORT_SYMBOL_GPL(__init_srcu_struct);
123
124 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
125
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126 /**
127 * init_srcu_struct - initialize a sleep-RCU structure
128 * @sp: structure to initialize.
129 *
130 * Must invoke this on a given srcu_struct before passing that srcu_struct
131 * to any other function. Each srcu_struct represents a separate domain
132 * of SRCU protection.
133 */
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134 int init_srcu_struct(struct srcu_struct *sp)
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135 {
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136 return init_srcu_struct_fields(sp);
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137 }
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138 EXPORT_SYMBOL_GPL(init_srcu_struct);
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139
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140 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
141
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142 /*
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143 * Returns approximate total of the readers' ->seq[] values for the
144 * rank of per-CPU counters specified by idx.
145 */
146 static unsigned long srcu_readers_seq_idx(struct srcu_struct *sp, int idx)
147 {
148 int cpu;
149 unsigned long sum = 0;
150 unsigned long t;
151
152 for_each_possible_cpu(cpu) {
153 t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->seq[idx]);
154 sum += t;
155 }
156 return sum;
157 }
158
159 /*
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160 * Returns approximate number of readers active on the specified rank
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161 * of the per-CPU ->c[] counters.
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162 */
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163 static unsigned long srcu_readers_active_idx(struct srcu_struct *sp, int idx)
164 {
165 int cpu;
166 unsigned long sum = 0;
167 unsigned long t;
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168
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169 for_each_possible_cpu(cpu) {
170 t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx]);
171 sum += t;
172 }
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173 return sum;
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174 }
175
176 /*
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177 * Return true if the number of pre-existing readers is determined to
178 * be stably zero. An example unstable zero can occur if the call
179 * to srcu_readers_active_idx() misses an __srcu_read_lock() increment,
180 * but due to task migration, sees the corresponding __srcu_read_unlock()
181 * decrement. This can happen because srcu_readers_active_idx() takes
182 * time to sum the array, and might in fact be interrupted or preempted
183 * partway through the summation.
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184 */
185 static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx)
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186 {
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187 unsigned long seq;
188
189 seq = srcu_readers_seq_idx(sp, idx);
190
191 /*
192 * The following smp_mb() A pairs with the smp_mb() B located in
193 * __srcu_read_lock(). This pairing ensures that if an
194 * __srcu_read_lock() increments its counter after the summation
195 * in srcu_readers_active_idx(), then the corresponding SRCU read-side
196 * critical section will see any changes made prior to the start
197 * of the current SRCU grace period.
198 *
199 * Also, if the above call to srcu_readers_seq_idx() saw the
200 * increment of ->seq[], then the call to srcu_readers_active_idx()
201 * must see the increment of ->c[].
202 */
203 smp_mb(); /* A */
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204
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205 /*
206 * Note that srcu_readers_active_idx() can incorrectly return
207 * zero even though there is a pre-existing reader throughout.
208 * To see this, suppose that task A is in a very long SRCU
209 * read-side critical section that started on CPU 0, and that
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210 * no other reader exists, so that the sum of the counters
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211 * is equal to one. Then suppose that task B starts executing
212 * srcu_readers_active_idx(), summing up to CPU 1, and then that
213 * task C starts reading on CPU 0, so that its increment is not
214 * summed, but finishes reading on CPU 2, so that its decrement
215 * -is- summed. Then when task B completes its sum, it will
216 * incorrectly get zero, despite the fact that task A has been
217 * in its SRCU read-side critical section the whole time.
218 *
219 * We therefore do a validation step should srcu_readers_active_idx()
220 * return zero.
221 */
222 if (srcu_readers_active_idx(sp, idx) != 0)
223 return false;
224
225 /*
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226 * The remainder of this function is the validation step.
227 * The following smp_mb() D pairs with the smp_mb() C in
228 * __srcu_read_unlock(). If the __srcu_read_unlock() was seen
229 * by srcu_readers_active_idx() above, then any destructive
230 * operation performed after the grace period will happen after
231 * the corresponding SRCU read-side critical section.
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232 *
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233 * Note that there can be at most NR_CPUS worth of readers using
234 * the old index, which is not enough to overflow even a 32-bit
235 * integer. (Yes, this does mean that systems having more than
236 * a billion or so CPUs need to be 64-bit systems.) Therefore,
237 * the sum of the ->seq[] counters cannot possibly overflow.
238 * Therefore, the only way that the return values of the two
239 * calls to srcu_readers_seq_idx() can be equal is if there were
240 * no increments of the corresponding rank of ->seq[] counts
241 * in the interim. But the missed-increment scenario laid out
242 * above includes an increment of the ->seq[] counter by
243 * the corresponding __srcu_read_lock(). Therefore, if this
244 * scenario occurs, the return values from the two calls to
245 * srcu_readers_seq_idx() will differ, and thus the validation
246 * step below suffices.
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247 */
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248 smp_mb(); /* D */
249
250 return srcu_readers_seq_idx(sp, idx) == seq;
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251 }
252
253 /**
254 * srcu_readers_active - returns approximate number of readers.
255 * @sp: which srcu_struct to count active readers (holding srcu_read_lock).
256 *
257 * Note that this is not an atomic primitive, and can therefore suffer
258 * severe errors when invoked on an active srcu_struct. That said, it
259 * can be useful as an error check at cleanup time.
260 */
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261 static int srcu_readers_active(struct srcu_struct *sp)
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262 {
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263 int cpu;
264 unsigned long sum = 0;
265
266 for_each_possible_cpu(cpu) {
267 sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[0]);
268 sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[1]);
269 }
270 return sum;
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271 }
272
273 /**
274 * cleanup_srcu_struct - deconstruct a sleep-RCU structure
275 * @sp: structure to clean up.
276 *
277 * Must invoke this after you are finished using a given srcu_struct that
278 * was initialized via init_srcu_struct(), else you leak memory.
279 */
280 void cleanup_srcu_struct(struct srcu_struct *sp)
281 {
282 int sum;
283
284 sum = srcu_readers_active(sp);
285 WARN_ON(sum); /* Leakage unless caller handles error. */
286 if (sum != 0)
287 return;
288 free_percpu(sp->per_cpu_ref);
289 sp->per_cpu_ref = NULL;
290 }
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291 EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
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292
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293 /*
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294 * Counts the new reader in the appropriate per-CPU element of the
295 * srcu_struct. Must be called from process context.
296 * Returns an index that must be passed to the matching srcu_read_unlock().
297 */
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298 int __srcu_read_lock(struct srcu_struct *sp)
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299 {
300 int idx;
301
302 preempt_disable();
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303 idx = rcu_dereference_index_check(sp->completed,
304 rcu_read_lock_sched_held()) & 0x1;
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305 ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) += 1;
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306 smp_mb(); /* B */ /* Avoid leaking the critical section. */
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307 ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->seq[idx]) += 1;
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308 preempt_enable();
309 return idx;
310 }
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311 EXPORT_SYMBOL_GPL(__srcu_read_lock);
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312
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313 /*
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314 * Removes the count for the old reader from the appropriate per-CPU
315 * element of the srcu_struct. Note that this may well be a different
316 * CPU than that which was incremented by the corresponding srcu_read_lock().
317 * Must be called from process context.
318 */
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319 void __srcu_read_unlock(struct srcu_struct *sp, int idx)
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320 {
321 preempt_disable();
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322 smp_mb(); /* C */ /* Avoid leaking the critical section. */
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323 ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) -= 1;
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324 preempt_enable();
325 }
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326 EXPORT_SYMBOL_GPL(__srcu_read_unlock);
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327
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328 /*
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329 * We use an adaptive strategy for synchronize_srcu() and especially for
330 * synchronize_srcu_expedited(). We spin for a fixed time period
331 * (defined below) to allow SRCU readers to exit their read-side critical
332 * sections. If there are still some readers after 10 microseconds,
333 * we repeatedly block for 1-millisecond time periods. This approach
334 * has done well in testing, so there is no need for a config parameter.
335 */
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336 #define SRCU_RETRY_CHECK_DELAY 5
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337 #define SYNCHRONIZE_SRCU_TRYCOUNT 2
338 #define SYNCHRONIZE_SRCU_EXP_TRYCOUNT 12
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339
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340 /*
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341 * @@@ Wait until all pre-existing readers complete. Such readers
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342 * will have used the index specified by "idx".
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343 * the caller should ensures the ->completed is not changed while checking
344 * and idx = (->completed & 1) ^ 1
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345 */
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346 static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount)
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347 {
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348 for (;;) {
349 if (srcu_readers_active_idx_check(sp, idx))
350 return true;
351 if (--trycount <= 0)
352 return false;
353 udelay(SRCU_RETRY_CHECK_DELAY);
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354 }
355 }
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356
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357 /*
358 * Increment the ->completed counter so that future SRCU readers will
359 * use the other rank of the ->c[] and ->seq[] arrays. This allows
360 * us to wait for pre-existing readers in a starvation-free manner.
361 */
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362 static void srcu_flip(struct srcu_struct *sp)
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363 {
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364 sp->completed++;
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365 }
366
367 /*
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368 * Enqueue an SRCU callback on the specified srcu_struct structure,
369 * initiating grace-period processing if it is not already running.
370 */
371 void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
372 void (*func)(struct rcu_head *head))
373 {
374 unsigned long flags;
375
376 head->next = NULL;
377 head->func = func;
378 spin_lock_irqsave(&sp->queue_lock, flags);
379 rcu_batch_queue(&sp->batch_queue, head);
380 if (!sp->running) {
381 sp->running = true;
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382 schedule_delayed_work(&sp->work, 0);
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383 }
384 spin_unlock_irqrestore(&sp->queue_lock, flags);
385 }
386 EXPORT_SYMBOL_GPL(call_srcu);
387
388 struct rcu_synchronize {
389 struct rcu_head head;
390 struct completion completion;
391 };
392
393 /*
394 * Awaken the corresponding synchronize_srcu() instance now that a
395 * grace period has elapsed.
396 */
397 static void wakeme_after_rcu(struct rcu_head *head)
398 {
399 struct rcu_synchronize *rcu;
400
401 rcu = container_of(head, struct rcu_synchronize, head);
402 complete(&rcu->completion);
403 }
404
405 static void srcu_advance_batches(struct srcu_struct *sp, int trycount);
406 static void srcu_reschedule(struct srcu_struct *sp);
407
408 /*
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409 * Helper function for synchronize_srcu() and synchronize_srcu_expedited().
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410 */
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411 static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
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412 {
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413 struct rcu_synchronize rcu;
414 struct rcu_head *head = &rcu.head;
415 bool done = false;
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416
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417 rcu_lockdep_assert(!lock_is_held(&sp->dep_map) &&
418 !lock_is_held(&rcu_bh_lock_map) &&
419 !lock_is_held(&rcu_lock_map) &&
420 !lock_is_held(&rcu_sched_lock_map),
421 "Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section");
422
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423 init_completion(&rcu.completion);
424
425 head->next = NULL;
426 head->func = wakeme_after_rcu;
427 spin_lock_irq(&sp->queue_lock);
428 if (!sp->running) {
429 /* steal the processing owner */
430 sp->running = true;
431 rcu_batch_queue(&sp->batch_check0, head);
432 spin_unlock_irq(&sp->queue_lock);
433
434 srcu_advance_batches(sp, trycount);
435 if (!rcu_batch_empty(&sp->batch_done)) {
436 BUG_ON(sp->batch_done.head != head);
437 rcu_batch_dequeue(&sp->batch_done);
438 done = true;
439 }
440 /* give the processing owner to work_struct */
441 srcu_reschedule(sp);
442 } else {
443 rcu_batch_queue(&sp->batch_queue, head);
444 spin_unlock_irq(&sp->queue_lock);
445 }
944ce9a @laijs rcu: Flip ->completed only once per SRCU grace period
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446
931ea9d @laijs rcu: Implement per-domain single-threaded call_srcu() state machine
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447 if (!done)
448 wait_for_completion(&rcu.completion);
621934e [PATCH] srcu-3: RCU variant permitting read-side blocking
Paul E. McKenney authored
449 }
450
451 /**
0cd397d @paulmck rcu: Add synchronize_srcu_expedited()
paulmck authored
452 * synchronize_srcu - wait for prior SRCU read-side critical-section completion
453 * @sp: srcu_struct with which to synchronize.
454 *
455 * Flip the completed counter, and wait for the old count to drain to zero.
456 * As with classic RCU, the updater must use some separate means of
457 * synchronizing concurrent updates. Can block; must be called from
458 * process context.
459 *
460 * Note that it is illegal to call synchronize_srcu() from the corresponding
461 * SRCU read-side critical section; doing so will result in deadlock.
462 * However, it is perfectly legal to call synchronize_srcu() on one
463 * srcu_struct from some other srcu_struct's read-side critical section.
464 */
465 void synchronize_srcu(struct srcu_struct *sp)
466 {
d9792ed @laijs rcu: Use single value to handle expedited SRCU grace periods
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467 __synchronize_srcu(sp, SYNCHRONIZE_SRCU_TRYCOUNT);
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paulmck authored
468 }
469 EXPORT_SYMBOL_GPL(synchronize_srcu);
470
471 /**
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472 * synchronize_srcu_expedited - Brute-force SRCU grace period
0cd397d @paulmck rcu: Add synchronize_srcu_expedited()
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473 * @sp: srcu_struct with which to synchronize.
474 *
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475 * Wait for an SRCU grace period to elapse, but be more aggressive about
476 * spinning rather than blocking when waiting.
0cd397d @paulmck rcu: Add synchronize_srcu_expedited()
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477 *
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478 * Note that it is illegal to call this function while holding any lock
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479 * that is acquired by a CPU-hotplug notifier. It is also illegal to call
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paulmck authored
480 * synchronize_srcu_expedited() from the corresponding SRCU read-side
481 * critical section; doing so will result in deadlock. However, it is
482 * perfectly legal to call synchronize_srcu_expedited() on one srcu_struct
483 * from some other srcu_struct's read-side critical section, as long as
484 * the resulting graph of srcu_structs is acyclic.
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485 */
486 void synchronize_srcu_expedited(struct srcu_struct *sp)
487 {
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488 __synchronize_srcu(sp, SYNCHRONIZE_SRCU_EXP_TRYCOUNT);
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paulmck authored
489 }
490 EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
491
492 /**
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laijs authored
493 * srcu_barrier - Wait until all in-flight call_srcu() callbacks complete.
494 */
495 void srcu_barrier(struct srcu_struct *sp)
496 {
497 synchronize_srcu(sp);
498 }
499 EXPORT_SYMBOL_GPL(srcu_barrier);
500
501 /**
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502 * srcu_batches_completed - return batches completed.
503 * @sp: srcu_struct on which to report batch completion.
504 *
505 * Report the number of batches, correlated with, but not necessarily
506 * precisely the same as, the number of grace periods that have elapsed.
507 */
508 long srcu_batches_completed(struct srcu_struct *sp)
509 {
510 return sp->completed;
511 }
512 EXPORT_SYMBOL_GPL(srcu_batches_completed);
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laijs authored
513
514 #define SRCU_CALLBACK_BATCH 10
515 #define SRCU_INTERVAL 1
516
517 /*
518 * Move any new SRCU callbacks to the first stage of the SRCU grace
519 * period pipeline.
520 */
521 static void srcu_collect_new(struct srcu_struct *sp)
522 {
523 if (!rcu_batch_empty(&sp->batch_queue)) {
524 spin_lock_irq(&sp->queue_lock);
525 rcu_batch_move(&sp->batch_check0, &sp->batch_queue);
526 spin_unlock_irq(&sp->queue_lock);
527 }
528 }
529
530 /*
531 * Core SRCU state machine. Advance callbacks from ->batch_check0 to
532 * ->batch_check1 and then to ->batch_done as readers drain.
533 */
534 static void srcu_advance_batches(struct srcu_struct *sp, int trycount)
535 {
536 int idx = 1 ^ (sp->completed & 1);
537
538 /*
539 * Because readers might be delayed for an extended period after
540 * fetching ->completed for their index, at any point in time there
541 * might well be readers using both idx=0 and idx=1. We therefore
542 * need to wait for readers to clear from both index values before
543 * invoking a callback.
544 */
545
546 if (rcu_batch_empty(&sp->batch_check0) &&
547 rcu_batch_empty(&sp->batch_check1))
548 return; /* no callbacks need to be advanced */
549
550 if (!try_check_zero(sp, idx, trycount))
551 return; /* failed to advance, will try after SRCU_INTERVAL */
552
553 /*
554 * The callbacks in ->batch_check1 have already done with their
555 * first zero check and flip back when they were enqueued on
556 * ->batch_check0 in a previous invocation of srcu_advance_batches().
557 * (Presumably try_check_zero() returned false during that
558 * invocation, leaving the callbacks stranded on ->batch_check1.)
559 * They are therefore ready to invoke, so move them to ->batch_done.
560 */
561 rcu_batch_move(&sp->batch_done, &sp->batch_check1);
562
563 if (rcu_batch_empty(&sp->batch_check0))
564 return; /* no callbacks need to be advanced */
565 srcu_flip(sp);
566
567 /*
568 * The callbacks in ->batch_check0 just finished their
569 * first check zero and flip, so move them to ->batch_check1
570 * for future checking on the other idx.
571 */
572 rcu_batch_move(&sp->batch_check1, &sp->batch_check0);
573
574 /*
575 * SRCU read-side critical sections are normally short, so check
576 * at least twice in quick succession after a flip.
577 */
578 trycount = trycount < 2 ? 2 : trycount;
579 if (!try_check_zero(sp, idx^1, trycount))
580 return; /* failed to advance, will try after SRCU_INTERVAL */
581
582 /*
583 * The callbacks in ->batch_check1 have now waited for all
584 * pre-existing readers using both idx values. They are therefore
585 * ready to invoke, so move them to ->batch_done.
586 */
587 rcu_batch_move(&sp->batch_done, &sp->batch_check1);
588 }
589
590 /*
591 * Invoke a limited number of SRCU callbacks that have passed through
592 * their grace period. If there are more to do, SRCU will reschedule
593 * the workqueue.
594 */
595 static void srcu_invoke_callbacks(struct srcu_struct *sp)
596 {
597 int i;
598 struct rcu_head *head;
599
600 for (i = 0; i < SRCU_CALLBACK_BATCH; i++) {
601 head = rcu_batch_dequeue(&sp->batch_done);
602 if (!head)
603 break;
604 local_bh_disable();
605 head->func(head);
606 local_bh_enable();
607 }
608 }
609
610 /*
611 * Finished one round of SRCU grace period. Start another if there are
612 * more SRCU callbacks queued, otherwise put SRCU into not-running state.
613 */
614 static void srcu_reschedule(struct srcu_struct *sp)
615 {
616 bool pending = true;
617
618 if (rcu_batch_empty(&sp->batch_done) &&
619 rcu_batch_empty(&sp->batch_check1) &&
620 rcu_batch_empty(&sp->batch_check0) &&
621 rcu_batch_empty(&sp->batch_queue)) {
622 spin_lock_irq(&sp->queue_lock);
623 if (rcu_batch_empty(&sp->batch_done) &&
624 rcu_batch_empty(&sp->batch_check1) &&
625 rcu_batch_empty(&sp->batch_check0) &&
626 rcu_batch_empty(&sp->batch_queue)) {
627 sp->running = false;
628 pending = false;
629 }
630 spin_unlock_irq(&sp->queue_lock);
631 }
632
633 if (pending)
3b07e9c workqueue: deprecate system_nrt[_freezable]_wq
Tejun Heo authored
634 schedule_delayed_work(&sp->work, SRCU_INTERVAL);
931ea9d @laijs rcu: Implement per-domain single-threaded call_srcu() state machine
laijs authored
635 }
636
637 /*
638 * This is the work-queue function that handles SRCU grace periods.
639 */
640 static void process_srcu(struct work_struct *work)
641 {
642 struct srcu_struct *sp;
643
644 sp = container_of(work, struct srcu_struct, work.work);
645
646 srcu_collect_new(sp);
647 srcu_advance_batches(sp, 1);
648 srcu_invoke_callbacks(sp);
649 srcu_reschedule(sp);
650 }
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