Commit | Line | Data |
---|---|---|
fdee2e6d MD |
1 | /* |
2 | * urcu-bp.c | |
3 | * | |
4 | * Userspace RCU library, "bulletproof" version. | |
5 | * | |
6982d6d7 | 6 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
fdee2e6d MD |
7 | * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. |
8 | * | |
9 | * This library is free software; you can redistribute it and/or | |
10 | * modify it under the terms of the GNU Lesser General Public | |
11 | * License as published by the Free Software Foundation; either | |
12 | * version 2.1 of the License, or (at your option) any later version. | |
13 | * | |
14 | * This library is distributed in the hope that it will be useful, | |
15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | * Lesser General Public License for more details. | |
18 | * | |
19 | * You should have received a copy of the GNU Lesser General Public | |
20 | * License along with this library; if not, write to the Free Software | |
21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
22 | * | |
23 | * IBM's contributions to this file may be relicensed under LGPLv2 or later. | |
24 | */ | |
25 | ||
0617bf4c | 26 | #define _GNU_SOURCE |
71c811bf | 27 | #define _LGPL_SOURCE |
fdee2e6d MD |
28 | #include <stdio.h> |
29 | #include <pthread.h> | |
30 | #include <signal.h> | |
31 | #include <assert.h> | |
32 | #include <stdlib.h> | |
33 | #include <string.h> | |
34 | #include <errno.h> | |
35 | #include <poll.h> | |
36 | #include <unistd.h> | |
37 | #include <sys/mman.h> | |
38 | ||
d73fb81f | 39 | #include "urcu/wfcqueue.h" |
57760d44 | 40 | #include "urcu/map/urcu-bp.h" |
af7c2dbe | 41 | #include "urcu/static/urcu-bp.h" |
618b2595 | 42 | #include "urcu-pointer.h" |
bd252a04 | 43 | #include "urcu/tls-compat.h" |
71c811bf | 44 | |
4a6d7378 MD |
45 | #include "urcu-die.h" |
46 | ||
fdee2e6d | 47 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
71c811bf | 48 | #undef _LGPL_SOURCE |
fdee2e6d | 49 | #include "urcu-bp.h" |
71c811bf | 50 | #define _LGPL_SOURCE |
fdee2e6d | 51 | |
4c1ae2ea MD |
52 | #ifndef MAP_ANONYMOUS |
53 | #define MAP_ANONYMOUS MAP_ANON | |
54 | #endif | |
55 | ||
c7eaf61c MD |
56 | #ifdef __linux__ |
57 | static | |
58 | void *mremap_wrapper(void *old_address, size_t old_size, | |
59 | size_t new_size, int flags) | |
60 | { | |
61 | return mremap(old_address, old_size, new_size, flags); | |
62 | } | |
63 | #else | |
45a4872f MD |
64 | |
65 | #define MREMAP_MAYMOVE 1 | |
66 | #define MREMAP_FIXED 2 | |
67 | ||
68 | /* | |
69 | * mremap wrapper for non-Linux systems. Maps a RW, anonymous private mapping. | |
70 | * This is not generic. | |
71 | */ | |
c7eaf61c MD |
72 | static |
73 | void *mremap_wrapper(void *old_address, size_t old_size, | |
74 | size_t new_size, int flags) | |
45a4872f | 75 | { |
dc745ef6 | 76 | void *new_address; |
45a4872f MD |
77 | |
78 | assert(flags & MREMAP_MAYMOVE); | |
79 | assert(!(flags & MREMAP_FIXED)); | |
80 | new_address = mmap(old_address, new_size, | |
81 | PROT_READ | PROT_WRITE, | |
82 | MAP_ANONYMOUS | MAP_PRIVATE, | |
83 | -1, 0); | |
84 | if (new_address == MAP_FAILED) | |
85 | return MAP_FAILED; | |
86 | if (old_address) { | |
87 | memcpy(new_address, old_address, old_size); | |
88 | munmap(old_address, old_size); | |
89 | } | |
90 | return new_address; | |
91 | } | |
92 | #endif | |
93 | ||
fdee2e6d MD |
94 | /* Sleep delay in us */ |
95 | #define RCU_SLEEP_DELAY 1000 | |
96 | #define ARENA_INIT_ALLOC 16 | |
97 | ||
b7b6a8f5 PB |
98 | /* |
99 | * Active attempts to check for reader Q.S. before calling sleep(). | |
100 | */ | |
101 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
102 | ||
02be5561 | 103 | void __attribute__((destructor)) rcu_bp_exit(void); |
fdee2e6d | 104 | |
6abb4bd5 | 105 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
fdee2e6d MD |
106 | |
107 | #ifdef DEBUG_YIELD | |
1de4df4b MD |
108 | unsigned int rcu_yield_active; |
109 | DEFINE_URCU_TLS(unsigned int, rcu_rand_yield); | |
fdee2e6d MD |
110 | #endif |
111 | ||
112 | /* | |
113 | * Global grace period counter. | |
02be5561 | 114 | * Contains the current RCU_GP_CTR_PHASE. |
fdee2e6d MD |
115 | * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. |
116 | * Written to only by writer with mutex taken. Read by both writer and readers. | |
117 | */ | |
02be5561 | 118 | long rcu_gp_ctr = RCU_GP_COUNT; |
fdee2e6d MD |
119 | |
120 | /* | |
121 | * Pointer to registry elements. Written to only by each individual reader. Read | |
122 | * by both the reader and the writers. | |
123 | */ | |
bd252a04 | 124 | DEFINE_URCU_TLS(struct rcu_reader *, rcu_reader); |
fdee2e6d | 125 | |
16aa9ee8 | 126 | static CDS_LIST_HEAD(registry); |
fdee2e6d MD |
127 | |
128 | struct registry_arena { | |
129 | void *p; | |
130 | size_t len; | |
131 | size_t used; | |
132 | }; | |
133 | ||
134 | static struct registry_arena registry_arena; | |
135 | ||
4cf1675f MD |
136 | /* Saved fork signal mask, protected by rcu_gp_lock */ |
137 | static sigset_t saved_fork_signal_mask; | |
138 | ||
fdee2e6d MD |
139 | static void rcu_gc_registry(void); |
140 | ||
6abb4bd5 | 141 | static void mutex_lock(pthread_mutex_t *mutex) |
fdee2e6d MD |
142 | { |
143 | int ret; | |
144 | ||
145 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 146 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
147 | if (ret) |
148 | urcu_die(ret); | |
fdee2e6d | 149 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 150 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
151 | if (ret != EBUSY && ret != EINTR) |
152 | urcu_die(ret); | |
fdee2e6d MD |
153 | poll(NULL,0,10); |
154 | } | |
155 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
156 | } | |
157 | ||
6abb4bd5 | 158 | static void mutex_unlock(pthread_mutex_t *mutex) |
fdee2e6d MD |
159 | { |
160 | int ret; | |
161 | ||
6abb4bd5 | 162 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
163 | if (ret) |
164 | urcu_die(ret); | |
fdee2e6d MD |
165 | } |
166 | ||
dd61d077 | 167 | static void wait_for_readers(void) |
fdee2e6d | 168 | { |
16aa9ee8 | 169 | CDS_LIST_HEAD(qsreaders); |
fdee2e6d | 170 | int wait_loops = 0; |
02be5561 | 171 | struct rcu_reader *index, *tmp; |
fdee2e6d | 172 | |
fdee2e6d | 173 | /* |
dd61d077 MD |
174 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
175 | * indicate quiescence (not nested), or observe the current | |
176 | * rcu_gp_ctr value. | |
fdee2e6d MD |
177 | */ |
178 | for (;;) { | |
179 | wait_loops++; | |
16aa9ee8 | 180 | cds_list_for_each_entry_safe(index, tmp, ®istry, node) { |
fdee2e6d | 181 | if (!rcu_old_gp_ongoing(&index->ctr)) |
16aa9ee8 | 182 | cds_list_move(&index->node, &qsreaders); |
fdee2e6d MD |
183 | } |
184 | ||
16aa9ee8 | 185 | if (cds_list_empty(®istry)) { |
fdee2e6d MD |
186 | break; |
187 | } else { | |
188 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) | |
189 | usleep(RCU_SLEEP_DELAY); | |
190 | else | |
06f22bdb | 191 | caa_cpu_relax(); |
fdee2e6d MD |
192 | } |
193 | } | |
194 | /* put back the reader list in the registry */ | |
16aa9ee8 | 195 | cds_list_splice(&qsreaders, ®istry); |
fdee2e6d MD |
196 | } |
197 | ||
198 | void synchronize_rcu(void) | |
199 | { | |
200 | sigset_t newmask, oldmask; | |
201 | int ret; | |
202 | ||
203 | ret = sigemptyset(&newmask); | |
204 | assert(!ret); | |
205 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
206 | assert(!ret); | |
207 | ||
6abb4bd5 | 208 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 209 | |
16aa9ee8 | 210 | if (cds_list_empty(®istry)) |
2dfb8b5e | 211 | goto out; |
fdee2e6d MD |
212 | |
213 | /* All threads should read qparity before accessing data structure | |
2dfb8b5e | 214 | * where new ptr points to. */ |
fdee2e6d | 215 | /* Write new ptr before changing the qparity */ |
5481ddb3 | 216 | cmm_smp_mb(); |
fdee2e6d | 217 | |
2dfb8b5e MD |
218 | /* Remove old registry elements */ |
219 | rcu_gc_registry(); | |
fdee2e6d MD |
220 | |
221 | /* | |
dd61d077 MD |
222 | * Wait for readers to observe original parity or be quiescent. |
223 | */ | |
224 | wait_for_readers(); | |
225 | ||
226 | /* | |
227 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
228 | * model easier to understand. It does not have a big performance impact | |
229 | * anyway, given this is the write-side. | |
230 | */ | |
231 | cmm_smp_mb(); | |
232 | ||
233 | /* Switch parity: 0 -> 1, 1 -> 0 */ | |
234 | CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); | |
235 | ||
236 | /* | |
237 | * Must commit qparity update to memory before waiting for other parity | |
238 | * quiescent state. Failure to do so could result in the writer waiting | |
239 | * forever while new readers are always accessing data (no progress). | |
240 | * Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED. | |
fdee2e6d | 241 | */ |
fdee2e6d MD |
242 | |
243 | /* | |
5481ddb3 | 244 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
fdee2e6d MD |
245 | * model easier to understand. It does not have a big performance impact |
246 | * anyway, given this is the write-side. | |
247 | */ | |
5481ddb3 | 248 | cmm_smp_mb(); |
fdee2e6d | 249 | |
fdee2e6d | 250 | /* |
dd61d077 | 251 | * Wait for readers to observe new parity or be quiescent. |
fdee2e6d | 252 | */ |
dd61d077 | 253 | wait_for_readers(); |
fdee2e6d MD |
254 | |
255 | /* | |
2dfb8b5e MD |
256 | * Finish waiting for reader threads before letting the old ptr being |
257 | * freed. | |
fdee2e6d | 258 | */ |
5481ddb3 | 259 | cmm_smp_mb(); |
2dfb8b5e | 260 | out: |
6abb4bd5 | 261 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
262 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); |
263 | assert(!ret); | |
264 | } | |
265 | ||
266 | /* | |
267 | * library wrappers to be used by non-LGPL compatible source code. | |
268 | */ | |
269 | ||
270 | void rcu_read_lock(void) | |
271 | { | |
272 | _rcu_read_lock(); | |
273 | } | |
274 | ||
275 | void rcu_read_unlock(void) | |
276 | { | |
277 | _rcu_read_unlock(); | |
278 | } | |
279 | ||
280 | /* | |
281 | * only grow for now. | |
282 | */ | |
283 | static void resize_arena(struct registry_arena *arena, size_t len) | |
284 | { | |
285 | void *new_arena; | |
286 | ||
0617bf4c MD |
287 | if (!arena->p) |
288 | new_arena = mmap(arena->p, len, | |
289 | PROT_READ | PROT_WRITE, | |
290 | MAP_ANONYMOUS | MAP_PRIVATE, | |
291 | -1, 0); | |
292 | else | |
c7eaf61c MD |
293 | new_arena = mremap_wrapper(arena->p, arena->len, |
294 | len, MREMAP_MAYMOVE); | |
0617bf4c MD |
295 | assert(new_arena != MAP_FAILED); |
296 | ||
fdee2e6d MD |
297 | /* |
298 | * re-used the same region ? | |
299 | */ | |
300 | if (new_arena == arena->p) | |
301 | return; | |
302 | ||
fdee2e6d MD |
303 | bzero(new_arena + arena->len, len - arena->len); |
304 | arena->p = new_arena; | |
305 | } | |
306 | ||
307 | /* Called with signals off and mutex locked */ | |
308 | static void add_thread(void) | |
309 | { | |
02be5561 | 310 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
311 | |
312 | if (registry_arena.len | |
02be5561 | 313 | < registry_arena.used + sizeof(struct rcu_reader)) |
fdee2e6d | 314 | resize_arena(®istry_arena, |
2f8a5ae7 | 315 | caa_max(registry_arena.len << 1, ARENA_INIT_ALLOC)); |
fdee2e6d MD |
316 | /* |
317 | * Find a free spot. | |
318 | */ | |
02be5561 MD |
319 | for (rcu_reader_reg = registry_arena.p; |
320 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
321 | rcu_reader_reg++) { | |
322 | if (!rcu_reader_reg->alloc) | |
fdee2e6d MD |
323 | break; |
324 | } | |
02be5561 MD |
325 | rcu_reader_reg->alloc = 1; |
326 | registry_arena.used += sizeof(struct rcu_reader); | |
fdee2e6d MD |
327 | |
328 | /* Add to registry */ | |
02be5561 MD |
329 | rcu_reader_reg->tid = pthread_self(); |
330 | assert(rcu_reader_reg->ctr == 0); | |
16aa9ee8 | 331 | cds_list_add(&rcu_reader_reg->node, ®istry); |
bd252a04 | 332 | URCU_TLS(rcu_reader) = rcu_reader_reg; |
fdee2e6d MD |
333 | } |
334 | ||
335 | /* Called with signals off and mutex locked */ | |
336 | static void rcu_gc_registry(void) | |
337 | { | |
02be5561 | 338 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
339 | pthread_t tid; |
340 | int ret; | |
341 | ||
02be5561 MD |
342 | for (rcu_reader_reg = registry_arena.p; |
343 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
344 | rcu_reader_reg++) { | |
345 | if (!rcu_reader_reg->alloc) | |
fdee2e6d | 346 | continue; |
02be5561 | 347 | tid = rcu_reader_reg->tid; |
fdee2e6d MD |
348 | ret = pthread_kill(tid, 0); |
349 | assert(ret != EINVAL); | |
350 | if (ret == ESRCH) { | |
16aa9ee8 | 351 | cds_list_del(&rcu_reader_reg->node); |
79266051 | 352 | rcu_reader_reg->ctr = 0; |
02be5561 MD |
353 | rcu_reader_reg->alloc = 0; |
354 | registry_arena.used -= sizeof(struct rcu_reader); | |
fdee2e6d MD |
355 | } |
356 | } | |
357 | } | |
358 | ||
359 | /* Disable signals, take mutex, add to registry */ | |
360 | void rcu_bp_register(void) | |
361 | { | |
362 | sigset_t newmask, oldmask; | |
363 | int ret; | |
364 | ||
365 | ret = sigemptyset(&newmask); | |
366 | assert(!ret); | |
367 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
368 | assert(!ret); | |
369 | ||
370 | /* | |
371 | * Check if a signal concurrently registered our thread since | |
372 | * the check in rcu_read_lock(). */ | |
bd252a04 | 373 | if (URCU_TLS(rcu_reader)) |
fdee2e6d MD |
374 | goto end; |
375 | ||
6abb4bd5 | 376 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 377 | add_thread(); |
6abb4bd5 | 378 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
379 | end: |
380 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
381 | assert(!ret); | |
382 | } | |
383 | ||
9380711a | 384 | void rcu_bp_exit(void) |
fdee2e6d | 385 | { |
9380711a MD |
386 | if (registry_arena.p) |
387 | munmap(registry_arena.p, registry_arena.len); | |
fdee2e6d | 388 | } |
4cf1675f MD |
389 | |
390 | /* | |
391 | * Holding the rcu_gp_lock across fork will make sure we fork() don't race with | |
392 | * a concurrent thread executing with this same lock held. This ensures that the | |
393 | * registry is in a coherent state in the child. | |
394 | */ | |
395 | void rcu_bp_before_fork(void) | |
396 | { | |
397 | sigset_t newmask, oldmask; | |
398 | int ret; | |
399 | ||
400 | ret = sigemptyset(&newmask); | |
401 | assert(!ret); | |
402 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
403 | assert(!ret); | |
404 | mutex_lock(&rcu_gp_lock); | |
405 | saved_fork_signal_mask = oldmask; | |
406 | } | |
407 | ||
408 | void rcu_bp_after_fork_parent(void) | |
409 | { | |
410 | sigset_t oldmask; | |
411 | int ret; | |
412 | ||
413 | oldmask = saved_fork_signal_mask; | |
414 | mutex_unlock(&rcu_gp_lock); | |
415 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
416 | assert(!ret); | |
417 | } | |
418 | ||
419 | void rcu_bp_after_fork_child(void) | |
420 | { | |
421 | sigset_t oldmask; | |
422 | int ret; | |
423 | ||
424 | rcu_gc_registry(); | |
425 | oldmask = saved_fork_signal_mask; | |
426 | mutex_unlock(&rcu_gp_lock); | |
427 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
428 | assert(!ret); | |
429 | } | |
5e77fc1f | 430 | |
9b7981bb MD |
431 | void *rcu_dereference_sym_bp(void *p) |
432 | { | |
433 | return _rcu_dereference(p); | |
434 | } | |
435 | ||
5efd3cd2 MD |
436 | void *rcu_set_pointer_sym_bp(void **p, void *v) |
437 | { | |
438 | cmm_wmb(); | |
424d4ed5 MD |
439 | uatomic_set(p, v); |
440 | return v; | |
5efd3cd2 MD |
441 | } |
442 | ||
443 | void *rcu_xchg_pointer_sym_bp(void **p, void *v) | |
444 | { | |
445 | cmm_wmb(); | |
446 | return uatomic_xchg(p, v); | |
447 | } | |
448 | ||
449 | void *rcu_cmpxchg_pointer_sym_bp(void **p, void *old, void *_new) | |
450 | { | |
451 | cmm_wmb(); | |
452 | return uatomic_cmpxchg(p, old, _new); | |
453 | } | |
454 | ||
5e6b23a6 | 455 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 456 | |
5e77fc1f | 457 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 458 | #include "urcu-defer-impl.h" |