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 | ||
71c811bf | 39 | #include "urcu/wfqueue.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 | |
fdee2e6d | 45 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
71c811bf | 46 | #undef _LGPL_SOURCE |
fdee2e6d | 47 | #include "urcu-bp.h" |
71c811bf | 48 | #define _LGPL_SOURCE |
fdee2e6d | 49 | |
4c1ae2ea MD |
50 | #ifndef MAP_ANONYMOUS |
51 | #define MAP_ANONYMOUS MAP_ANON | |
52 | #endif | |
53 | ||
45a4872f MD |
54 | #ifndef __linux__ |
55 | ||
56 | #define MREMAP_MAYMOVE 1 | |
57 | #define MREMAP_FIXED 2 | |
58 | ||
59 | /* | |
60 | * mremap wrapper for non-Linux systems. Maps a RW, anonymous private mapping. | |
61 | * This is not generic. | |
62 | */ | |
63 | void *mremap(void *old_address, size_t old_size, size_t new_size, int flags) | |
64 | { | |
dc745ef6 | 65 | void *new_address; |
45a4872f MD |
66 | |
67 | assert(flags & MREMAP_MAYMOVE); | |
68 | assert(!(flags & MREMAP_FIXED)); | |
69 | new_address = mmap(old_address, new_size, | |
70 | PROT_READ | PROT_WRITE, | |
71 | MAP_ANONYMOUS | MAP_PRIVATE, | |
72 | -1, 0); | |
73 | if (new_address == MAP_FAILED) | |
74 | return MAP_FAILED; | |
75 | if (old_address) { | |
76 | memcpy(new_address, old_address, old_size); | |
77 | munmap(old_address, old_size); | |
78 | } | |
79 | return new_address; | |
80 | } | |
81 | #endif | |
82 | ||
fdee2e6d MD |
83 | /* Sleep delay in us */ |
84 | #define RCU_SLEEP_DELAY 1000 | |
85 | #define ARENA_INIT_ALLOC 16 | |
86 | ||
b7b6a8f5 PB |
87 | /* |
88 | * Active attempts to check for reader Q.S. before calling sleep(). | |
89 | */ | |
90 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
91 | ||
02be5561 | 92 | void __attribute__((destructor)) rcu_bp_exit(void); |
fdee2e6d | 93 | |
6abb4bd5 | 94 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
fdee2e6d MD |
95 | |
96 | #ifdef DEBUG_YIELD | |
97 | unsigned int yield_active; | |
bd252a04 | 98 | DEFINE_URCU_TLS(unsigned int, rand_yield); |
fdee2e6d MD |
99 | #endif |
100 | ||
101 | /* | |
102 | * Global grace period counter. | |
02be5561 | 103 | * Contains the current RCU_GP_CTR_PHASE. |
fdee2e6d MD |
104 | * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. |
105 | * Written to only by writer with mutex taken. Read by both writer and readers. | |
106 | */ | |
02be5561 | 107 | long rcu_gp_ctr = RCU_GP_COUNT; |
fdee2e6d MD |
108 | |
109 | /* | |
110 | * Pointer to registry elements. Written to only by each individual reader. Read | |
111 | * by both the reader and the writers. | |
112 | */ | |
bd252a04 | 113 | DEFINE_URCU_TLS(struct rcu_reader *, rcu_reader); |
fdee2e6d | 114 | |
16aa9ee8 | 115 | static CDS_LIST_HEAD(registry); |
fdee2e6d MD |
116 | |
117 | struct registry_arena { | |
118 | void *p; | |
119 | size_t len; | |
120 | size_t used; | |
121 | }; | |
122 | ||
123 | static struct registry_arena registry_arena; | |
124 | ||
4cf1675f MD |
125 | /* Saved fork signal mask, protected by rcu_gp_lock */ |
126 | static sigset_t saved_fork_signal_mask; | |
127 | ||
fdee2e6d MD |
128 | static void rcu_gc_registry(void); |
129 | ||
6abb4bd5 | 130 | static void mutex_lock(pthread_mutex_t *mutex) |
fdee2e6d MD |
131 | { |
132 | int ret; | |
133 | ||
134 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 135 | ret = pthread_mutex_lock(mutex); |
fdee2e6d MD |
136 | if (ret) { |
137 | perror("Error in pthread mutex lock"); | |
138 | exit(-1); | |
139 | } | |
140 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ | |
6abb4bd5 | 141 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
fdee2e6d MD |
142 | if (ret != EBUSY && ret != EINTR) { |
143 | printf("ret = %d, errno = %d\n", ret, errno); | |
144 | perror("Error in pthread mutex lock"); | |
145 | exit(-1); | |
146 | } | |
fdee2e6d MD |
147 | poll(NULL,0,10); |
148 | } | |
149 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
150 | } | |
151 | ||
6abb4bd5 | 152 | static void mutex_unlock(pthread_mutex_t *mutex) |
fdee2e6d MD |
153 | { |
154 | int ret; | |
155 | ||
6abb4bd5 | 156 | ret = pthread_mutex_unlock(mutex); |
fdee2e6d MD |
157 | if (ret) { |
158 | perror("Error in pthread mutex unlock"); | |
159 | exit(-1); | |
160 | } | |
161 | } | |
162 | ||
2dfb8b5e | 163 | void update_counter_and_wait(void) |
fdee2e6d | 164 | { |
16aa9ee8 | 165 | CDS_LIST_HEAD(qsreaders); |
fdee2e6d | 166 | int wait_loops = 0; |
02be5561 | 167 | struct rcu_reader *index, *tmp; |
fdee2e6d | 168 | |
32c15e4e | 169 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
6cf3827c | 170 | CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); |
2dfb8b5e MD |
171 | |
172 | /* | |
173 | * Must commit qparity update to memory before waiting for other parity | |
174 | * quiescent state. Failure to do so could result in the writer waiting | |
175 | * forever while new readers are always accessing data (no progress). | |
6cf3827c | 176 | * Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED. |
2dfb8b5e MD |
177 | */ |
178 | ||
179 | /* | |
5481ddb3 | 180 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
2dfb8b5e MD |
181 | * model easier to understand. It does not have a big performance impact |
182 | * anyway, given this is the write-side. | |
183 | */ | |
5481ddb3 | 184 | cmm_smp_mb(); |
2dfb8b5e | 185 | |
fdee2e6d | 186 | /* |
02be5561 | 187 | * Wait for each thread rcu_reader.ctr count to become 0. |
fdee2e6d MD |
188 | */ |
189 | for (;;) { | |
190 | wait_loops++; | |
16aa9ee8 | 191 | cds_list_for_each_entry_safe(index, tmp, ®istry, node) { |
fdee2e6d | 192 | if (!rcu_old_gp_ongoing(&index->ctr)) |
16aa9ee8 | 193 | cds_list_move(&index->node, &qsreaders); |
fdee2e6d MD |
194 | } |
195 | ||
16aa9ee8 | 196 | if (cds_list_empty(®istry)) { |
fdee2e6d MD |
197 | break; |
198 | } else { | |
199 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) | |
200 | usleep(RCU_SLEEP_DELAY); | |
201 | else | |
06f22bdb | 202 | caa_cpu_relax(); |
fdee2e6d MD |
203 | } |
204 | } | |
205 | /* put back the reader list in the registry */ | |
16aa9ee8 | 206 | cds_list_splice(&qsreaders, ®istry); |
fdee2e6d MD |
207 | } |
208 | ||
209 | void synchronize_rcu(void) | |
210 | { | |
211 | sigset_t newmask, oldmask; | |
212 | int ret; | |
213 | ||
214 | ret = sigemptyset(&newmask); | |
215 | assert(!ret); | |
216 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
217 | assert(!ret); | |
218 | ||
6abb4bd5 | 219 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 220 | |
16aa9ee8 | 221 | if (cds_list_empty(®istry)) |
2dfb8b5e | 222 | goto out; |
fdee2e6d MD |
223 | |
224 | /* All threads should read qparity before accessing data structure | |
2dfb8b5e | 225 | * where new ptr points to. */ |
fdee2e6d | 226 | /* Write new ptr before changing the qparity */ |
5481ddb3 | 227 | cmm_smp_mb(); |
fdee2e6d | 228 | |
2dfb8b5e MD |
229 | /* Remove old registry elements */ |
230 | rcu_gc_registry(); | |
fdee2e6d MD |
231 | |
232 | /* | |
233 | * Wait for previous parity to be empty of readers. | |
234 | */ | |
2dfb8b5e | 235 | update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ |
fdee2e6d MD |
236 | |
237 | /* | |
5481ddb3 | 238 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
fdee2e6d MD |
239 | * model easier to understand. It does not have a big performance impact |
240 | * anyway, given this is the write-side. | |
241 | */ | |
5481ddb3 | 242 | cmm_smp_mb(); |
fdee2e6d | 243 | |
fdee2e6d | 244 | /* |
2dfb8b5e | 245 | * Wait for previous parity to be empty of readers. |
fdee2e6d | 246 | */ |
2dfb8b5e | 247 | update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ |
fdee2e6d MD |
248 | |
249 | /* | |
2dfb8b5e MD |
250 | * Finish waiting for reader threads before letting the old ptr being |
251 | * freed. | |
fdee2e6d | 252 | */ |
5481ddb3 | 253 | cmm_smp_mb(); |
2dfb8b5e | 254 | out: |
6abb4bd5 | 255 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
256 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); |
257 | assert(!ret); | |
258 | } | |
259 | ||
260 | /* | |
261 | * library wrappers to be used by non-LGPL compatible source code. | |
262 | */ | |
263 | ||
264 | void rcu_read_lock(void) | |
265 | { | |
266 | _rcu_read_lock(); | |
267 | } | |
268 | ||
269 | void rcu_read_unlock(void) | |
270 | { | |
271 | _rcu_read_unlock(); | |
272 | } | |
273 | ||
274 | /* | |
275 | * only grow for now. | |
276 | */ | |
277 | static void resize_arena(struct registry_arena *arena, size_t len) | |
278 | { | |
279 | void *new_arena; | |
280 | ||
0617bf4c MD |
281 | if (!arena->p) |
282 | new_arena = mmap(arena->p, len, | |
283 | PROT_READ | PROT_WRITE, | |
284 | MAP_ANONYMOUS | MAP_PRIVATE, | |
285 | -1, 0); | |
286 | else | |
287 | new_arena = mremap(arena->p, arena->len, | |
288 | len, MREMAP_MAYMOVE); | |
289 | assert(new_arena != MAP_FAILED); | |
290 | ||
fdee2e6d MD |
291 | /* |
292 | * re-used the same region ? | |
293 | */ | |
294 | if (new_arena == arena->p) | |
295 | return; | |
296 | ||
fdee2e6d MD |
297 | bzero(new_arena + arena->len, len - arena->len); |
298 | arena->p = new_arena; | |
299 | } | |
300 | ||
301 | /* Called with signals off and mutex locked */ | |
302 | static void add_thread(void) | |
303 | { | |
02be5561 | 304 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
305 | |
306 | if (registry_arena.len | |
02be5561 | 307 | < registry_arena.used + sizeof(struct rcu_reader)) |
fdee2e6d | 308 | resize_arena(®istry_arena, |
2f8a5ae7 | 309 | caa_max(registry_arena.len << 1, ARENA_INIT_ALLOC)); |
fdee2e6d MD |
310 | /* |
311 | * Find a free spot. | |
312 | */ | |
02be5561 MD |
313 | for (rcu_reader_reg = registry_arena.p; |
314 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
315 | rcu_reader_reg++) { | |
316 | if (!rcu_reader_reg->alloc) | |
fdee2e6d MD |
317 | break; |
318 | } | |
02be5561 MD |
319 | rcu_reader_reg->alloc = 1; |
320 | registry_arena.used += sizeof(struct rcu_reader); | |
fdee2e6d MD |
321 | |
322 | /* Add to registry */ | |
02be5561 MD |
323 | rcu_reader_reg->tid = pthread_self(); |
324 | assert(rcu_reader_reg->ctr == 0); | |
16aa9ee8 | 325 | cds_list_add(&rcu_reader_reg->node, ®istry); |
bd252a04 | 326 | URCU_TLS(rcu_reader) = rcu_reader_reg; |
fdee2e6d MD |
327 | } |
328 | ||
329 | /* Called with signals off and mutex locked */ | |
330 | static void rcu_gc_registry(void) | |
331 | { | |
02be5561 | 332 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
333 | pthread_t tid; |
334 | int ret; | |
335 | ||
02be5561 MD |
336 | for (rcu_reader_reg = registry_arena.p; |
337 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
338 | rcu_reader_reg++) { | |
339 | if (!rcu_reader_reg->alloc) | |
fdee2e6d | 340 | continue; |
02be5561 | 341 | tid = rcu_reader_reg->tid; |
fdee2e6d MD |
342 | ret = pthread_kill(tid, 0); |
343 | assert(ret != EINVAL); | |
344 | if (ret == ESRCH) { | |
16aa9ee8 | 345 | cds_list_del(&rcu_reader_reg->node); |
79266051 | 346 | rcu_reader_reg->ctr = 0; |
02be5561 MD |
347 | rcu_reader_reg->alloc = 0; |
348 | registry_arena.used -= sizeof(struct rcu_reader); | |
fdee2e6d MD |
349 | } |
350 | } | |
351 | } | |
352 | ||
353 | /* Disable signals, take mutex, add to registry */ | |
354 | void rcu_bp_register(void) | |
355 | { | |
356 | sigset_t newmask, oldmask; | |
357 | int ret; | |
358 | ||
359 | ret = sigemptyset(&newmask); | |
360 | assert(!ret); | |
361 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
362 | assert(!ret); | |
363 | ||
364 | /* | |
365 | * Check if a signal concurrently registered our thread since | |
366 | * the check in rcu_read_lock(). */ | |
bd252a04 | 367 | if (URCU_TLS(rcu_reader)) |
fdee2e6d MD |
368 | goto end; |
369 | ||
6abb4bd5 | 370 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 371 | add_thread(); |
6abb4bd5 | 372 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
373 | end: |
374 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
375 | assert(!ret); | |
376 | } | |
377 | ||
9380711a | 378 | void rcu_bp_exit(void) |
fdee2e6d | 379 | { |
9380711a MD |
380 | if (registry_arena.p) |
381 | munmap(registry_arena.p, registry_arena.len); | |
fdee2e6d | 382 | } |
4cf1675f MD |
383 | |
384 | /* | |
385 | * Holding the rcu_gp_lock across fork will make sure we fork() don't race with | |
386 | * a concurrent thread executing with this same lock held. This ensures that the | |
387 | * registry is in a coherent state in the child. | |
388 | */ | |
389 | void rcu_bp_before_fork(void) | |
390 | { | |
391 | sigset_t newmask, oldmask; | |
392 | int ret; | |
393 | ||
394 | ret = sigemptyset(&newmask); | |
395 | assert(!ret); | |
396 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
397 | assert(!ret); | |
398 | mutex_lock(&rcu_gp_lock); | |
399 | saved_fork_signal_mask = oldmask; | |
400 | } | |
401 | ||
402 | void rcu_bp_after_fork_parent(void) | |
403 | { | |
404 | sigset_t oldmask; | |
405 | int ret; | |
406 | ||
407 | oldmask = saved_fork_signal_mask; | |
408 | mutex_unlock(&rcu_gp_lock); | |
409 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
410 | assert(!ret); | |
411 | } | |
412 | ||
413 | void rcu_bp_after_fork_child(void) | |
414 | { | |
415 | sigset_t oldmask; | |
416 | int ret; | |
417 | ||
418 | rcu_gc_registry(); | |
419 | oldmask = saved_fork_signal_mask; | |
420 | mutex_unlock(&rcu_gp_lock); | |
421 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
422 | assert(!ret); | |
423 | } | |
5e77fc1f | 424 | |
9b7981bb MD |
425 | void *rcu_dereference_sym_bp(void *p) |
426 | { | |
427 | return _rcu_dereference(p); | |
428 | } | |
429 | ||
5efd3cd2 MD |
430 | void *rcu_set_pointer_sym_bp(void **p, void *v) |
431 | { | |
432 | cmm_wmb(); | |
433 | return uatomic_set(p, v); | |
434 | } | |
435 | ||
436 | void *rcu_xchg_pointer_sym_bp(void **p, void *v) | |
437 | { | |
438 | cmm_wmb(); | |
439 | return uatomic_xchg(p, v); | |
440 | } | |
441 | ||
442 | void *rcu_cmpxchg_pointer_sym_bp(void **p, void *old, void *_new) | |
443 | { | |
444 | cmm_wmb(); | |
445 | return uatomic_cmpxchg(p, old, _new); | |
446 | } | |
447 | ||
5e6b23a6 | 448 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 449 | |
5e77fc1f | 450 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 451 | #include "urcu-defer-impl.h" |