Commit | Line | Data |
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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" |
71c811bf | 42 | |
fdee2e6d | 43 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
71c811bf | 44 | #undef _LGPL_SOURCE |
fdee2e6d | 45 | #include "urcu-bp.h" |
71c811bf | 46 | #define _LGPL_SOURCE |
fdee2e6d | 47 | |
4c1ae2ea MD |
48 | #ifndef MAP_ANONYMOUS |
49 | #define MAP_ANONYMOUS MAP_ANON | |
50 | #endif | |
51 | ||
45a4872f MD |
52 | #ifndef __linux__ |
53 | ||
54 | #define MREMAP_MAYMOVE 1 | |
55 | #define MREMAP_FIXED 2 | |
56 | ||
57 | /* | |
58 | * mremap wrapper for non-Linux systems. Maps a RW, anonymous private mapping. | |
59 | * This is not generic. | |
60 | */ | |
61 | void *mremap(void *old_address, size_t old_size, size_t new_size, int flags) | |
62 | { | |
dc745ef6 | 63 | void *new_address; |
45a4872f MD |
64 | |
65 | assert(flags & MREMAP_MAYMOVE); | |
66 | assert(!(flags & MREMAP_FIXED)); | |
67 | new_address = mmap(old_address, new_size, | |
68 | PROT_READ | PROT_WRITE, | |
69 | MAP_ANONYMOUS | MAP_PRIVATE, | |
70 | -1, 0); | |
71 | if (new_address == MAP_FAILED) | |
72 | return MAP_FAILED; | |
73 | if (old_address) { | |
74 | memcpy(new_address, old_address, old_size); | |
75 | munmap(old_address, old_size); | |
76 | } | |
77 | return new_address; | |
78 | } | |
79 | #endif | |
80 | ||
fdee2e6d MD |
81 | /* Sleep delay in us */ |
82 | #define RCU_SLEEP_DELAY 1000 | |
83 | #define ARENA_INIT_ALLOC 16 | |
84 | ||
b7b6a8f5 PB |
85 | /* |
86 | * Active attempts to check for reader Q.S. before calling sleep(). | |
87 | */ | |
88 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
89 | ||
02be5561 | 90 | void __attribute__((destructor)) rcu_bp_exit(void); |
fdee2e6d | 91 | |
6abb4bd5 | 92 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
fdee2e6d MD |
93 | |
94 | #ifdef DEBUG_YIELD | |
95 | unsigned int yield_active; | |
96 | unsigned int __thread rand_yield; | |
97 | #endif | |
98 | ||
99 | /* | |
100 | * Global grace period counter. | |
02be5561 | 101 | * Contains the current RCU_GP_CTR_PHASE. |
fdee2e6d MD |
102 | * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. |
103 | * Written to only by writer with mutex taken. Read by both writer and readers. | |
104 | */ | |
02be5561 | 105 | long rcu_gp_ctr = RCU_GP_COUNT; |
fdee2e6d MD |
106 | |
107 | /* | |
108 | * Pointer to registry elements. Written to only by each individual reader. Read | |
109 | * by both the reader and the writers. | |
110 | */ | |
02be5561 | 111 | struct rcu_reader __thread *rcu_reader; |
fdee2e6d | 112 | |
16aa9ee8 | 113 | static CDS_LIST_HEAD(registry); |
fdee2e6d MD |
114 | |
115 | struct registry_arena { | |
116 | void *p; | |
117 | size_t len; | |
118 | size_t used; | |
119 | }; | |
120 | ||
121 | static struct registry_arena registry_arena; | |
122 | ||
4cf1675f MD |
123 | /* Saved fork signal mask, protected by rcu_gp_lock */ |
124 | static sigset_t saved_fork_signal_mask; | |
125 | ||
fdee2e6d MD |
126 | static void rcu_gc_registry(void); |
127 | ||
6abb4bd5 | 128 | static void mutex_lock(pthread_mutex_t *mutex) |
fdee2e6d MD |
129 | { |
130 | int ret; | |
131 | ||
132 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 133 | ret = pthread_mutex_lock(mutex); |
fdee2e6d MD |
134 | if (ret) { |
135 | perror("Error in pthread mutex lock"); | |
136 | exit(-1); | |
137 | } | |
138 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ | |
6abb4bd5 | 139 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
fdee2e6d MD |
140 | if (ret != EBUSY && ret != EINTR) { |
141 | printf("ret = %d, errno = %d\n", ret, errno); | |
142 | perror("Error in pthread mutex lock"); | |
143 | exit(-1); | |
144 | } | |
fdee2e6d MD |
145 | poll(NULL,0,10); |
146 | } | |
147 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
148 | } | |
149 | ||
6abb4bd5 | 150 | static void mutex_unlock(pthread_mutex_t *mutex) |
fdee2e6d MD |
151 | { |
152 | int ret; | |
153 | ||
6abb4bd5 | 154 | ret = pthread_mutex_unlock(mutex); |
fdee2e6d MD |
155 | if (ret) { |
156 | perror("Error in pthread mutex unlock"); | |
157 | exit(-1); | |
158 | } | |
159 | } | |
160 | ||
2dfb8b5e | 161 | void update_counter_and_wait(void) |
fdee2e6d | 162 | { |
16aa9ee8 | 163 | CDS_LIST_HEAD(qsreaders); |
fdee2e6d | 164 | int wait_loops = 0; |
02be5561 | 165 | struct rcu_reader *index, *tmp; |
fdee2e6d | 166 | |
32c15e4e | 167 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
6cf3827c | 168 | CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); |
2dfb8b5e MD |
169 | |
170 | /* | |
171 | * Must commit qparity update to memory before waiting for other parity | |
172 | * quiescent state. Failure to do so could result in the writer waiting | |
173 | * forever while new readers are always accessing data (no progress). | |
6cf3827c | 174 | * Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED. |
2dfb8b5e MD |
175 | */ |
176 | ||
177 | /* | |
5481ddb3 | 178 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
2dfb8b5e MD |
179 | * model easier to understand. It does not have a big performance impact |
180 | * anyway, given this is the write-side. | |
181 | */ | |
5481ddb3 | 182 | cmm_smp_mb(); |
2dfb8b5e | 183 | |
fdee2e6d | 184 | /* |
02be5561 | 185 | * Wait for each thread rcu_reader.ctr count to become 0. |
fdee2e6d MD |
186 | */ |
187 | for (;;) { | |
188 | wait_loops++; | |
16aa9ee8 | 189 | cds_list_for_each_entry_safe(index, tmp, ®istry, node) { |
fdee2e6d | 190 | if (!rcu_old_gp_ongoing(&index->ctr)) |
16aa9ee8 | 191 | cds_list_move(&index->node, &qsreaders); |
fdee2e6d MD |
192 | } |
193 | ||
16aa9ee8 | 194 | if (cds_list_empty(®istry)) { |
fdee2e6d MD |
195 | break; |
196 | } else { | |
197 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) | |
198 | usleep(RCU_SLEEP_DELAY); | |
199 | else | |
06f22bdb | 200 | caa_cpu_relax(); |
fdee2e6d MD |
201 | } |
202 | } | |
203 | /* put back the reader list in the registry */ | |
16aa9ee8 | 204 | cds_list_splice(&qsreaders, ®istry); |
fdee2e6d MD |
205 | } |
206 | ||
207 | void synchronize_rcu(void) | |
208 | { | |
209 | sigset_t newmask, oldmask; | |
210 | int ret; | |
211 | ||
212 | ret = sigemptyset(&newmask); | |
213 | assert(!ret); | |
214 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
215 | assert(!ret); | |
216 | ||
6abb4bd5 | 217 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 218 | |
16aa9ee8 | 219 | if (cds_list_empty(®istry)) |
2dfb8b5e | 220 | goto out; |
fdee2e6d MD |
221 | |
222 | /* All threads should read qparity before accessing data structure | |
2dfb8b5e | 223 | * where new ptr points to. */ |
fdee2e6d | 224 | /* Write new ptr before changing the qparity */ |
5481ddb3 | 225 | cmm_smp_mb(); |
fdee2e6d | 226 | |
2dfb8b5e MD |
227 | /* Remove old registry elements */ |
228 | rcu_gc_registry(); | |
fdee2e6d MD |
229 | |
230 | /* | |
231 | * Wait for previous parity to be empty of readers. | |
232 | */ | |
2dfb8b5e | 233 | update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ |
fdee2e6d MD |
234 | |
235 | /* | |
5481ddb3 | 236 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
fdee2e6d MD |
237 | * model easier to understand. It does not have a big performance impact |
238 | * anyway, given this is the write-side. | |
239 | */ | |
5481ddb3 | 240 | cmm_smp_mb(); |
fdee2e6d | 241 | |
fdee2e6d | 242 | /* |
2dfb8b5e | 243 | * Wait for previous parity to be empty of readers. |
fdee2e6d | 244 | */ |
2dfb8b5e | 245 | update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ |
fdee2e6d MD |
246 | |
247 | /* | |
2dfb8b5e MD |
248 | * Finish waiting for reader threads before letting the old ptr being |
249 | * freed. | |
fdee2e6d | 250 | */ |
5481ddb3 | 251 | cmm_smp_mb(); |
2dfb8b5e | 252 | out: |
6abb4bd5 | 253 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
254 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); |
255 | assert(!ret); | |
256 | } | |
257 | ||
258 | /* | |
259 | * library wrappers to be used by non-LGPL compatible source code. | |
260 | */ | |
261 | ||
262 | void rcu_read_lock(void) | |
263 | { | |
264 | _rcu_read_lock(); | |
265 | } | |
266 | ||
267 | void rcu_read_unlock(void) | |
268 | { | |
269 | _rcu_read_unlock(); | |
270 | } | |
271 | ||
272 | /* | |
273 | * only grow for now. | |
274 | */ | |
275 | static void resize_arena(struct registry_arena *arena, size_t len) | |
276 | { | |
277 | void *new_arena; | |
278 | ||
0617bf4c MD |
279 | if (!arena->p) |
280 | new_arena = mmap(arena->p, len, | |
281 | PROT_READ | PROT_WRITE, | |
282 | MAP_ANONYMOUS | MAP_PRIVATE, | |
283 | -1, 0); | |
284 | else | |
285 | new_arena = mremap(arena->p, arena->len, | |
286 | len, MREMAP_MAYMOVE); | |
287 | assert(new_arena != MAP_FAILED); | |
288 | ||
fdee2e6d MD |
289 | /* |
290 | * re-used the same region ? | |
291 | */ | |
292 | if (new_arena == arena->p) | |
293 | return; | |
294 | ||
fdee2e6d MD |
295 | bzero(new_arena + arena->len, len - arena->len); |
296 | arena->p = new_arena; | |
297 | } | |
298 | ||
299 | /* Called with signals off and mutex locked */ | |
300 | static void add_thread(void) | |
301 | { | |
02be5561 | 302 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
303 | |
304 | if (registry_arena.len | |
02be5561 | 305 | < registry_arena.used + sizeof(struct rcu_reader)) |
fdee2e6d | 306 | resize_arena(®istry_arena, |
2f8a5ae7 | 307 | caa_max(registry_arena.len << 1, ARENA_INIT_ALLOC)); |
fdee2e6d MD |
308 | /* |
309 | * Find a free spot. | |
310 | */ | |
02be5561 MD |
311 | for (rcu_reader_reg = registry_arena.p; |
312 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
313 | rcu_reader_reg++) { | |
314 | if (!rcu_reader_reg->alloc) | |
fdee2e6d MD |
315 | break; |
316 | } | |
02be5561 MD |
317 | rcu_reader_reg->alloc = 1; |
318 | registry_arena.used += sizeof(struct rcu_reader); | |
fdee2e6d MD |
319 | |
320 | /* Add to registry */ | |
02be5561 MD |
321 | rcu_reader_reg->tid = pthread_self(); |
322 | assert(rcu_reader_reg->ctr == 0); | |
16aa9ee8 | 323 | cds_list_add(&rcu_reader_reg->node, ®istry); |
02be5561 | 324 | rcu_reader = rcu_reader_reg; |
fdee2e6d MD |
325 | } |
326 | ||
327 | /* Called with signals off and mutex locked */ | |
328 | static void rcu_gc_registry(void) | |
329 | { | |
02be5561 | 330 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
331 | pthread_t tid; |
332 | int ret; | |
333 | ||
02be5561 MD |
334 | for (rcu_reader_reg = registry_arena.p; |
335 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
336 | rcu_reader_reg++) { | |
337 | if (!rcu_reader_reg->alloc) | |
fdee2e6d | 338 | continue; |
02be5561 | 339 | tid = rcu_reader_reg->tid; |
fdee2e6d MD |
340 | ret = pthread_kill(tid, 0); |
341 | assert(ret != EINVAL); | |
342 | if (ret == ESRCH) { | |
16aa9ee8 | 343 | cds_list_del(&rcu_reader_reg->node); |
79266051 | 344 | rcu_reader_reg->ctr = 0; |
02be5561 MD |
345 | rcu_reader_reg->alloc = 0; |
346 | registry_arena.used -= sizeof(struct rcu_reader); | |
fdee2e6d MD |
347 | } |
348 | } | |
349 | } | |
350 | ||
351 | /* Disable signals, take mutex, add to registry */ | |
352 | void rcu_bp_register(void) | |
353 | { | |
354 | sigset_t newmask, oldmask; | |
355 | int ret; | |
356 | ||
357 | ret = sigemptyset(&newmask); | |
358 | assert(!ret); | |
359 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
360 | assert(!ret); | |
361 | ||
362 | /* | |
363 | * Check if a signal concurrently registered our thread since | |
364 | * the check in rcu_read_lock(). */ | |
02be5561 | 365 | if (rcu_reader) |
fdee2e6d MD |
366 | goto end; |
367 | ||
6abb4bd5 | 368 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 369 | add_thread(); |
6abb4bd5 | 370 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
371 | end: |
372 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
373 | assert(!ret); | |
374 | } | |
375 | ||
9380711a | 376 | void rcu_bp_exit(void) |
fdee2e6d | 377 | { |
9380711a MD |
378 | if (registry_arena.p) |
379 | munmap(registry_arena.p, registry_arena.len); | |
fdee2e6d | 380 | } |
4cf1675f MD |
381 | |
382 | /* | |
383 | * Holding the rcu_gp_lock across fork will make sure we fork() don't race with | |
384 | * a concurrent thread executing with this same lock held. This ensures that the | |
385 | * registry is in a coherent state in the child. | |
386 | */ | |
387 | void rcu_bp_before_fork(void) | |
388 | { | |
389 | sigset_t newmask, oldmask; | |
390 | int ret; | |
391 | ||
392 | ret = sigemptyset(&newmask); | |
393 | assert(!ret); | |
394 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
395 | assert(!ret); | |
396 | mutex_lock(&rcu_gp_lock); | |
397 | saved_fork_signal_mask = oldmask; | |
398 | } | |
399 | ||
400 | void rcu_bp_after_fork_parent(void) | |
401 | { | |
402 | sigset_t oldmask; | |
403 | int ret; | |
404 | ||
405 | oldmask = saved_fork_signal_mask; | |
406 | mutex_unlock(&rcu_gp_lock); | |
407 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
408 | assert(!ret); | |
409 | } | |
410 | ||
411 | void rcu_bp_after_fork_child(void) | |
412 | { | |
413 | sigset_t oldmask; | |
414 | int ret; | |
415 | ||
416 | rcu_gc_registry(); | |
417 | oldmask = saved_fork_signal_mask; | |
418 | mutex_unlock(&rcu_gp_lock); | |
419 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
420 | assert(!ret); | |
421 | } | |
5e77fc1f PM |
422 | |
423 | #include "urcu-call-rcu-impl.h" | |
0376e7b2 | 424 | #include "urcu-defer-impl.h" |