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 |
fdee2e6d MD |
27 | #include <stdio.h> |
28 | #include <pthread.h> | |
29 | #include <signal.h> | |
30 | #include <assert.h> | |
31 | #include <stdlib.h> | |
32 | #include <string.h> | |
33 | #include <errno.h> | |
34 | #include <poll.h> | |
35 | #include <unistd.h> | |
36 | #include <sys/mman.h> | |
37 | ||
57760d44 | 38 | #include "urcu/map/urcu-bp.h" |
5e77fc1f | 39 | |
af7c2dbe | 40 | #include "urcu/static/urcu-bp.h" |
fdee2e6d MD |
41 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
42 | #include "urcu-bp.h" | |
43 | ||
4c1ae2ea MD |
44 | #ifndef MAP_ANONYMOUS |
45 | #define MAP_ANONYMOUS MAP_ANON | |
46 | #endif | |
47 | ||
45a4872f MD |
48 | #ifndef __linux__ |
49 | ||
50 | #define MREMAP_MAYMOVE 1 | |
51 | #define MREMAP_FIXED 2 | |
52 | ||
53 | /* | |
54 | * mremap wrapper for non-Linux systems. Maps a RW, anonymous private mapping. | |
55 | * This is not generic. | |
56 | */ | |
57 | void *mremap(void *old_address, size_t old_size, size_t new_size, int flags) | |
58 | { | |
dc745ef6 | 59 | void *new_address; |
45a4872f MD |
60 | |
61 | assert(flags & MREMAP_MAYMOVE); | |
62 | assert(!(flags & MREMAP_FIXED)); | |
63 | new_address = mmap(old_address, new_size, | |
64 | PROT_READ | PROT_WRITE, | |
65 | MAP_ANONYMOUS | MAP_PRIVATE, | |
66 | -1, 0); | |
67 | if (new_address == MAP_FAILED) | |
68 | return MAP_FAILED; | |
69 | if (old_address) { | |
70 | memcpy(new_address, old_address, old_size); | |
71 | munmap(old_address, old_size); | |
72 | } | |
73 | return new_address; | |
74 | } | |
75 | #endif | |
76 | ||
fdee2e6d MD |
77 | /* Sleep delay in us */ |
78 | #define RCU_SLEEP_DELAY 1000 | |
79 | #define ARENA_INIT_ALLOC 16 | |
80 | ||
b7b6a8f5 PB |
81 | /* |
82 | * Active attempts to check for reader Q.S. before calling sleep(). | |
83 | */ | |
84 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
85 | ||
02be5561 | 86 | void __attribute__((destructor)) rcu_bp_exit(void); |
fdee2e6d | 87 | |
6abb4bd5 | 88 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
fdee2e6d MD |
89 | |
90 | #ifdef DEBUG_YIELD | |
91 | unsigned int yield_active; | |
92 | unsigned int __thread rand_yield; | |
93 | #endif | |
94 | ||
95 | /* | |
96 | * Global grace period counter. | |
02be5561 | 97 | * Contains the current RCU_GP_CTR_PHASE. |
fdee2e6d MD |
98 | * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. |
99 | * Written to only by writer with mutex taken. Read by both writer and readers. | |
100 | */ | |
02be5561 | 101 | long rcu_gp_ctr = RCU_GP_COUNT; |
fdee2e6d MD |
102 | |
103 | /* | |
104 | * Pointer to registry elements. Written to only by each individual reader. Read | |
105 | * by both the reader and the writers. | |
106 | */ | |
02be5561 | 107 | struct rcu_reader __thread *rcu_reader; |
fdee2e6d | 108 | |
16aa9ee8 | 109 | static CDS_LIST_HEAD(registry); |
fdee2e6d MD |
110 | |
111 | struct registry_arena { | |
112 | void *p; | |
113 | size_t len; | |
114 | size_t used; | |
115 | }; | |
116 | ||
117 | static struct registry_arena registry_arena; | |
118 | ||
4cf1675f MD |
119 | /* Saved fork signal mask, protected by rcu_gp_lock */ |
120 | static sigset_t saved_fork_signal_mask; | |
121 | ||
fdee2e6d MD |
122 | static void rcu_gc_registry(void); |
123 | ||
6abb4bd5 | 124 | static void mutex_lock(pthread_mutex_t *mutex) |
fdee2e6d MD |
125 | { |
126 | int ret; | |
127 | ||
128 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 129 | ret = pthread_mutex_lock(mutex); |
fdee2e6d MD |
130 | if (ret) { |
131 | perror("Error in pthread mutex lock"); | |
132 | exit(-1); | |
133 | } | |
134 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ | |
6abb4bd5 | 135 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
fdee2e6d MD |
136 | if (ret != EBUSY && ret != EINTR) { |
137 | printf("ret = %d, errno = %d\n", ret, errno); | |
138 | perror("Error in pthread mutex lock"); | |
139 | exit(-1); | |
140 | } | |
fdee2e6d MD |
141 | poll(NULL,0,10); |
142 | } | |
143 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
144 | } | |
145 | ||
6abb4bd5 | 146 | static void mutex_unlock(pthread_mutex_t *mutex) |
fdee2e6d MD |
147 | { |
148 | int ret; | |
149 | ||
6abb4bd5 | 150 | ret = pthread_mutex_unlock(mutex); |
fdee2e6d MD |
151 | if (ret) { |
152 | perror("Error in pthread mutex unlock"); | |
153 | exit(-1); | |
154 | } | |
155 | } | |
156 | ||
2dfb8b5e | 157 | void update_counter_and_wait(void) |
fdee2e6d | 158 | { |
16aa9ee8 | 159 | CDS_LIST_HEAD(qsreaders); |
fdee2e6d | 160 | int wait_loops = 0; |
02be5561 | 161 | struct rcu_reader *index, *tmp; |
fdee2e6d | 162 | |
32c15e4e | 163 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
6cf3827c | 164 | CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); |
2dfb8b5e MD |
165 | |
166 | /* | |
167 | * Must commit qparity update to memory before waiting for other parity | |
168 | * quiescent state. Failure to do so could result in the writer waiting | |
169 | * forever while new readers are always accessing data (no progress). | |
6cf3827c | 170 | * Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED. |
2dfb8b5e MD |
171 | */ |
172 | ||
173 | /* | |
5481ddb3 | 174 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
2dfb8b5e MD |
175 | * model easier to understand. It does not have a big performance impact |
176 | * anyway, given this is the write-side. | |
177 | */ | |
5481ddb3 | 178 | cmm_smp_mb(); |
2dfb8b5e | 179 | |
fdee2e6d | 180 | /* |
02be5561 | 181 | * Wait for each thread rcu_reader.ctr count to become 0. |
fdee2e6d MD |
182 | */ |
183 | for (;;) { | |
184 | wait_loops++; | |
16aa9ee8 | 185 | cds_list_for_each_entry_safe(index, tmp, ®istry, node) { |
fdee2e6d | 186 | if (!rcu_old_gp_ongoing(&index->ctr)) |
16aa9ee8 | 187 | cds_list_move(&index->node, &qsreaders); |
fdee2e6d MD |
188 | } |
189 | ||
16aa9ee8 | 190 | if (cds_list_empty(®istry)) { |
fdee2e6d MD |
191 | break; |
192 | } else { | |
193 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) | |
194 | usleep(RCU_SLEEP_DELAY); | |
195 | else | |
06f22bdb | 196 | caa_cpu_relax(); |
fdee2e6d MD |
197 | } |
198 | } | |
199 | /* put back the reader list in the registry */ | |
16aa9ee8 | 200 | cds_list_splice(&qsreaders, ®istry); |
fdee2e6d MD |
201 | } |
202 | ||
203 | void synchronize_rcu(void) | |
204 | { | |
205 | sigset_t newmask, oldmask; | |
206 | int ret; | |
207 | ||
208 | ret = sigemptyset(&newmask); | |
209 | assert(!ret); | |
210 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
211 | assert(!ret); | |
212 | ||
6abb4bd5 | 213 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 214 | |
16aa9ee8 | 215 | if (cds_list_empty(®istry)) |
2dfb8b5e | 216 | goto out; |
fdee2e6d MD |
217 | |
218 | /* All threads should read qparity before accessing data structure | |
2dfb8b5e | 219 | * where new ptr points to. */ |
fdee2e6d | 220 | /* Write new ptr before changing the qparity */ |
5481ddb3 | 221 | cmm_smp_mb(); |
fdee2e6d | 222 | |
2dfb8b5e MD |
223 | /* Remove old registry elements */ |
224 | rcu_gc_registry(); | |
fdee2e6d MD |
225 | |
226 | /* | |
227 | * Wait for previous parity to be empty of readers. | |
228 | */ | |
2dfb8b5e | 229 | update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ |
fdee2e6d MD |
230 | |
231 | /* | |
5481ddb3 | 232 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
fdee2e6d MD |
233 | * model easier to understand. It does not have a big performance impact |
234 | * anyway, given this is the write-side. | |
235 | */ | |
5481ddb3 | 236 | cmm_smp_mb(); |
fdee2e6d | 237 | |
fdee2e6d | 238 | /* |
2dfb8b5e | 239 | * Wait for previous parity to be empty of readers. |
fdee2e6d | 240 | */ |
2dfb8b5e | 241 | update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ |
fdee2e6d MD |
242 | |
243 | /* | |
2dfb8b5e MD |
244 | * Finish waiting for reader threads before letting the old ptr being |
245 | * freed. | |
fdee2e6d | 246 | */ |
5481ddb3 | 247 | cmm_smp_mb(); |
2dfb8b5e | 248 | out: |
6abb4bd5 | 249 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
250 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); |
251 | assert(!ret); | |
252 | } | |
253 | ||
254 | /* | |
255 | * library wrappers to be used by non-LGPL compatible source code. | |
256 | */ | |
257 | ||
258 | void rcu_read_lock(void) | |
259 | { | |
260 | _rcu_read_lock(); | |
261 | } | |
262 | ||
263 | void rcu_read_unlock(void) | |
264 | { | |
265 | _rcu_read_unlock(); | |
266 | } | |
267 | ||
268 | /* | |
269 | * only grow for now. | |
270 | */ | |
271 | static void resize_arena(struct registry_arena *arena, size_t len) | |
272 | { | |
273 | void *new_arena; | |
274 | ||
0617bf4c MD |
275 | if (!arena->p) |
276 | new_arena = mmap(arena->p, len, | |
277 | PROT_READ | PROT_WRITE, | |
278 | MAP_ANONYMOUS | MAP_PRIVATE, | |
279 | -1, 0); | |
280 | else | |
281 | new_arena = mremap(arena->p, arena->len, | |
282 | len, MREMAP_MAYMOVE); | |
283 | assert(new_arena != MAP_FAILED); | |
284 | ||
fdee2e6d MD |
285 | /* |
286 | * re-used the same region ? | |
287 | */ | |
288 | if (new_arena == arena->p) | |
289 | return; | |
290 | ||
fdee2e6d MD |
291 | bzero(new_arena + arena->len, len - arena->len); |
292 | arena->p = new_arena; | |
293 | } | |
294 | ||
295 | /* Called with signals off and mutex locked */ | |
296 | static void add_thread(void) | |
297 | { | |
02be5561 | 298 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
299 | |
300 | if (registry_arena.len | |
02be5561 | 301 | < registry_arena.used + sizeof(struct rcu_reader)) |
fdee2e6d | 302 | resize_arena(®istry_arena, |
2f8a5ae7 | 303 | caa_max(registry_arena.len << 1, ARENA_INIT_ALLOC)); |
fdee2e6d MD |
304 | /* |
305 | * Find a free spot. | |
306 | */ | |
02be5561 MD |
307 | for (rcu_reader_reg = registry_arena.p; |
308 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
309 | rcu_reader_reg++) { | |
310 | if (!rcu_reader_reg->alloc) | |
fdee2e6d MD |
311 | break; |
312 | } | |
02be5561 MD |
313 | rcu_reader_reg->alloc = 1; |
314 | registry_arena.used += sizeof(struct rcu_reader); | |
fdee2e6d MD |
315 | |
316 | /* Add to registry */ | |
02be5561 MD |
317 | rcu_reader_reg->tid = pthread_self(); |
318 | assert(rcu_reader_reg->ctr == 0); | |
16aa9ee8 | 319 | cds_list_add(&rcu_reader_reg->node, ®istry); |
02be5561 | 320 | rcu_reader = rcu_reader_reg; |
fdee2e6d MD |
321 | } |
322 | ||
323 | /* Called with signals off and mutex locked */ | |
324 | static void rcu_gc_registry(void) | |
325 | { | |
02be5561 | 326 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
327 | pthread_t tid; |
328 | int ret; | |
329 | ||
02be5561 MD |
330 | for (rcu_reader_reg = registry_arena.p; |
331 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
332 | rcu_reader_reg++) { | |
333 | if (!rcu_reader_reg->alloc) | |
fdee2e6d | 334 | continue; |
02be5561 | 335 | tid = rcu_reader_reg->tid; |
fdee2e6d MD |
336 | ret = pthread_kill(tid, 0); |
337 | assert(ret != EINVAL); | |
338 | if (ret == ESRCH) { | |
16aa9ee8 | 339 | cds_list_del(&rcu_reader_reg->node); |
79266051 | 340 | rcu_reader_reg->ctr = 0; |
02be5561 MD |
341 | rcu_reader_reg->alloc = 0; |
342 | registry_arena.used -= sizeof(struct rcu_reader); | |
fdee2e6d MD |
343 | } |
344 | } | |
345 | } | |
346 | ||
347 | /* Disable signals, take mutex, add to registry */ | |
348 | void rcu_bp_register(void) | |
349 | { | |
350 | sigset_t newmask, oldmask; | |
351 | int ret; | |
352 | ||
353 | ret = sigemptyset(&newmask); | |
354 | assert(!ret); | |
355 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
356 | assert(!ret); | |
357 | ||
358 | /* | |
359 | * Check if a signal concurrently registered our thread since | |
360 | * the check in rcu_read_lock(). */ | |
02be5561 | 361 | if (rcu_reader) |
fdee2e6d MD |
362 | goto end; |
363 | ||
6abb4bd5 | 364 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 365 | add_thread(); |
6abb4bd5 | 366 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
367 | end: |
368 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
369 | assert(!ret); | |
370 | } | |
371 | ||
02be5561 | 372 | void rcu_bp_exit() |
fdee2e6d MD |
373 | { |
374 | munmap(registry_arena.p, registry_arena.len); | |
375 | } | |
4cf1675f MD |
376 | |
377 | /* | |
378 | * Holding the rcu_gp_lock across fork will make sure we fork() don't race with | |
379 | * a concurrent thread executing with this same lock held. This ensures that the | |
380 | * registry is in a coherent state in the child. | |
381 | */ | |
382 | void rcu_bp_before_fork(void) | |
383 | { | |
384 | sigset_t newmask, oldmask; | |
385 | int ret; | |
386 | ||
387 | ret = sigemptyset(&newmask); | |
388 | assert(!ret); | |
389 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
390 | assert(!ret); | |
391 | mutex_lock(&rcu_gp_lock); | |
392 | saved_fork_signal_mask = oldmask; | |
393 | } | |
394 | ||
395 | void rcu_bp_after_fork_parent(void) | |
396 | { | |
397 | sigset_t oldmask; | |
398 | int ret; | |
399 | ||
400 | oldmask = saved_fork_signal_mask; | |
401 | mutex_unlock(&rcu_gp_lock); | |
402 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
403 | assert(!ret); | |
404 | } | |
405 | ||
406 | void rcu_bp_after_fork_child(void) | |
407 | { | |
408 | sigset_t oldmask; | |
409 | int ret; | |
410 | ||
411 | rcu_gc_registry(); | |
412 | oldmask = saved_fork_signal_mask; | |
413 | mutex_unlock(&rcu_gp_lock); | |
414 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
415 | assert(!ret); | |
416 | } | |
5e77fc1f PM |
417 | |
418 | #include "urcu-call-rcu-impl.h" | |
0376e7b2 | 419 | #include "urcu-defer-impl.h" |