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 | ||
c7eaf61c MD |
54 | #ifdef __linux__ |
55 | static | |
56 | void *mremap_wrapper(void *old_address, size_t old_size, | |
57 | size_t new_size, int flags) | |
58 | { | |
59 | return mremap(old_address, old_size, new_size, flags); | |
60 | } | |
61 | #else | |
45a4872f MD |
62 | |
63 | #define MREMAP_MAYMOVE 1 | |
64 | #define MREMAP_FIXED 2 | |
65 | ||
66 | /* | |
67 | * mremap wrapper for non-Linux systems. Maps a RW, anonymous private mapping. | |
68 | * This is not generic. | |
69 | */ | |
c7eaf61c MD |
70 | static |
71 | void *mremap_wrapper(void *old_address, size_t old_size, | |
72 | size_t new_size, int flags) | |
45a4872f | 73 | { |
dc745ef6 | 74 | void *new_address; |
45a4872f MD |
75 | |
76 | assert(flags & MREMAP_MAYMOVE); | |
77 | assert(!(flags & MREMAP_FIXED)); | |
78 | new_address = mmap(old_address, new_size, | |
79 | PROT_READ | PROT_WRITE, | |
80 | MAP_ANONYMOUS | MAP_PRIVATE, | |
81 | -1, 0); | |
82 | if (new_address == MAP_FAILED) | |
83 | return MAP_FAILED; | |
84 | if (old_address) { | |
85 | memcpy(new_address, old_address, old_size); | |
86 | munmap(old_address, old_size); | |
87 | } | |
88 | return new_address; | |
89 | } | |
90 | #endif | |
91 | ||
fdee2e6d MD |
92 | /* Sleep delay in us */ |
93 | #define RCU_SLEEP_DELAY 1000 | |
94 | #define ARENA_INIT_ALLOC 16 | |
95 | ||
b7b6a8f5 PB |
96 | /* |
97 | * Active attempts to check for reader Q.S. before calling sleep(). | |
98 | */ | |
99 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
100 | ||
02be5561 | 101 | void __attribute__((destructor)) rcu_bp_exit(void); |
fdee2e6d | 102 | |
6abb4bd5 | 103 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
fdee2e6d MD |
104 | |
105 | #ifdef DEBUG_YIELD | |
106 | unsigned int yield_active; | |
bd252a04 | 107 | DEFINE_URCU_TLS(unsigned int, rand_yield); |
fdee2e6d MD |
108 | #endif |
109 | ||
110 | /* | |
111 | * Global grace period counter. | |
02be5561 | 112 | * Contains the current RCU_GP_CTR_PHASE. |
fdee2e6d MD |
113 | * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. |
114 | * Written to only by writer with mutex taken. Read by both writer and readers. | |
115 | */ | |
02be5561 | 116 | long rcu_gp_ctr = RCU_GP_COUNT; |
fdee2e6d MD |
117 | |
118 | /* | |
119 | * Pointer to registry elements. Written to only by each individual reader. Read | |
120 | * by both the reader and the writers. | |
121 | */ | |
bd252a04 | 122 | DEFINE_URCU_TLS(struct rcu_reader *, rcu_reader); |
fdee2e6d | 123 | |
16aa9ee8 | 124 | static CDS_LIST_HEAD(registry); |
fdee2e6d MD |
125 | |
126 | struct registry_arena { | |
127 | void *p; | |
128 | size_t len; | |
129 | size_t used; | |
130 | }; | |
131 | ||
132 | static struct registry_arena registry_arena; | |
133 | ||
4cf1675f MD |
134 | /* Saved fork signal mask, protected by rcu_gp_lock */ |
135 | static sigset_t saved_fork_signal_mask; | |
136 | ||
fdee2e6d MD |
137 | static void rcu_gc_registry(void); |
138 | ||
6abb4bd5 | 139 | static void mutex_lock(pthread_mutex_t *mutex) |
fdee2e6d MD |
140 | { |
141 | int ret; | |
142 | ||
143 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 144 | ret = pthread_mutex_lock(mutex); |
fdee2e6d MD |
145 | if (ret) { |
146 | perror("Error in pthread mutex lock"); | |
147 | exit(-1); | |
148 | } | |
149 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ | |
6abb4bd5 | 150 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
fdee2e6d MD |
151 | if (ret != EBUSY && ret != EINTR) { |
152 | printf("ret = %d, errno = %d\n", ret, errno); | |
153 | perror("Error in pthread mutex lock"); | |
154 | exit(-1); | |
155 | } | |
fdee2e6d MD |
156 | poll(NULL,0,10); |
157 | } | |
158 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
159 | } | |
160 | ||
6abb4bd5 | 161 | static void mutex_unlock(pthread_mutex_t *mutex) |
fdee2e6d MD |
162 | { |
163 | int ret; | |
164 | ||
6abb4bd5 | 165 | ret = pthread_mutex_unlock(mutex); |
fdee2e6d MD |
166 | if (ret) { |
167 | perror("Error in pthread mutex unlock"); | |
168 | exit(-1); | |
169 | } | |
170 | } | |
171 | ||
2dfb8b5e | 172 | void update_counter_and_wait(void) |
fdee2e6d | 173 | { |
16aa9ee8 | 174 | CDS_LIST_HEAD(qsreaders); |
fdee2e6d | 175 | int wait_loops = 0; |
02be5561 | 176 | struct rcu_reader *index, *tmp; |
fdee2e6d | 177 | |
32c15e4e | 178 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
6cf3827c | 179 | CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); |
2dfb8b5e MD |
180 | |
181 | /* | |
182 | * Must commit qparity update to memory before waiting for other parity | |
183 | * quiescent state. Failure to do so could result in the writer waiting | |
184 | * forever while new readers are always accessing data (no progress). | |
6cf3827c | 185 | * Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED. |
2dfb8b5e MD |
186 | */ |
187 | ||
188 | /* | |
5481ddb3 | 189 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
2dfb8b5e MD |
190 | * model easier to understand. It does not have a big performance impact |
191 | * anyway, given this is the write-side. | |
192 | */ | |
5481ddb3 | 193 | cmm_smp_mb(); |
2dfb8b5e | 194 | |
fdee2e6d | 195 | /* |
02be5561 | 196 | * Wait for each thread rcu_reader.ctr count to become 0. |
fdee2e6d MD |
197 | */ |
198 | for (;;) { | |
199 | wait_loops++; | |
16aa9ee8 | 200 | cds_list_for_each_entry_safe(index, tmp, ®istry, node) { |
fdee2e6d | 201 | if (!rcu_old_gp_ongoing(&index->ctr)) |
16aa9ee8 | 202 | cds_list_move(&index->node, &qsreaders); |
fdee2e6d MD |
203 | } |
204 | ||
16aa9ee8 | 205 | if (cds_list_empty(®istry)) { |
fdee2e6d MD |
206 | break; |
207 | } else { | |
208 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) | |
209 | usleep(RCU_SLEEP_DELAY); | |
210 | else | |
06f22bdb | 211 | caa_cpu_relax(); |
fdee2e6d MD |
212 | } |
213 | } | |
214 | /* put back the reader list in the registry */ | |
16aa9ee8 | 215 | cds_list_splice(&qsreaders, ®istry); |
fdee2e6d MD |
216 | } |
217 | ||
218 | void synchronize_rcu(void) | |
219 | { | |
220 | sigset_t newmask, oldmask; | |
221 | int ret; | |
222 | ||
223 | ret = sigemptyset(&newmask); | |
224 | assert(!ret); | |
225 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
226 | assert(!ret); | |
227 | ||
6abb4bd5 | 228 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 229 | |
16aa9ee8 | 230 | if (cds_list_empty(®istry)) |
2dfb8b5e | 231 | goto out; |
fdee2e6d MD |
232 | |
233 | /* All threads should read qparity before accessing data structure | |
2dfb8b5e | 234 | * where new ptr points to. */ |
fdee2e6d | 235 | /* Write new ptr before changing the qparity */ |
5481ddb3 | 236 | cmm_smp_mb(); |
fdee2e6d | 237 | |
2dfb8b5e MD |
238 | /* Remove old registry elements */ |
239 | rcu_gc_registry(); | |
fdee2e6d MD |
240 | |
241 | /* | |
242 | * Wait for previous parity to be empty of readers. | |
243 | */ | |
2dfb8b5e | 244 | update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ |
fdee2e6d MD |
245 | |
246 | /* | |
5481ddb3 | 247 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
fdee2e6d MD |
248 | * model easier to understand. It does not have a big performance impact |
249 | * anyway, given this is the write-side. | |
250 | */ | |
5481ddb3 | 251 | cmm_smp_mb(); |
fdee2e6d | 252 | |
fdee2e6d | 253 | /* |
2dfb8b5e | 254 | * Wait for previous parity to be empty of readers. |
fdee2e6d | 255 | */ |
2dfb8b5e | 256 | update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ |
fdee2e6d MD |
257 | |
258 | /* | |
2dfb8b5e MD |
259 | * Finish waiting for reader threads before letting the old ptr being |
260 | * freed. | |
fdee2e6d | 261 | */ |
5481ddb3 | 262 | cmm_smp_mb(); |
2dfb8b5e | 263 | out: |
6abb4bd5 | 264 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
265 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); |
266 | assert(!ret); | |
267 | } | |
268 | ||
269 | /* | |
270 | * library wrappers to be used by non-LGPL compatible source code. | |
271 | */ | |
272 | ||
273 | void rcu_read_lock(void) | |
274 | { | |
275 | _rcu_read_lock(); | |
276 | } | |
277 | ||
278 | void rcu_read_unlock(void) | |
279 | { | |
280 | _rcu_read_unlock(); | |
281 | } | |
282 | ||
283 | /* | |
284 | * only grow for now. | |
285 | */ | |
286 | static void resize_arena(struct registry_arena *arena, size_t len) | |
287 | { | |
288 | void *new_arena; | |
289 | ||
0617bf4c MD |
290 | if (!arena->p) |
291 | new_arena = mmap(arena->p, len, | |
292 | PROT_READ | PROT_WRITE, | |
293 | MAP_ANONYMOUS | MAP_PRIVATE, | |
294 | -1, 0); | |
295 | else | |
c7eaf61c MD |
296 | new_arena = mremap_wrapper(arena->p, arena->len, |
297 | len, MREMAP_MAYMOVE); | |
0617bf4c MD |
298 | assert(new_arena != MAP_FAILED); |
299 | ||
fdee2e6d MD |
300 | /* |
301 | * re-used the same region ? | |
302 | */ | |
303 | if (new_arena == arena->p) | |
304 | return; | |
305 | ||
fdee2e6d MD |
306 | bzero(new_arena + arena->len, len - arena->len); |
307 | arena->p = new_arena; | |
308 | } | |
309 | ||
310 | /* Called with signals off and mutex locked */ | |
311 | static void add_thread(void) | |
312 | { | |
02be5561 | 313 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
314 | |
315 | if (registry_arena.len | |
02be5561 | 316 | < registry_arena.used + sizeof(struct rcu_reader)) |
fdee2e6d | 317 | resize_arena(®istry_arena, |
2f8a5ae7 | 318 | caa_max(registry_arena.len << 1, ARENA_INIT_ALLOC)); |
fdee2e6d MD |
319 | /* |
320 | * Find a free spot. | |
321 | */ | |
02be5561 MD |
322 | for (rcu_reader_reg = registry_arena.p; |
323 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
324 | rcu_reader_reg++) { | |
325 | if (!rcu_reader_reg->alloc) | |
fdee2e6d MD |
326 | break; |
327 | } | |
02be5561 MD |
328 | rcu_reader_reg->alloc = 1; |
329 | registry_arena.used += sizeof(struct rcu_reader); | |
fdee2e6d MD |
330 | |
331 | /* Add to registry */ | |
02be5561 MD |
332 | rcu_reader_reg->tid = pthread_self(); |
333 | assert(rcu_reader_reg->ctr == 0); | |
16aa9ee8 | 334 | cds_list_add(&rcu_reader_reg->node, ®istry); |
bd252a04 | 335 | URCU_TLS(rcu_reader) = rcu_reader_reg; |
fdee2e6d MD |
336 | } |
337 | ||
338 | /* Called with signals off and mutex locked */ | |
339 | static void rcu_gc_registry(void) | |
340 | { | |
02be5561 | 341 | struct rcu_reader *rcu_reader_reg; |
fdee2e6d MD |
342 | pthread_t tid; |
343 | int ret; | |
344 | ||
02be5561 MD |
345 | for (rcu_reader_reg = registry_arena.p; |
346 | (void *)rcu_reader_reg < registry_arena.p + registry_arena.len; | |
347 | rcu_reader_reg++) { | |
348 | if (!rcu_reader_reg->alloc) | |
fdee2e6d | 349 | continue; |
02be5561 | 350 | tid = rcu_reader_reg->tid; |
fdee2e6d MD |
351 | ret = pthread_kill(tid, 0); |
352 | assert(ret != EINVAL); | |
353 | if (ret == ESRCH) { | |
16aa9ee8 | 354 | cds_list_del(&rcu_reader_reg->node); |
79266051 | 355 | rcu_reader_reg->ctr = 0; |
02be5561 MD |
356 | rcu_reader_reg->alloc = 0; |
357 | registry_arena.used -= sizeof(struct rcu_reader); | |
fdee2e6d MD |
358 | } |
359 | } | |
360 | } | |
361 | ||
362 | /* Disable signals, take mutex, add to registry */ | |
363 | void rcu_bp_register(void) | |
364 | { | |
365 | sigset_t newmask, oldmask; | |
366 | int ret; | |
367 | ||
368 | ret = sigemptyset(&newmask); | |
369 | assert(!ret); | |
370 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
371 | assert(!ret); | |
372 | ||
373 | /* | |
374 | * Check if a signal concurrently registered our thread since | |
375 | * the check in rcu_read_lock(). */ | |
bd252a04 | 376 | if (URCU_TLS(rcu_reader)) |
fdee2e6d MD |
377 | goto end; |
378 | ||
6abb4bd5 | 379 | mutex_lock(&rcu_gp_lock); |
fdee2e6d | 380 | add_thread(); |
6abb4bd5 | 381 | mutex_unlock(&rcu_gp_lock); |
fdee2e6d MD |
382 | end: |
383 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
384 | assert(!ret); | |
385 | } | |
386 | ||
9380711a | 387 | void rcu_bp_exit(void) |
fdee2e6d | 388 | { |
9380711a MD |
389 | if (registry_arena.p) |
390 | munmap(registry_arena.p, registry_arena.len); | |
fdee2e6d | 391 | } |
4cf1675f MD |
392 | |
393 | /* | |
394 | * Holding the rcu_gp_lock across fork will make sure we fork() don't race with | |
395 | * a concurrent thread executing with this same lock held. This ensures that the | |
396 | * registry is in a coherent state in the child. | |
397 | */ | |
398 | void rcu_bp_before_fork(void) | |
399 | { | |
400 | sigset_t newmask, oldmask; | |
401 | int ret; | |
402 | ||
403 | ret = sigemptyset(&newmask); | |
404 | assert(!ret); | |
405 | ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); | |
406 | assert(!ret); | |
407 | mutex_lock(&rcu_gp_lock); | |
408 | saved_fork_signal_mask = oldmask; | |
409 | } | |
410 | ||
411 | void rcu_bp_after_fork_parent(void) | |
412 | { | |
413 | sigset_t oldmask; | |
414 | int ret; | |
415 | ||
416 | oldmask = saved_fork_signal_mask; | |
417 | mutex_unlock(&rcu_gp_lock); | |
418 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
419 | assert(!ret); | |
420 | } | |
421 | ||
422 | void rcu_bp_after_fork_child(void) | |
423 | { | |
424 | sigset_t oldmask; | |
425 | int ret; | |
426 | ||
427 | rcu_gc_registry(); | |
428 | oldmask = saved_fork_signal_mask; | |
429 | mutex_unlock(&rcu_gp_lock); | |
430 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
431 | assert(!ret); | |
432 | } | |
5e77fc1f | 433 | |
9b7981bb MD |
434 | void *rcu_dereference_sym_bp(void *p) |
435 | { | |
436 | return _rcu_dereference(p); | |
437 | } | |
438 | ||
5efd3cd2 MD |
439 | void *rcu_set_pointer_sym_bp(void **p, void *v) |
440 | { | |
441 | cmm_wmb(); | |
442 | return uatomic_set(p, v); | |
443 | } | |
444 | ||
445 | void *rcu_xchg_pointer_sym_bp(void **p, void *v) | |
446 | { | |
447 | cmm_wmb(); | |
448 | return uatomic_xchg(p, v); | |
449 | } | |
450 | ||
451 | void *rcu_cmpxchg_pointer_sym_bp(void **p, void *old, void *_new) | |
452 | { | |
453 | cmm_wmb(); | |
454 | return uatomic_cmpxchg(p, old, _new); | |
455 | } | |
456 | ||
5e6b23a6 | 457 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 458 | |
5e77fc1f | 459 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 460 | #include "urcu-defer-impl.h" |