| 1 | // SPDX-FileCopyrightText: 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| 2 | // |
| 3 | // SPDX-License-Identifier: LGPL-2.1-or-later |
| 4 | |
| 5 | /* |
| 6 | * Userspace RCU library - batch memory reclamation with kernel API |
| 7 | */ |
| 8 | |
| 9 | #define _LGPL_SOURCE |
| 10 | #include <stdio.h> |
| 11 | #include <pthread.h> |
| 12 | #include <signal.h> |
| 13 | #include <stdlib.h> |
| 14 | #include <stdint.h> |
| 15 | #include <string.h> |
| 16 | #include <errno.h> |
| 17 | #include <poll.h> |
| 18 | #include <sys/time.h> |
| 19 | #include <unistd.h> |
| 20 | #include <sched.h> |
| 21 | |
| 22 | #include "compat-getcpu.h" |
| 23 | #include <urcu/assert.h> |
| 24 | #include <urcu/wfcqueue.h> |
| 25 | #include <urcu/call-rcu.h> |
| 26 | #include <urcu/pointer.h> |
| 27 | #include <urcu/list.h> |
| 28 | #include <urcu/futex.h> |
| 29 | #include <urcu/tls-compat.h> |
| 30 | #include <urcu/ref.h> |
| 31 | #include "urcu-die.h" |
| 32 | #include "urcu-utils.h" |
| 33 | #include "compat-smp.h" |
| 34 | |
| 35 | #define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */ |
| 36 | #define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1) |
| 37 | |
| 38 | /* Data structure that identifies a call_rcu thread. */ |
| 39 | |
| 40 | struct call_rcu_data { |
| 41 | /* |
| 42 | * We do not align head on a different cache-line than tail |
| 43 | * mainly because call_rcu callback-invocation threads use |
| 44 | * batching ("splice") to get an entire list of callbacks, which |
| 45 | * effectively empties the queue, and requires to touch the tail |
| 46 | * anyway. |
| 47 | */ |
| 48 | struct cds_wfcq_tail cbs_tail; |
| 49 | struct cds_wfcq_head cbs_head; |
| 50 | unsigned long flags; |
| 51 | int32_t futex; |
| 52 | unsigned long qlen; /* maintained for debugging. */ |
| 53 | pthread_t tid; |
| 54 | int cpu_affinity; |
| 55 | unsigned long gp_count; |
| 56 | struct cds_list_head list; |
| 57 | } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
| 58 | |
| 59 | struct call_rcu_completion { |
| 60 | int barrier_count; |
| 61 | int32_t futex; |
| 62 | struct urcu_ref ref; |
| 63 | }; |
| 64 | |
| 65 | struct call_rcu_completion_work { |
| 66 | struct rcu_head head; |
| 67 | struct call_rcu_completion *completion; |
| 68 | }; |
| 69 | |
| 70 | enum crdf_flags { |
| 71 | CRDF_FLAG_JOIN_THREAD = (1 << 0), |
| 72 | }; |
| 73 | |
| 74 | /* |
| 75 | * List of all call_rcu_data structures to keep valgrind happy. |
| 76 | * Protected by call_rcu_mutex. |
| 77 | */ |
| 78 | |
| 79 | static CDS_LIST_HEAD(call_rcu_data_list); |
| 80 | |
| 81 | /* Link a thread using call_rcu() to its call_rcu thread. */ |
| 82 | |
| 83 | static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data); |
| 84 | |
| 85 | /* |
| 86 | * Guard call_rcu thread creation and atfork handlers. |
| 87 | */ |
| 88 | static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER; |
| 89 | |
| 90 | /* If a given thread does not have its own call_rcu thread, this is default. */ |
| 91 | |
| 92 | static struct call_rcu_data *default_call_rcu_data; |
| 93 | |
| 94 | static struct urcu_atfork *registered_rculfhash_atfork; |
| 95 | |
| 96 | /* |
| 97 | * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are |
| 98 | * available, then we can have call_rcu threads assigned to individual |
| 99 | * CPUs rather than only to specific threads. |
| 100 | */ |
| 101 | |
| 102 | #if defined(HAVE_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID)) |
| 103 | |
| 104 | /* |
| 105 | * Pointer to array of pointers to per-CPU call_rcu_data structures |
| 106 | * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an |
| 107 | * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a |
| 108 | * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer |
| 109 | * without mutex. The call_rcu_mutex protects updates. |
| 110 | */ |
| 111 | |
| 112 | static struct call_rcu_data **per_cpu_call_rcu_data; |
| 113 | static long cpus_array_len; |
| 114 | |
| 115 | static void cpus_array_len_reset(void) |
| 116 | { |
| 117 | cpus_array_len = 0; |
| 118 | } |
| 119 | |
| 120 | /* Allocate the array if it has not already been allocated. */ |
| 121 | |
| 122 | static void alloc_cpu_call_rcu_data(void) |
| 123 | { |
| 124 | struct call_rcu_data **p; |
| 125 | static int warned = 0; |
| 126 | |
| 127 | if (cpus_array_len != 0) |
| 128 | return; |
| 129 | cpus_array_len = get_possible_cpus_array_len(); |
| 130 | if (cpus_array_len <= 0) { |
| 131 | return; |
| 132 | } |
| 133 | p = malloc(cpus_array_len * sizeof(*per_cpu_call_rcu_data)); |
| 134 | if (p != NULL) { |
| 135 | memset(p, '\0', cpus_array_len * sizeof(*per_cpu_call_rcu_data)); |
| 136 | rcu_set_pointer(&per_cpu_call_rcu_data, p); |
| 137 | } else { |
| 138 | if (!warned) { |
| 139 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); |
| 140 | } |
| 141 | warned = 1; |
| 142 | } |
| 143 | } |
| 144 | |
| 145 | #else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */ |
| 146 | |
| 147 | /* |
| 148 | * per_cpu_call_rcu_data should be constant, but some functions below, used both |
| 149 | * for cases where cpu number is available and not available, assume it it not |
| 150 | * constant. |
| 151 | */ |
| 152 | static struct call_rcu_data **per_cpu_call_rcu_data = NULL; |
| 153 | static const long cpus_array_len = -1; |
| 154 | |
| 155 | static void cpus_array_len_reset(void) |
| 156 | { |
| 157 | } |
| 158 | |
| 159 | static void alloc_cpu_call_rcu_data(void) |
| 160 | { |
| 161 | } |
| 162 | |
| 163 | #endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */ |
| 164 | |
| 165 | /* Acquire the specified pthread mutex. */ |
| 166 | |
| 167 | static void call_rcu_lock(pthread_mutex_t *pmp) |
| 168 | { |
| 169 | int ret; |
| 170 | |
| 171 | ret = pthread_mutex_lock(pmp); |
| 172 | if (ret) |
| 173 | urcu_die(ret); |
| 174 | } |
| 175 | |
| 176 | /* Release the specified pthread mutex. */ |
| 177 | |
| 178 | static void call_rcu_unlock(pthread_mutex_t *pmp) |
| 179 | { |
| 180 | int ret; |
| 181 | |
| 182 | ret = pthread_mutex_unlock(pmp); |
| 183 | if (ret) |
| 184 | urcu_die(ret); |
| 185 | } |
| 186 | |
| 187 | /* |
| 188 | * Periodically retry setting CPU affinity if we migrate. |
| 189 | * Losing affinity can be caused by CPU hotunplug/hotplug, or by |
| 190 | * cpuset(7). |
| 191 | */ |
| 192 | #ifdef HAVE_SCHED_SETAFFINITY |
| 193 | static |
| 194 | int set_thread_cpu_affinity(struct call_rcu_data *crdp) |
| 195 | { |
| 196 | cpu_set_t mask; |
| 197 | int ret; |
| 198 | |
| 199 | if (crdp->cpu_affinity < 0) |
| 200 | return 0; |
| 201 | if (++crdp->gp_count & SET_AFFINITY_CHECK_PERIOD_MASK) |
| 202 | return 0; |
| 203 | if (urcu_sched_getcpu() == crdp->cpu_affinity) |
| 204 | return 0; |
| 205 | |
| 206 | CPU_ZERO(&mask); |
| 207 | CPU_SET(crdp->cpu_affinity, &mask); |
| 208 | ret = sched_setaffinity(0, sizeof(mask), &mask); |
| 209 | |
| 210 | /* |
| 211 | * EINVAL is fine: can be caused by hotunplugged CPUs, or by |
| 212 | * cpuset(7). This is why we should always retry if we detect |
| 213 | * migration. |
| 214 | */ |
| 215 | if (ret && errno == EINVAL) { |
| 216 | ret = 0; |
| 217 | errno = 0; |
| 218 | } |
| 219 | return ret; |
| 220 | } |
| 221 | #else |
| 222 | static |
| 223 | int set_thread_cpu_affinity(struct call_rcu_data *crdp __attribute__((unused))) |
| 224 | { |
| 225 | return 0; |
| 226 | } |
| 227 | #endif |
| 228 | |
| 229 | static void call_rcu_wait(struct call_rcu_data *crdp) |
| 230 | { |
| 231 | /* Read call_rcu list before read futex */ |
| 232 | cmm_smp_mb(); |
| 233 | while (uatomic_read(&crdp->futex) == -1) { |
| 234 | if (!futex_async(&crdp->futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { |
| 235 | /* |
| 236 | * Prior queued wakeups queued by unrelated code |
| 237 | * using the same address can cause futex wait to |
| 238 | * return 0 even through the futex value is still |
| 239 | * -1 (spurious wakeups). Check the value again |
| 240 | * in user-space to validate whether it really |
| 241 | * differs from -1. |
| 242 | */ |
| 243 | continue; |
| 244 | } |
| 245 | switch (errno) { |
| 246 | case EAGAIN: |
| 247 | /* Value already changed. */ |
| 248 | return; |
| 249 | case EINTR: |
| 250 | /* Retry if interrupted by signal. */ |
| 251 | break; /* Get out of switch. Check again. */ |
| 252 | default: |
| 253 | /* Unexpected error. */ |
| 254 | urcu_die(errno); |
| 255 | } |
| 256 | } |
| 257 | } |
| 258 | |
| 259 | static void call_rcu_wake_up(struct call_rcu_data *crdp) |
| 260 | { |
| 261 | /* Write to call_rcu list before reading/writing futex */ |
| 262 | cmm_smp_mb(); |
| 263 | if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) { |
| 264 | uatomic_set(&crdp->futex, 0); |
| 265 | if (futex_async(&crdp->futex, FUTEX_WAKE, 1, |
| 266 | NULL, NULL, 0) < 0) |
| 267 | urcu_die(errno); |
| 268 | } |
| 269 | } |
| 270 | |
| 271 | static void call_rcu_completion_wait(struct call_rcu_completion *completion) |
| 272 | { |
| 273 | /* Read completion barrier count before read futex */ |
| 274 | cmm_smp_mb(); |
| 275 | while (uatomic_read(&completion->futex) == -1) { |
| 276 | if (!futex_async(&completion->futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { |
| 277 | /* |
| 278 | * Prior queued wakeups queued by unrelated code |
| 279 | * using the same address can cause futex wait to |
| 280 | * return 0 even through the futex value is still |
| 281 | * -1 (spurious wakeups). Check the value again |
| 282 | * in user-space to validate whether it really |
| 283 | * differs from -1. |
| 284 | */ |
| 285 | continue; |
| 286 | } |
| 287 | switch (errno) { |
| 288 | case EAGAIN: |
| 289 | /* Value already changed. */ |
| 290 | return; |
| 291 | case EINTR: |
| 292 | /* Retry if interrupted by signal. */ |
| 293 | break; /* Get out of switch. Check again. */ |
| 294 | default: |
| 295 | /* Unexpected error. */ |
| 296 | urcu_die(errno); |
| 297 | } |
| 298 | } |
| 299 | } |
| 300 | |
| 301 | static void call_rcu_completion_wake_up(struct call_rcu_completion *completion) |
| 302 | { |
| 303 | /* Write to completion barrier count before reading/writing futex */ |
| 304 | cmm_smp_mb(); |
| 305 | if (caa_unlikely(uatomic_read(&completion->futex) == -1)) { |
| 306 | uatomic_set(&completion->futex, 0); |
| 307 | if (futex_async(&completion->futex, FUTEX_WAKE, 1, |
| 308 | NULL, NULL, 0) < 0) |
| 309 | urcu_die(errno); |
| 310 | } |
| 311 | } |
| 312 | |
| 313 | /* This is the code run by each call_rcu thread. */ |
| 314 | |
| 315 | static void *call_rcu_thread(void *arg) |
| 316 | { |
| 317 | unsigned long cbcount; |
| 318 | struct call_rcu_data *crdp = (struct call_rcu_data *) arg; |
| 319 | int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT); |
| 320 | |
| 321 | if (set_thread_cpu_affinity(crdp)) |
| 322 | urcu_die(errno); |
| 323 | |
| 324 | /* |
| 325 | * If callbacks take a read-side lock, we need to be registered. |
| 326 | */ |
| 327 | rcu_register_thread(); |
| 328 | |
| 329 | URCU_TLS(thread_call_rcu_data) = crdp; |
| 330 | if (!rt) { |
| 331 | uatomic_dec(&crdp->futex); |
| 332 | /* Decrement futex before reading call_rcu list */ |
| 333 | cmm_smp_mb(); |
| 334 | } |
| 335 | for (;;) { |
| 336 | struct cds_wfcq_head cbs_tmp_head; |
| 337 | struct cds_wfcq_tail cbs_tmp_tail; |
| 338 | struct cds_wfcq_node *cbs, *cbs_tmp_n; |
| 339 | enum cds_wfcq_ret splice_ret; |
| 340 | |
| 341 | if (set_thread_cpu_affinity(crdp)) |
| 342 | urcu_die(errno); |
| 343 | |
| 344 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) { |
| 345 | /* |
| 346 | * Pause requested. Become quiescent: remove |
| 347 | * ourself from all global lists, and don't |
| 348 | * process any callback. The callback lists may |
| 349 | * still be non-empty though. |
| 350 | */ |
| 351 | rcu_unregister_thread(); |
| 352 | cmm_smp_mb__before_uatomic_or(); |
| 353 | uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED); |
| 354 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0) |
| 355 | (void) poll(NULL, 0, 1); |
| 356 | uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED); |
| 357 | cmm_smp_mb__after_uatomic_and(); |
| 358 | rcu_register_thread(); |
| 359 | } |
| 360 | |
| 361 | cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail); |
| 362 | splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head, |
| 363 | &cbs_tmp_tail, &crdp->cbs_head, &crdp->cbs_tail); |
| 364 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK); |
| 365 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY); |
| 366 | if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) { |
| 367 | synchronize_rcu(); |
| 368 | cbcount = 0; |
| 369 | __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head, |
| 370 | &cbs_tmp_tail, cbs, cbs_tmp_n) { |
| 371 | struct rcu_head *rhp; |
| 372 | |
| 373 | rhp = caa_container_of(cbs, |
| 374 | struct rcu_head, next); |
| 375 | rhp->func(rhp); |
| 376 | cbcount++; |
| 377 | } |
| 378 | uatomic_sub(&crdp->qlen, cbcount); |
| 379 | } |
| 380 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP) |
| 381 | break; |
| 382 | rcu_thread_offline(); |
| 383 | if (!rt) { |
| 384 | if (cds_wfcq_empty(&crdp->cbs_head, |
| 385 | &crdp->cbs_tail)) { |
| 386 | call_rcu_wait(crdp); |
| 387 | (void) poll(NULL, 0, 10); |
| 388 | uatomic_dec(&crdp->futex); |
| 389 | /* |
| 390 | * Decrement futex before reading |
| 391 | * call_rcu list. |
| 392 | */ |
| 393 | cmm_smp_mb(); |
| 394 | } else { |
| 395 | (void) poll(NULL, 0, 10); |
| 396 | } |
| 397 | } else { |
| 398 | (void) poll(NULL, 0, 10); |
| 399 | } |
| 400 | rcu_thread_online(); |
| 401 | } |
| 402 | if (!rt) { |
| 403 | /* |
| 404 | * Read call_rcu list before write futex. |
| 405 | */ |
| 406 | cmm_smp_mb(); |
| 407 | uatomic_set(&crdp->futex, 0); |
| 408 | } |
| 409 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED); |
| 410 | rcu_unregister_thread(); |
| 411 | return NULL; |
| 412 | } |
| 413 | |
| 414 | /* |
| 415 | * Create both a call_rcu thread and the corresponding call_rcu_data |
| 416 | * structure, linking the structure in as specified. Caller must hold |
| 417 | * call_rcu_mutex. |
| 418 | */ |
| 419 | |
| 420 | static void call_rcu_data_init(struct call_rcu_data **crdpp, |
| 421 | unsigned long flags, |
| 422 | int cpu_affinity) |
| 423 | { |
| 424 | struct call_rcu_data *crdp; |
| 425 | int ret; |
| 426 | sigset_t newmask, oldmask; |
| 427 | |
| 428 | crdp = malloc(sizeof(*crdp)); |
| 429 | if (crdp == NULL) |
| 430 | urcu_die(errno); |
| 431 | memset(crdp, '\0', sizeof(*crdp)); |
| 432 | cds_wfcq_init(&crdp->cbs_head, &crdp->cbs_tail); |
| 433 | crdp->qlen = 0; |
| 434 | crdp->futex = 0; |
| 435 | crdp->flags = flags; |
| 436 | cds_list_add(&crdp->list, &call_rcu_data_list); |
| 437 | crdp->cpu_affinity = cpu_affinity; |
| 438 | crdp->gp_count = 0; |
| 439 | rcu_set_pointer(crdpp, crdp); |
| 440 | |
| 441 | ret = sigfillset(&newmask); |
| 442 | urcu_posix_assert(!ret); |
| 443 | ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask); |
| 444 | urcu_posix_assert(!ret); |
| 445 | |
| 446 | ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp); |
| 447 | if (ret) |
| 448 | urcu_die(ret); |
| 449 | |
| 450 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); |
| 451 | urcu_posix_assert(!ret); |
| 452 | } |
| 453 | |
| 454 | /* |
| 455 | * Return a pointer to the call_rcu_data structure for the specified |
| 456 | * CPU, returning NULL if there is none. We cannot automatically |
| 457 | * created it because the platform we are running on might not define |
| 458 | * urcu_sched_getcpu(). |
| 459 | * |
| 460 | * The call to this function and use of the returned call_rcu_data |
| 461 | * should be protected by RCU read-side lock. |
| 462 | */ |
| 463 | |
| 464 | struct call_rcu_data *get_cpu_call_rcu_data(int cpu) |
| 465 | { |
| 466 | static int warned = 0; |
| 467 | struct call_rcu_data **pcpu_crdp; |
| 468 | |
| 469 | pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data); |
| 470 | if (pcpu_crdp == NULL) |
| 471 | return NULL; |
| 472 | if (!warned && cpus_array_len > 0 && (cpu < 0 || cpus_array_len <= cpu)) { |
| 473 | fprintf(stderr, "[error] liburcu: get CPU # out of range\n"); |
| 474 | warned = 1; |
| 475 | } |
| 476 | if (cpu < 0 || cpus_array_len <= cpu) |
| 477 | return NULL; |
| 478 | return rcu_dereference(pcpu_crdp[cpu]); |
| 479 | } |
| 480 | |
| 481 | /* |
| 482 | * Return the tid corresponding to the call_rcu thread whose |
| 483 | * call_rcu_data structure is specified. |
| 484 | */ |
| 485 | |
| 486 | pthread_t get_call_rcu_thread(struct call_rcu_data *crdp) |
| 487 | { |
| 488 | return crdp->tid; |
| 489 | } |
| 490 | |
| 491 | /* |
| 492 | * Create a call_rcu_data structure (with thread) and return a pointer. |
| 493 | */ |
| 494 | |
| 495 | static struct call_rcu_data *__create_call_rcu_data(unsigned long flags, |
| 496 | int cpu_affinity) |
| 497 | { |
| 498 | struct call_rcu_data *crdp; |
| 499 | |
| 500 | call_rcu_data_init(&crdp, flags, cpu_affinity); |
| 501 | return crdp; |
| 502 | } |
| 503 | |
| 504 | struct call_rcu_data *create_call_rcu_data(unsigned long flags, |
| 505 | int cpu_affinity) |
| 506 | { |
| 507 | struct call_rcu_data *crdp; |
| 508 | |
| 509 | call_rcu_lock(&call_rcu_mutex); |
| 510 | crdp = __create_call_rcu_data(flags, cpu_affinity); |
| 511 | call_rcu_unlock(&call_rcu_mutex); |
| 512 | return crdp; |
| 513 | } |
| 514 | |
| 515 | /* |
| 516 | * Set the specified CPU to use the specified call_rcu_data structure. |
| 517 | * |
| 518 | * Use NULL to remove a CPU's call_rcu_data structure, but it is |
| 519 | * the caller's responsibility to dispose of the removed structure. |
| 520 | * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure |
| 521 | * (prior to NULLing it out, of course). |
| 522 | * |
| 523 | * The caller must wait for a grace-period to pass between return from |
| 524 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the |
| 525 | * previous call rcu data as argument. |
| 526 | */ |
| 527 | |
| 528 | int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp) |
| 529 | { |
| 530 | static int warned = 0; |
| 531 | |
| 532 | call_rcu_lock(&call_rcu_mutex); |
| 533 | alloc_cpu_call_rcu_data(); |
| 534 | if (cpu < 0 || cpus_array_len <= cpu) { |
| 535 | if (!warned) { |
| 536 | fprintf(stderr, "[error] liburcu: set CPU # out of range\n"); |
| 537 | warned = 1; |
| 538 | } |
| 539 | call_rcu_unlock(&call_rcu_mutex); |
| 540 | errno = EINVAL; |
| 541 | return -EINVAL; |
| 542 | } |
| 543 | |
| 544 | if (per_cpu_call_rcu_data == NULL) { |
| 545 | call_rcu_unlock(&call_rcu_mutex); |
| 546 | errno = ENOMEM; |
| 547 | return -ENOMEM; |
| 548 | } |
| 549 | |
| 550 | if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) { |
| 551 | call_rcu_unlock(&call_rcu_mutex); |
| 552 | errno = EEXIST; |
| 553 | return -EEXIST; |
| 554 | } |
| 555 | |
| 556 | rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp); |
| 557 | call_rcu_unlock(&call_rcu_mutex); |
| 558 | return 0; |
| 559 | } |
| 560 | |
| 561 | /* |
| 562 | * Return a pointer to the default call_rcu_data structure, creating |
| 563 | * one if need be. |
| 564 | * |
| 565 | * The call to this function with intent to use the returned |
| 566 | * call_rcu_data should be protected by RCU read-side lock. |
| 567 | */ |
| 568 | |
| 569 | struct call_rcu_data *get_default_call_rcu_data(void) |
| 570 | { |
| 571 | struct call_rcu_data *crdp; |
| 572 | |
| 573 | crdp = rcu_dereference(default_call_rcu_data); |
| 574 | if (crdp != NULL) |
| 575 | return crdp; |
| 576 | |
| 577 | call_rcu_lock(&call_rcu_mutex); |
| 578 | if (default_call_rcu_data == NULL) |
| 579 | call_rcu_data_init(&default_call_rcu_data, 0, -1); |
| 580 | crdp = default_call_rcu_data; |
| 581 | call_rcu_unlock(&call_rcu_mutex); |
| 582 | |
| 583 | return crdp; |
| 584 | } |
| 585 | |
| 586 | /* |
| 587 | * Return the call_rcu_data structure that applies to the currently |
| 588 | * running thread. Any call_rcu_data structure assigned specifically |
| 589 | * to this thread has first priority, followed by any call_rcu_data |
| 590 | * structure assigned to the CPU on which the thread is running, |
| 591 | * followed by the default call_rcu_data structure. If there is not |
| 592 | * yet a default call_rcu_data structure, one will be created. |
| 593 | * |
| 594 | * Calls to this function and use of the returned call_rcu_data should |
| 595 | * be protected by RCU read-side lock. |
| 596 | */ |
| 597 | struct call_rcu_data *get_call_rcu_data(void) |
| 598 | { |
| 599 | struct call_rcu_data *crd; |
| 600 | |
| 601 | if (URCU_TLS(thread_call_rcu_data) != NULL) |
| 602 | return URCU_TLS(thread_call_rcu_data); |
| 603 | |
| 604 | if (cpus_array_len > 0) { |
| 605 | crd = get_cpu_call_rcu_data(urcu_sched_getcpu()); |
| 606 | if (crd) |
| 607 | return crd; |
| 608 | } |
| 609 | |
| 610 | return get_default_call_rcu_data(); |
| 611 | } |
| 612 | |
| 613 | /* |
| 614 | * Return a pointer to this task's call_rcu_data if there is one. |
| 615 | */ |
| 616 | |
| 617 | struct call_rcu_data *get_thread_call_rcu_data(void) |
| 618 | { |
| 619 | return URCU_TLS(thread_call_rcu_data); |
| 620 | } |
| 621 | |
| 622 | /* |
| 623 | * Set this task's call_rcu_data structure as specified, regardless |
| 624 | * of whether or not this task already had one. (This allows switching |
| 625 | * to and from real-time call_rcu threads, for example.) |
| 626 | * |
| 627 | * Use NULL to remove a thread's call_rcu_data structure, but it is |
| 628 | * the caller's responsibility to dispose of the removed structure. |
| 629 | * Use get_thread_call_rcu_data() to obtain a pointer to the old structure |
| 630 | * (prior to NULLing it out, of course). |
| 631 | */ |
| 632 | |
| 633 | void set_thread_call_rcu_data(struct call_rcu_data *crdp) |
| 634 | { |
| 635 | URCU_TLS(thread_call_rcu_data) = crdp; |
| 636 | } |
| 637 | |
| 638 | /* |
| 639 | * Create a separate call_rcu thread for each CPU. This does not |
| 640 | * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data() |
| 641 | * function if you want that behavior. Should be paired with |
| 642 | * free_all_cpu_call_rcu_data() to teardown these call_rcu worker |
| 643 | * threads. |
| 644 | */ |
| 645 | |
| 646 | int create_all_cpu_call_rcu_data(unsigned long flags) |
| 647 | { |
| 648 | int i; |
| 649 | struct call_rcu_data *crdp; |
| 650 | int ret; |
| 651 | |
| 652 | call_rcu_lock(&call_rcu_mutex); |
| 653 | alloc_cpu_call_rcu_data(); |
| 654 | call_rcu_unlock(&call_rcu_mutex); |
| 655 | if (cpus_array_len <= 0) { |
| 656 | errno = EINVAL; |
| 657 | return -EINVAL; |
| 658 | } |
| 659 | if (per_cpu_call_rcu_data == NULL) { |
| 660 | errno = ENOMEM; |
| 661 | return -ENOMEM; |
| 662 | } |
| 663 | for (i = 0; i < cpus_array_len; i++) { |
| 664 | call_rcu_lock(&call_rcu_mutex); |
| 665 | if (get_cpu_call_rcu_data(i)) { |
| 666 | call_rcu_unlock(&call_rcu_mutex); |
| 667 | continue; |
| 668 | } |
| 669 | crdp = __create_call_rcu_data(flags, i); |
| 670 | if (crdp == NULL) { |
| 671 | call_rcu_unlock(&call_rcu_mutex); |
| 672 | errno = ENOMEM; |
| 673 | return -ENOMEM; |
| 674 | } |
| 675 | call_rcu_unlock(&call_rcu_mutex); |
| 676 | if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) { |
| 677 | call_rcu_data_free(crdp); |
| 678 | |
| 679 | /* it has been created by other thread */ |
| 680 | if (ret == -EEXIST) |
| 681 | continue; |
| 682 | |
| 683 | return ret; |
| 684 | } |
| 685 | } |
| 686 | return 0; |
| 687 | } |
| 688 | |
| 689 | /* |
| 690 | * Wake up the call_rcu thread corresponding to the specified |
| 691 | * call_rcu_data structure. |
| 692 | */ |
| 693 | static void wake_call_rcu_thread(struct call_rcu_data *crdp) |
| 694 | { |
| 695 | if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) |
| 696 | call_rcu_wake_up(crdp); |
| 697 | } |
| 698 | |
| 699 | static void _call_rcu(struct rcu_head *head, |
| 700 | void (*func)(struct rcu_head *head), |
| 701 | struct call_rcu_data *crdp) |
| 702 | { |
| 703 | cds_wfcq_node_init(&head->next); |
| 704 | head->func = func; |
| 705 | cds_wfcq_enqueue(&crdp->cbs_head, &crdp->cbs_tail, &head->next); |
| 706 | uatomic_inc(&crdp->qlen); |
| 707 | wake_call_rcu_thread(crdp); |
| 708 | } |
| 709 | |
| 710 | /* |
| 711 | * Schedule a function to be invoked after a following grace period. |
| 712 | * This is the only function that must be called -- the others are |
| 713 | * only present to allow applications to tune their use of RCU for |
| 714 | * maximum performance. |
| 715 | * |
| 716 | * Note that unless a call_rcu thread has not already been created, |
| 717 | * the first invocation of call_rcu() will create one. So, if you |
| 718 | * need the first invocation of call_rcu() to be fast, make sure |
| 719 | * to create a call_rcu thread first. One way to accomplish this is |
| 720 | * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data(). |
| 721 | * |
| 722 | * call_rcu must be called by registered RCU read-side threads. |
| 723 | */ |
| 724 | void call_rcu(struct rcu_head *head, |
| 725 | void (*func)(struct rcu_head *head)) |
| 726 | { |
| 727 | struct call_rcu_data *crdp; |
| 728 | |
| 729 | /* Holding rcu read-side lock across use of per-cpu crdp */ |
| 730 | _rcu_read_lock(); |
| 731 | crdp = get_call_rcu_data(); |
| 732 | _call_rcu(head, func, crdp); |
| 733 | _rcu_read_unlock(); |
| 734 | } |
| 735 | |
| 736 | /* |
| 737 | * Free up the specified call_rcu_data structure, terminating the |
| 738 | * associated call_rcu thread. The caller must have previously |
| 739 | * removed the call_rcu_data structure from per-thread or per-CPU |
| 740 | * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU |
| 741 | * call_rcu_data structures or set_thread_call_rcu_data(NULL) for |
| 742 | * per-thread call_rcu_data structures. |
| 743 | * |
| 744 | * We silently refuse to free up the default call_rcu_data structure |
| 745 | * because that is where we put any leftover callbacks. Note that |
| 746 | * the possibility of self-spawning callbacks makes it impossible |
| 747 | * to execute all the callbacks in finite time without putting any |
| 748 | * newly spawned callbacks somewhere else. The "somewhere else" of |
| 749 | * last resort is the default call_rcu_data structure. |
| 750 | * |
| 751 | * We also silently refuse to free NULL pointers. This simplifies |
| 752 | * the calling code. |
| 753 | * |
| 754 | * The caller must wait for a grace-period to pass between return from |
| 755 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the |
| 756 | * previous call rcu data as argument. |
| 757 | * |
| 758 | * Note: introducing __cds_wfcq_splice_blocking() in this function fixed |
| 759 | * a list corruption bug in the 0.7.x series. The equivalent fix |
| 760 | * appeared in 0.6.8 for the stable-0.6 branch. |
| 761 | */ |
| 762 | static |
| 763 | void _call_rcu_data_free(struct call_rcu_data *crdp, unsigned int flags) |
| 764 | { |
| 765 | if (crdp == NULL || crdp == default_call_rcu_data) { |
| 766 | return; |
| 767 | } |
| 768 | if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) { |
| 769 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP); |
| 770 | wake_call_rcu_thread(crdp); |
| 771 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) |
| 772 | (void) poll(NULL, 0, 1); |
| 773 | } |
| 774 | call_rcu_lock(&call_rcu_mutex); |
| 775 | if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) { |
| 776 | call_rcu_unlock(&call_rcu_mutex); |
| 777 | /* Create default call rcu data if need be. */ |
| 778 | /* CBs queued here will be handed to the default list. */ |
| 779 | (void) get_default_call_rcu_data(); |
| 780 | call_rcu_lock(&call_rcu_mutex); |
| 781 | __cds_wfcq_splice_blocking(&default_call_rcu_data->cbs_head, |
| 782 | &default_call_rcu_data->cbs_tail, |
| 783 | &crdp->cbs_head, &crdp->cbs_tail); |
| 784 | uatomic_add(&default_call_rcu_data->qlen, |
| 785 | uatomic_read(&crdp->qlen)); |
| 786 | wake_call_rcu_thread(default_call_rcu_data); |
| 787 | } |
| 788 | |
| 789 | cds_list_del(&crdp->list); |
| 790 | call_rcu_unlock(&call_rcu_mutex); |
| 791 | |
| 792 | if (flags & CRDF_FLAG_JOIN_THREAD) { |
| 793 | int ret; |
| 794 | |
| 795 | ret = pthread_join(get_call_rcu_thread(crdp), NULL); |
| 796 | if (ret) |
| 797 | urcu_die(ret); |
| 798 | } |
| 799 | free(crdp); |
| 800 | } |
| 801 | |
| 802 | void call_rcu_data_free(struct call_rcu_data *crdp) |
| 803 | { |
| 804 | _call_rcu_data_free(crdp, CRDF_FLAG_JOIN_THREAD); |
| 805 | } |
| 806 | |
| 807 | /* |
| 808 | * Clean up all the per-CPU call_rcu threads. |
| 809 | */ |
| 810 | void free_all_cpu_call_rcu_data(void) |
| 811 | { |
| 812 | int cpu; |
| 813 | struct call_rcu_data **crdp; |
| 814 | static int warned = 0; |
| 815 | |
| 816 | if (cpus_array_len <= 0) |
| 817 | return; |
| 818 | |
| 819 | crdp = malloc(sizeof(*crdp) * cpus_array_len); |
| 820 | if (!crdp) { |
| 821 | if (!warned) { |
| 822 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); |
| 823 | } |
| 824 | warned = 1; |
| 825 | return; |
| 826 | } |
| 827 | |
| 828 | for (cpu = 0; cpu < cpus_array_len; cpu++) { |
| 829 | crdp[cpu] = get_cpu_call_rcu_data(cpu); |
| 830 | if (crdp[cpu] == NULL) |
| 831 | continue; |
| 832 | set_cpu_call_rcu_data(cpu, NULL); |
| 833 | } |
| 834 | /* |
| 835 | * Wait for call_rcu sites acting as RCU readers of the |
| 836 | * call_rcu_data to become quiescent. |
| 837 | */ |
| 838 | synchronize_rcu(); |
| 839 | for (cpu = 0; cpu < cpus_array_len; cpu++) { |
| 840 | if (crdp[cpu] == NULL) |
| 841 | continue; |
| 842 | call_rcu_data_free(crdp[cpu]); |
| 843 | } |
| 844 | free(crdp); |
| 845 | } |
| 846 | |
| 847 | static |
| 848 | void free_completion(struct urcu_ref *ref) |
| 849 | { |
| 850 | struct call_rcu_completion *completion; |
| 851 | |
| 852 | completion = caa_container_of(ref, struct call_rcu_completion, ref); |
| 853 | free(completion); |
| 854 | } |
| 855 | |
| 856 | static |
| 857 | void _rcu_barrier_complete(struct rcu_head *head) |
| 858 | { |
| 859 | struct call_rcu_completion_work *work; |
| 860 | struct call_rcu_completion *completion; |
| 861 | |
| 862 | work = caa_container_of(head, struct call_rcu_completion_work, head); |
| 863 | completion = work->completion; |
| 864 | if (!uatomic_sub_return(&completion->barrier_count, 1)) |
| 865 | call_rcu_completion_wake_up(completion); |
| 866 | urcu_ref_put(&completion->ref, free_completion); |
| 867 | free(work); |
| 868 | } |
| 869 | |
| 870 | /* |
| 871 | * Wait for all in-flight call_rcu callbacks to complete execution. |
| 872 | */ |
| 873 | void rcu_barrier(void) |
| 874 | { |
| 875 | struct call_rcu_data *crdp; |
| 876 | struct call_rcu_completion *completion; |
| 877 | int count = 0; |
| 878 | int was_online; |
| 879 | |
| 880 | /* Put in offline state in QSBR. */ |
| 881 | was_online = _rcu_read_ongoing(); |
| 882 | if (was_online) |
| 883 | rcu_thread_offline(); |
| 884 | /* |
| 885 | * Calling a rcu_barrier() within a RCU read-side critical |
| 886 | * section is an error. |
| 887 | */ |
| 888 | if (_rcu_read_ongoing()) { |
| 889 | static int warned = 0; |
| 890 | |
| 891 | if (!warned) { |
| 892 | fprintf(stderr, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n"); |
| 893 | } |
| 894 | warned = 1; |
| 895 | goto online; |
| 896 | } |
| 897 | |
| 898 | completion = calloc(sizeof(*completion), 1); |
| 899 | if (!completion) |
| 900 | urcu_die(errno); |
| 901 | |
| 902 | call_rcu_lock(&call_rcu_mutex); |
| 903 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) |
| 904 | count++; |
| 905 | |
| 906 | /* Referenced by rcu_barrier() and each call_rcu thread. */ |
| 907 | urcu_ref_set(&completion->ref, count + 1); |
| 908 | completion->barrier_count = count; |
| 909 | |
| 910 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { |
| 911 | struct call_rcu_completion_work *work; |
| 912 | |
| 913 | work = calloc(sizeof(*work), 1); |
| 914 | if (!work) |
| 915 | urcu_die(errno); |
| 916 | work->completion = completion; |
| 917 | _call_rcu(&work->head, _rcu_barrier_complete, crdp); |
| 918 | } |
| 919 | call_rcu_unlock(&call_rcu_mutex); |
| 920 | |
| 921 | /* Wait for them */ |
| 922 | for (;;) { |
| 923 | uatomic_dec(&completion->futex); |
| 924 | /* Decrement futex before reading barrier_count */ |
| 925 | cmm_smp_mb(); |
| 926 | if (!uatomic_read(&completion->barrier_count)) |
| 927 | break; |
| 928 | call_rcu_completion_wait(completion); |
| 929 | } |
| 930 | |
| 931 | urcu_ref_put(&completion->ref, free_completion); |
| 932 | |
| 933 | online: |
| 934 | if (was_online) |
| 935 | rcu_thread_online(); |
| 936 | } |
| 937 | |
| 938 | /* |
| 939 | * Acquire the call_rcu_mutex in order to ensure that the child sees |
| 940 | * all of the call_rcu() data structures in a consistent state. Ensure |
| 941 | * that all call_rcu threads are in a quiescent state across fork. |
| 942 | * Suitable for pthread_atfork() and friends. |
| 943 | */ |
| 944 | void call_rcu_before_fork(void) |
| 945 | { |
| 946 | struct call_rcu_data *crdp; |
| 947 | struct urcu_atfork *atfork; |
| 948 | |
| 949 | call_rcu_lock(&call_rcu_mutex); |
| 950 | |
| 951 | atfork = registered_rculfhash_atfork; |
| 952 | if (atfork) |
| 953 | atfork->before_fork(atfork->priv); |
| 954 | |
| 955 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { |
| 956 | uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSE); |
| 957 | cmm_smp_mb__after_uatomic_or(); |
| 958 | wake_call_rcu_thread(crdp); |
| 959 | } |
| 960 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { |
| 961 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0) |
| 962 | (void) poll(NULL, 0, 1); |
| 963 | } |
| 964 | } |
| 965 | |
| 966 | /* |
| 967 | * Clean up call_rcu data structures in the parent of a successful fork() |
| 968 | * that is not followed by exec() in the child. Suitable for |
| 969 | * pthread_atfork() and friends. |
| 970 | */ |
| 971 | void call_rcu_after_fork_parent(void) |
| 972 | { |
| 973 | struct call_rcu_data *crdp; |
| 974 | struct urcu_atfork *atfork; |
| 975 | |
| 976 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) |
| 977 | uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE); |
| 978 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { |
| 979 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) != 0) |
| 980 | (void) poll(NULL, 0, 1); |
| 981 | } |
| 982 | atfork = registered_rculfhash_atfork; |
| 983 | if (atfork) |
| 984 | atfork->after_fork_parent(atfork->priv); |
| 985 | call_rcu_unlock(&call_rcu_mutex); |
| 986 | } |
| 987 | |
| 988 | /* |
| 989 | * Clean up call_rcu data structures in the child of a successful fork() |
| 990 | * that is not followed by exec(). Suitable for pthread_atfork() and |
| 991 | * friends. |
| 992 | */ |
| 993 | void call_rcu_after_fork_child(void) |
| 994 | { |
| 995 | struct call_rcu_data *crdp, *next; |
| 996 | struct urcu_atfork *atfork; |
| 997 | |
| 998 | /* Release the mutex. */ |
| 999 | call_rcu_unlock(&call_rcu_mutex); |
| 1000 | |
| 1001 | atfork = registered_rculfhash_atfork; |
| 1002 | if (atfork) |
| 1003 | atfork->after_fork_child(atfork->priv); |
| 1004 | |
| 1005 | /* Do nothing when call_rcu() has not been used */ |
| 1006 | if (cds_list_empty(&call_rcu_data_list)) |
| 1007 | return; |
| 1008 | |
| 1009 | /* |
| 1010 | * Allocate a new default call_rcu_data structure in order |
| 1011 | * to get a working call_rcu thread to go with it. |
| 1012 | */ |
| 1013 | default_call_rcu_data = NULL; |
| 1014 | (void)get_default_call_rcu_data(); |
| 1015 | |
| 1016 | /* Cleanup call_rcu_data pointers before use */ |
| 1017 | cpus_array_len_reset(); |
| 1018 | free(per_cpu_call_rcu_data); |
| 1019 | rcu_set_pointer(&per_cpu_call_rcu_data, NULL); |
| 1020 | URCU_TLS(thread_call_rcu_data) = NULL; |
| 1021 | |
| 1022 | /* |
| 1023 | * Dispose of all of the rest of the call_rcu_data structures. |
| 1024 | * Leftover call_rcu callbacks will be merged into the new |
| 1025 | * default call_rcu thread queue. |
| 1026 | */ |
| 1027 | cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) { |
| 1028 | if (crdp == default_call_rcu_data) |
| 1029 | continue; |
| 1030 | uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED); |
| 1031 | /* |
| 1032 | * Do not join the thread because it does not exist in |
| 1033 | * the child. |
| 1034 | */ |
| 1035 | _call_rcu_data_free(crdp, 0); |
| 1036 | } |
| 1037 | } |
| 1038 | |
| 1039 | void urcu_register_rculfhash_atfork(struct urcu_atfork *atfork) |
| 1040 | { |
| 1041 | if (CMM_LOAD_SHARED(registered_rculfhash_atfork)) |
| 1042 | return; |
| 1043 | call_rcu_lock(&call_rcu_mutex); |
| 1044 | if (!registered_rculfhash_atfork) |
| 1045 | registered_rculfhash_atfork = atfork; |
| 1046 | call_rcu_unlock(&call_rcu_mutex); |
| 1047 | } |
| 1048 | |
| 1049 | /* |
| 1050 | * This unregistration function is deprecated, meant only for internal |
| 1051 | * use by rculfhash. |
| 1052 | */ |
| 1053 | __attribute__((__noreturn__)) |
| 1054 | void urcu_unregister_rculfhash_atfork(struct urcu_atfork *atfork __attribute__((unused))) |
| 1055 | { |
| 1056 | urcu_die(EPERM); |
| 1057 | } |
| 1058 | |
| 1059 | /* |
| 1060 | * Teardown the default call_rcu worker thread if there are no queued |
| 1061 | * callbacks on process exit. This prevents leaking memory. |
| 1062 | * |
| 1063 | * Here is how an application can ensure graceful teardown of this |
| 1064 | * worker thread: |
| 1065 | * |
| 1066 | * - An application queuing call_rcu callbacks should invoke |
| 1067 | * rcu_barrier() before it exits. |
| 1068 | * - When chaining call_rcu callbacks, the number of calls to |
| 1069 | * rcu_barrier() on application exit must match at least the maximum |
| 1070 | * number of chained callbacks. |
| 1071 | * - If an application chains callbacks endlessly, it would have to be |
| 1072 | * modified to stop chaining callbacks when it detects an application |
| 1073 | * exit (e.g. with a flag), and wait for quiescence with rcu_barrier() |
| 1074 | * after setting that flag. |
| 1075 | * - The statements above apply to a library which queues call_rcu |
| 1076 | * callbacks, only it needs to invoke rcu_barrier in its library |
| 1077 | * destructor. |
| 1078 | * |
| 1079 | * Note that this function does not presume it is being called when the |
| 1080 | * application is single-threaded even though this is invoked from a |
| 1081 | * destructor: this function synchronizes against concurrent calls to |
| 1082 | * get_default_call_rcu_data(). |
| 1083 | */ |
| 1084 | static void urcu_call_rcu_exit(void) |
| 1085 | { |
| 1086 | struct call_rcu_data *crdp; |
| 1087 | bool teardown = true; |
| 1088 | |
| 1089 | if (default_call_rcu_data == NULL) |
| 1090 | return; |
| 1091 | call_rcu_lock(&call_rcu_mutex); |
| 1092 | /* |
| 1093 | * If the application leaves callbacks in the default call_rcu |
| 1094 | * worker queue, keep the default worker in place. |
| 1095 | */ |
| 1096 | crdp = default_call_rcu_data; |
| 1097 | if (!crdp) { |
| 1098 | teardown = false; |
| 1099 | goto unlock; |
| 1100 | } |
| 1101 | if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) { |
| 1102 | teardown = false; |
| 1103 | goto unlock; |
| 1104 | } |
| 1105 | rcu_set_pointer(&default_call_rcu_data, NULL); |
| 1106 | unlock: |
| 1107 | call_rcu_unlock(&call_rcu_mutex); |
| 1108 | if (teardown) { |
| 1109 | synchronize_rcu(); |
| 1110 | call_rcu_data_free(crdp); |
| 1111 | } |
| 1112 | } |