| 1 | /* |
| 2 | * lttng-ust-comm.c |
| 3 | * |
| 4 | * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca> |
| 5 | * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 6 | * |
| 7 | * This library is free software; you can redistribute it and/or |
| 8 | * modify it under the terms of the GNU Lesser General Public |
| 9 | * License as published by the Free Software Foundation; only |
| 10 | * version 2.1 of the License. |
| 11 | * |
| 12 | * This library is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 15 | * Lesser General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU Lesser General Public |
| 18 | * License along with this library; if not, write to the Free Software |
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 20 | */ |
| 21 | |
| 22 | #define _LGPL_SOURCE |
| 23 | #include <sys/types.h> |
| 24 | #include <sys/socket.h> |
| 25 | #include <sys/mman.h> |
| 26 | #include <sys/stat.h> |
| 27 | #include <sys/types.h> |
| 28 | #include <sys/wait.h> |
| 29 | #include <fcntl.h> |
| 30 | #include <unistd.h> |
| 31 | #include <errno.h> |
| 32 | #include <pthread.h> |
| 33 | #include <semaphore.h> |
| 34 | #include <time.h> |
| 35 | #include <assert.h> |
| 36 | #include <signal.h> |
| 37 | #include <urcu/uatomic.h> |
| 38 | #include <urcu/futex.h> |
| 39 | #include <urcu/compiler.h> |
| 40 | |
| 41 | #include <lttng/ust-events.h> |
| 42 | #include <lttng/ust-abi.h> |
| 43 | #include <lttng/ust.h> |
| 44 | #include <lttng/ust-error.h> |
| 45 | #include <ust-comm.h> |
| 46 | #include <usterr-signal-safe.h> |
| 47 | #include <helper.h> |
| 48 | #include "tracepoint-internal.h" |
| 49 | #include "lttng-tracer-core.h" |
| 50 | #include "compat.h" |
| 51 | #include "../libringbuffer/tlsfixup.h" |
| 52 | |
| 53 | /* |
| 54 | * Has lttng ust comm constructor been called ? |
| 55 | */ |
| 56 | static int initialized; |
| 57 | |
| 58 | /* |
| 59 | * The ust_lock/ust_unlock lock is used as a communication thread mutex. |
| 60 | * Held when handling a command, also held by fork() to deal with |
| 61 | * removal of threads, and by exit path. |
| 62 | */ |
| 63 | |
| 64 | /* Should the ust comm thread quit ? */ |
| 65 | static int lttng_ust_comm_should_quit; |
| 66 | |
| 67 | /* |
| 68 | * Wait for either of these before continuing to the main |
| 69 | * program: |
| 70 | * - the register_done message from sessiond daemon |
| 71 | * (will let the sessiond daemon enable sessions before main |
| 72 | * starts.) |
| 73 | * - sessiond daemon is not reachable. |
| 74 | * - timeout (ensuring applications are resilient to session |
| 75 | * daemon problems). |
| 76 | */ |
| 77 | static sem_t constructor_wait; |
| 78 | /* |
| 79 | * Doing this for both the global and local sessiond. |
| 80 | */ |
| 81 | static int sem_count = { 2 }; |
| 82 | |
| 83 | /* |
| 84 | * Counting nesting within lttng-ust. Used to ensure that calling fork() |
| 85 | * from liblttng-ust does not execute the pre/post fork handlers. |
| 86 | */ |
| 87 | static int __thread lttng_ust_nest_count; |
| 88 | |
| 89 | /* |
| 90 | * Info about socket and associated listener thread. |
| 91 | */ |
| 92 | struct sock_info { |
| 93 | const char *name; |
| 94 | pthread_t ust_listener; /* listener thread */ |
| 95 | int root_handle; |
| 96 | int constructor_sem_posted; |
| 97 | int allowed; |
| 98 | int global; |
| 99 | int thread_active; |
| 100 | |
| 101 | char sock_path[PATH_MAX]; |
| 102 | int socket; |
| 103 | |
| 104 | char wait_shm_path[PATH_MAX]; |
| 105 | char *wait_shm_mmap; |
| 106 | }; |
| 107 | |
| 108 | /* Socket from app (connect) to session daemon (listen) for communication */ |
| 109 | struct sock_info global_apps = { |
| 110 | .name = "global", |
| 111 | .global = 1, |
| 112 | |
| 113 | .root_handle = -1, |
| 114 | .allowed = 1, |
| 115 | .thread_active = 0, |
| 116 | |
| 117 | .sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK, |
| 118 | .socket = -1, |
| 119 | |
| 120 | .wait_shm_path = DEFAULT_GLOBAL_APPS_WAIT_SHM_PATH, |
| 121 | }; |
| 122 | |
| 123 | /* TODO: allow global_apps_sock_path override */ |
| 124 | |
| 125 | struct sock_info local_apps = { |
| 126 | .name = "local", |
| 127 | .global = 0, |
| 128 | .root_handle = -1, |
| 129 | .allowed = 0, /* Check setuid bit first */ |
| 130 | .thread_active = 0, |
| 131 | |
| 132 | .socket = -1, |
| 133 | }; |
| 134 | |
| 135 | static int wait_poll_fallback; |
| 136 | |
| 137 | extern void lttng_ring_buffer_client_overwrite_init(void); |
| 138 | extern void lttng_ring_buffer_client_discard_init(void); |
| 139 | extern void lttng_ring_buffer_metadata_client_init(void); |
| 140 | extern void lttng_ring_buffer_client_overwrite_exit(void); |
| 141 | extern void lttng_ring_buffer_client_discard_exit(void); |
| 142 | extern void lttng_ring_buffer_metadata_client_exit(void); |
| 143 | |
| 144 | /* |
| 145 | * Force a read (imply TLS fixup for dlopen) of TLS variables. |
| 146 | */ |
| 147 | static |
| 148 | void lttng_fixup_nest_count_tls(void) |
| 149 | { |
| 150 | asm volatile ("" : : "m" (lttng_ust_nest_count)); |
| 151 | } |
| 152 | |
| 153 | static |
| 154 | int setup_local_apps(void) |
| 155 | { |
| 156 | const char *home_dir; |
| 157 | uid_t uid; |
| 158 | |
| 159 | uid = getuid(); |
| 160 | /* |
| 161 | * Disallow per-user tracing for setuid binaries. |
| 162 | */ |
| 163 | if (uid != geteuid()) { |
| 164 | assert(local_apps.allowed == 0); |
| 165 | return 0; |
| 166 | } |
| 167 | home_dir = (const char *) getenv("HOME"); |
| 168 | if (!home_dir) { |
| 169 | WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing."); |
| 170 | assert(local_apps.allowed == 0); |
| 171 | return -ENOENT; |
| 172 | } |
| 173 | local_apps.allowed = 1; |
| 174 | snprintf(local_apps.sock_path, PATH_MAX, |
| 175 | DEFAULT_HOME_APPS_UNIX_SOCK, home_dir); |
| 176 | snprintf(local_apps.wait_shm_path, PATH_MAX, |
| 177 | DEFAULT_HOME_APPS_WAIT_SHM_PATH, uid); |
| 178 | return 0; |
| 179 | } |
| 180 | |
| 181 | static |
| 182 | int register_app_to_sessiond(int socket) |
| 183 | { |
| 184 | ssize_t ret; |
| 185 | struct { |
| 186 | uint32_t major; |
| 187 | uint32_t minor; |
| 188 | pid_t pid; |
| 189 | pid_t ppid; |
| 190 | uid_t uid; |
| 191 | gid_t gid; |
| 192 | uint32_t bits_per_long; |
| 193 | char name[16]; /* process name */ |
| 194 | } reg_msg; |
| 195 | |
| 196 | reg_msg.major = LTTNG_UST_COMM_VERSION_MAJOR; |
| 197 | reg_msg.minor = LTTNG_UST_COMM_VERSION_MINOR; |
| 198 | reg_msg.pid = getpid(); |
| 199 | reg_msg.ppid = getppid(); |
| 200 | reg_msg.uid = getuid(); |
| 201 | reg_msg.gid = getgid(); |
| 202 | reg_msg.bits_per_long = CAA_BITS_PER_LONG; |
| 203 | lttng_ust_getprocname(reg_msg.name); |
| 204 | |
| 205 | ret = ustcomm_send_unix_sock(socket, ®_msg, sizeof(reg_msg)); |
| 206 | if (ret >= 0 && ret != sizeof(reg_msg)) |
| 207 | return -EIO; |
| 208 | return ret; |
| 209 | } |
| 210 | |
| 211 | static |
| 212 | int send_reply(int sock, struct ustcomm_ust_reply *lur) |
| 213 | { |
| 214 | ssize_t len; |
| 215 | |
| 216 | len = ustcomm_send_unix_sock(sock, lur, sizeof(*lur)); |
| 217 | switch (len) { |
| 218 | case sizeof(*lur): |
| 219 | DBG("message successfully sent"); |
| 220 | return 0; |
| 221 | default: |
| 222 | if (len == -ECONNRESET) { |
| 223 | DBG("remote end closed connection"); |
| 224 | return 0; |
| 225 | } |
| 226 | if (len < 0) |
| 227 | return len; |
| 228 | DBG("incorrect message size: %zd", len); |
| 229 | return -EINVAL; |
| 230 | } |
| 231 | } |
| 232 | |
| 233 | static |
| 234 | int handle_register_done(struct sock_info *sock_info) |
| 235 | { |
| 236 | int ret; |
| 237 | |
| 238 | if (sock_info->constructor_sem_posted) |
| 239 | return 0; |
| 240 | sock_info->constructor_sem_posted = 1; |
| 241 | if (uatomic_read(&sem_count) <= 0) { |
| 242 | return 0; |
| 243 | } |
| 244 | ret = uatomic_add_return(&sem_count, -1); |
| 245 | if (ret == 0) { |
| 246 | ret = sem_post(&constructor_wait); |
| 247 | assert(!ret); |
| 248 | } |
| 249 | return 0; |
| 250 | } |
| 251 | |
| 252 | static |
| 253 | int handle_message(struct sock_info *sock_info, |
| 254 | int sock, struct ustcomm_ust_msg *lum) |
| 255 | { |
| 256 | int ret = 0; |
| 257 | const struct lttng_ust_objd_ops *ops; |
| 258 | struct ustcomm_ust_reply lur; |
| 259 | int shm_fd, wait_fd; |
| 260 | union ust_args args; |
| 261 | ssize_t len; |
| 262 | |
| 263 | ust_lock(); |
| 264 | |
| 265 | memset(&lur, 0, sizeof(lur)); |
| 266 | |
| 267 | if (lttng_ust_comm_should_quit) { |
| 268 | ret = -EPERM; |
| 269 | goto end; |
| 270 | } |
| 271 | |
| 272 | ops = objd_ops(lum->handle); |
| 273 | if (!ops) { |
| 274 | ret = -ENOENT; |
| 275 | goto end; |
| 276 | } |
| 277 | |
| 278 | switch (lum->cmd) { |
| 279 | case LTTNG_UST_REGISTER_DONE: |
| 280 | if (lum->handle == LTTNG_UST_ROOT_HANDLE) |
| 281 | ret = handle_register_done(sock_info); |
| 282 | else |
| 283 | ret = -EINVAL; |
| 284 | break; |
| 285 | case LTTNG_UST_RELEASE: |
| 286 | if (lum->handle == LTTNG_UST_ROOT_HANDLE) |
| 287 | ret = -EPERM; |
| 288 | else |
| 289 | ret = lttng_ust_objd_unref(lum->handle); |
| 290 | break; |
| 291 | case LTTNG_UST_FILTER: |
| 292 | { |
| 293 | /* Receive filter data */ |
| 294 | struct lttng_ust_filter_bytecode_node *bytecode; |
| 295 | |
| 296 | if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) { |
| 297 | ERR("Filter data size is too large: %u bytes", |
| 298 | lum->u.filter.data_size); |
| 299 | ret = -EINVAL; |
| 300 | goto error; |
| 301 | } |
| 302 | |
| 303 | if (lum->u.filter.reloc_offset > lum->u.filter.data_size) { |
| 304 | ERR("Filter reloc offset %u is not within data", |
| 305 | lum->u.filter.reloc_offset); |
| 306 | ret = -EINVAL; |
| 307 | goto error; |
| 308 | } |
| 309 | |
| 310 | bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size); |
| 311 | if (!bytecode) { |
| 312 | ret = -ENOMEM; |
| 313 | goto error; |
| 314 | } |
| 315 | len = ustcomm_recv_unix_sock(sock, bytecode->bc.data, |
| 316 | lum->u.filter.data_size); |
| 317 | switch (len) { |
| 318 | case 0: /* orderly shutdown */ |
| 319 | ret = 0; |
| 320 | free(bytecode); |
| 321 | goto error; |
| 322 | default: |
| 323 | if (len == lum->u.filter.data_size) { |
| 324 | DBG("filter data received"); |
| 325 | break; |
| 326 | } else if (len < 0) { |
| 327 | DBG("Receive failed from lttng-sessiond with errno %d", (int) -len); |
| 328 | if (len == -ECONNRESET) { |
| 329 | ERR("%s remote end closed connection", sock_info->name); |
| 330 | ret = len; |
| 331 | free(bytecode); |
| 332 | goto error; |
| 333 | } |
| 334 | ret = len; |
| 335 | goto end; |
| 336 | } else { |
| 337 | DBG("incorrect filter data message size: %zd", len); |
| 338 | ret = -EINVAL; |
| 339 | free(bytecode); |
| 340 | goto end; |
| 341 | } |
| 342 | } |
| 343 | bytecode->bc.len = lum->u.filter.data_size; |
| 344 | bytecode->bc.reloc_offset = lum->u.filter.reloc_offset; |
| 345 | bytecode->bc.seqnum = lum->u.filter.seqnum; |
| 346 | if (ops->cmd) { |
| 347 | ret = ops->cmd(lum->handle, lum->cmd, |
| 348 | (unsigned long) bytecode, |
| 349 | &args, sock_info); |
| 350 | if (ret) { |
| 351 | free(bytecode); |
| 352 | } |
| 353 | /* don't free bytecode if everything went fine. */ |
| 354 | } else { |
| 355 | ret = -ENOSYS; |
| 356 | free(bytecode); |
| 357 | } |
| 358 | break; |
| 359 | } |
| 360 | default: |
| 361 | if (ops->cmd) |
| 362 | ret = ops->cmd(lum->handle, lum->cmd, |
| 363 | (unsigned long) &lum->u, |
| 364 | &args, sock_info); |
| 365 | else |
| 366 | ret = -ENOSYS; |
| 367 | break; |
| 368 | } |
| 369 | |
| 370 | end: |
| 371 | lur.handle = lum->handle; |
| 372 | lur.cmd = lum->cmd; |
| 373 | lur.ret_val = ret; |
| 374 | if (ret >= 0) { |
| 375 | lur.ret_code = LTTNG_UST_OK; |
| 376 | } else { |
| 377 | /* |
| 378 | * Use -LTTNG_UST_ERR as wildcard for UST internal |
| 379 | * error that are not caused by the transport, except if |
| 380 | * we already have a more precise error message to |
| 381 | * report. |
| 382 | */ |
| 383 | if (ret > -LTTNG_UST_ERR) { |
| 384 | /* Translate code to UST error. */ |
| 385 | switch (ret) { |
| 386 | case -EEXIST: |
| 387 | lur.ret_code = -LTTNG_UST_ERR_EXIST; |
| 388 | break; |
| 389 | case -EINVAL: |
| 390 | lur.ret_code = -LTTNG_UST_ERR_INVAL; |
| 391 | break; |
| 392 | case -ENOENT: |
| 393 | lur.ret_code = -LTTNG_UST_ERR_NOENT; |
| 394 | break; |
| 395 | case -EPERM: |
| 396 | lur.ret_code = -LTTNG_UST_ERR_PERM; |
| 397 | break; |
| 398 | case -ENOSYS: |
| 399 | lur.ret_code = -LTTNG_UST_ERR_NOSYS; |
| 400 | break; |
| 401 | default: |
| 402 | lur.ret_code = -LTTNG_UST_ERR; |
| 403 | break; |
| 404 | } |
| 405 | } else { |
| 406 | lur.ret_code = ret; |
| 407 | } |
| 408 | } |
| 409 | if (ret >= 0) { |
| 410 | switch (lum->cmd) { |
| 411 | case LTTNG_UST_STREAM: |
| 412 | /* |
| 413 | * Special-case reply to send stream info. |
| 414 | * Use lum.u output. |
| 415 | */ |
| 416 | lur.u.stream.memory_map_size = *args.stream.memory_map_size; |
| 417 | shm_fd = *args.stream.shm_fd; |
| 418 | wait_fd = *args.stream.wait_fd; |
| 419 | break; |
| 420 | case LTTNG_UST_METADATA: |
| 421 | case LTTNG_UST_CHANNEL: |
| 422 | lur.u.channel.memory_map_size = *args.channel.memory_map_size; |
| 423 | shm_fd = *args.channel.shm_fd; |
| 424 | wait_fd = *args.channel.wait_fd; |
| 425 | break; |
| 426 | case LTTNG_UST_TRACER_VERSION: |
| 427 | lur.u.version = lum->u.version; |
| 428 | break; |
| 429 | case LTTNG_UST_TRACEPOINT_LIST_GET: |
| 430 | memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint)); |
| 431 | break; |
| 432 | } |
| 433 | } |
| 434 | ret = send_reply(sock, &lur); |
| 435 | if (ret < 0) { |
| 436 | DBG("error sending reply"); |
| 437 | goto error; |
| 438 | } |
| 439 | |
| 440 | if ((lum->cmd == LTTNG_UST_STREAM |
| 441 | || lum->cmd == LTTNG_UST_CHANNEL |
| 442 | || lum->cmd == LTTNG_UST_METADATA) |
| 443 | && lur.ret_code == LTTNG_UST_OK) { |
| 444 | int sendret = 0; |
| 445 | |
| 446 | /* we also need to send the file descriptors. */ |
| 447 | ret = ustcomm_send_fds_unix_sock(sock, |
| 448 | &shm_fd, &shm_fd, |
| 449 | 1, sizeof(int)); |
| 450 | if (ret < 0) { |
| 451 | ERR("send shm_fd"); |
| 452 | sendret = ret; |
| 453 | } |
| 454 | /* |
| 455 | * The sessiond expects 2 file descriptors, even upon |
| 456 | * error. |
| 457 | */ |
| 458 | ret = ustcomm_send_fds_unix_sock(sock, |
| 459 | &wait_fd, &wait_fd, |
| 460 | 1, sizeof(int)); |
| 461 | if (ret < 0) { |
| 462 | perror("send wait_fd"); |
| 463 | goto error; |
| 464 | } |
| 465 | if (sendret) { |
| 466 | ret = sendret; |
| 467 | goto error; |
| 468 | } |
| 469 | } |
| 470 | /* |
| 471 | * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field |
| 472 | * after the reply. |
| 473 | */ |
| 474 | if (lur.ret_code == LTTNG_UST_OK) { |
| 475 | switch (lum->cmd) { |
| 476 | case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET: |
| 477 | len = ustcomm_send_unix_sock(sock, |
| 478 | &args.field_list.entry, |
| 479 | sizeof(args.field_list.entry)); |
| 480 | if (len < 0) { |
| 481 | ret = len; |
| 482 | goto error; |
| 483 | } |
| 484 | if (len != sizeof(args.field_list.entry)) { |
| 485 | ret = -EINVAL; |
| 486 | goto error; |
| 487 | } |
| 488 | } |
| 489 | } |
| 490 | /* |
| 491 | * We still have the memory map reference, and the fds have been |
| 492 | * sent to the sessiond. We can therefore close those fds. Note |
| 493 | * that we keep the write side of the wait_fd open, but close |
| 494 | * the read side. |
| 495 | */ |
| 496 | if (lur.ret_code == LTTNG_UST_OK) { |
| 497 | switch (lum->cmd) { |
| 498 | case LTTNG_UST_STREAM: |
| 499 | if (shm_fd >= 0) { |
| 500 | ret = close(shm_fd); |
| 501 | if (ret) { |
| 502 | PERROR("Error closing stream shm_fd"); |
| 503 | } |
| 504 | *args.stream.shm_fd = -1; |
| 505 | } |
| 506 | if (wait_fd >= 0) { |
| 507 | ret = close(wait_fd); |
| 508 | if (ret) { |
| 509 | PERROR("Error closing stream wait_fd"); |
| 510 | } |
| 511 | *args.stream.wait_fd = -1; |
| 512 | } |
| 513 | break; |
| 514 | case LTTNG_UST_METADATA: |
| 515 | case LTTNG_UST_CHANNEL: |
| 516 | if (shm_fd >= 0) { |
| 517 | ret = close(shm_fd); |
| 518 | if (ret) { |
| 519 | PERROR("Error closing channel shm_fd"); |
| 520 | } |
| 521 | *args.channel.shm_fd = -1; |
| 522 | } |
| 523 | if (wait_fd >= 0) { |
| 524 | ret = close(wait_fd); |
| 525 | if (ret) { |
| 526 | PERROR("Error closing channel wait_fd"); |
| 527 | } |
| 528 | *args.channel.wait_fd = -1; |
| 529 | } |
| 530 | break; |
| 531 | } |
| 532 | } |
| 533 | |
| 534 | error: |
| 535 | ust_unlock(); |
| 536 | return ret; |
| 537 | } |
| 538 | |
| 539 | static |
| 540 | void cleanup_sock_info(struct sock_info *sock_info, int exiting) |
| 541 | { |
| 542 | int ret; |
| 543 | |
| 544 | if (sock_info->socket != -1) { |
| 545 | ret = ustcomm_close_unix_sock(sock_info->socket); |
| 546 | if (ret) { |
| 547 | ERR("Error closing apps socket"); |
| 548 | } |
| 549 | sock_info->socket = -1; |
| 550 | } |
| 551 | if (sock_info->root_handle != -1) { |
| 552 | ret = lttng_ust_objd_unref(sock_info->root_handle); |
| 553 | if (ret) { |
| 554 | ERR("Error unref root handle"); |
| 555 | } |
| 556 | sock_info->root_handle = -1; |
| 557 | } |
| 558 | sock_info->constructor_sem_posted = 0; |
| 559 | /* |
| 560 | * wait_shm_mmap is used by listener threads outside of the |
| 561 | * ust lock, so we cannot tear it down ourselves, because we |
| 562 | * cannot join on these threads. Leave this task to the OS |
| 563 | * process exit. |
| 564 | */ |
| 565 | if (!exiting && sock_info->wait_shm_mmap) { |
| 566 | ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE)); |
| 567 | if (ret) { |
| 568 | ERR("Error unmapping wait shm"); |
| 569 | } |
| 570 | sock_info->wait_shm_mmap = NULL; |
| 571 | } |
| 572 | } |
| 573 | |
| 574 | /* |
| 575 | * Using fork to set umask in the child process (not multi-thread safe). |
| 576 | * We deal with the shm_open vs ftruncate race (happening when the |
| 577 | * sessiond owns the shm and does not let everybody modify it, to ensure |
| 578 | * safety against shm_unlink) by simply letting the mmap fail and |
| 579 | * retrying after a few seconds. |
| 580 | * For global shm, everybody has rw access to it until the sessiond |
| 581 | * starts. |
| 582 | */ |
| 583 | static |
| 584 | int get_wait_shm(struct sock_info *sock_info, size_t mmap_size) |
| 585 | { |
| 586 | int wait_shm_fd, ret; |
| 587 | pid_t pid; |
| 588 | |
| 589 | /* |
| 590 | * Try to open read-only. |
| 591 | */ |
| 592 | wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0); |
| 593 | if (wait_shm_fd >= 0) { |
| 594 | goto end; |
| 595 | } else if (wait_shm_fd < 0 && errno != ENOENT) { |
| 596 | /* |
| 597 | * Real-only open did not work, and it's not because the |
| 598 | * entry was not present. It's a failure that prohibits |
| 599 | * using shm. |
| 600 | */ |
| 601 | ERR("Error opening shm %s", sock_info->wait_shm_path); |
| 602 | goto end; |
| 603 | } |
| 604 | /* |
| 605 | * If the open failed because the file did not exist, try |
| 606 | * creating it ourself. |
| 607 | */ |
| 608 | lttng_ust_nest_count++; |
| 609 | pid = fork(); |
| 610 | lttng_ust_nest_count--; |
| 611 | if (pid > 0) { |
| 612 | int status; |
| 613 | |
| 614 | /* |
| 615 | * Parent: wait for child to return, in which case the |
| 616 | * shared memory map will have been created. |
| 617 | */ |
| 618 | pid = wait(&status); |
| 619 | if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { |
| 620 | wait_shm_fd = -1; |
| 621 | goto end; |
| 622 | } |
| 623 | /* |
| 624 | * Try to open read-only again after creation. |
| 625 | */ |
| 626 | wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0); |
| 627 | if (wait_shm_fd < 0) { |
| 628 | /* |
| 629 | * Real-only open did not work. It's a failure |
| 630 | * that prohibits using shm. |
| 631 | */ |
| 632 | ERR("Error opening shm %s", sock_info->wait_shm_path); |
| 633 | goto end; |
| 634 | } |
| 635 | goto end; |
| 636 | } else if (pid == 0) { |
| 637 | int create_mode; |
| 638 | |
| 639 | /* Child */ |
| 640 | create_mode = S_IRUSR | S_IWUSR | S_IRGRP; |
| 641 | if (sock_info->global) |
| 642 | create_mode |= S_IROTH | S_IWGRP | S_IWOTH; |
| 643 | /* |
| 644 | * We're alone in a child process, so we can modify the |
| 645 | * process-wide umask. |
| 646 | */ |
| 647 | umask(~create_mode); |
| 648 | /* |
| 649 | * Try creating shm (or get rw access). |
| 650 | * We don't do an exclusive open, because we allow other |
| 651 | * processes to create+ftruncate it concurrently. |
| 652 | */ |
| 653 | wait_shm_fd = shm_open(sock_info->wait_shm_path, |
| 654 | O_RDWR | O_CREAT, create_mode); |
| 655 | if (wait_shm_fd >= 0) { |
| 656 | ret = ftruncate(wait_shm_fd, mmap_size); |
| 657 | if (ret) { |
| 658 | PERROR("ftruncate"); |
| 659 | _exit(EXIT_FAILURE); |
| 660 | } |
| 661 | _exit(EXIT_SUCCESS); |
| 662 | } |
| 663 | /* |
| 664 | * For local shm, we need to have rw access to accept |
| 665 | * opening it: this means the local sessiond will be |
| 666 | * able to wake us up. For global shm, we open it even |
| 667 | * if rw access is not granted, because the root.root |
| 668 | * sessiond will be able to override all rights and wake |
| 669 | * us up. |
| 670 | */ |
| 671 | if (!sock_info->global && errno != EACCES) { |
| 672 | ERR("Error opening shm %s", sock_info->wait_shm_path); |
| 673 | _exit(EXIT_FAILURE); |
| 674 | } |
| 675 | /* |
| 676 | * The shm exists, but we cannot open it RW. Report |
| 677 | * success. |
| 678 | */ |
| 679 | _exit(EXIT_SUCCESS); |
| 680 | } else { |
| 681 | return -1; |
| 682 | } |
| 683 | end: |
| 684 | if (wait_shm_fd >= 0 && !sock_info->global) { |
| 685 | struct stat statbuf; |
| 686 | |
| 687 | /* |
| 688 | * Ensure that our user is the owner of the shm file for |
| 689 | * local shm. If we do not own the file, it means our |
| 690 | * sessiond will not have access to wake us up (there is |
| 691 | * probably a rogue process trying to fake our |
| 692 | * sessiond). Fallback to polling method in this case. |
| 693 | */ |
| 694 | ret = fstat(wait_shm_fd, &statbuf); |
| 695 | if (ret) { |
| 696 | PERROR("fstat"); |
| 697 | goto error_close; |
| 698 | } |
| 699 | if (statbuf.st_uid != getuid()) |
| 700 | goto error_close; |
| 701 | } |
| 702 | return wait_shm_fd; |
| 703 | |
| 704 | error_close: |
| 705 | ret = close(wait_shm_fd); |
| 706 | if (ret) { |
| 707 | PERROR("Error closing fd"); |
| 708 | } |
| 709 | return -1; |
| 710 | } |
| 711 | |
| 712 | static |
| 713 | char *get_map_shm(struct sock_info *sock_info) |
| 714 | { |
| 715 | size_t mmap_size = sysconf(_SC_PAGE_SIZE); |
| 716 | int wait_shm_fd, ret; |
| 717 | char *wait_shm_mmap; |
| 718 | |
| 719 | wait_shm_fd = get_wait_shm(sock_info, mmap_size); |
| 720 | if (wait_shm_fd < 0) { |
| 721 | goto error; |
| 722 | } |
| 723 | wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ, |
| 724 | MAP_SHARED, wait_shm_fd, 0); |
| 725 | /* close shm fd immediately after taking the mmap reference */ |
| 726 | ret = close(wait_shm_fd); |
| 727 | if (ret) { |
| 728 | PERROR("Error closing fd"); |
| 729 | } |
| 730 | if (wait_shm_mmap == MAP_FAILED) { |
| 731 | DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode."); |
| 732 | goto error; |
| 733 | } |
| 734 | return wait_shm_mmap; |
| 735 | |
| 736 | error: |
| 737 | return NULL; |
| 738 | } |
| 739 | |
| 740 | static |
| 741 | void wait_for_sessiond(struct sock_info *sock_info) |
| 742 | { |
| 743 | int ret; |
| 744 | |
| 745 | ust_lock(); |
| 746 | if (lttng_ust_comm_should_quit) { |
| 747 | goto quit; |
| 748 | } |
| 749 | if (wait_poll_fallback) { |
| 750 | goto error; |
| 751 | } |
| 752 | if (!sock_info->wait_shm_mmap) { |
| 753 | sock_info->wait_shm_mmap = get_map_shm(sock_info); |
| 754 | if (!sock_info->wait_shm_mmap) |
| 755 | goto error; |
| 756 | } |
| 757 | ust_unlock(); |
| 758 | |
| 759 | DBG("Waiting for %s apps sessiond", sock_info->name); |
| 760 | /* Wait for futex wakeup */ |
| 761 | if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) { |
| 762 | ret = futex_async((int32_t *) sock_info->wait_shm_mmap, |
| 763 | FUTEX_WAIT, 0, NULL, NULL, 0); |
| 764 | if (ret < 0) { |
| 765 | if (errno == EFAULT) { |
| 766 | wait_poll_fallback = 1; |
| 767 | DBG( |
| 768 | "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) " |
| 769 | "do not support FUTEX_WAKE on read-only memory mappings correctly. " |
| 770 | "Please upgrade your kernel " |
| 771 | "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel " |
| 772 | "mainline). LTTng-UST will use polling mode fallback."); |
| 773 | if (ust_debug()) |
| 774 | PERROR("futex"); |
| 775 | } |
| 776 | } |
| 777 | } |
| 778 | return; |
| 779 | |
| 780 | quit: |
| 781 | ust_unlock(); |
| 782 | return; |
| 783 | |
| 784 | error: |
| 785 | ust_unlock(); |
| 786 | return; |
| 787 | } |
| 788 | |
| 789 | /* |
| 790 | * This thread does not allocate any resource, except within |
| 791 | * handle_message, within mutex protection. This mutex protects against |
| 792 | * fork and exit. |
| 793 | * The other moment it allocates resources is at socket connection, which |
| 794 | * is also protected by the mutex. |
| 795 | */ |
| 796 | static |
| 797 | void *ust_listener_thread(void *arg) |
| 798 | { |
| 799 | struct sock_info *sock_info = arg; |
| 800 | int sock, ret, prev_connect_failed = 0, has_waited = 0; |
| 801 | |
| 802 | /* Restart trying to connect to the session daemon */ |
| 803 | restart: |
| 804 | if (prev_connect_failed) { |
| 805 | /* Wait for sessiond availability with pipe */ |
| 806 | wait_for_sessiond(sock_info); |
| 807 | if (has_waited) { |
| 808 | has_waited = 0; |
| 809 | /* |
| 810 | * Sleep for 5 seconds before retrying after a |
| 811 | * sequence of failure / wait / failure. This |
| 812 | * deals with a killed or broken session daemon. |
| 813 | */ |
| 814 | sleep(5); |
| 815 | } |
| 816 | has_waited = 1; |
| 817 | prev_connect_failed = 0; |
| 818 | } |
| 819 | ust_lock(); |
| 820 | |
| 821 | if (lttng_ust_comm_should_quit) { |
| 822 | goto quit; |
| 823 | } |
| 824 | |
| 825 | if (sock_info->socket != -1) { |
| 826 | ret = ustcomm_close_unix_sock(sock_info->socket); |
| 827 | if (ret) { |
| 828 | ERR("Error closing %s apps socket", sock_info->name); |
| 829 | } |
| 830 | sock_info->socket = -1; |
| 831 | } |
| 832 | |
| 833 | /* Register */ |
| 834 | ret = ustcomm_connect_unix_sock(sock_info->sock_path); |
| 835 | if (ret < 0) { |
| 836 | DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name); |
| 837 | prev_connect_failed = 1; |
| 838 | /* |
| 839 | * If we cannot find the sessiond daemon, don't delay |
| 840 | * constructor execution. |
| 841 | */ |
| 842 | ret = handle_register_done(sock_info); |
| 843 | assert(!ret); |
| 844 | ust_unlock(); |
| 845 | goto restart; |
| 846 | } |
| 847 | |
| 848 | sock_info->socket = sock = ret; |
| 849 | |
| 850 | /* |
| 851 | * Create only one root handle per listener thread for the whole |
| 852 | * process lifetime, so we ensure we get ID which is statically |
| 853 | * assigned to the root handle. |
| 854 | */ |
| 855 | if (sock_info->root_handle == -1) { |
| 856 | ret = lttng_abi_create_root_handle(); |
| 857 | if (ret < 0) { |
| 858 | ERR("Error creating root handle"); |
| 859 | goto quit; |
| 860 | } |
| 861 | sock_info->root_handle = ret; |
| 862 | } |
| 863 | |
| 864 | ret = register_app_to_sessiond(sock); |
| 865 | if (ret < 0) { |
| 866 | ERR("Error registering to %s apps socket", sock_info->name); |
| 867 | prev_connect_failed = 1; |
| 868 | /* |
| 869 | * If we cannot register to the sessiond daemon, don't |
| 870 | * delay constructor execution. |
| 871 | */ |
| 872 | ret = handle_register_done(sock_info); |
| 873 | assert(!ret); |
| 874 | ust_unlock(); |
| 875 | goto restart; |
| 876 | } |
| 877 | ust_unlock(); |
| 878 | |
| 879 | for (;;) { |
| 880 | ssize_t len; |
| 881 | struct ustcomm_ust_msg lum; |
| 882 | |
| 883 | len = ustcomm_recv_unix_sock(sock, &lum, sizeof(lum)); |
| 884 | switch (len) { |
| 885 | case 0: /* orderly shutdown */ |
| 886 | DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name); |
| 887 | ust_lock(); |
| 888 | if (lttng_ust_comm_should_quit) { |
| 889 | goto quit; |
| 890 | } |
| 891 | /* |
| 892 | * Either sessiond has shutdown or refused us by closing the socket. |
| 893 | * In either case, we don't want to delay construction execution, |
| 894 | * and we need to wait before retry. |
| 895 | */ |
| 896 | prev_connect_failed = 1; |
| 897 | /* |
| 898 | * If we cannot register to the sessiond daemon, don't |
| 899 | * delay constructor execution. |
| 900 | */ |
| 901 | ret = handle_register_done(sock_info); |
| 902 | assert(!ret); |
| 903 | ust_unlock(); |
| 904 | goto end; |
| 905 | case sizeof(lum): |
| 906 | DBG("message received"); |
| 907 | ret = handle_message(sock_info, sock, &lum); |
| 908 | if (ret) { |
| 909 | ERR("Error handling message for %s socket", sock_info->name); |
| 910 | } |
| 911 | continue; |
| 912 | default: |
| 913 | if (len < 0) { |
| 914 | DBG("Receive failed from lttng-sessiond with errno %d", (int) -len); |
| 915 | } else { |
| 916 | DBG("incorrect message size (%s socket): %zd", sock_info->name, len); |
| 917 | } |
| 918 | if (len == -ECONNRESET) { |
| 919 | DBG("%s remote end closed connection", sock_info->name); |
| 920 | goto end; |
| 921 | } |
| 922 | goto end; |
| 923 | } |
| 924 | |
| 925 | } |
| 926 | end: |
| 927 | ust_lock(); |
| 928 | if (lttng_ust_comm_should_quit) { |
| 929 | goto quit; |
| 930 | } |
| 931 | /* Cleanup socket handles before trying to reconnect */ |
| 932 | lttng_ust_objd_table_owner_cleanup(sock_info); |
| 933 | ust_unlock(); |
| 934 | goto restart; /* try to reconnect */ |
| 935 | |
| 936 | quit: |
| 937 | sock_info->thread_active = 0; |
| 938 | ust_unlock(); |
| 939 | return NULL; |
| 940 | } |
| 941 | |
| 942 | /* |
| 943 | * Return values: -1: don't wait. 0: wait forever. 1: timeout wait. |
| 944 | */ |
| 945 | static |
| 946 | int get_timeout(struct timespec *constructor_timeout) |
| 947 | { |
| 948 | long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS; |
| 949 | char *str_delay; |
| 950 | int ret; |
| 951 | |
| 952 | str_delay = getenv("LTTNG_UST_REGISTER_TIMEOUT"); |
| 953 | if (str_delay) { |
| 954 | constructor_delay_ms = strtol(str_delay, NULL, 10); |
| 955 | } |
| 956 | |
| 957 | switch (constructor_delay_ms) { |
| 958 | case -1:/* fall-through */ |
| 959 | case 0: |
| 960 | return constructor_delay_ms; |
| 961 | default: |
| 962 | break; |
| 963 | } |
| 964 | |
| 965 | /* |
| 966 | * If we are unable to find the current time, don't wait. |
| 967 | */ |
| 968 | ret = clock_gettime(CLOCK_REALTIME, constructor_timeout); |
| 969 | if (ret) { |
| 970 | return -1; |
| 971 | } |
| 972 | constructor_timeout->tv_sec += constructor_delay_ms / 1000UL; |
| 973 | constructor_timeout->tv_nsec += |
| 974 | (constructor_delay_ms % 1000UL) * 1000000UL; |
| 975 | if (constructor_timeout->tv_nsec >= 1000000000UL) { |
| 976 | constructor_timeout->tv_sec++; |
| 977 | constructor_timeout->tv_nsec -= 1000000000UL; |
| 978 | } |
| 979 | return 1; |
| 980 | } |
| 981 | |
| 982 | /* |
| 983 | * sessiond monitoring thread: monitor presence of global and per-user |
| 984 | * sessiond by polling the application common named pipe. |
| 985 | */ |
| 986 | void __attribute__((constructor)) lttng_ust_init(void) |
| 987 | { |
| 988 | struct timespec constructor_timeout; |
| 989 | sigset_t sig_all_blocked, orig_parent_mask; |
| 990 | pthread_attr_t thread_attr; |
| 991 | int timeout_mode; |
| 992 | int ret; |
| 993 | |
| 994 | if (uatomic_xchg(&initialized, 1) == 1) |
| 995 | return; |
| 996 | |
| 997 | /* |
| 998 | * Fixup interdependency between TLS fixup mutex (which happens |
| 999 | * to be the dynamic linker mutex) and ust_lock, taken within |
| 1000 | * the ust lock. |
| 1001 | */ |
| 1002 | lttng_fixup_event_tls(); |
| 1003 | lttng_fixup_ringbuffer_tls(); |
| 1004 | lttng_fixup_vtid_tls(); |
| 1005 | lttng_fixup_nest_count_tls(); |
| 1006 | lttng_fixup_procname_tls(); |
| 1007 | |
| 1008 | /* |
| 1009 | * We want precise control over the order in which we construct |
| 1010 | * our sub-libraries vs starting to receive commands from |
| 1011 | * sessiond (otherwise leading to errors when trying to create |
| 1012 | * sessiond before the init functions are completed). |
| 1013 | */ |
| 1014 | init_usterr(); |
| 1015 | init_tracepoint(); |
| 1016 | lttng_ring_buffer_metadata_client_init(); |
| 1017 | lttng_ring_buffer_client_overwrite_init(); |
| 1018 | lttng_ring_buffer_client_discard_init(); |
| 1019 | |
| 1020 | timeout_mode = get_timeout(&constructor_timeout); |
| 1021 | |
| 1022 | ret = sem_init(&constructor_wait, 0, 0); |
| 1023 | assert(!ret); |
| 1024 | |
| 1025 | ret = setup_local_apps(); |
| 1026 | if (ret) { |
| 1027 | DBG("local apps setup returned %d", ret); |
| 1028 | } |
| 1029 | |
| 1030 | /* A new thread created by pthread_create inherits the signal mask |
| 1031 | * from the parent. To avoid any signal being received by the |
| 1032 | * listener thread, we block all signals temporarily in the parent, |
| 1033 | * while we create the listener thread. |
| 1034 | */ |
| 1035 | sigfillset(&sig_all_blocked); |
| 1036 | ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask); |
| 1037 | if (ret) { |
| 1038 | ERR("pthread_sigmask: %s", strerror(ret)); |
| 1039 | } |
| 1040 | |
| 1041 | ret = pthread_attr_init(&thread_attr); |
| 1042 | if (ret) { |
| 1043 | ERR("pthread_attr_init: %s", strerror(ret)); |
| 1044 | } |
| 1045 | ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED); |
| 1046 | if (ret) { |
| 1047 | ERR("pthread_attr_setdetachstate: %s", strerror(ret)); |
| 1048 | } |
| 1049 | |
| 1050 | ust_lock(); |
| 1051 | ret = pthread_create(&global_apps.ust_listener, &thread_attr, |
| 1052 | ust_listener_thread, &global_apps); |
| 1053 | if (ret) { |
| 1054 | ERR("pthread_create global: %s", strerror(ret)); |
| 1055 | } |
| 1056 | global_apps.thread_active = 1; |
| 1057 | ust_unlock(); |
| 1058 | |
| 1059 | if (local_apps.allowed) { |
| 1060 | ust_lock(); |
| 1061 | ret = pthread_create(&local_apps.ust_listener, &thread_attr, |
| 1062 | ust_listener_thread, &local_apps); |
| 1063 | if (ret) { |
| 1064 | ERR("pthread_create local: %s", strerror(ret)); |
| 1065 | } |
| 1066 | local_apps.thread_active = 1; |
| 1067 | ust_unlock(); |
| 1068 | } else { |
| 1069 | handle_register_done(&local_apps); |
| 1070 | } |
| 1071 | ret = pthread_attr_destroy(&thread_attr); |
| 1072 | if (ret) { |
| 1073 | ERR("pthread_attr_destroy: %s", strerror(ret)); |
| 1074 | } |
| 1075 | |
| 1076 | /* Restore original signal mask in parent */ |
| 1077 | ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL); |
| 1078 | if (ret) { |
| 1079 | ERR("pthread_sigmask: %s", strerror(ret)); |
| 1080 | } |
| 1081 | |
| 1082 | switch (timeout_mode) { |
| 1083 | case 1: /* timeout wait */ |
| 1084 | do { |
| 1085 | ret = sem_timedwait(&constructor_wait, |
| 1086 | &constructor_timeout); |
| 1087 | } while (ret < 0 && errno == EINTR); |
| 1088 | if (ret < 0 && errno == ETIMEDOUT) { |
| 1089 | ERR("Timed out waiting for lttng-sessiond"); |
| 1090 | } else { |
| 1091 | assert(!ret); |
| 1092 | } |
| 1093 | break; |
| 1094 | case -1:/* wait forever */ |
| 1095 | do { |
| 1096 | ret = sem_wait(&constructor_wait); |
| 1097 | } while (ret < 0 && errno == EINTR); |
| 1098 | assert(!ret); |
| 1099 | break; |
| 1100 | case 0: /* no timeout */ |
| 1101 | break; |
| 1102 | } |
| 1103 | } |
| 1104 | |
| 1105 | static |
| 1106 | void lttng_ust_cleanup(int exiting) |
| 1107 | { |
| 1108 | cleanup_sock_info(&global_apps, exiting); |
| 1109 | if (local_apps.allowed) { |
| 1110 | cleanup_sock_info(&local_apps, exiting); |
| 1111 | } |
| 1112 | /* |
| 1113 | * The teardown in this function all affect data structures |
| 1114 | * accessed under the UST lock by the listener thread. This |
| 1115 | * lock, along with the lttng_ust_comm_should_quit flag, ensure |
| 1116 | * that none of these threads are accessing this data at this |
| 1117 | * point. |
| 1118 | */ |
| 1119 | lttng_ust_abi_exit(); |
| 1120 | lttng_ust_events_exit(); |
| 1121 | lttng_ring_buffer_client_discard_exit(); |
| 1122 | lttng_ring_buffer_client_overwrite_exit(); |
| 1123 | lttng_ring_buffer_metadata_client_exit(); |
| 1124 | exit_tracepoint(); |
| 1125 | if (!exiting) { |
| 1126 | /* Reinitialize values for fork */ |
| 1127 | sem_count = 2; |
| 1128 | lttng_ust_comm_should_quit = 0; |
| 1129 | initialized = 0; |
| 1130 | } |
| 1131 | } |
| 1132 | |
| 1133 | void __attribute__((destructor)) lttng_ust_exit(void) |
| 1134 | { |
| 1135 | int ret; |
| 1136 | |
| 1137 | /* |
| 1138 | * Using pthread_cancel here because: |
| 1139 | * A) we don't want to hang application teardown. |
| 1140 | * B) the thread is not allocating any resource. |
| 1141 | */ |
| 1142 | |
| 1143 | /* |
| 1144 | * Require the communication thread to quit. Synchronize with |
| 1145 | * mutexes to ensure it is not in a mutex critical section when |
| 1146 | * pthread_cancel is later called. |
| 1147 | */ |
| 1148 | ust_lock(); |
| 1149 | lttng_ust_comm_should_quit = 1; |
| 1150 | |
| 1151 | /* cancel threads */ |
| 1152 | if (global_apps.thread_active) { |
| 1153 | ret = pthread_cancel(global_apps.ust_listener); |
| 1154 | if (ret) { |
| 1155 | ERR("Error cancelling global ust listener thread: %s", |
| 1156 | strerror(ret)); |
| 1157 | } else { |
| 1158 | global_apps.thread_active = 0; |
| 1159 | } |
| 1160 | } |
| 1161 | if (local_apps.thread_active) { |
| 1162 | ret = pthread_cancel(local_apps.ust_listener); |
| 1163 | if (ret) { |
| 1164 | ERR("Error cancelling local ust listener thread: %s", |
| 1165 | strerror(ret)); |
| 1166 | } else { |
| 1167 | local_apps.thread_active = 0; |
| 1168 | } |
| 1169 | } |
| 1170 | ust_unlock(); |
| 1171 | |
| 1172 | /* |
| 1173 | * Do NOT join threads: use of sys_futex makes it impossible to |
| 1174 | * join the threads without using async-cancel, but async-cancel |
| 1175 | * is delivered by a signal, which could hit the target thread |
| 1176 | * anywhere in its code path, including while the ust_lock() is |
| 1177 | * held, causing a deadlock for the other thread. Let the OS |
| 1178 | * cleanup the threads if there are stalled in a syscall. |
| 1179 | */ |
| 1180 | lttng_ust_cleanup(1); |
| 1181 | } |
| 1182 | |
| 1183 | /* |
| 1184 | * We exclude the worker threads across fork and clone (except |
| 1185 | * CLONE_VM), because these system calls only keep the forking thread |
| 1186 | * running in the child. Therefore, we don't want to call fork or clone |
| 1187 | * in the middle of an tracepoint or ust tracing state modification. |
| 1188 | * Holding this mutex protects these structures across fork and clone. |
| 1189 | */ |
| 1190 | void ust_before_fork(sigset_t *save_sigset) |
| 1191 | { |
| 1192 | /* |
| 1193 | * Disable signals. This is to avoid that the child intervenes |
| 1194 | * before it is properly setup for tracing. It is safer to |
| 1195 | * disable all signals, because then we know we are not breaking |
| 1196 | * anything by restoring the original mask. |
| 1197 | */ |
| 1198 | sigset_t all_sigs; |
| 1199 | int ret; |
| 1200 | |
| 1201 | if (lttng_ust_nest_count) |
| 1202 | return; |
| 1203 | /* Disable signals */ |
| 1204 | sigfillset(&all_sigs); |
| 1205 | ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset); |
| 1206 | if (ret == -1) { |
| 1207 | PERROR("sigprocmask"); |
| 1208 | } |
| 1209 | ust_lock(); |
| 1210 | rcu_bp_before_fork(); |
| 1211 | } |
| 1212 | |
| 1213 | static void ust_after_fork_common(sigset_t *restore_sigset) |
| 1214 | { |
| 1215 | int ret; |
| 1216 | |
| 1217 | DBG("process %d", getpid()); |
| 1218 | ust_unlock(); |
| 1219 | /* Restore signals */ |
| 1220 | ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL); |
| 1221 | if (ret == -1) { |
| 1222 | PERROR("sigprocmask"); |
| 1223 | } |
| 1224 | } |
| 1225 | |
| 1226 | void ust_after_fork_parent(sigset_t *restore_sigset) |
| 1227 | { |
| 1228 | if (lttng_ust_nest_count) |
| 1229 | return; |
| 1230 | DBG("process %d", getpid()); |
| 1231 | rcu_bp_after_fork_parent(); |
| 1232 | /* Release mutexes and reenable signals */ |
| 1233 | ust_after_fork_common(restore_sigset); |
| 1234 | } |
| 1235 | |
| 1236 | /* |
| 1237 | * After fork, in the child, we need to cleanup all the leftover state, |
| 1238 | * except the worker thread which already magically disappeared thanks |
| 1239 | * to the weird Linux fork semantics. After tyding up, we call |
| 1240 | * lttng_ust_init() again to start over as a new PID. |
| 1241 | * |
| 1242 | * This is meant for forks() that have tracing in the child between the |
| 1243 | * fork and following exec call (if there is any). |
| 1244 | */ |
| 1245 | void ust_after_fork_child(sigset_t *restore_sigset) |
| 1246 | { |
| 1247 | if (lttng_ust_nest_count) |
| 1248 | return; |
| 1249 | DBG("process %d", getpid()); |
| 1250 | /* Release urcu mutexes */ |
| 1251 | rcu_bp_after_fork_child(); |
| 1252 | lttng_ust_cleanup(0); |
| 1253 | lttng_context_vtid_reset(); |
| 1254 | /* Release mutexes and reenable signals */ |
| 1255 | ust_after_fork_common(restore_sigset); |
| 1256 | lttng_ust_init(); |
| 1257 | } |