libust/lttng-ust-comm.c

   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 #include <sys/types.h>
  23 #include <sys/socket.h>
  24 #include <sys/prctl.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
  39 #include <lttng-ust-comm.h>
  40 #include <ust/usterr-signal-safe.h>
  41 #include <ust/lttng-ust-abi.h>
  42 #include <ust/tracepoint.h>
  43 #include <ust/tracepoint-internal.h>
  44 #include <ust/ust.h>
  45 #include "ltt-tracer-core.h"
  46
  47 /*
  48  * Has lttng ust comm constructor been called ?
  49  */
  50 static int initialized;
  51
  52 /*
  53  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  54  * Held when handling a command, also held by fork() to deal with
  55  * removal of threads, and by exit path.
  56  */
  57
  58 /* Should the ust comm thread quit ? */
  59 static int lttng_ust_comm_should_quit;
  60
  61 /*
  62  * Wait for either of these before continuing to the main
  63  * program:
  64  * - the register_done message from sessiond daemon
  65  *   (will let the sessiond daemon enable sessions before main
  66  *   starts.)
  67  * - sessiond daemon is not reachable.
  68  * - timeout (ensuring applications are resilient to session
  69  *   daemon problems).
  70  */
  71 static sem_t constructor_wait;
  72 /*
  73  * Doing this for both the global and local sessiond.
  74  */
  75 static int sem_count = { 2 };
  76
  77 /*
  78  * Info about socket and associated listener thread.
  79  */
  80 struct sock_info {
  81         const char *name;
  82         pthread_t ust_listener; /* listener thread */
  83         int root_handle;
  84         int constructor_sem_posted;
  85         int allowed;
  86         int global;
  87
  88         char sock_path[PATH_MAX];
  89         int socket;
  90
  91         char wait_shm_path[PATH_MAX];
  92         char *wait_shm_mmap;
  93 };
  94
  95 /* Socket from app (connect) to session daemon (listen) for communication */
  96 struct sock_info global_apps = {
  97         .name = "global",
  98         .global = 1,
  99
 100         .root_handle = -1,
 101         .allowed = 1,
 102
 103         .sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
 104         .socket = -1,
 105
 106         .wait_shm_path = DEFAULT_GLOBAL_APPS_WAIT_SHM_PATH,
 107 };
 108
 109 /* TODO: allow global_apps_sock_path override */
 110
 111 struct sock_info local_apps = {
 112         .name = "local",
 113         .global = 0,
 114         .root_handle = -1,
 115         .allowed = 0,   /* Check setuid bit first */
 116
 117         .socket = -1,
 118 };
 119
 120 extern void ltt_ring_buffer_client_overwrite_init(void);
 121 extern void ltt_ring_buffer_client_discard_init(void);
 122 extern void ltt_ring_buffer_metadata_client_init(void);
 123 extern void ltt_ring_buffer_client_overwrite_exit(void);
 124 extern void ltt_ring_buffer_client_discard_exit(void);
 125 extern void ltt_ring_buffer_metadata_client_exit(void);
 126
 127 static
 128 int setup_local_apps(void)
 129 {
 130         const char *home_dir;
 131         uid_t uid;
 132
 133         uid = getuid();
 134         /*
 135          * Disallow per-user tracing for setuid binaries.
 136          */
 137         if (uid != geteuid()) {
 138                 local_apps.allowed = 0;
 139                 return 0;
 140         } else {
 141                 local_apps.allowed = 1;
 142         }
 143         home_dir = (const char *) getenv("HOME");
 144         if (!home_dir)
 145                 return -ENOENT;
 146         snprintf(local_apps.sock_path, PATH_MAX,
 147                  DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
 148         snprintf(local_apps.wait_shm_path, PATH_MAX,
 149                  DEFAULT_HOME_APPS_WAIT_SHM_PATH, uid);
 150         return 0;
 151 }
 152
 153 static
 154 int register_app_to_sessiond(int socket)
 155 {
 156         ssize_t ret;
 157         int prctl_ret;
 158         struct {
 159                 uint32_t major;
 160                 uint32_t minor;
 161                 pid_t pid;
 162                 pid_t ppid;
 163                 uid_t uid;
 164                 gid_t gid;
 165                 char name[16];  /* process name */
 166         } reg_msg;
 167
 168         reg_msg.major = LTTNG_UST_COMM_VERSION_MAJOR;
 169         reg_msg.minor = LTTNG_UST_COMM_VERSION_MINOR;
 170         reg_msg.pid = getpid();
 171         reg_msg.ppid = getppid();
 172         reg_msg.uid = getuid();
 173         reg_msg.gid = getgid();
 174         prctl_ret = prctl(PR_GET_NAME, (unsigned long) reg_msg.name, 0, 0, 0);
 175         if (prctl_ret) {
 176                 ERR("Error executing prctl");
 177                 return -errno;
 178         }
 179
 180         ret = lttcomm_send_unix_sock(socket, &reg_msg, sizeof(reg_msg));
 181         if (ret >= 0 && ret != sizeof(reg_msg))
 182                 return -EIO;
 183         return ret;
 184 }
 185
 186 static
 187 int send_reply(int sock, struct lttcomm_ust_reply *lur)
 188 {
 189         ssize_t len;
 190
 191         len = lttcomm_send_unix_sock(sock, lur, sizeof(*lur));
 192         switch (len) {
 193         case sizeof(*lur):
 194                 DBG("message successfully sent");
 195                 return 0;
 196         case -1:
 197                 if (errno == ECONNRESET) {
 198                         printf("remote end closed connection\n");
 199                         return 0;
 200                 }
 201                 return -1;
 202         default:
 203                 printf("incorrect message size: %zd\n", len);
 204                 return -1;
 205         }
 206 }
 207
 208 static
 209 int handle_register_done(struct sock_info *sock_info)
 210 {
 211         int ret;
 212
 213         if (sock_info->constructor_sem_posted)
 214                 return 0;
 215         sock_info->constructor_sem_posted = 1;
 216         ret = uatomic_add_return(&sem_count, -1);
 217         if (ret == 0) {
 218                 ret = sem_post(&constructor_wait);
 219                 assert(!ret);
 220         }
 221         return 0;
 222 }
 223
 224 static
 225 int handle_message(struct sock_info *sock_info,
 226                 int sock, struct lttcomm_ust_msg *lum)
 227 {
 228         int ret = 0;
 229         const struct objd_ops *ops;
 230         struct lttcomm_ust_reply lur;
 231
 232         ust_lock();
 233
 234         memset(&lur, 0, sizeof(lur));
 235
 236         if (lttng_ust_comm_should_quit) {
 237                 ret = -EPERM;
 238                 goto end;
 239         }
 240
 241         ops = objd_ops(lum->handle);
 242         if (!ops) {
 243                 ret = -ENOENT;
 244                 goto end;
 245         }
 246
 247         switch (lum->cmd) {
 248         case LTTNG_UST_REGISTER_DONE:
 249                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 250                         ret = handle_register_done(sock_info);
 251                 else
 252                         ret = -EINVAL;
 253                 break;
 254         case LTTNG_UST_RELEASE:
 255                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 256                         ret = -EPERM;
 257                 else
 258                         ret = objd_unref(lum->handle);
 259                 break;
 260         default:
 261                 if (ops->cmd)
 262                         ret = ops->cmd(lum->handle, lum->cmd,
 263                                         (unsigned long) &lum->u);
 264                 else
 265                         ret = -ENOSYS;
 266                 break;
 267         }
 268
 269 end:
 270         lur.handle = lum->handle;
 271         lur.cmd = lum->cmd;
 272         lur.ret_val = ret;
 273         if (ret >= 0) {
 274                 lur.ret_code = LTTCOMM_OK;
 275         } else {
 276                 lur.ret_code = LTTCOMM_SESSION_FAIL;
 277         }
 278         ret = send_reply(sock, &lur);
 279
 280         ust_unlock();
 281         return ret;
 282 }
 283
 284 static
 285 void cleanup_sock_info(struct sock_info *sock_info)
 286 {
 287         int ret;
 288
 289         if (sock_info->socket != -1) {
 290                 ret = close(sock_info->socket);
 291                 if (ret) {
 292                         ERR("Error closing apps socket");
 293                 }
 294                 sock_info->socket = -1;
 295         }
 296         if (sock_info->root_handle != -1) {
 297                 ret = objd_unref(sock_info->root_handle);
 298                 if (ret) {
 299                         ERR("Error unref root handle");
 300                 }
 301                 sock_info->root_handle = -1;
 302         }
 303         sock_info->constructor_sem_posted = 0;
 304         if (sock_info->wait_shm_mmap) {
 305                 ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
 306                 if (ret) {
 307                         ERR("Error unmapping wait shm");
 308                 }
 309                 sock_info->wait_shm_mmap = NULL;
 310         }
 311 }
 312
 313 /*
 314  * Using fork to set umask to 0777 in the child process (not
 315  * multi-thread safe).
 316  */
 317 static
 318 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 319 {
 320         int wait_shm_fd, ret;
 321         int read_mode;
 322         pid_t pid;
 323
 324         /*
 325          * At this point, we should be able to open it for
 326          * reading. If it fails, then it's because there is
 327          * something wrong: bail out in that case.
 328          */
 329         read_mode = S_IRUSR | S_IRGRP;
 330         if (sock_info->global)
 331                 read_mode |= S_IROTH;
 332
 333         /*
 334          * Try to open read-only. If it is set read-only, it
 335          * means the shm size has been already set with
 336          * ftruncate. Note: all processes creating shm need to
 337          * call ftruncate on the shm before restricting its
 338          * access rights to read-only. The shm should never be
 339          * unlinked. It a rogue process try to create a non-accessible
 340          * shm or to unlink it, the worse-case scenario is that we don't
 341          * use the shm wakeup method and sleep/retry instead.
 342          */
 343         wait_shm_fd = shm_open(sock_info->wait_shm_path,
 344                         O_RDONLY, read_mode);
 345         if (wait_shm_fd >= 0) {
 346                 goto end;
 347         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 348                 /*
 349                  * Real-only open did not work. It's a failure
 350                  * that prohibits using shm.
 351                  */
 352                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 353                 goto end;
 354         }
 355
 356         /*
 357          * If the open failed because the file did not exist, try
 358          * creating it ourself.
 359          */
 360         pid = fork();
 361         if (pid > 0) {
 362                 int status;
 363
 364                 /*
 365                  * Parent: wait for child to return, in which case the
 366                  * shared memory map will have been created.
 367                  */
 368                 pid = wait(&status);
 369                 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 370                         wait_shm_fd = -1;
 371                         goto end;
 372                 }
 373                 /*
 374                  * Try to open read-only again after creation.
 375                  */
 376                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 377                                 O_RDONLY, read_mode);
 378                 if (wait_shm_fd < 0) {
 379                         /*
 380                          * Real-only open did not work. It's a failure
 381                          * that prohibits using shm.
 382                          */
 383                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 384                         goto end;
 385                 }
 386                 goto end;
 387         } else if (pid == 0) {
 388                 int create_mode;
 389
 390                 /* Child */
 391                 create_mode = S_IRUSR | S_IRGRP | S_IWUSR | S_IWGRP;
 392                 if (sock_info->global)
 393                         create_mode |= S_IROTH | S_IWOTH;
 394                 /*
 395                  * We're alone in a child process, so we can modify the
 396                  * process-wide umask.
 397                  */
 398                 umask(create_mode);
 399                 /*
 400                  * First try creating shm (or get rw access). We need to start
 401                  * by this because of the ftruncate vs concurrent map race.
 402                  * We need to give write access to everyone because of the
 403                  * ftruncate vs mmap race too. We don't do an exclusive
 404                  * open, because we allow other processes to
 405                  * create+ftruncate it concurrently.
 406                  */
 407                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 408                                 O_RDWR | O_CREAT, create_mode);
 409                 if (wait_shm_fd >= 0) {
 410                         ret = ftruncate(wait_shm_fd, mmap_size);
 411                         if (ret) {
 412                                 PERROR("ftruncate");
 413                                 exit(EXIT_FAILURE);
 414                         }
 415                         ret = fchmod(wait_shm_fd, read_mode);
 416                         if (ret) {
 417                                 PERROR("fchmod");
 418                                 exit(EXIT_FAILURE);
 419                         }
 420                         exit(EXIT_SUCCESS);
 421                 }
 422                 if (errno != EACCES) {
 423                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 424                         exit(EXIT_FAILURE);
 425                 }
 426                 /*
 427                  * The shm exists, but we cannot open it RW. It means it
 428                  * has already been setup and ftruncated, so we can
 429                  * let the child exit.
 430                  */
 431                 exit(EXIT_SUCCESS);
 432         } else {
 433                 return -1;
 434         }
 435 end:
 436         return wait_shm_fd;
 437 }
 438
 439 static
 440 char *get_map_shm(struct sock_info *sock_info)
 441 {
 442         size_t mmap_size = sysconf(_SC_PAGE_SIZE);
 443         int wait_shm_fd, ret;
 444         char *wait_shm_mmap;
 445
 446         wait_shm_fd = get_wait_shm(sock_info, mmap_size);
 447         if (wait_shm_fd < 0) {
 448                 goto error;
 449         }
 450         wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
 451                   MAP_SHARED, wait_shm_fd, 0);
 452         if (wait_shm_mmap == MAP_FAILED) {
 453                 PERROR("mmap");
 454                 goto error;
 455         }
 456         /* close shm fd immediately after taking the mmap reference */
 457         ret = close(wait_shm_fd);
 458         if (ret) {
 459                 ERR("Error closing fd");
 460         }
 461         return wait_shm_mmap;
 462
 463 error:
 464         return NULL;
 465 }
 466
 467 static
 468 void wait_for_sessiond(struct sock_info *sock_info)
 469 {
 470         ust_lock();
 471         if (lttng_ust_comm_should_quit) {
 472                 goto quit;
 473         }
 474         if (!sock_info->wait_shm_mmap) {
 475                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
 476                 if (!sock_info->wait_shm_mmap)
 477                         goto error;
 478         }
 479         ust_unlock();
 480
 481         DBG("Waiting for %s apps sessiond", sock_info->name);
 482         /* Wait for futex wakeup TODO */
 483         sleep(5);
 484
 485         return;
 486
 487 quit:
 488         ust_unlock();
 489         return;
 490
 491 error:
 492         ust_unlock();
 493         /* Error handling: fallback on a 5 seconds sleep. */
 494         sleep(5);
 495         return;
 496 }
 497
 498 /*
 499  * This thread does not allocate any resource, except within
 500  * handle_message, within mutex protection. This mutex protects against
 501  * fork and exit.
 502  * The other moment it allocates resources is at socket connexion, which
 503  * is also protected by the mutex.
 504  */
 505 static
 506 void *ust_listener_thread(void *arg)
 507 {
 508         struct sock_info *sock_info = arg;
 509         int sock, ret;
 510
 511         /* Restart trying to connect to the session daemon */
 512 restart:
 513         ust_lock();
 514
 515         if (lttng_ust_comm_should_quit) {
 516                 ust_unlock();
 517                 goto quit;
 518         }
 519
 520         if (sock_info->socket != -1) {
 521                 ret = close(sock_info->socket);
 522                 if (ret) {
 523                         ERR("Error closing %s apps socket", sock_info->name);
 524                 }
 525                 sock_info->socket = -1;
 526         }
 527
 528         /* Register */
 529         ret = lttcomm_connect_unix_sock(sock_info->sock_path);
 530         if (ret < 0) {
 531                 ERR("Error connecting to %s apps socket", sock_info->name);
 532                 /*
 533                  * If we cannot find the sessiond daemon, don't delay
 534                  * constructor execution.
 535                  */
 536                 ret = handle_register_done(sock_info);
 537                 assert(!ret);
 538                 ust_unlock();
 539
 540                 /* Wait for sessiond availability with pipe */
 541                 wait_for_sessiond(sock_info);
 542                 goto restart;
 543         }
 544
 545         sock_info->socket = sock = ret;
 546
 547         /*
 548          * Create only one root handle per listener thread for the whole
 549          * process lifetime.
 550          */
 551         if (sock_info->root_handle == -1) {
 552                 ret = lttng_abi_create_root_handle();
 553                 if (ret) {
 554                         ERR("Error creating root handle");
 555                         ust_unlock();
 556                         goto quit;
 557                 }
 558                 sock_info->root_handle = ret;
 559         }
 560
 561         ret = register_app_to_sessiond(sock);
 562         if (ret < 0) {
 563                 ERR("Error registering to %s apps socket", sock_info->name);
 564                 /*
 565                  * If we cannot register to the sessiond daemon, don't
 566                  * delay constructor execution.
 567                  */
 568                 ret = handle_register_done(sock_info);
 569                 assert(!ret);
 570                 ust_unlock();
 571                 wait_for_sessiond(sock_info);
 572                 goto restart;
 573         }
 574         ust_unlock();
 575
 576         for (;;) {
 577                 ssize_t len;
 578                 struct lttcomm_ust_msg lum;
 579
 580                 len = lttcomm_recv_unix_sock(sock, &lum, sizeof(lum));
 581                 switch (len) {
 582                 case 0: /* orderly shutdown */
 583                         DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
 584                         goto end;
 585                 case sizeof(lum):
 586                         DBG("message received\n");
 587                         ret = handle_message(sock_info, sock, &lum);
 588                         if (ret < 0) {
 589                                 ERR("Error handling message for %s socket", sock_info->name);
 590                         }
 591                         continue;
 592                 case -1:
 593                         if (errno == ECONNRESET) {
 594                                 ERR("%s remote end closed connection\n", sock_info->name);
 595                                 goto end;
 596                         }
 597                         goto end;
 598                 default:
 599                         ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
 600                         continue;
 601                 }
 602
 603         }
 604 end:
 605         goto restart;   /* try to reconnect */
 606 quit:
 607         return NULL;
 608 }
 609
 610 /*
 611  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 612  */
 613 static
 614 int get_timeout(struct timespec *constructor_timeout)
 615 {
 616         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 617         char *str_delay;
 618         int ret;
 619
 620         str_delay = getenv("UST_REGISTER_TIMEOUT");
 621         if (str_delay) {
 622                 constructor_delay_ms = strtol(str_delay, NULL, 10);
 623         }
 624
 625         switch (constructor_delay_ms) {
 626         case -1:/* fall-through */
 627         case 0:
 628                 return constructor_delay_ms;
 629         default:
 630                 break;
 631         }
 632
 633         /*
 634          * If we are unable to find the current time, don't wait.
 635          */
 636         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 637         if (ret) {
 638                 return -1;
 639         }
 640         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 641         constructor_timeout->tv_nsec +=
 642                 (constructor_delay_ms % 1000UL) * 1000000UL;
 643         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 644                 constructor_timeout->tv_sec++;
 645                 constructor_timeout->tv_nsec -= 1000000000UL;
 646         }
 647         return 1;
 648 }
 649
 650 /*
 651  * sessiond monitoring thread: monitor presence of global and per-user
 652  * sessiond by polling the application common named pipe.
 653  */
 654 /* TODO */
 655
 656 void __attribute__((constructor)) lttng_ust_init(void)
 657 {
 658         struct timespec constructor_timeout;
 659         int timeout_mode;
 660         int ret;
 661
 662         if (uatomic_xchg(&initialized, 1) == 1)
 663                 return;
 664
 665         /*
 666          * We want precise control over the order in which we construct
 667          * our sub-libraries vs starting to receive commands from
 668          * sessiond (otherwise leading to errors when trying to create
 669          * sessiond before the init functions are completed).
 670          */
 671         init_usterr();
 672         init_tracepoint();
 673         ltt_ring_buffer_metadata_client_init();
 674         ltt_ring_buffer_client_overwrite_init();
 675         ltt_ring_buffer_client_discard_init();
 676
 677         timeout_mode = get_timeout(&constructor_timeout);
 678
 679         ret = sem_init(&constructor_wait, 0, 0);
 680         assert(!ret);
 681
 682         ret = setup_local_apps();
 683         if (ret) {
 684                 ERR("Error setting up to local apps");
 685         }
 686         ret = pthread_create(&local_apps.ust_listener, NULL,
 687                         ust_listener_thread, &local_apps);
 688
 689         if (local_apps.allowed) {
 690                 ret = pthread_create(&global_apps.ust_listener, NULL,
 691                                 ust_listener_thread, &global_apps);
 692         } else {
 693                 handle_register_done(&local_apps);
 694         }
 695
 696         switch (timeout_mode) {
 697         case 1: /* timeout wait */
 698                 do {
 699                         ret = sem_timedwait(&constructor_wait,
 700                                         &constructor_timeout);
 701                 } while (ret < 0 && errno == EINTR);
 702                 if (ret < 0 && errno == ETIMEDOUT) {
 703                         ERR("Timed out waiting for ltt-sessiond");
 704                 } else {
 705                         assert(!ret);
 706                 }
 707                 break;
 708         case -1:/* wait forever */
 709                 do {
 710                         ret = sem_wait(&constructor_wait);
 711                 } while (ret < 0 && errno == EINTR);
 712                 assert(!ret);
 713                 break;
 714         case 0: /* no timeout */
 715                 break;
 716         }
 717 }
 718
 719 static
 720 void lttng_ust_cleanup(int exiting)
 721 {
 722         cleanup_sock_info(&global_apps);
 723         if (local_apps.allowed) {
 724                 cleanup_sock_info(&local_apps);
 725         }
 726         lttng_ust_abi_exit();
 727         ltt_events_exit();
 728         ltt_ring_buffer_client_discard_exit();
 729         ltt_ring_buffer_client_overwrite_exit();
 730         ltt_ring_buffer_metadata_client_exit();
 731         exit_tracepoint();
 732         if (!exiting) {
 733                 /* Reinitialize values for fork */
 734                 sem_count = 2;
 735                 lttng_ust_comm_should_quit = 0;
 736                 initialized = 0;
 737         }
 738 }
 739
 740 void __attribute__((destructor)) lttng_ust_exit(void)
 741 {
 742         int ret;
 743
 744         /*
 745          * Using pthread_cancel here because:
 746          * A) we don't want to hang application teardown.
 747          * B) the thread is not allocating any resource.
 748          */
 749
 750         /*
 751          * Require the communication thread to quit. Synchronize with
 752          * mutexes to ensure it is not in a mutex critical section when
 753          * pthread_cancel is later called.
 754          */
 755         ust_lock();
 756         lttng_ust_comm_should_quit = 1;
 757         ust_unlock();
 758
 759         ret = pthread_cancel(global_apps.ust_listener);
 760         if (ret) {
 761                 ERR("Error cancelling global ust listener thread");
 762         }
 763         if (local_apps.allowed) {
 764                 ret = pthread_cancel(local_apps.ust_listener);
 765                 if (ret) {
 766                         ERR("Error cancelling local ust listener thread");
 767                 }
 768         }
 769         lttng_ust_cleanup(1);
 770 }
 771
 772 /*
 773  * We exclude the worker threads across fork and clone (except
 774  * CLONE_VM), because these system calls only keep the forking thread
 775  * running in the child.  Therefore, we don't want to call fork or clone
 776  * in the middle of an tracepoint or ust tracing state modification.
 777  * Holding this mutex protects these structures across fork and clone.
 778  */
 779 void ust_before_fork(ust_fork_info_t *fork_info)
 780 {
 781         /*
 782          * Disable signals. This is to avoid that the child intervenes
 783          * before it is properly setup for tracing. It is safer to
 784          * disable all signals, because then we know we are not breaking
 785          * anything by restoring the original mask.
 786          */
 787         sigset_t all_sigs;
 788         int ret;
 789
 790         /* Disable signals */
 791         sigfillset(&all_sigs);
 792         ret = sigprocmask(SIG_BLOCK, &all_sigs, &fork_info->orig_sigs);
 793         if (ret == -1) {
 794                 PERROR("sigprocmask");
 795         }
 796         ust_lock();
 797         rcu_bp_before_fork();
 798 }
 799
 800 static void ust_after_fork_common(ust_fork_info_t *fork_info)
 801 {
 802         int ret;
 803
 804         DBG("process %d", getpid());
 805         ust_unlock();
 806         /* Restore signals */
 807         ret = sigprocmask(SIG_SETMASK, &fork_info->orig_sigs, NULL);
 808         if (ret == -1) {
 809                 PERROR("sigprocmask");
 810         }
 811 }
 812
 813 void ust_after_fork_parent(ust_fork_info_t *fork_info)
 814 {
 815         DBG("process %d", getpid());
 816         rcu_bp_after_fork_parent();
 817         /* Release mutexes and reenable signals */
 818         ust_after_fork_common(fork_info);
 819 }
 820
 821 /*
 822  * After fork, in the child, we need to cleanup all the leftover state,
 823  * except the worker thread which already magically disappeared thanks
 824  * to the weird Linux fork semantics. After tyding up, we call
 825  * lttng_ust_init() again to start over as a new PID.
 826  *
 827  * This is meant for forks() that have tracing in the child between the
 828  * fork and following exec call (if there is any).
 829  */
 830 void ust_after_fork_child(ust_fork_info_t *fork_info)
 831 {
 832         DBG("process %d", getpid());
 833         /* Release urcu mutexes */
 834         rcu_bp_after_fork_child();
 835         lttng_ust_cleanup(0);
 836         /* Release mutexes and reenable signals */
 837         ust_after_fork_common(fork_info);
 838         lttng_ust_init();
 839 }