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 #define _LGPL_SOURCE
  23 #include <sys/types.h>
  24 #include <sys/socket.h>
  25 #include <sys/prctl.h>
  26 #include <sys/mman.h>
  27 #include <sys/stat.h>
  28 #include <sys/types.h>
  29 #include <sys/wait.h>
  30 #include <fcntl.h>
  31 #include <unistd.h>
  32 #include <errno.h>
  33 #include <pthread.h>
  34 #include <semaphore.h>
  35 #include <time.h>
  36 #include <assert.h>
  37 #include <signal.h>
  38 #include <urcu/uatomic.h>
  39 #include <urcu/futex.h>
  40
  41 #include <lttng-ust-comm.h>
  42 #include <ust/usterr-signal-safe.h>
  43 #include <ust/lttng-ust-abi.h>
  44 #include <ust/tracepoint.h>
  45 #include <ust/tracepoint-internal.h>
  46 #include <ust/ust.h>
  47 #include "ltt-tracer-core.h"
  48
  49 /*
  50  * Has lttng ust comm constructor been called ?
  51  */
  52 static int initialized;
  53
  54 /*
  55  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  56  * Held when handling a command, also held by fork() to deal with
  57  * removal of threads, and by exit path.
  58  */
  59
  60 /* Should the ust comm thread quit ? */
  61 static int lttng_ust_comm_should_quit;
  62
  63 /*
  64  * Wait for either of these before continuing to the main
  65  * program:
  66  * - the register_done message from sessiond daemon
  67  *   (will let the sessiond daemon enable sessions before main
  68  *   starts.)
  69  * - sessiond daemon is not reachable.
  70  * - timeout (ensuring applications are resilient to session
  71  *   daemon problems).
  72  */
  73 static sem_t constructor_wait;
  74 /*
  75  * Doing this for both the global and local sessiond.
  76  */
  77 static int sem_count = { 2 };
  78
  79 /*
  80  * Info about socket and associated listener thread.
  81  */
  82 struct sock_info {
  83         const char *name;
  84         pthread_t ust_listener; /* listener thread */
  85         int root_handle;
  86         int constructor_sem_posted;
  87         int allowed;
  88         int global;
  89
  90         char sock_path[PATH_MAX];
  91         int socket;
  92
  93         char wait_shm_path[PATH_MAX];
  94         char *wait_shm_mmap;
  95 };
  96
  97 /* Socket from app (connect) to session daemon (listen) for communication */
  98 struct sock_info global_apps = {
  99         .name = "global",
 100         .global = 1,
 101
 102         .root_handle = -1,
 103         .allowed = 1,
 104
 105         .sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
 106         .socket = -1,
 107
 108         .wait_shm_path = DEFAULT_GLOBAL_APPS_WAIT_SHM_PATH,
 109 };
 110
 111 /* TODO: allow global_apps_sock_path override */
 112
 113 struct sock_info local_apps = {
 114         .name = "local",
 115         .global = 0,
 116         .root_handle = -1,
 117         .allowed = 0,   /* Check setuid bit first */
 118
 119         .socket = -1,
 120 };
 121
 122 static int wait_poll_fallback;
 123
 124 extern void ltt_ring_buffer_client_overwrite_init(void);
 125 extern void ltt_ring_buffer_client_discard_init(void);
 126 extern void ltt_ring_buffer_metadata_client_init(void);
 127 extern void ltt_ring_buffer_client_overwrite_exit(void);
 128 extern void ltt_ring_buffer_client_discard_exit(void);
 129 extern void ltt_ring_buffer_metadata_client_exit(void);
 130
 131 static
 132 int setup_local_apps(void)
 133 {
 134         const char *home_dir;
 135         uid_t uid;
 136
 137         uid = getuid();
 138         /*
 139          * Disallow per-user tracing for setuid binaries.
 140          */
 141         if (uid != geteuid()) {
 142                 local_apps.allowed = 0;
 143                 return 0;
 144         } else {
 145                 local_apps.allowed = 1;
 146         }
 147         home_dir = (const char *) getenv("HOME");
 148         if (!home_dir)
 149                 return -ENOENT;
 150         snprintf(local_apps.sock_path, PATH_MAX,
 151                  DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
 152         snprintf(local_apps.wait_shm_path, PATH_MAX,
 153                  DEFAULT_HOME_APPS_WAIT_SHM_PATH, uid);
 154         return 0;
 155 }
 156
 157 static
 158 int register_app_to_sessiond(int socket)
 159 {
 160         ssize_t ret;
 161         int prctl_ret;
 162         struct {
 163                 uint32_t major;
 164                 uint32_t minor;
 165                 pid_t pid;
 166                 pid_t ppid;
 167                 uid_t uid;
 168                 gid_t gid;
 169                 char name[16];  /* process name */
 170         } reg_msg;
 171
 172         reg_msg.major = LTTNG_UST_COMM_VERSION_MAJOR;
 173         reg_msg.minor = LTTNG_UST_COMM_VERSION_MINOR;
 174         reg_msg.pid = getpid();
 175         reg_msg.ppid = getppid();
 176         reg_msg.uid = getuid();
 177         reg_msg.gid = getgid();
 178         prctl_ret = prctl(PR_GET_NAME, (unsigned long) reg_msg.name, 0, 0, 0);
 179         if (prctl_ret) {
 180                 ERR("Error executing prctl");
 181                 return -errno;
 182         }
 183
 184         ret = lttcomm_send_unix_sock(socket, &reg_msg, sizeof(reg_msg));
 185         if (ret >= 0 && ret != sizeof(reg_msg))
 186                 return -EIO;
 187         return ret;
 188 }
 189
 190 static
 191 int send_reply(int sock, struct lttcomm_ust_reply *lur)
 192 {
 193         ssize_t len;
 194
 195         len = lttcomm_send_unix_sock(sock, lur, sizeof(*lur));
 196         switch (len) {
 197         case sizeof(*lur):
 198                 DBG("message successfully sent");
 199                 return 0;
 200         case -1:
 201                 if (errno == ECONNRESET) {
 202                         printf("remote end closed connection\n");
 203                         return 0;
 204                 }
 205                 return -1;
 206         default:
 207                 printf("incorrect message size: %zd\n", len);
 208                 return -1;
 209         }
 210 }
 211
 212 static
 213 int handle_register_done(struct sock_info *sock_info)
 214 {
 215         int ret;
 216
 217         if (sock_info->constructor_sem_posted)
 218                 return 0;
 219         sock_info->constructor_sem_posted = 1;
 220         ret = uatomic_add_return(&sem_count, -1);
 221         if (ret == 0) {
 222                 ret = sem_post(&constructor_wait);
 223                 assert(!ret);
 224         }
 225         return 0;
 226 }
 227
 228 static
 229 int handle_message(struct sock_info *sock_info,
 230                 int sock, struct lttcomm_ust_msg *lum)
 231 {
 232         int ret = 0;
 233         const struct objd_ops *ops;
 234         struct lttcomm_ust_reply lur;
 235
 236         ust_lock();
 237
 238         memset(&lur, 0, sizeof(lur));
 239
 240         if (lttng_ust_comm_should_quit) {
 241                 ret = -EPERM;
 242                 goto end;
 243         }
 244
 245         ops = objd_ops(lum->handle);
 246         if (!ops) {
 247                 ret = -ENOENT;
 248                 goto end;
 249         }
 250
 251         switch (lum->cmd) {
 252         case LTTNG_UST_REGISTER_DONE:
 253                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 254                         ret = handle_register_done(sock_info);
 255                 else
 256                         ret = -EINVAL;
 257                 break;
 258         case LTTNG_UST_RELEASE:
 259                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 260                         ret = -EPERM;
 261                 else
 262                         ret = objd_unref(lum->handle);
 263                 break;
 264         default:
 265                 if (ops->cmd)
 266                         ret = ops->cmd(lum->handle, lum->cmd,
 267                                         (unsigned long) &lum->u);
 268                 else
 269                         ret = -ENOSYS;
 270                 break;
 271         }
 272
 273 end:
 274         lur.handle = lum->handle;
 275         lur.cmd = lum->cmd;
 276         lur.ret_val = ret;
 277         if (ret >= 0) {
 278                 lur.ret_code = LTTCOMM_OK;
 279         } else {
 280                 lur.ret_code = LTTCOMM_SESSION_FAIL;
 281         }
 282         ret = send_reply(sock, &lur);
 283
 284         ust_unlock();
 285         return ret;
 286 }
 287
 288 static
 289 void cleanup_sock_info(struct sock_info *sock_info)
 290 {
 291         int ret;
 292
 293         if (sock_info->socket != -1) {
 294                 ret = close(sock_info->socket);
 295                 if (ret) {
 296                         ERR("Error closing apps socket");
 297                 }
 298                 sock_info->socket = -1;
 299         }
 300         if (sock_info->root_handle != -1) {
 301                 ret = objd_unref(sock_info->root_handle);
 302                 if (ret) {
 303                         ERR("Error unref root handle");
 304                 }
 305                 sock_info->root_handle = -1;
 306         }
 307         sock_info->constructor_sem_posted = 0;
 308         if (sock_info->wait_shm_mmap) {
 309                 ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
 310                 if (ret) {
 311                         ERR("Error unmapping wait shm");
 312                 }
 313                 sock_info->wait_shm_mmap = NULL;
 314         }
 315 }
 316
 317 /*
 318  * Using fork to set umask in the child process (not multi-thread safe).
 319  * We deal with the shm_open vs ftruncate race (happening when the
 320  * sessiond owns the shm and does not let everybody modify it, to ensure
 321  * safety against shm_unlink) by simply letting the mmap fail and
 322  * retrying after a few seconds.
 323  * For global shm, everybody has rw access to it until the sessiond
 324  * starts.
 325  */
 326 static
 327 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 328 {
 329         int wait_shm_fd, ret;
 330         pid_t pid;
 331
 332         /*
 333          * Try to open read-only.
 334          */
 335         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 336         if (wait_shm_fd >= 0) {
 337                 goto end;
 338         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 339                 /*
 340                  * Real-only open did not work, and it's not because the
 341                  * entry was not present. It's a failure that prohibits
 342                  * using shm.
 343                  */
 344                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 345                 goto end;
 346         }
 347         /*
 348          * If the open failed because the file did not exist, try
 349          * creating it ourself.
 350          */
 351         pid = fork();
 352         if (pid > 0) {
 353                 int status;
 354
 355                 /*
 356                  * Parent: wait for child to return, in which case the
 357                  * shared memory map will have been created.
 358                  */
 359                 pid = wait(&status);
 360                 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 361                         wait_shm_fd = -1;
 362                         goto end;
 363                 }
 364                 /*
 365                  * Try to open read-only again after creation.
 366                  */
 367                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 368                 if (wait_shm_fd < 0) {
 369                         /*
 370                          * Real-only open did not work. It's a failure
 371                          * that prohibits using shm.
 372                          */
 373                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 374                         goto end;
 375                 }
 376                 goto end;
 377         } else if (pid == 0) {
 378                 int create_mode;
 379
 380                 /* Child */
 381                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
 382                 if (sock_info->global)
 383                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
 384                 /*
 385                  * We're alone in a child process, so we can modify the
 386                  * process-wide umask.
 387                  */
 388                 umask(~create_mode);
 389                 /*
 390                  * Try creating shm (or get rw access).
 391                  * We don't do an exclusive open, because we allow other
 392                  * processes to create+ftruncate it concurrently.
 393                  */
 394                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 395                                 O_RDWR | O_CREAT, create_mode);
 396                 if (wait_shm_fd >= 0) {
 397                         ret = ftruncate(wait_shm_fd, mmap_size);
 398                         if (ret) {
 399                                 PERROR("ftruncate");
 400                                 exit(EXIT_FAILURE);
 401                         }
 402                         exit(EXIT_SUCCESS);
 403                 }
 404                 /*
 405                  * For local shm, we need to have rw access to accept
 406                  * opening it: this means the local sessiond will be
 407                  * able to wake us up. For global shm, we open it even
 408                  * if rw access is not granted, because the root.root
 409                  * sessiond will be able to override all rights and wake
 410                  * us up.
 411                  */
 412                 if (!sock_info->global && errno != EACCES) {
 413                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 414                         exit(EXIT_FAILURE);
 415                 }
 416                 /*
 417                  * The shm exists, but we cannot open it RW. Report
 418                  * success.
 419                  */
 420                 exit(EXIT_SUCCESS);
 421         } else {
 422                 return -1;
 423         }
 424 end:
 425         if (wait_shm_fd >= 0 && !sock_info->global) {
 426                 struct stat statbuf;
 427
 428                 /*
 429                  * Ensure that our user is the owner of the shm file for
 430                  * local shm. If we do not own the file, it means our
 431                  * sessiond will not have access to wake us up (there is
 432                  * probably a rogue process trying to fake our
 433                  * sessiond). Fallback to polling method in this case.
 434                  */
 435                 ret = fstat(wait_shm_fd, &statbuf);
 436                 if (ret) {
 437                         PERROR("fstat");
 438                         goto error_close;
 439                 }
 440                 if (statbuf.st_uid != getuid())
 441                         goto error_close;
 442         }
 443         return wait_shm_fd;
 444
 445 error_close:
 446         ret = close(wait_shm_fd);
 447         if (ret) {
 448                 PERROR("Error closing fd");
 449         }
 450         return -1;
 451 }
 452
 453 static
 454 char *get_map_shm(struct sock_info *sock_info)
 455 {
 456         size_t mmap_size = sysconf(_SC_PAGE_SIZE);
 457         int wait_shm_fd, ret;
 458         char *wait_shm_mmap;
 459
 460         wait_shm_fd = get_wait_shm(sock_info, mmap_size);
 461         if (wait_shm_fd < 0) {
 462                 goto error;
 463         }
 464         wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
 465                   MAP_SHARED, wait_shm_fd, 0);
 466         /* close shm fd immediately after taking the mmap reference */
 467         ret = close(wait_shm_fd);
 468         if (ret) {
 469                 PERROR("Error closing fd");
 470         }
 471         if (wait_shm_mmap == MAP_FAILED) {
 472                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
 473                 goto error;
 474         }
 475         return wait_shm_mmap;
 476
 477 error:
 478         return NULL;
 479 }
 480
 481 static
 482 void wait_for_sessiond(struct sock_info *sock_info)
 483 {
 484         int ret;
 485
 486         ust_lock();
 487         if (lttng_ust_comm_should_quit) {
 488                 goto quit;
 489         }
 490         if (wait_poll_fallback) {
 491                 goto error;
 492         }
 493         if (!sock_info->wait_shm_mmap) {
 494                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
 495                 if (!sock_info->wait_shm_mmap)
 496                         goto error;
 497         }
 498         ust_unlock();
 499
 500         DBG("Waiting for %s apps sessiond", sock_info->name);
 501         /* Wait for futex wakeup */
 502         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
 503                 ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
 504                         FUTEX_WAIT, 0, NULL, NULL, 0);
 505                 if (ret < 0) {
 506                         if (errno == EFAULT) {
 507                                 wait_poll_fallback = 1;
 508                                 ERR(
 509 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
 510 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
 511 "Please upgrade your kernel "
 512 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
 513 "mainline). LTTng-UST will use polling mode fallback.");
 514                         }
 515                         PERROR("futex");
 516                 }
 517         }
 518         return;
 519
 520 quit:
 521         ust_unlock();
 522         return;
 523
 524 error:
 525         ust_unlock();
 526         return;
 527 }
 528
 529 /*
 530  * This thread does not allocate any resource, except within
 531  * handle_message, within mutex protection. This mutex protects against
 532  * fork and exit.
 533  * The other moment it allocates resources is at socket connexion, which
 534  * is also protected by the mutex.
 535  */
 536 static
 537 void *ust_listener_thread(void *arg)
 538 {
 539         struct sock_info *sock_info = arg;
 540         int sock, ret, prev_connect_failed = 0, has_waited = 0;
 541
 542         /* Restart trying to connect to the session daemon */
 543 restart:
 544         if (prev_connect_failed) {
 545                 /* Wait for sessiond availability with pipe */
 546                 wait_for_sessiond(sock_info);
 547                 if (has_waited) {
 548                         has_waited = 0;
 549                         /*
 550                          * Sleep for 5 seconds before retrying after a
 551                          * sequence of failure / wait / failure. This
 552                          * deals with a killed or broken session daemon.
 553                          */
 554                         sleep(5);
 555                 }
 556                 has_waited = 1;
 557                 prev_connect_failed = 0;
 558         }
 559         ust_lock();
 560
 561         if (lttng_ust_comm_should_quit) {
 562                 ust_unlock();
 563                 goto quit;
 564         }
 565
 566         if (sock_info->socket != -1) {
 567                 ret = close(sock_info->socket);
 568                 if (ret) {
 569                         ERR("Error closing %s apps socket", sock_info->name);
 570                 }
 571                 sock_info->socket = -1;
 572         }
 573
 574         /* Register */
 575         ret = lttcomm_connect_unix_sock(sock_info->sock_path);
 576         if (ret < 0) {
 577                 ERR("Error connecting to %s apps socket", sock_info->name);
 578                 prev_connect_failed = 1;
 579                 /*
 580                  * If we cannot find the sessiond daemon, don't delay
 581                  * constructor execution.
 582                  */
 583                 ret = handle_register_done(sock_info);
 584                 assert(!ret);
 585                 ust_unlock();
 586                 goto restart;
 587         }
 588
 589         sock_info->socket = sock = ret;
 590
 591         /*
 592          * Create only one root handle per listener thread for the whole
 593          * process lifetime.
 594          */
 595         if (sock_info->root_handle == -1) {
 596                 ret = lttng_abi_create_root_handle();
 597                 if (ret) {
 598                         ERR("Error creating root handle");
 599                         ust_unlock();
 600                         goto quit;
 601                 }
 602                 sock_info->root_handle = ret;
 603         }
 604
 605         ret = register_app_to_sessiond(sock);
 606         if (ret < 0) {
 607                 ERR("Error registering to %s apps socket", sock_info->name);
 608                 prev_connect_failed = 1;
 609                 /*
 610                  * If we cannot register to the sessiond daemon, don't
 611                  * delay constructor execution.
 612                  */
 613                 ret = handle_register_done(sock_info);
 614                 assert(!ret);
 615                 ust_unlock();
 616                 goto restart;
 617         }
 618         ust_unlock();
 619
 620         for (;;) {
 621                 ssize_t len;
 622                 struct lttcomm_ust_msg lum;
 623
 624                 len = lttcomm_recv_unix_sock(sock, &lum, sizeof(lum));
 625                 switch (len) {
 626                 case 0: /* orderly shutdown */
 627                         DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
 628                         goto end;
 629                 case sizeof(lum):
 630                         DBG("message received\n");
 631                         ret = handle_message(sock_info, sock, &lum);
 632                         if (ret < 0) {
 633                                 ERR("Error handling message for %s socket", sock_info->name);
 634                         }
 635                         continue;
 636                 case -1:
 637                         if (errno == ECONNRESET) {
 638                                 ERR("%s remote end closed connection\n", sock_info->name);
 639                                 goto end;
 640                         }
 641                         goto end;
 642                 default:
 643                         ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
 644                         continue;
 645                 }
 646
 647         }
 648 end:
 649         goto restart;   /* try to reconnect */
 650 quit:
 651         return NULL;
 652 }
 653
 654 /*
 655  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 656  */
 657 static
 658 int get_timeout(struct timespec *constructor_timeout)
 659 {
 660         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 661         char *str_delay;
 662         int ret;
 663
 664         str_delay = getenv("UST_REGISTER_TIMEOUT");
 665         if (str_delay) {
 666                 constructor_delay_ms = strtol(str_delay, NULL, 10);
 667         }
 668
 669         switch (constructor_delay_ms) {
 670         case -1:/* fall-through */
 671         case 0:
 672                 return constructor_delay_ms;
 673         default:
 674                 break;
 675         }
 676
 677         /*
 678          * If we are unable to find the current time, don't wait.
 679          */
 680         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 681         if (ret) {
 682                 return -1;
 683         }
 684         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 685         constructor_timeout->tv_nsec +=
 686                 (constructor_delay_ms % 1000UL) * 1000000UL;
 687         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 688                 constructor_timeout->tv_sec++;
 689                 constructor_timeout->tv_nsec -= 1000000000UL;
 690         }
 691         return 1;
 692 }
 693
 694 /*
 695  * sessiond monitoring thread: monitor presence of global and per-user
 696  * sessiond by polling the application common named pipe.
 697  */
 698 /* TODO */
 699
 700 void __attribute__((constructor)) lttng_ust_init(void)
 701 {
 702         struct timespec constructor_timeout;
 703         int timeout_mode;
 704         int ret;
 705
 706         if (uatomic_xchg(&initialized, 1) == 1)
 707                 return;
 708
 709         /*
 710          * We want precise control over the order in which we construct
 711          * our sub-libraries vs starting to receive commands from
 712          * sessiond (otherwise leading to errors when trying to create
 713          * sessiond before the init functions are completed).
 714          */
 715         init_usterr();
 716         init_tracepoint();
 717         ltt_ring_buffer_metadata_client_init();
 718         ltt_ring_buffer_client_overwrite_init();
 719         ltt_ring_buffer_client_discard_init();
 720
 721         timeout_mode = get_timeout(&constructor_timeout);
 722
 723         ret = sem_init(&constructor_wait, 0, 0);
 724         assert(!ret);
 725
 726         ret = setup_local_apps();
 727         if (ret) {
 728                 ERR("Error setting up to local apps");
 729         }
 730         ret = pthread_create(&local_apps.ust_listener, NULL,
 731                         ust_listener_thread, &local_apps);
 732
 733         if (local_apps.allowed) {
 734                 ret = pthread_create(&global_apps.ust_listener, NULL,
 735                                 ust_listener_thread, &global_apps);
 736         } else {
 737                 handle_register_done(&local_apps);
 738         }
 739
 740         switch (timeout_mode) {
 741         case 1: /* timeout wait */
 742                 do {
 743                         ret = sem_timedwait(&constructor_wait,
 744                                         &constructor_timeout);
 745                 } while (ret < 0 && errno == EINTR);
 746                 if (ret < 0 && errno == ETIMEDOUT) {
 747                         ERR("Timed out waiting for ltt-sessiond");
 748                 } else {
 749                         assert(!ret);
 750                 }
 751                 break;
 752         case -1:/* wait forever */
 753                 do {
 754                         ret = sem_wait(&constructor_wait);
 755                 } while (ret < 0 && errno == EINTR);
 756                 assert(!ret);
 757                 break;
 758         case 0: /* no timeout */
 759                 break;
 760         }
 761 }
 762
 763 static
 764 void lttng_ust_cleanup(int exiting)
 765 {
 766         cleanup_sock_info(&global_apps);
 767         if (local_apps.allowed) {
 768                 cleanup_sock_info(&local_apps);
 769         }
 770         lttng_ust_abi_exit();
 771         ltt_events_exit();
 772         ltt_ring_buffer_client_discard_exit();
 773         ltt_ring_buffer_client_overwrite_exit();
 774         ltt_ring_buffer_metadata_client_exit();
 775         exit_tracepoint();
 776         if (!exiting) {
 777                 /* Reinitialize values for fork */
 778                 sem_count = 2;
 779                 lttng_ust_comm_should_quit = 0;
 780                 initialized = 0;
 781         }
 782 }
 783
 784 void __attribute__((destructor)) lttng_ust_exit(void)
 785 {
 786         int ret;
 787
 788         /*
 789          * Using pthread_cancel here because:
 790          * A) we don't want to hang application teardown.
 791          * B) the thread is not allocating any resource.
 792          */
 793
 794         /*
 795          * Require the communication thread to quit. Synchronize with
 796          * mutexes to ensure it is not in a mutex critical section when
 797          * pthread_cancel is later called.
 798          */
 799         ust_lock();
 800         lttng_ust_comm_should_quit = 1;
 801         ust_unlock();
 802
 803         ret = pthread_cancel(global_apps.ust_listener);
 804         if (ret) {
 805                 ERR("Error cancelling global ust listener thread");
 806         }
 807         if (local_apps.allowed) {
 808                 ret = pthread_cancel(local_apps.ust_listener);
 809                 if (ret) {
 810                         ERR("Error cancelling local ust listener thread");
 811                 }
 812         }
 813         lttng_ust_cleanup(1);
 814 }
 815
 816 /*
 817  * We exclude the worker threads across fork and clone (except
 818  * CLONE_VM), because these system calls only keep the forking thread
 819  * running in the child.  Therefore, we don't want to call fork or clone
 820  * in the middle of an tracepoint or ust tracing state modification.
 821  * Holding this mutex protects these structures across fork and clone.
 822  */
 823 void ust_before_fork(ust_fork_info_t *fork_info)
 824 {
 825         /*
 826          * Disable signals. This is to avoid that the child intervenes
 827          * before it is properly setup for tracing. It is safer to
 828          * disable all signals, because then we know we are not breaking
 829          * anything by restoring the original mask.
 830          */
 831         sigset_t all_sigs;
 832         int ret;
 833
 834         /* Disable signals */
 835         sigfillset(&all_sigs);
 836         ret = sigprocmask(SIG_BLOCK, &all_sigs, &fork_info->orig_sigs);
 837         if (ret == -1) {
 838                 PERROR("sigprocmask");
 839         }
 840         ust_lock();
 841         rcu_bp_before_fork();
 842 }
 843
 844 static void ust_after_fork_common(ust_fork_info_t *fork_info)
 845 {
 846         int ret;
 847
 848         DBG("process %d", getpid());
 849         ust_unlock();
 850         /* Restore signals */
 851         ret = sigprocmask(SIG_SETMASK, &fork_info->orig_sigs, NULL);
 852         if (ret == -1) {
 853                 PERROR("sigprocmask");
 854         }
 855 }
 856
 857 void ust_after_fork_parent(ust_fork_info_t *fork_info)
 858 {
 859         DBG("process %d", getpid());
 860         rcu_bp_after_fork_parent();
 861         /* Release mutexes and reenable signals */
 862         ust_after_fork_common(fork_info);
 863 }
 864
 865 /*
 866  * After fork, in the child, we need to cleanup all the leftover state,
 867  * except the worker thread which already magically disappeared thanks
 868  * to the weird Linux fork semantics. After tyding up, we call
 869  * lttng_ust_init() again to start over as a new PID.
 870  *
 871  * This is meant for forks() that have tracing in the child between the
 872  * fork and following exec call (if there is any).
 873  */
 874 void ust_after_fork_child(ust_fork_info_t *fork_info)
 875 {
 876         DBG("process %d", getpid());
 877         /* Release urcu mutexes */
 878         rcu_bp_after_fork_child();
 879         lttng_ust_cleanup(0);
 880         /* Release mutexes and reenable signals */
 881         ust_after_fork_common(fork_info);
 882         lttng_ust_init();
 883 }