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         if (uatomic_read(&sem_count) <= 0) {
 221                 return 0;
 222         }
 223         ret = uatomic_add_return(&sem_count, -1);
 224         if (ret == 0) {
 225                 ret = sem_post(&constructor_wait);
 226                 assert(!ret);
 227         }
 228         return 0;
 229 }
 230
 231 static
 232 int handle_message(struct sock_info *sock_info,
 233                 int sock, struct lttcomm_ust_msg *lum)
 234 {
 235         int ret = 0;
 236         const struct objd_ops *ops;
 237         struct lttcomm_ust_reply lur;
 238
 239         ust_lock();
 240
 241         memset(&lur, 0, sizeof(lur));
 242
 243         if (lttng_ust_comm_should_quit) {
 244                 ret = -EPERM;
 245                 goto end;
 246         }
 247
 248         ops = objd_ops(lum->handle);
 249         if (!ops) {
 250                 ret = -ENOENT;
 251                 goto end;
 252         }
 253
 254         switch (lum->cmd) {
 255         case LTTNG_UST_REGISTER_DONE:
 256                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 257                         ret = handle_register_done(sock_info);
 258                 else
 259                         ret = -EINVAL;
 260                 break;
 261         case LTTNG_UST_RELEASE:
 262                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 263                         ret = -EPERM;
 264                 else
 265                         ret = objd_unref(lum->handle);
 266                 break;
 267         default:
 268                 if (ops->cmd)
 269                         ret = ops->cmd(lum->handle, lum->cmd,
 270                                         (unsigned long) &lum->u);
 271                 else
 272                         ret = -ENOSYS;
 273                 break;
 274         }
 275
 276 end:
 277         lur.handle = lum->handle;
 278         lur.cmd = lum->cmd;
 279         lur.ret_val = ret;
 280         if (ret >= 0) {
 281                 lur.ret_code = LTTCOMM_OK;
 282         } else {
 283                 lur.ret_code = LTTCOMM_SESSION_FAIL;
 284         }
 285         ret = send_reply(sock, &lur);
 286
 287         ust_unlock();
 288         return ret;
 289 }
 290
 291 static
 292 void cleanup_sock_info(struct sock_info *sock_info)
 293 {
 294         int ret;
 295
 296         if (sock_info->socket != -1) {
 297                 ret = close(sock_info->socket);
 298                 if (ret) {
 299                         ERR("Error closing apps socket");
 300                 }
 301                 sock_info->socket = -1;
 302         }
 303         if (sock_info->root_handle != -1) {
 304                 ret = objd_unref(sock_info->root_handle);
 305                 if (ret) {
 306                         ERR("Error unref root handle");
 307                 }
 308                 sock_info->root_handle = -1;
 309         }
 310         sock_info->constructor_sem_posted = 0;
 311         if (sock_info->wait_shm_mmap) {
 312                 ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
 313                 if (ret) {
 314                         ERR("Error unmapping wait shm");
 315                 }
 316                 sock_info->wait_shm_mmap = NULL;
 317         }
 318 }
 319
 320 /*
 321  * Using fork to set umask in the child process (not multi-thread safe).
 322  * We deal with the shm_open vs ftruncate race (happening when the
 323  * sessiond owns the shm and does not let everybody modify it, to ensure
 324  * safety against shm_unlink) by simply letting the mmap fail and
 325  * retrying after a few seconds.
 326  * For global shm, everybody has rw access to it until the sessiond
 327  * starts.
 328  */
 329 static
 330 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 331 {
 332         int wait_shm_fd, ret;
 333         pid_t pid;
 334
 335         /*
 336          * Try to open read-only.
 337          */
 338         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 339         if (wait_shm_fd >= 0) {
 340                 goto end;
 341         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 342                 /*
 343                  * Real-only open did not work, and it's not because the
 344                  * entry was not present. It's a failure that prohibits
 345                  * using shm.
 346                  */
 347                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 348                 goto end;
 349         }
 350         /*
 351          * If the open failed because the file did not exist, try
 352          * creating it ourself.
 353          */
 354         pid = fork();
 355         if (pid > 0) {
 356                 int status;
 357
 358                 /*
 359                  * Parent: wait for child to return, in which case the
 360                  * shared memory map will have been created.
 361                  */
 362                 pid = wait(&status);
 363                 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 364                         wait_shm_fd = -1;
 365                         goto end;
 366                 }
 367                 /*
 368                  * Try to open read-only again after creation.
 369                  */
 370                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 371                 if (wait_shm_fd < 0) {
 372                         /*
 373                          * Real-only open did not work. It's a failure
 374                          * that prohibits using shm.
 375                          */
 376                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 377                         goto end;
 378                 }
 379                 goto end;
 380         } else if (pid == 0) {
 381                 int create_mode;
 382
 383                 /* Child */
 384                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
 385                 if (sock_info->global)
 386                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
 387                 /*
 388                  * We're alone in a child process, so we can modify the
 389                  * process-wide umask.
 390                  */
 391                 umask(~create_mode);
 392                 /*
 393                  * Try creating shm (or get rw access).
 394                  * We don't do an exclusive open, because we allow other
 395                  * processes to create+ftruncate it concurrently.
 396                  */
 397                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 398                                 O_RDWR | O_CREAT, create_mode);
 399                 if (wait_shm_fd >= 0) {
 400                         ret = ftruncate(wait_shm_fd, mmap_size);
 401                         if (ret) {
 402                                 PERROR("ftruncate");
 403                                 exit(EXIT_FAILURE);
 404                         }
 405                         exit(EXIT_SUCCESS);
 406                 }
 407                 /*
 408                  * For local shm, we need to have rw access to accept
 409                  * opening it: this means the local sessiond will be
 410                  * able to wake us up. For global shm, we open it even
 411                  * if rw access is not granted, because the root.root
 412                  * sessiond will be able to override all rights and wake
 413                  * us up.
 414                  */
 415                 if (!sock_info->global && errno != EACCES) {
 416                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 417                         exit(EXIT_FAILURE);
 418                 }
 419                 /*
 420                  * The shm exists, but we cannot open it RW. Report
 421                  * success.
 422                  */
 423                 exit(EXIT_SUCCESS);
 424         } else {
 425                 return -1;
 426         }
 427 end:
 428         if (wait_shm_fd >= 0 && !sock_info->global) {
 429                 struct stat statbuf;
 430
 431                 /*
 432                  * Ensure that our user is the owner of the shm file for
 433                  * local shm. If we do not own the file, it means our
 434                  * sessiond will not have access to wake us up (there is
 435                  * probably a rogue process trying to fake our
 436                  * sessiond). Fallback to polling method in this case.
 437                  */
 438                 ret = fstat(wait_shm_fd, &statbuf);
 439                 if (ret) {
 440                         PERROR("fstat");
 441                         goto error_close;
 442                 }
 443                 if (statbuf.st_uid != getuid())
 444                         goto error_close;
 445         }
 446         return wait_shm_fd;
 447
 448 error_close:
 449         ret = close(wait_shm_fd);
 450         if (ret) {
 451                 PERROR("Error closing fd");
 452         }
 453         return -1;
 454 }
 455
 456 static
 457 char *get_map_shm(struct sock_info *sock_info)
 458 {
 459         size_t mmap_size = sysconf(_SC_PAGE_SIZE);
 460         int wait_shm_fd, ret;
 461         char *wait_shm_mmap;
 462
 463         wait_shm_fd = get_wait_shm(sock_info, mmap_size);
 464         if (wait_shm_fd < 0) {
 465                 goto error;
 466         }
 467         wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
 468                   MAP_SHARED, wait_shm_fd, 0);
 469         /* close shm fd immediately after taking the mmap reference */
 470         ret = close(wait_shm_fd);
 471         if (ret) {
 472                 PERROR("Error closing fd");
 473         }
 474         if (wait_shm_mmap == MAP_FAILED) {
 475                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
 476                 goto error;
 477         }
 478         return wait_shm_mmap;
 479
 480 error:
 481         return NULL;
 482 }
 483
 484 static
 485 void wait_for_sessiond(struct sock_info *sock_info)
 486 {
 487         int ret;
 488
 489         ust_lock();
 490         if (lttng_ust_comm_should_quit) {
 491                 goto quit;
 492         }
 493         if (wait_poll_fallback) {
 494                 goto error;
 495         }
 496         if (!sock_info->wait_shm_mmap) {
 497                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
 498                 if (!sock_info->wait_shm_mmap)
 499                         goto error;
 500         }
 501         ust_unlock();
 502
 503         DBG("Waiting for %s apps sessiond", sock_info->name);
 504         /* Wait for futex wakeup */
 505         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
 506                 ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
 507                         FUTEX_WAIT, 0, NULL, NULL, 0);
 508                 if (ret < 0) {
 509                         if (errno == EFAULT) {
 510                                 wait_poll_fallback = 1;
 511                                 ERR(
 512 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
 513 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
 514 "Please upgrade your kernel "
 515 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
 516 "mainline). LTTng-UST will use polling mode fallback.");
 517                         }
 518                         PERROR("futex");
 519                 }
 520         }
 521         return;
 522
 523 quit:
 524         ust_unlock();
 525         return;
 526
 527 error:
 528         ust_unlock();
 529         return;
 530 }
 531
 532 /*
 533  * This thread does not allocate any resource, except within
 534  * handle_message, within mutex protection. This mutex protects against
 535  * fork and exit.
 536  * The other moment it allocates resources is at socket connexion, which
 537  * is also protected by the mutex.
 538  */
 539 static
 540 void *ust_listener_thread(void *arg)
 541 {
 542         struct sock_info *sock_info = arg;
 543         int sock, ret, prev_connect_failed = 0, has_waited = 0;
 544
 545         /* Restart trying to connect to the session daemon */
 546 restart:
 547         if (prev_connect_failed) {
 548                 /* Wait for sessiond availability with pipe */
 549                 wait_for_sessiond(sock_info);
 550                 if (has_waited) {
 551                         has_waited = 0;
 552                         /*
 553                          * Sleep for 5 seconds before retrying after a
 554                          * sequence of failure / wait / failure. This
 555                          * deals with a killed or broken session daemon.
 556                          */
 557                         sleep(5);
 558                 }
 559                 has_waited = 1;
 560                 prev_connect_failed = 0;
 561         }
 562         ust_lock();
 563
 564         if (lttng_ust_comm_should_quit) {
 565                 ust_unlock();
 566                 goto quit;
 567         }
 568
 569         if (sock_info->socket != -1) {
 570                 ret = close(sock_info->socket);
 571                 if (ret) {
 572                         ERR("Error closing %s apps socket", sock_info->name);
 573                 }
 574                 sock_info->socket = -1;
 575         }
 576
 577         /* Register */
 578         ret = lttcomm_connect_unix_sock(sock_info->sock_path);
 579         if (ret < 0) {
 580                 ERR("Error connecting to %s apps socket", sock_info->name);
 581                 prev_connect_failed = 1;
 582                 /*
 583                  * If we cannot find the sessiond daemon, don't delay
 584                  * constructor execution.
 585                  */
 586                 ret = handle_register_done(sock_info);
 587                 assert(!ret);
 588                 ust_unlock();
 589                 goto restart;
 590         }
 591
 592         sock_info->socket = sock = ret;
 593
 594         /*
 595          * Create only one root handle per listener thread for the whole
 596          * process lifetime.
 597          */
 598         if (sock_info->root_handle == -1) {
 599                 ret = lttng_abi_create_root_handle();
 600                 if (ret) {
 601                         ERR("Error creating root handle");
 602                         ust_unlock();
 603                         goto quit;
 604                 }
 605                 sock_info->root_handle = ret;
 606         }
 607
 608         ret = register_app_to_sessiond(sock);
 609         if (ret < 0) {
 610                 ERR("Error registering to %s apps socket", sock_info->name);
 611                 prev_connect_failed = 1;
 612                 /*
 613                  * If we cannot register to the sessiond daemon, don't
 614                  * delay constructor execution.
 615                  */
 616                 ret = handle_register_done(sock_info);
 617                 assert(!ret);
 618                 ust_unlock();
 619                 goto restart;
 620         }
 621         ust_unlock();
 622
 623         for (;;) {
 624                 ssize_t len;
 625                 struct lttcomm_ust_msg lum;
 626
 627                 len = lttcomm_recv_unix_sock(sock, &lum, sizeof(lum));
 628                 switch (len) {
 629                 case 0: /* orderly shutdown */
 630                         DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
 631                         goto end;
 632                 case sizeof(lum):
 633                         DBG("message received\n");
 634                         ret = handle_message(sock_info, sock, &lum);
 635                         if (ret < 0) {
 636                                 ERR("Error handling message for %s socket", sock_info->name);
 637                         }
 638                         continue;
 639                 case -1:
 640                         if (errno == ECONNRESET) {
 641                                 ERR("%s remote end closed connection\n", sock_info->name);
 642                                 goto end;
 643                         }
 644                         goto end;
 645                 default:
 646                         ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
 647                         continue;
 648                 }
 649
 650         }
 651 end:
 652         goto restart;   /* try to reconnect */
 653 quit:
 654         return NULL;
 655 }
 656
 657 /*
 658  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 659  */
 660 static
 661 int get_timeout(struct timespec *constructor_timeout)
 662 {
 663         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 664         char *str_delay;
 665         int ret;
 666
 667         str_delay = getenv("UST_REGISTER_TIMEOUT");
 668         if (str_delay) {
 669                 constructor_delay_ms = strtol(str_delay, NULL, 10);
 670         }
 671
 672         switch (constructor_delay_ms) {
 673         case -1:/* fall-through */
 674         case 0:
 675                 return constructor_delay_ms;
 676         default:
 677                 break;
 678         }
 679
 680         /*
 681          * If we are unable to find the current time, don't wait.
 682          */
 683         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 684         if (ret) {
 685                 return -1;
 686         }
 687         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 688         constructor_timeout->tv_nsec +=
 689                 (constructor_delay_ms % 1000UL) * 1000000UL;
 690         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 691                 constructor_timeout->tv_sec++;
 692                 constructor_timeout->tv_nsec -= 1000000000UL;
 693         }
 694         return 1;
 695 }
 696
 697 /*
 698  * sessiond monitoring thread: monitor presence of global and per-user
 699  * sessiond by polling the application common named pipe.
 700  */
 701 /* TODO */
 702
 703 void __attribute__((constructor)) lttng_ust_init(void)
 704 {
 705         struct timespec constructor_timeout;
 706         int timeout_mode;
 707         int ret;
 708
 709         if (uatomic_xchg(&initialized, 1) == 1)
 710                 return;
 711
 712         /*
 713          * We want precise control over the order in which we construct
 714          * our sub-libraries vs starting to receive commands from
 715          * sessiond (otherwise leading to errors when trying to create
 716          * sessiond before the init functions are completed).
 717          */
 718         init_usterr();
 719         init_tracepoint();
 720         ltt_ring_buffer_metadata_client_init();
 721         ltt_ring_buffer_client_overwrite_init();
 722         ltt_ring_buffer_client_discard_init();
 723
 724         timeout_mode = get_timeout(&constructor_timeout);
 725
 726         ret = sem_init(&constructor_wait, 0, 0);
 727         assert(!ret);
 728
 729         ret = setup_local_apps();
 730         if (ret) {
 731                 ERR("Error setting up to local apps");
 732         }
 733         ret = pthread_create(&local_apps.ust_listener, NULL,
 734                         ust_listener_thread, &local_apps);
 735
 736         if (local_apps.allowed) {
 737                 ret = pthread_create(&global_apps.ust_listener, NULL,
 738                                 ust_listener_thread, &global_apps);
 739         } else {
 740                 handle_register_done(&local_apps);
 741         }
 742
 743         switch (timeout_mode) {
 744         case 1: /* timeout wait */
 745                 do {
 746                         ret = sem_timedwait(&constructor_wait,
 747                                         &constructor_timeout);
 748                 } while (ret < 0 && errno == EINTR);
 749                 if (ret < 0 && errno == ETIMEDOUT) {
 750                         ERR("Timed out waiting for ltt-sessiond");
 751                 } else {
 752                         assert(!ret);
 753                 }
 754                 break;
 755         case -1:/* wait forever */
 756                 do {
 757                         ret = sem_wait(&constructor_wait);
 758                 } while (ret < 0 && errno == EINTR);
 759                 assert(!ret);
 760                 break;
 761         case 0: /* no timeout */
 762                 break;
 763         }
 764 }
 765
 766 static
 767 void lttng_ust_cleanup(int exiting)
 768 {
 769         cleanup_sock_info(&global_apps);
 770         if (local_apps.allowed) {
 771                 cleanup_sock_info(&local_apps);
 772         }
 773         lttng_ust_abi_exit();
 774         ltt_events_exit();
 775         ltt_ring_buffer_client_discard_exit();
 776         ltt_ring_buffer_client_overwrite_exit();
 777         ltt_ring_buffer_metadata_client_exit();
 778         exit_tracepoint();
 779         if (!exiting) {
 780                 /* Reinitialize values for fork */
 781                 sem_count = 2;
 782                 lttng_ust_comm_should_quit = 0;
 783                 initialized = 0;
 784         }
 785 }
 786
 787 void __attribute__((destructor)) lttng_ust_exit(void)
 788 {
 789         int ret;
 790
 791         /*
 792          * Using pthread_cancel here because:
 793          * A) we don't want to hang application teardown.
 794          * B) the thread is not allocating any resource.
 795          */
 796
 797         /*
 798          * Require the communication thread to quit. Synchronize with
 799          * mutexes to ensure it is not in a mutex critical section when
 800          * pthread_cancel is later called.
 801          */
 802         ust_lock();
 803         lttng_ust_comm_should_quit = 1;
 804         ust_unlock();
 805
 806         ret = pthread_cancel(global_apps.ust_listener);
 807         if (ret) {
 808                 ERR("Error cancelling global ust listener thread");
 809         }
 810         if (local_apps.allowed) {
 811                 ret = pthread_cancel(local_apps.ust_listener);
 812                 if (ret) {
 813                         ERR("Error cancelling local ust listener thread");
 814                 }
 815         }
 816         lttng_ust_cleanup(1);
 817 }
 818
 819 /*
 820  * We exclude the worker threads across fork and clone (except
 821  * CLONE_VM), because these system calls only keep the forking thread
 822  * running in the child.  Therefore, we don't want to call fork or clone
 823  * in the middle of an tracepoint or ust tracing state modification.
 824  * Holding this mutex protects these structures across fork and clone.
 825  */
 826 void ust_before_fork(ust_fork_info_t *fork_info)
 827 {
 828         /*
 829          * Disable signals. This is to avoid that the child intervenes
 830          * before it is properly setup for tracing. It is safer to
 831          * disable all signals, because then we know we are not breaking
 832          * anything by restoring the original mask.
 833          */
 834         sigset_t all_sigs;
 835         int ret;
 836
 837         /* Disable signals */
 838         sigfillset(&all_sigs);
 839         ret = sigprocmask(SIG_BLOCK, &all_sigs, &fork_info->orig_sigs);
 840         if (ret == -1) {
 841                 PERROR("sigprocmask");
 842         }
 843         ust_lock();
 844         rcu_bp_before_fork();
 845 }
 846
 847 static void ust_after_fork_common(ust_fork_info_t *fork_info)
 848 {
 849         int ret;
 850
 851         DBG("process %d", getpid());
 852         ust_unlock();
 853         /* Restore signals */
 854         ret = sigprocmask(SIG_SETMASK, &fork_info->orig_sigs, NULL);
 855         if (ret == -1) {
 856                 PERROR("sigprocmask");
 857         }
 858 }
 859
 860 void ust_after_fork_parent(ust_fork_info_t *fork_info)
 861 {
 862         DBG("process %d", getpid());
 863         rcu_bp_after_fork_parent();
 864         /* Release mutexes and reenable signals */
 865         ust_after_fork_common(fork_info);
 866 }
 867
 868 /*
 869  * After fork, in the child, we need to cleanup all the leftover state,
 870  * except the worker thread which already magically disappeared thanks
 871  * to the weird Linux fork semantics. After tyding up, we call
 872  * lttng_ust_init() again to start over as a new PID.
 873  *
 874  * This is meant for forks() that have tracing in the child between the
 875  * fork and following exec call (if there is any).
 876  */
 877 void ust_after_fork_child(ust_fork_info_t *fork_info)
 878 {
 879         DBG("process %d", getpid());
 880         /* Release urcu mutexes */
 881         rcu_bp_after_fork_child();
 882         lttng_ust_cleanup(0);
 883         /* Release mutexes and reenable signals */
 884         ust_after_fork_common(fork_info);
 885         lttng_ust_init();
 886 }