liblttng-ust/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-events.h>
  42 #include <lttng/ust-abi.h>
  43 #include <lttng/ust.h>
  44 #include <ust-comm.h>
  45 #include <usterr-signal-safe.h>
  46 #include "tracepoint-internal.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 = ustcomm_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 ustcomm_ust_reply *lur)
 192 {
 193         ssize_t len;
 194
 195         len = ustcomm_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 ustcomm_ust_msg *lum)
 234 {
 235         int ret = 0;
 236         const struct lttng_ust_objd_ops *ops;
 237         struct ustcomm_ust_reply lur;
 238         int shm_fd, wait_fd;
 239
 240         ust_lock();
 241
 242         memset(&lur, 0, sizeof(lur));
 243
 244         if (lttng_ust_comm_should_quit) {
 245                 ret = -EPERM;
 246                 goto end;
 247         }
 248
 249         ops = objd_ops(lum->handle);
 250         if (!ops) {
 251                 ret = -ENOENT;
 252                 goto end;
 253         }
 254
 255         switch (lum->cmd) {
 256         case LTTNG_UST_REGISTER_DONE:
 257                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 258                         ret = handle_register_done(sock_info);
 259                 else
 260                         ret = -EINVAL;
 261                 break;
 262         case LTTNG_UST_RELEASE:
 263                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 264                         ret = -EPERM;
 265                 else
 266                         ret = lttng_ust_objd_unref(lum->handle);
 267                 break;
 268         default:
 269                 if (ops->cmd)
 270                         ret = ops->cmd(lum->handle, lum->cmd,
 271                                         (unsigned long) &lum->u);
 272                 else
 273                         ret = -ENOSYS;
 274                 break;
 275         }
 276
 277 end:
 278         lur.handle = lum->handle;
 279         lur.cmd = lum->cmd;
 280         lur.ret_val = ret;
 281         if (ret >= 0) {
 282                 lur.ret_code = USTCOMM_OK;
 283         } else {
 284                 //lur.ret_code = USTCOMM_SESSION_FAIL;
 285                 lur.ret_code = ret;
 286         }
 287         switch (lum->cmd) {
 288         case LTTNG_UST_STREAM:
 289                 /*
 290                  * Special-case reply to send stream info.
 291                  * Use lum.u output.
 292                  */
 293                 lur.u.stream.memory_map_size = lum->u.stream.memory_map_size;
 294                 shm_fd = lum->u.stream.shm_fd;
 295                 wait_fd = lum->u.stream.wait_fd;
 296                 break;
 297         case LTTNG_UST_METADATA:
 298         case LTTNG_UST_CHANNEL:
 299                 lur.u.channel.memory_map_size = lum->u.channel.memory_map_size;
 300                 shm_fd = lum->u.channel.shm_fd;
 301                 wait_fd = lum->u.channel.wait_fd;
 302                 break;
 303         case LTTNG_UST_TRACER_VERSION:
 304                 lur.u.version = lum->u.version;
 305                 break;
 306         case LTTNG_UST_TRACEPOINT_LIST_GET:
 307                 memcpy(lur.u.tracepoint_list_entry,
 308                         lum->u.tracepoint_list_entry,
 309                         LTTNG_UST_SYM_NAME_LEN);
 310                 break;
 311         }
 312         ret = send_reply(sock, &lur);
 313         if (ret < 0) {
 314                 perror("error sending reply");
 315                 goto error;
 316         }
 317
 318         if ((lum->cmd == LTTNG_UST_STREAM
 319              || lum->cmd == LTTNG_UST_CHANNEL
 320              || lum->cmd == LTTNG_UST_METADATA)
 321                         && lur.ret_code == USTCOMM_OK) {
 322                 /* we also need to send the file descriptors. */
 323                 ret = ustcomm_send_fds_unix_sock(sock,
 324                         &shm_fd, &shm_fd,
 325                         1, sizeof(int));
 326                 if (ret < 0) {
 327                         perror("send shm_fd");
 328                         goto error;
 329                 }
 330                 ret = ustcomm_send_fds_unix_sock(sock,
 331                         &wait_fd, &wait_fd,
 332                         1, sizeof(int));
 333                 if (ret < 0) {
 334                         perror("send wait_fd");
 335                         goto error;
 336                 }
 337         }
 338 error:
 339         ust_unlock();
 340         return ret;
 341 }
 342
 343 static
 344 void cleanup_sock_info(struct sock_info *sock_info)
 345 {
 346         int ret;
 347
 348         if (sock_info->socket != -1) {
 349                 ret = close(sock_info->socket);
 350                 if (ret) {
 351                         ERR("Error closing apps socket");
 352                 }
 353                 sock_info->socket = -1;
 354         }
 355         if (sock_info->root_handle != -1) {
 356                 ret = lttng_ust_objd_unref(sock_info->root_handle);
 357                 if (ret) {
 358                         ERR("Error unref root handle");
 359                 }
 360                 sock_info->root_handle = -1;
 361         }
 362         sock_info->constructor_sem_posted = 0;
 363         if (sock_info->wait_shm_mmap) {
 364                 ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
 365                 if (ret) {
 366                         ERR("Error unmapping wait shm");
 367                 }
 368                 sock_info->wait_shm_mmap = NULL;
 369         }
 370 }
 371
 372 /*
 373  * Using fork to set umask in the child process (not multi-thread safe).
 374  * We deal with the shm_open vs ftruncate race (happening when the
 375  * sessiond owns the shm and does not let everybody modify it, to ensure
 376  * safety against shm_unlink) by simply letting the mmap fail and
 377  * retrying after a few seconds.
 378  * For global shm, everybody has rw access to it until the sessiond
 379  * starts.
 380  */
 381 static
 382 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 383 {
 384         int wait_shm_fd, ret;
 385         pid_t pid;
 386
 387         /*
 388          * Try to open read-only.
 389          */
 390         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 391         if (wait_shm_fd >= 0) {
 392                 goto end;
 393         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 394                 /*
 395                  * Real-only open did not work, and it's not because the
 396                  * entry was not present. It's a failure that prohibits
 397                  * using shm.
 398                  */
 399                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 400                 goto end;
 401         }
 402         /*
 403          * If the open failed because the file did not exist, try
 404          * creating it ourself.
 405          */
 406         pid = fork();
 407         if (pid > 0) {
 408                 int status;
 409
 410                 /*
 411                  * Parent: wait for child to return, in which case the
 412                  * shared memory map will have been created.
 413                  */
 414                 pid = wait(&status);
 415                 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 416                         wait_shm_fd = -1;
 417                         goto end;
 418                 }
 419                 /*
 420                  * Try to open read-only again after creation.
 421                  */
 422                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 423                 if (wait_shm_fd < 0) {
 424                         /*
 425                          * Real-only open did not work. It's a failure
 426                          * that prohibits using shm.
 427                          */
 428                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 429                         goto end;
 430                 }
 431                 goto end;
 432         } else if (pid == 0) {
 433                 int create_mode;
 434
 435                 /* Child */
 436                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
 437                 if (sock_info->global)
 438                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
 439                 /*
 440                  * We're alone in a child process, so we can modify the
 441                  * process-wide umask.
 442                  */
 443                 umask(~create_mode);
 444                 /*
 445                  * Try creating shm (or get rw access).
 446                  * We don't do an exclusive open, because we allow other
 447                  * processes to create+ftruncate it concurrently.
 448                  */
 449                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 450                                 O_RDWR | O_CREAT, create_mode);
 451                 if (wait_shm_fd >= 0) {
 452                         ret = ftruncate(wait_shm_fd, mmap_size);
 453                         if (ret) {
 454                                 PERROR("ftruncate");
 455                                 exit(EXIT_FAILURE);
 456                         }
 457                         exit(EXIT_SUCCESS);
 458                 }
 459                 /*
 460                  * For local shm, we need to have rw access to accept
 461                  * opening it: this means the local sessiond will be
 462                  * able to wake us up. For global shm, we open it even
 463                  * if rw access is not granted, because the root.root
 464                  * sessiond will be able to override all rights and wake
 465                  * us up.
 466                  */
 467                 if (!sock_info->global && errno != EACCES) {
 468                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 469                         exit(EXIT_FAILURE);
 470                 }
 471                 /*
 472                  * The shm exists, but we cannot open it RW. Report
 473                  * success.
 474                  */
 475                 exit(EXIT_SUCCESS);
 476         } else {
 477                 return -1;
 478         }
 479 end:
 480         if (wait_shm_fd >= 0 && !sock_info->global) {
 481                 struct stat statbuf;
 482
 483                 /*
 484                  * Ensure that our user is the owner of the shm file for
 485                  * local shm. If we do not own the file, it means our
 486                  * sessiond will not have access to wake us up (there is
 487                  * probably a rogue process trying to fake our
 488                  * sessiond). Fallback to polling method in this case.
 489                  */
 490                 ret = fstat(wait_shm_fd, &statbuf);
 491                 if (ret) {
 492                         PERROR("fstat");
 493                         goto error_close;
 494                 }
 495                 if (statbuf.st_uid != getuid())
 496                         goto error_close;
 497         }
 498         return wait_shm_fd;
 499
 500 error_close:
 501         ret = close(wait_shm_fd);
 502         if (ret) {
 503                 PERROR("Error closing fd");
 504         }
 505         return -1;
 506 }
 507
 508 static
 509 char *get_map_shm(struct sock_info *sock_info)
 510 {
 511         size_t mmap_size = sysconf(_SC_PAGE_SIZE);
 512         int wait_shm_fd, ret;
 513         char *wait_shm_mmap;
 514
 515         wait_shm_fd = get_wait_shm(sock_info, mmap_size);
 516         if (wait_shm_fd < 0) {
 517                 goto error;
 518         }
 519         wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
 520                   MAP_SHARED, wait_shm_fd, 0);
 521         /* close shm fd immediately after taking the mmap reference */
 522         ret = close(wait_shm_fd);
 523         if (ret) {
 524                 PERROR("Error closing fd");
 525         }
 526         if (wait_shm_mmap == MAP_FAILED) {
 527                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
 528                 goto error;
 529         }
 530         return wait_shm_mmap;
 531
 532 error:
 533         return NULL;
 534 }
 535
 536 static
 537 void wait_for_sessiond(struct sock_info *sock_info)
 538 {
 539         int ret;
 540
 541         ust_lock();
 542         if (lttng_ust_comm_should_quit) {
 543                 goto quit;
 544         }
 545         if (wait_poll_fallback) {
 546                 goto error;
 547         }
 548         if (!sock_info->wait_shm_mmap) {
 549                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
 550                 if (!sock_info->wait_shm_mmap)
 551                         goto error;
 552         }
 553         ust_unlock();
 554
 555         DBG("Waiting for %s apps sessiond", sock_info->name);
 556         /* Wait for futex wakeup */
 557         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
 558                 ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
 559                         FUTEX_WAIT, 0, NULL, NULL, 0);
 560                 if (ret < 0) {
 561                         if (errno == EFAULT) {
 562                                 wait_poll_fallback = 1;
 563                                 WARN(
 564 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
 565 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
 566 "Please upgrade your kernel "
 567 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
 568 "mainline). LTTng-UST will use polling mode fallback.");
 569                         }
 570                         PERROR("futex");
 571                 }
 572         }
 573         return;
 574
 575 quit:
 576         ust_unlock();
 577         return;
 578
 579 error:
 580         ust_unlock();
 581         return;
 582 }
 583
 584 /*
 585  * This thread does not allocate any resource, except within
 586  * handle_message, within mutex protection. This mutex protects against
 587  * fork and exit.
 588  * The other moment it allocates resources is at socket connexion, which
 589  * is also protected by the mutex.
 590  */
 591 static
 592 void *ust_listener_thread(void *arg)
 593 {
 594         struct sock_info *sock_info = arg;
 595         int sock, ret, prev_connect_failed = 0, has_waited = 0;
 596
 597         /* Restart trying to connect to the session daemon */
 598 restart:
 599         if (prev_connect_failed) {
 600                 /* Wait for sessiond availability with pipe */
 601                 wait_for_sessiond(sock_info);
 602                 if (has_waited) {
 603                         has_waited = 0;
 604                         /*
 605                          * Sleep for 5 seconds before retrying after a
 606                          * sequence of failure / wait / failure. This
 607                          * deals with a killed or broken session daemon.
 608                          */
 609                         sleep(5);
 610                 }
 611                 has_waited = 1;
 612                 prev_connect_failed = 0;
 613         }
 614         ust_lock();
 615
 616         if (lttng_ust_comm_should_quit) {
 617                 ust_unlock();
 618                 goto quit;
 619         }
 620
 621         if (sock_info->socket != -1) {
 622                 ret = close(sock_info->socket);
 623                 if (ret) {
 624                         ERR("Error closing %s apps socket", sock_info->name);
 625                 }
 626                 sock_info->socket = -1;
 627         }
 628
 629         /* Register */
 630         ret = ustcomm_connect_unix_sock(sock_info->sock_path);
 631         if (ret < 0) {
 632                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
 633                 prev_connect_failed = 1;
 634                 /*
 635                  * If we cannot find the sessiond daemon, don't delay
 636                  * constructor execution.
 637                  */
 638                 ret = handle_register_done(sock_info);
 639                 assert(!ret);
 640                 ust_unlock();
 641                 goto restart;
 642         }
 643
 644         sock_info->socket = sock = ret;
 645
 646         /*
 647          * Create only one root handle per listener thread for the whole
 648          * process lifetime.
 649          */
 650         if (sock_info->root_handle == -1) {
 651                 ret = lttng_abi_create_root_handle();
 652                 if (ret < 0) {
 653                         ERR("Error creating root handle");
 654                         ust_unlock();
 655                         goto quit;
 656                 }
 657                 sock_info->root_handle = ret;
 658         }
 659
 660         ret = register_app_to_sessiond(sock);
 661         if (ret < 0) {
 662                 ERR("Error registering to %s apps socket", sock_info->name);
 663                 prev_connect_failed = 1;
 664                 /*
 665                  * If we cannot register to the sessiond daemon, don't
 666                  * delay constructor execution.
 667                  */
 668                 ret = handle_register_done(sock_info);
 669                 assert(!ret);
 670                 ust_unlock();
 671                 goto restart;
 672         }
 673         ust_unlock();
 674
 675         for (;;) {
 676                 ssize_t len;
 677                 struct ustcomm_ust_msg lum;
 678
 679                 len = ustcomm_recv_unix_sock(sock, &lum, sizeof(lum));
 680                 switch (len) {
 681                 case 0: /* orderly shutdown */
 682                         DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
 683                         goto end;
 684                 case sizeof(lum):
 685                         DBG("message received\n");
 686                         ret = handle_message(sock_info, sock, &lum);
 687                         if (ret < 0) {
 688                                 ERR("Error handling message for %s socket", sock_info->name);
 689                         }
 690                         continue;
 691                 case -1:
 692                         if (errno == ECONNRESET) {
 693                                 ERR("%s remote end closed connection\n", sock_info->name);
 694                                 goto end;
 695                         }
 696                         goto end;
 697                 default:
 698                         ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
 699                         continue;
 700                 }
 701
 702         }
 703 end:
 704         goto restart;   /* try to reconnect */
 705 quit:
 706         return NULL;
 707 }
 708
 709 /*
 710  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 711  */
 712 static
 713 int get_timeout(struct timespec *constructor_timeout)
 714 {
 715         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 716         char *str_delay;
 717         int ret;
 718
 719         str_delay = getenv("LTTNG_UST_REGISTER_TIMEOUT");
 720         if (str_delay) {
 721                 constructor_delay_ms = strtol(str_delay, NULL, 10);
 722         }
 723
 724         switch (constructor_delay_ms) {
 725         case -1:/* fall-through */
 726         case 0:
 727                 return constructor_delay_ms;
 728         default:
 729                 break;
 730         }
 731
 732         /*
 733          * If we are unable to find the current time, don't wait.
 734          */
 735         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 736         if (ret) {
 737                 return -1;
 738         }
 739         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 740         constructor_timeout->tv_nsec +=
 741                 (constructor_delay_ms % 1000UL) * 1000000UL;
 742         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 743                 constructor_timeout->tv_sec++;
 744                 constructor_timeout->tv_nsec -= 1000000000UL;
 745         }
 746         return 1;
 747 }
 748
 749 /*
 750  * sessiond monitoring thread: monitor presence of global and per-user
 751  * sessiond by polling the application common named pipe.
 752  */
 753 /* TODO */
 754
 755 void __attribute__((constructor)) lttng_ust_init(void)
 756 {
 757         struct timespec constructor_timeout;
 758         int timeout_mode;
 759         int ret;
 760
 761         if (uatomic_xchg(&initialized, 1) == 1)
 762                 return;
 763
 764         /*
 765          * We want precise control over the order in which we construct
 766          * our sub-libraries vs starting to receive commands from
 767          * sessiond (otherwise leading to errors when trying to create
 768          * sessiond before the init functions are completed).
 769          */
 770         init_usterr();
 771         init_tracepoint();
 772         ltt_ring_buffer_metadata_client_init();
 773         ltt_ring_buffer_client_overwrite_init();
 774         ltt_ring_buffer_client_discard_init();
 775
 776         timeout_mode = get_timeout(&constructor_timeout);
 777
 778         ret = sem_init(&constructor_wait, 0, 0);
 779         assert(!ret);
 780
 781         ret = setup_local_apps();
 782         if (ret) {
 783                 ERR("Error setting up to local apps");
 784         }
 785         ret = pthread_create(&local_apps.ust_listener, NULL,
 786                         ust_listener_thread, &local_apps);
 787
 788         if (local_apps.allowed) {
 789                 ret = pthread_create(&global_apps.ust_listener, NULL,
 790                                 ust_listener_thread, &global_apps);
 791         } else {
 792                 handle_register_done(&local_apps);
 793         }
 794
 795         switch (timeout_mode) {
 796         case 1: /* timeout wait */
 797                 do {
 798                         ret = sem_timedwait(&constructor_wait,
 799                                         &constructor_timeout);
 800                 } while (ret < 0 && errno == EINTR);
 801                 if (ret < 0 && errno == ETIMEDOUT) {
 802                         ERR("Timed out waiting for ltt-sessiond");
 803                 } else {
 804                         assert(!ret);
 805                 }
 806                 break;
 807         case -1:/* wait forever */
 808                 do {
 809                         ret = sem_wait(&constructor_wait);
 810                 } while (ret < 0 && errno == EINTR);
 811                 assert(!ret);
 812                 break;
 813         case 0: /* no timeout */
 814                 break;
 815         }
 816 }
 817
 818 static
 819 void lttng_ust_cleanup(int exiting)
 820 {
 821         cleanup_sock_info(&global_apps);
 822         if (local_apps.allowed) {
 823                 cleanup_sock_info(&local_apps);
 824         }
 825         lttng_ust_abi_exit();
 826         lttng_ust_events_exit();
 827         ltt_ring_buffer_client_discard_exit();
 828         ltt_ring_buffer_client_overwrite_exit();
 829         ltt_ring_buffer_metadata_client_exit();
 830         exit_tracepoint();
 831         if (!exiting) {
 832                 /* Reinitialize values for fork */
 833                 sem_count = 2;
 834                 lttng_ust_comm_should_quit = 0;
 835                 initialized = 0;
 836         }
 837 }
 838
 839 void __attribute__((destructor)) lttng_ust_exit(void)
 840 {
 841         int ret;
 842
 843         /*
 844          * Using pthread_cancel here because:
 845          * A) we don't want to hang application teardown.
 846          * B) the thread is not allocating any resource.
 847          */
 848
 849         /*
 850          * Require the communication thread to quit. Synchronize with
 851          * mutexes to ensure it is not in a mutex critical section when
 852          * pthread_cancel is later called.
 853          */
 854         ust_lock();
 855         lttng_ust_comm_should_quit = 1;
 856         ust_unlock();
 857
 858         ret = pthread_cancel(global_apps.ust_listener);
 859         if (ret) {
 860                 ERR("Error cancelling global ust listener thread");
 861         }
 862         if (local_apps.allowed) {
 863                 ret = pthread_cancel(local_apps.ust_listener);
 864                 if (ret) {
 865                         ERR("Error cancelling local ust listener thread");
 866                 }
 867         }
 868         lttng_ust_cleanup(1);
 869 }
 870
 871 /*
 872  * We exclude the worker threads across fork and clone (except
 873  * CLONE_VM), because these system calls only keep the forking thread
 874  * running in the child.  Therefore, we don't want to call fork or clone
 875  * in the middle of an tracepoint or ust tracing state modification.
 876  * Holding this mutex protects these structures across fork and clone.
 877  */
 878 void ust_before_fork(sigset_t *save_sigset)
 879 {
 880         /*
 881          * Disable signals. This is to avoid that the child intervenes
 882          * before it is properly setup for tracing. It is safer to
 883          * disable all signals, because then we know we are not breaking
 884          * anything by restoring the original mask.
 885          */
 886         sigset_t all_sigs;
 887         int ret;
 888
 889         /* Disable signals */
 890         sigfillset(&all_sigs);
 891         ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
 892         if (ret == -1) {
 893                 PERROR("sigprocmask");
 894         }
 895         ust_lock();
 896         rcu_bp_before_fork();
 897 }
 898
 899 static void ust_after_fork_common(sigset_t *restore_sigset)
 900 {
 901         int ret;
 902
 903         DBG("process %d", getpid());
 904         ust_unlock();
 905         /* Restore signals */
 906         ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
 907         if (ret == -1) {
 908                 PERROR("sigprocmask");
 909         }
 910 }
 911
 912 void ust_after_fork_parent(sigset_t *restore_sigset)
 913 {
 914         DBG("process %d", getpid());
 915         rcu_bp_after_fork_parent();
 916         /* Release mutexes and reenable signals */
 917         ust_after_fork_common(restore_sigset);
 918 }
 919
 920 /*
 921  * After fork, in the child, we need to cleanup all the leftover state,
 922  * except the worker thread which already magically disappeared thanks
 923  * to the weird Linux fork semantics. After tyding up, we call
 924  * lttng_ust_init() again to start over as a new PID.
 925  *
 926  * This is meant for forks() that have tracing in the child between the
 927  * fork and following exec call (if there is any).
 928  */
 929 void ust_after_fork_child(sigset_t *restore_sigset)
 930 {
 931         DBG("process %d", getpid());
 932         /* Release urcu mutexes */
 933         rcu_bp_after_fork_child();
 934         lttng_ust_cleanup(0);
 935         lttng_context_vtid_reset();
 936         /* Release mutexes and reenable signals */
 937         ust_after_fork_common(restore_sigset);
 938         lttng_ust_init();
 939 }