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/lttng-events.h>
  43 #include <ust/usterr-signal-safe.h>
  44 #include <ust/lttng-ust-abi.h>
  45 #include <ust/tracepoint.h>
  46 #include <ust/tracepoint-internal.h>
  47 #include <ust/ust.h>
  48 #include "ltt-tracer-core.h"
  49
  50 /*
  51  * Has lttng ust comm constructor been called ?
  52  */
  53 static int initialized;
  54
  55 /*
  56  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  57  * Held when handling a command, also held by fork() to deal with
  58  * removal of threads, and by exit path.
  59  */
  60
  61 /* Should the ust comm thread quit ? */
  62 static int lttng_ust_comm_should_quit;
  63
  64 /*
  65  * Wait for either of these before continuing to the main
  66  * program:
  67  * - the register_done message from sessiond daemon
  68  *   (will let the sessiond daemon enable sessions before main
  69  *   starts.)
  70  * - sessiond daemon is not reachable.
  71  * - timeout (ensuring applications are resilient to session
  72  *   daemon problems).
  73  */
  74 static sem_t constructor_wait;
  75 /*
  76  * Doing this for both the global and local sessiond.
  77  */
  78 static int sem_count = { 2 };
  79
  80 /*
  81  * Info about socket and associated listener thread.
  82  */
  83 struct sock_info {
  84         const char *name;
  85         pthread_t ust_listener; /* listener thread */
  86         int root_handle;
  87         int constructor_sem_posted;
  88         int allowed;
  89         int global;
  90
  91         char sock_path[PATH_MAX];
  92         int socket;
  93
  94         char wait_shm_path[PATH_MAX];
  95         char *wait_shm_mmap;
  96 };
  97
  98 /* Socket from app (connect) to session daemon (listen) for communication */
  99 struct sock_info global_apps = {
 100         .name = "global",
 101         .global = 1,
 102
 103         .root_handle = -1,
 104         .allowed = 1,
 105
 106         .sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
 107         .socket = -1,
 108
 109         .wait_shm_path = DEFAULT_GLOBAL_APPS_WAIT_SHM_PATH,
 110 };
 111
 112 /* TODO: allow global_apps_sock_path override */
 113
 114 struct sock_info local_apps = {
 115         .name = "local",
 116         .global = 0,
 117         .root_handle = -1,
 118         .allowed = 0,   /* Check setuid bit first */
 119
 120         .socket = -1,
 121 };
 122
 123 static int wait_poll_fallback;
 124
 125 extern void ltt_ring_buffer_client_overwrite_init(void);
 126 extern void ltt_ring_buffer_client_discard_init(void);
 127 extern void ltt_ring_buffer_metadata_client_init(void);
 128 extern void ltt_ring_buffer_client_overwrite_exit(void);
 129 extern void ltt_ring_buffer_client_discard_exit(void);
 130 extern void ltt_ring_buffer_metadata_client_exit(void);
 131
 132 static
 133 int setup_local_apps(void)
 134 {
 135         const char *home_dir;
 136         uid_t uid;
 137
 138         uid = getuid();
 139         /*
 140          * Disallow per-user tracing for setuid binaries.
 141          */
 142         if (uid != geteuid()) {
 143                 local_apps.allowed = 0;
 144                 return 0;
 145         } else {
 146                 local_apps.allowed = 1;
 147         }
 148         home_dir = (const char *) getenv("HOME");
 149         if (!home_dir)
 150                 return -ENOENT;
 151         snprintf(local_apps.sock_path, PATH_MAX,
 152                  DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
 153         snprintf(local_apps.wait_shm_path, PATH_MAX,
 154                  DEFAULT_HOME_APPS_WAIT_SHM_PATH, uid);
 155         return 0;
 156 }
 157
 158 static
 159 int register_app_to_sessiond(int socket)
 160 {
 161         ssize_t ret;
 162         int prctl_ret;
 163         struct {
 164                 uint32_t major;
 165                 uint32_t minor;
 166                 pid_t pid;
 167                 pid_t ppid;
 168                 uid_t uid;
 169                 gid_t gid;
 170                 char name[16];  /* process name */
 171         } reg_msg;
 172
 173         reg_msg.major = LTTNG_UST_COMM_VERSION_MAJOR;
 174         reg_msg.minor = LTTNG_UST_COMM_VERSION_MINOR;
 175         reg_msg.pid = getpid();
 176         reg_msg.ppid = getppid();
 177         reg_msg.uid = getuid();
 178         reg_msg.gid = getgid();
 179         prctl_ret = prctl(PR_GET_NAME, (unsigned long) reg_msg.name, 0, 0, 0);
 180         if (prctl_ret) {
 181                 ERR("Error executing prctl");
 182                 return -errno;
 183         }
 184
 185         ret = lttcomm_send_unix_sock(socket, &reg_msg, sizeof(reg_msg));
 186         if (ret >= 0 && ret != sizeof(reg_msg))
 187                 return -EIO;
 188         return ret;
 189 }
 190
 191 static
 192 int send_reply(int sock, struct lttcomm_ust_reply *lur)
 193 {
 194         ssize_t len;
 195
 196         len = lttcomm_send_unix_sock(sock, lur, sizeof(*lur));
 197         switch (len) {
 198         case sizeof(*lur):
 199                 DBG("message successfully sent");
 200                 return 0;
 201         case -1:
 202                 if (errno == ECONNRESET) {
 203                         printf("remote end closed connection\n");
 204                         return 0;
 205                 }
 206                 return -1;
 207         default:
 208                 printf("incorrect message size: %zd\n", len);
 209                 return -1;
 210         }
 211 }
 212
 213 static
 214 int handle_register_done(struct sock_info *sock_info)
 215 {
 216         int ret;
 217
 218         if (sock_info->constructor_sem_posted)
 219                 return 0;
 220         sock_info->constructor_sem_posted = 1;
 221         if (uatomic_read(&sem_count) <= 0) {
 222                 return 0;
 223         }
 224         ret = uatomic_add_return(&sem_count, -1);
 225         if (ret == 0) {
 226                 ret = sem_post(&constructor_wait);
 227                 assert(!ret);
 228         }
 229         return 0;
 230 }
 231
 232 static
 233 int handle_message(struct sock_info *sock_info,
 234                 int sock, struct lttcomm_ust_msg *lum)
 235 {
 236         int ret = 0;
 237         const struct objd_ops *ops;
 238         struct lttcomm_ust_reply lur;
 239         int shm_fd, wait_fd;
 240
 241         ust_lock();
 242
 243         memset(&lur, 0, sizeof(lur));
 244
 245         if (lttng_ust_comm_should_quit) {
 246                 ret = -EPERM;
 247                 goto end;
 248         }
 249
 250         ops = objd_ops(lum->handle);
 251         if (!ops) {
 252                 ret = -ENOENT;
 253                 goto end;
 254         }
 255
 256         switch (lum->cmd) {
 257         case LTTNG_UST_REGISTER_DONE:
 258                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 259                         ret = handle_register_done(sock_info);
 260                 else
 261                         ret = -EINVAL;
 262                 break;
 263         case LTTNG_UST_RELEASE:
 264                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 265                         ret = -EPERM;
 266                 else
 267                         ret = objd_unref(lum->handle);
 268                 break;
 269         default:
 270                 if (ops->cmd)
 271                         ret = ops->cmd(lum->handle, lum->cmd,
 272                                         (unsigned long) &lum->u);
 273                 else
 274                         ret = -ENOSYS;
 275                 break;
 276         }
 277
 278 end:
 279         lur.handle = lum->handle;
 280         lur.cmd = lum->cmd;
 281         lur.ret_val = ret;
 282         if (ret >= 0) {
 283                 lur.ret_code = LTTCOMM_OK;
 284         } else {
 285                 //lur.ret_code = LTTCOMM_SESSION_FAIL;
 286                 lur.ret_code = ret;
 287         }
 288         switch (lum->cmd) {
 289         case LTTNG_UST_STREAM:
 290                 /*
 291                  * Special-case reply to send stream info.
 292                  * Use lum.u output.
 293                  */
 294                 lur.u.stream.memory_map_size = lum->u.stream.memory_map_size;
 295                 shm_fd = lum->u.stream.shm_fd;
 296                 wait_fd = lum->u.stream.wait_fd;
 297                 break;
 298         case LTTNG_UST_METADATA:
 299         case LTTNG_UST_CHANNEL:
 300                 lur.u.channel.memory_map_size = lum->u.channel.memory_map_size;
 301                 shm_fd = lum->u.channel.shm_fd;
 302                 wait_fd = lum->u.channel.wait_fd;
 303                 break;
 304         }
 305         ret = send_reply(sock, &lur);
 306         if (ret < 0) {
 307                 perror("error sending reply");
 308                 goto error;
 309         }
 310
 311         if ((lum->cmd == LTTNG_UST_STREAM
 312              || lum->cmd == LTTNG_UST_CHANNEL
 313              || lum->cmd == LTTNG_UST_METADATA)
 314                         && lur.ret_code == LTTCOMM_OK) {
 315                 /* we also need to send the file descriptors. */
 316                 ret = lttcomm_send_fds_unix_sock(sock,
 317                         &shm_fd, &shm_fd,
 318                         1, sizeof(int));
 319                 if (ret < 0) {
 320                         perror("send shm_fd");
 321                         goto error;
 322                 }
 323                 ret = lttcomm_send_fds_unix_sock(sock,
 324                         &wait_fd, &wait_fd,
 325                         1, sizeof(int));
 326                 if (ret < 0) {
 327                         perror("send wait_fd");
 328                         goto error;
 329                 }
 330         }
 331 error:
 332         ust_unlock();
 333         return ret;
 334 }
 335
 336 static
 337 void cleanup_sock_info(struct sock_info *sock_info)
 338 {
 339         int ret;
 340
 341         if (sock_info->socket != -1) {
 342                 ret = close(sock_info->socket);
 343                 if (ret) {
 344                         ERR("Error closing apps socket");
 345                 }
 346                 sock_info->socket = -1;
 347         }
 348         if (sock_info->root_handle != -1) {
 349                 ret = objd_unref(sock_info->root_handle);
 350                 if (ret) {
 351                         ERR("Error unref root handle");
 352                 }
 353                 sock_info->root_handle = -1;
 354         }
 355         sock_info->constructor_sem_posted = 0;
 356         if (sock_info->wait_shm_mmap) {
 357                 ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
 358                 if (ret) {
 359                         ERR("Error unmapping wait shm");
 360                 }
 361                 sock_info->wait_shm_mmap = NULL;
 362         }
 363 }
 364
 365 /*
 366  * Using fork to set umask in the child process (not multi-thread safe).
 367  * We deal with the shm_open vs ftruncate race (happening when the
 368  * sessiond owns the shm and does not let everybody modify it, to ensure
 369  * safety against shm_unlink) by simply letting the mmap fail and
 370  * retrying after a few seconds.
 371  * For global shm, everybody has rw access to it until the sessiond
 372  * starts.
 373  */
 374 static
 375 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 376 {
 377         int wait_shm_fd, ret;
 378         pid_t pid;
 379
 380         /*
 381          * Try to open read-only.
 382          */
 383         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 384         if (wait_shm_fd >= 0) {
 385                 goto end;
 386         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 387                 /*
 388                  * Real-only open did not work, and it's not because the
 389                  * entry was not present. It's a failure that prohibits
 390                  * using shm.
 391                  */
 392                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 393                 goto end;
 394         }
 395         /*
 396          * If the open failed because the file did not exist, try
 397          * creating it ourself.
 398          */
 399         pid = fork();
 400         if (pid > 0) {
 401                 int status;
 402
 403                 /*
 404                  * Parent: wait for child to return, in which case the
 405                  * shared memory map will have been created.
 406                  */
 407                 pid = wait(&status);
 408                 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 409                         wait_shm_fd = -1;
 410                         goto end;
 411                 }
 412                 /*
 413                  * Try to open read-only again after creation.
 414                  */
 415                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 416                 if (wait_shm_fd < 0) {
 417                         /*
 418                          * Real-only open did not work. It's a failure
 419                          * that prohibits using shm.
 420                          */
 421                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 422                         goto end;
 423                 }
 424                 goto end;
 425         } else if (pid == 0) {
 426                 int create_mode;
 427
 428                 /* Child */
 429                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
 430                 if (sock_info->global)
 431                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
 432                 /*
 433                  * We're alone in a child process, so we can modify the
 434                  * process-wide umask.
 435                  */
 436                 umask(~create_mode);
 437                 /*
 438                  * Try creating shm (or get rw access).
 439                  * We don't do an exclusive open, because we allow other
 440                  * processes to create+ftruncate it concurrently.
 441                  */
 442                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 443                                 O_RDWR | O_CREAT, create_mode);
 444                 if (wait_shm_fd >= 0) {
 445                         ret = ftruncate(wait_shm_fd, mmap_size);
 446                         if (ret) {
 447                                 PERROR("ftruncate");
 448                                 exit(EXIT_FAILURE);
 449                         }
 450                         exit(EXIT_SUCCESS);
 451                 }
 452                 /*
 453                  * For local shm, we need to have rw access to accept
 454                  * opening it: this means the local sessiond will be
 455                  * able to wake us up. For global shm, we open it even
 456                  * if rw access is not granted, because the root.root
 457                  * sessiond will be able to override all rights and wake
 458                  * us up.
 459                  */
 460                 if (!sock_info->global && errno != EACCES) {
 461                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 462                         exit(EXIT_FAILURE);
 463                 }
 464                 /*
 465                  * The shm exists, but we cannot open it RW. Report
 466                  * success.
 467                  */
 468                 exit(EXIT_SUCCESS);
 469         } else {
 470                 return -1;
 471         }
 472 end:
 473         if (wait_shm_fd >= 0 && !sock_info->global) {
 474                 struct stat statbuf;
 475
 476                 /*
 477                  * Ensure that our user is the owner of the shm file for
 478                  * local shm. If we do not own the file, it means our
 479                  * sessiond will not have access to wake us up (there is
 480                  * probably a rogue process trying to fake our
 481                  * sessiond). Fallback to polling method in this case.
 482                  */
 483                 ret = fstat(wait_shm_fd, &statbuf);
 484                 if (ret) {
 485                         PERROR("fstat");
 486                         goto error_close;
 487                 }
 488                 if (statbuf.st_uid != getuid())
 489                         goto error_close;
 490         }
 491         return wait_shm_fd;
 492
 493 error_close:
 494         ret = close(wait_shm_fd);
 495         if (ret) {
 496                 PERROR("Error closing fd");
 497         }
 498         return -1;
 499 }
 500
 501 static
 502 char *get_map_shm(struct sock_info *sock_info)
 503 {
 504         size_t mmap_size = sysconf(_SC_PAGE_SIZE);
 505         int wait_shm_fd, ret;
 506         char *wait_shm_mmap;
 507
 508         wait_shm_fd = get_wait_shm(sock_info, mmap_size);
 509         if (wait_shm_fd < 0) {
 510                 goto error;
 511         }
 512         wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
 513                   MAP_SHARED, wait_shm_fd, 0);
 514         /* close shm fd immediately after taking the mmap reference */
 515         ret = close(wait_shm_fd);
 516         if (ret) {
 517                 PERROR("Error closing fd");
 518         }
 519         if (wait_shm_mmap == MAP_FAILED) {
 520                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
 521                 goto error;
 522         }
 523         return wait_shm_mmap;
 524
 525 error:
 526         return NULL;
 527 }
 528
 529 static
 530 void wait_for_sessiond(struct sock_info *sock_info)
 531 {
 532         int ret;
 533
 534         ust_lock();
 535         if (lttng_ust_comm_should_quit) {
 536                 goto quit;
 537         }
 538         if (wait_poll_fallback) {
 539                 goto error;
 540         }
 541         if (!sock_info->wait_shm_mmap) {
 542                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
 543                 if (!sock_info->wait_shm_mmap)
 544                         goto error;
 545         }
 546         ust_unlock();
 547
 548         DBG("Waiting for %s apps sessiond", sock_info->name);
 549         /* Wait for futex wakeup */
 550         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
 551                 ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
 552                         FUTEX_WAIT, 0, NULL, NULL, 0);
 553                 if (ret < 0) {
 554                         if (errno == EFAULT) {
 555                                 wait_poll_fallback = 1;
 556                                 ERR(
 557 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
 558 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
 559 "Please upgrade your kernel "
 560 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
 561 "mainline). LTTng-UST will use polling mode fallback.");
 562                         }
 563                         PERROR("futex");
 564                 }
 565         }
 566         return;
 567
 568 quit:
 569         ust_unlock();
 570         return;
 571
 572 error:
 573         ust_unlock();
 574         return;
 575 }
 576
 577 /*
 578  * This thread does not allocate any resource, except within
 579  * handle_message, within mutex protection. This mutex protects against
 580  * fork and exit.
 581  * The other moment it allocates resources is at socket connexion, which
 582  * is also protected by the mutex.
 583  */
 584 static
 585 void *ust_listener_thread(void *arg)
 586 {
 587         struct sock_info *sock_info = arg;
 588         int sock, ret, prev_connect_failed = 0, has_waited = 0;
 589
 590         /* Restart trying to connect to the session daemon */
 591 restart:
 592         if (prev_connect_failed) {
 593                 /* Wait for sessiond availability with pipe */
 594                 wait_for_sessiond(sock_info);
 595                 if (has_waited) {
 596                         has_waited = 0;
 597                         /*
 598                          * Sleep for 5 seconds before retrying after a
 599                          * sequence of failure / wait / failure. This
 600                          * deals with a killed or broken session daemon.
 601                          */
 602                         sleep(5);
 603                 }
 604                 has_waited = 1;
 605                 prev_connect_failed = 0;
 606         }
 607         ust_lock();
 608
 609         if (lttng_ust_comm_should_quit) {
 610                 ust_unlock();
 611                 goto quit;
 612         }
 613
 614         if (sock_info->socket != -1) {
 615                 ret = close(sock_info->socket);
 616                 if (ret) {
 617                         ERR("Error closing %s apps socket", sock_info->name);
 618                 }
 619                 sock_info->socket = -1;
 620         }
 621
 622         /* Register */
 623         ret = lttcomm_connect_unix_sock(sock_info->sock_path);
 624         if (ret < 0) {
 625                 ERR("Error connecting to %s apps socket", sock_info->name);
 626                 prev_connect_failed = 1;
 627                 /*
 628                  * If we cannot find the sessiond daemon, don't delay
 629                  * constructor execution.
 630                  */
 631                 ret = handle_register_done(sock_info);
 632                 assert(!ret);
 633                 ust_unlock();
 634                 goto restart;
 635         }
 636
 637         sock_info->socket = sock = ret;
 638
 639         /*
 640          * Create only one root handle per listener thread for the whole
 641          * process lifetime.
 642          */
 643         if (sock_info->root_handle == -1) {
 644                 ret = lttng_abi_create_root_handle();
 645                 if (ret < 0) {
 646                         ERR("Error creating root handle");
 647                         ust_unlock();
 648                         goto quit;
 649                 }
 650                 sock_info->root_handle = ret;
 651         }
 652
 653         ret = register_app_to_sessiond(sock);
 654         if (ret < 0) {
 655                 ERR("Error registering to %s apps socket", sock_info->name);
 656                 prev_connect_failed = 1;
 657                 /*
 658                  * If we cannot register to the sessiond daemon, don't
 659                  * delay constructor execution.
 660                  */
 661                 ret = handle_register_done(sock_info);
 662                 assert(!ret);
 663                 ust_unlock();
 664                 goto restart;
 665         }
 666         ust_unlock();
 667
 668         for (;;) {
 669                 ssize_t len;
 670                 struct lttcomm_ust_msg lum;
 671
 672                 len = lttcomm_recv_unix_sock(sock, &lum, sizeof(lum));
 673                 switch (len) {
 674                 case 0: /* orderly shutdown */
 675                         DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
 676                         goto end;
 677                 case sizeof(lum):
 678                         DBG("message received\n");
 679                         ret = handle_message(sock_info, sock, &lum);
 680                         if (ret < 0) {
 681                                 ERR("Error handling message for %s socket", sock_info->name);
 682                         }
 683                         continue;
 684                 case -1:
 685                         if (errno == ECONNRESET) {
 686                                 ERR("%s remote end closed connection\n", sock_info->name);
 687                                 goto end;
 688                         }
 689                         goto end;
 690                 default:
 691                         ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
 692                         continue;
 693                 }
 694
 695         }
 696 end:
 697         goto restart;   /* try to reconnect */
 698 quit:
 699         return NULL;
 700 }
 701
 702 /*
 703  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 704  */
 705 static
 706 int get_timeout(struct timespec *constructor_timeout)
 707 {
 708         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 709         char *str_delay;
 710         int ret;
 711
 712         str_delay = getenv("UST_REGISTER_TIMEOUT");
 713         if (str_delay) {
 714                 constructor_delay_ms = strtol(str_delay, NULL, 10);
 715         }
 716
 717         switch (constructor_delay_ms) {
 718         case -1:/* fall-through */
 719         case 0:
 720                 return constructor_delay_ms;
 721         default:
 722                 break;
 723         }
 724
 725         /*
 726          * If we are unable to find the current time, don't wait.
 727          */
 728         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 729         if (ret) {
 730                 return -1;
 731         }
 732         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 733         constructor_timeout->tv_nsec +=
 734                 (constructor_delay_ms % 1000UL) * 1000000UL;
 735         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 736                 constructor_timeout->tv_sec++;
 737                 constructor_timeout->tv_nsec -= 1000000000UL;
 738         }
 739         return 1;
 740 }
 741
 742 /*
 743  * sessiond monitoring thread: monitor presence of global and per-user
 744  * sessiond by polling the application common named pipe.
 745  */
 746 /* TODO */
 747
 748 void __attribute__((constructor)) lttng_ust_init(void)
 749 {
 750         struct timespec constructor_timeout;
 751         int timeout_mode;
 752         int ret;
 753
 754         if (uatomic_xchg(&initialized, 1) == 1)
 755                 return;
 756
 757         /*
 758          * We want precise control over the order in which we construct
 759          * our sub-libraries vs starting to receive commands from
 760          * sessiond (otherwise leading to errors when trying to create
 761          * sessiond before the init functions are completed).
 762          */
 763         init_usterr();
 764         init_tracepoint();
 765         ltt_ring_buffer_metadata_client_init();
 766         ltt_ring_buffer_client_overwrite_init();
 767         ltt_ring_buffer_client_discard_init();
 768
 769         timeout_mode = get_timeout(&constructor_timeout);
 770
 771         ret = sem_init(&constructor_wait, 0, 0);
 772         assert(!ret);
 773
 774         ret = setup_local_apps();
 775         if (ret) {
 776                 ERR("Error setting up to local apps");
 777         }
 778         ret = pthread_create(&local_apps.ust_listener, NULL,
 779                         ust_listener_thread, &local_apps);
 780
 781         if (local_apps.allowed) {
 782                 ret = pthread_create(&global_apps.ust_listener, NULL,
 783                                 ust_listener_thread, &global_apps);
 784         } else {
 785                 handle_register_done(&local_apps);
 786         }
 787
 788         switch (timeout_mode) {
 789         case 1: /* timeout wait */
 790                 do {
 791                         ret = sem_timedwait(&constructor_wait,
 792                                         &constructor_timeout);
 793                 } while (ret < 0 && errno == EINTR);
 794                 if (ret < 0 && errno == ETIMEDOUT) {
 795                         ERR("Timed out waiting for ltt-sessiond");
 796                 } else {
 797                         assert(!ret);
 798                 }
 799                 break;
 800         case -1:/* wait forever */
 801                 do {
 802                         ret = sem_wait(&constructor_wait);
 803                 } while (ret < 0 && errno == EINTR);
 804                 assert(!ret);
 805                 break;
 806         case 0: /* no timeout */
 807                 break;
 808         }
 809 }
 810
 811 static
 812 void lttng_ust_cleanup(int exiting)
 813 {
 814         cleanup_sock_info(&global_apps);
 815         if (local_apps.allowed) {
 816                 cleanup_sock_info(&local_apps);
 817         }
 818         lttng_ust_abi_exit();
 819         ltt_events_exit();
 820         ltt_ring_buffer_client_discard_exit();
 821         ltt_ring_buffer_client_overwrite_exit();
 822         ltt_ring_buffer_metadata_client_exit();
 823         exit_tracepoint();
 824         if (!exiting) {
 825                 /* Reinitialize values for fork */
 826                 sem_count = 2;
 827                 lttng_ust_comm_should_quit = 0;
 828                 initialized = 0;
 829         }
 830 }
 831
 832 void __attribute__((destructor)) lttng_ust_exit(void)
 833 {
 834         int ret;
 835
 836         /*
 837          * Using pthread_cancel here because:
 838          * A) we don't want to hang application teardown.
 839          * B) the thread is not allocating any resource.
 840          */
 841
 842         /*
 843          * Require the communication thread to quit. Synchronize with
 844          * mutexes to ensure it is not in a mutex critical section when
 845          * pthread_cancel is later called.
 846          */
 847         ust_lock();
 848         lttng_ust_comm_should_quit = 1;
 849         ust_unlock();
 850
 851         ret = pthread_cancel(global_apps.ust_listener);
 852         if (ret) {
 853                 ERR("Error cancelling global ust listener thread");
 854         }
 855         if (local_apps.allowed) {
 856                 ret = pthread_cancel(local_apps.ust_listener);
 857                 if (ret) {
 858                         ERR("Error cancelling local ust listener thread");
 859                 }
 860         }
 861         lttng_ust_cleanup(1);
 862 }
 863
 864 /*
 865  * We exclude the worker threads across fork and clone (except
 866  * CLONE_VM), because these system calls only keep the forking thread
 867  * running in the child.  Therefore, we don't want to call fork or clone
 868  * in the middle of an tracepoint or ust tracing state modification.
 869  * Holding this mutex protects these structures across fork and clone.
 870  */
 871 void ust_before_fork(ust_fork_info_t *fork_info)
 872 {
 873         /*
 874          * Disable signals. This is to avoid that the child intervenes
 875          * before it is properly setup for tracing. It is safer to
 876          * disable all signals, because then we know we are not breaking
 877          * anything by restoring the original mask.
 878          */
 879         sigset_t all_sigs;
 880         int ret;
 881
 882         /* Disable signals */
 883         sigfillset(&all_sigs);
 884         ret = sigprocmask(SIG_BLOCK, &all_sigs, &fork_info->orig_sigs);
 885         if (ret == -1) {
 886                 PERROR("sigprocmask");
 887         }
 888         ust_lock();
 889         rcu_bp_before_fork();
 890 }
 891
 892 static void ust_after_fork_common(ust_fork_info_t *fork_info)
 893 {
 894         int ret;
 895
 896         DBG("process %d", getpid());
 897         ust_unlock();
 898         /* Restore signals */
 899         ret = sigprocmask(SIG_SETMASK, &fork_info->orig_sigs, NULL);
 900         if (ret == -1) {
 901                 PERROR("sigprocmask");
 902         }
 903 }
 904
 905 void ust_after_fork_parent(ust_fork_info_t *fork_info)
 906 {
 907         DBG("process %d", getpid());
 908         rcu_bp_after_fork_parent();
 909         /* Release mutexes and reenable signals */
 910         ust_after_fork_common(fork_info);
 911 }
 912
 913 /*
 914  * After fork, in the child, we need to cleanup all the leftover state,
 915  * except the worker thread which already magically disappeared thanks
 916  * to the weird Linux fork semantics. After tyding up, we call
 917  * lttng_ust_init() again to start over as a new PID.
 918  *
 919  * This is meant for forks() that have tracing in the child between the
 920  * fork and following exec call (if there is any).
 921  */
 922 void ust_after_fork_child(ust_fork_info_t *fork_info)
 923 {
 924         DBG("process %d", getpid());
 925         /* Release urcu mutexes */
 926         rcu_bp_after_fork_child();
 927         lttng_ust_cleanup(0);
 928         lttng_context_vtid_reset();
 929         /* Release mutexes and reenable signals */
 930         ust_after_fork_common(fork_info);
 931         lttng_ust_init();
 932 }