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 #define _GNU_SOURCE
  24 #include <sys/types.h>
  25 #include <sys/socket.h>
  26 #include <sys/mman.h>
  27 #include <sys/stat.h>
  28 #include <sys/types.h>
  29 #include <sys/wait.h>
  30 #include <dlfcn.h>
  31 #include <fcntl.h>
  32 #include <unistd.h>
  33 #include <errno.h>
  34 #include <pthread.h>
  35 #include <semaphore.h>
  36 #include <time.h>
  37 #include <assert.h>
  38 #include <signal.h>
  39 #include <limits.h>
  40 #include <urcu/uatomic.h>
  41 #include <urcu/futex.h>
  42 #include <urcu/compiler.h>
  43
  44 #include <lttng/ust-events.h>
  45 #include <lttng/ust-abi.h>
  46 #include <lttng/ust.h>
  47 #include <lttng/ust-error.h>
  48 #include <lttng/ust-ctl.h>
  49 #include <urcu/tls-compat.h>
  50 #include <ust-comm.h>
  51 #include <ust-fd.h>
  52 #include <usterr-signal-safe.h>
  53 #include <helper.h>
  54 #include "tracepoint-internal.h"
  55 #include "lttng-tracer-core.h"
  56 #include "compat.h"
  57 #include "../libringbuffer/rb-init.h"
  58 #include "lttng-ust-statedump.h"
  59 #include "clock.h"
  60 #include "../libringbuffer/getcpu.h"
  61 #include "getenv.h"
  62
  63 /* Concatenate lttng ust shared library name with its major version number. */
  64 #define LTTNG_UST_LIB_SO_NAME "liblttng-ust.so." __ust_stringify(CONFIG_LTTNG_UST_LIBRARY_VERSION_MAJOR)
  65
  66 /*
  67  * Has lttng ust comm constructor been called ?
  68  */
  69 static int initialized;
  70
  71 /*
  72  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  73  * Held when handling a command, also held by fork() to deal with
  74  * removal of threads, and by exit path.
  75  *
  76  * The UST lock is the centralized mutex across UST tracing control and
  77  * probe registration.
  78  *
  79  * ust_exit_mutex must never nest in ust_mutex.
  80  *
  81  * ust_fork_mutex must never nest in ust_mutex.
  82  *
  83  * ust_mutex_nest is a per-thread nesting counter, allowing the perf
  84  * counter lazy initialization called by events within the statedump,
  85  * which traces while the ust_mutex is held.
  86  *
  87  * ust_lock nests within the dynamic loader lock (within glibc) because
  88  * it is taken within the library constructor.
  89  */
  90 static pthread_mutex_t ust_mutex = PTHREAD_MUTEX_INITIALIZER;
  91
  92 /* Allow nesting the ust_mutex within the same thread. */
  93 static DEFINE_URCU_TLS(int, ust_mutex_nest);
  94
  95 /*
  96  * ust_exit_mutex protects thread_active variable wrt thread exit. It
  97  * cannot be done by ust_mutex because pthread_cancel(), which takes an
  98  * internal libc lock, cannot nest within ust_mutex.
  99  *
 100  * It never nests within a ust_mutex.
 101  */
 102 static pthread_mutex_t ust_exit_mutex = PTHREAD_MUTEX_INITIALIZER;
 103
 104 /*
 105  * ust_fork_mutex protects base address statedump tracing against forks. It
 106  * prevents the dynamic loader lock to be taken (by base address statedump
 107  * tracing) while a fork is happening, thus preventing deadlock issues with
 108  * the dynamic loader lock.
 109  */
 110 static pthread_mutex_t ust_fork_mutex = PTHREAD_MUTEX_INITIALIZER;
 111
 112 /* Should the ust comm thread quit ? */
 113 static int lttng_ust_comm_should_quit;
 114
 115 /*
 116  * This variable can be tested by applications to check whether
 117  * lttng-ust is loaded. They simply have to define their own
 118  * "lttng_ust_loaded" weak symbol, and test it. It is set to 1 by the
 119  * library constructor.
 120  */
 121 int lttng_ust_loaded __attribute__((weak));
 122
 123 /*
 124  * Return 0 on success, -1 if should quit.
 125  * The lock is taken in both cases.
 126  * Signal-safe.
 127  */
 128 int ust_lock(void)
 129 {
 130         sigset_t sig_all_blocked, orig_mask;
 131         int ret, oldstate;
 132
 133         ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
 134         if (ret) {
 135                 ERR("pthread_setcancelstate: %s", strerror(ret));
 136         }
 137         if (oldstate != PTHREAD_CANCEL_ENABLE) {
 138                 ERR("pthread_setcancelstate: unexpected oldstate");
 139         }
 140         sigfillset(&sig_all_blocked);
 141         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
 142         if (ret) {
 143                 ERR("pthread_sigmask: %s", strerror(ret));
 144         }
 145         if (!URCU_TLS(ust_mutex_nest)++)
 146                 pthread_mutex_lock(&ust_mutex);
 147         ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
 148         if (ret) {
 149                 ERR("pthread_sigmask: %s", strerror(ret));
 150         }
 151         if (lttng_ust_comm_should_quit) {
 152                 return -1;
 153         } else {
 154                 return 0;
 155         }
 156 }
 157
 158 /*
 159  * ust_lock_nocheck() can be used in constructors/destructors, because
 160  * they are already nested within the dynamic loader lock, and therefore
 161  * have exclusive access against execution of liblttng-ust destructor.
 162  * Signal-safe.
 163  */
 164 void ust_lock_nocheck(void)
 165 {
 166         sigset_t sig_all_blocked, orig_mask;
 167         int ret, oldstate;
 168
 169         ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
 170         if (ret) {
 171                 ERR("pthread_setcancelstate: %s", strerror(ret));
 172         }
 173         if (oldstate != PTHREAD_CANCEL_ENABLE) {
 174                 ERR("pthread_setcancelstate: unexpected oldstate");
 175         }
 176         sigfillset(&sig_all_blocked);
 177         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
 178         if (ret) {
 179                 ERR("pthread_sigmask: %s", strerror(ret));
 180         }
 181         if (!URCU_TLS(ust_mutex_nest)++)
 182                 pthread_mutex_lock(&ust_mutex);
 183         ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
 184         if (ret) {
 185                 ERR("pthread_sigmask: %s", strerror(ret));
 186         }
 187 }
 188
 189 /*
 190  * Signal-safe.
 191  */
 192 void ust_unlock(void)
 193 {
 194         sigset_t sig_all_blocked, orig_mask;
 195         int ret, oldstate;
 196
 197         sigfillset(&sig_all_blocked);
 198         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
 199         if (ret) {
 200                 ERR("pthread_sigmask: %s", strerror(ret));
 201         }
 202         if (!--URCU_TLS(ust_mutex_nest))
 203                 pthread_mutex_unlock(&ust_mutex);
 204         ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
 205         if (ret) {
 206                 ERR("pthread_sigmask: %s", strerror(ret));
 207         }
 208         ret = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &oldstate);
 209         if (ret) {
 210                 ERR("pthread_setcancelstate: %s", strerror(ret));
 211         }
 212         if (oldstate != PTHREAD_CANCEL_DISABLE) {
 213                 ERR("pthread_setcancelstate: unexpected oldstate");
 214         }
 215 }
 216
 217 /*
 218  * Wait for either of these before continuing to the main
 219  * program:
 220  * - the register_done message from sessiond daemon
 221  *   (will let the sessiond daemon enable sessions before main
 222  *   starts.)
 223  * - sessiond daemon is not reachable.
 224  * - timeout (ensuring applications are resilient to session
 225  *   daemon problems).
 226  */
 227 static sem_t constructor_wait;
 228 /*
 229  * Doing this for both the global and local sessiond.
 230  */
 231 static int sem_count = { 2 };
 232
 233 /*
 234  * Counting nesting within lttng-ust. Used to ensure that calling fork()
 235  * from liblttng-ust does not execute the pre/post fork handlers.
 236  */
 237 static DEFINE_URCU_TLS(int, lttng_ust_nest_count);
 238
 239 /*
 240  * Info about socket and associated listener thread.
 241  */
 242 struct sock_info {
 243         const char *name;
 244         pthread_t ust_listener; /* listener thread */
 245         int root_handle;
 246         int constructor_sem_posted;
 247         int allowed;
 248         int global;
 249         int thread_active;
 250
 251         char sock_path[PATH_MAX];
 252         int socket;
 253         int notify_socket;
 254
 255         char wait_shm_path[PATH_MAX];
 256         char *wait_shm_mmap;
 257         /* Keep track of lazy state dump not performed yet. */
 258         int statedump_pending;
 259 };
 260
 261 /* Socket from app (connect) to session daemon (listen) for communication */
 262 struct sock_info global_apps = {
 263         .name = "global",
 264         .global = 1,
 265
 266         .root_handle = -1,
 267         .allowed = 0,
 268         .thread_active = 0,
 269
 270         .sock_path = LTTNG_DEFAULT_RUNDIR "/" LTTNG_UST_SOCK_FILENAME,
 271         .socket = -1,
 272         .notify_socket = -1,
 273
 274         .wait_shm_path = "/" LTTNG_UST_WAIT_FILENAME,
 275
 276         .statedump_pending = 0,
 277 };
 278
 279 /* TODO: allow global_apps_sock_path override */
 280
 281 struct sock_info local_apps = {
 282         .name = "local",
 283         .global = 0,
 284         .root_handle = -1,
 285         .allowed = 0,   /* Check setuid bit first */
 286         .thread_active = 0,
 287
 288         .socket = -1,
 289         .notify_socket = -1,
 290
 291         .statedump_pending = 0,
 292 };
 293
 294 static int wait_poll_fallback;
 295
 296 static const char *cmd_name_mapping[] = {
 297         [ LTTNG_UST_RELEASE ] = "Release",
 298         [ LTTNG_UST_SESSION ] = "Create Session",
 299         [ LTTNG_UST_TRACER_VERSION ] = "Get Tracer Version",
 300
 301         [ LTTNG_UST_TRACEPOINT_LIST ] = "Create Tracepoint List",
 302         [ LTTNG_UST_WAIT_QUIESCENT ] = "Wait for Quiescent State",
 303         [ LTTNG_UST_REGISTER_DONE ] = "Registration Done",
 304         [ LTTNG_UST_TRACEPOINT_FIELD_LIST ] = "Create Tracepoint Field List",
 305
 306         /* Session FD commands */
 307         [ LTTNG_UST_CHANNEL ] = "Create Channel",
 308         [ LTTNG_UST_SESSION_START ] = "Start Session",
 309         [ LTTNG_UST_SESSION_STOP ] = "Stop Session",
 310
 311         /* Channel FD commands */
 312         [ LTTNG_UST_STREAM ] = "Create Stream",
 313         [ LTTNG_UST_EVENT ] = "Create Event",
 314
 315         /* Event and Channel FD commands */
 316         [ LTTNG_UST_CONTEXT ] = "Create Context",
 317         [ LTTNG_UST_FLUSH_BUFFER ] = "Flush Buffer",
 318
 319         /* Event, Channel and Session commands */
 320         [ LTTNG_UST_ENABLE ] = "Enable",
 321         [ LTTNG_UST_DISABLE ] = "Disable",
 322
 323         /* Tracepoint list commands */
 324         [ LTTNG_UST_TRACEPOINT_LIST_GET ] = "List Next Tracepoint",
 325         [ LTTNG_UST_TRACEPOINT_FIELD_LIST_GET ] = "List Next Tracepoint Field",
 326
 327         /* Event FD commands */
 328         [ LTTNG_UST_FILTER ] = "Create Filter",
 329         [ LTTNG_UST_EXCLUSION ] = "Add exclusions to event",
 330 };
 331
 332 static const char *str_timeout;
 333 static int got_timeout_env;
 334
 335 extern void lttng_ring_buffer_client_overwrite_init(void);
 336 extern void lttng_ring_buffer_client_overwrite_rt_init(void);
 337 extern void lttng_ring_buffer_client_discard_init(void);
 338 extern void lttng_ring_buffer_client_discard_rt_init(void);
 339 extern void lttng_ring_buffer_metadata_client_init(void);
 340 extern void lttng_ring_buffer_client_overwrite_exit(void);
 341 extern void lttng_ring_buffer_client_overwrite_rt_exit(void);
 342 extern void lttng_ring_buffer_client_discard_exit(void);
 343 extern void lttng_ring_buffer_client_discard_rt_exit(void);
 344 extern void lttng_ring_buffer_metadata_client_exit(void);
 345
 346 static char *get_map_shm(struct sock_info *sock_info);
 347
 348 ssize_t lttng_ust_read(int fd, void *buf, size_t len)
 349 {
 350         ssize_t ret;
 351         size_t copied = 0, to_copy = len;
 352
 353         do {
 354                 ret = read(fd, buf + copied, to_copy);
 355                 if (ret > 0) {
 356                         copied += ret;
 357                         to_copy -= ret;
 358                 }
 359         } while ((ret > 0 && to_copy > 0)
 360                 || (ret < 0 && errno == EINTR));
 361         if (ret > 0) {
 362                 ret = copied;
 363         }
 364         return ret;
 365 }
 366 /*
 367  * Returns the HOME directory path. Caller MUST NOT free(3) the returned
 368  * pointer.
 369  */
 370 static
 371 const char *get_lttng_home_dir(void)
 372 {
 373        const char *val;
 374
 375        val = (const char *) lttng_getenv("LTTNG_HOME");
 376        if (val != NULL) {
 377                return val;
 378        }
 379        return (const char *) lttng_getenv("HOME");
 380 }
 381
 382 /*
 383  * Force a read (imply TLS fixup for dlopen) of TLS variables.
 384  */
 385 static
 386 void lttng_fixup_nest_count_tls(void)
 387 {
 388         asm volatile ("" : : "m" (URCU_TLS(lttng_ust_nest_count)));
 389 }
 390
 391 static
 392 void lttng_fixup_ust_mutex_nest_tls(void)
 393 {
 394         asm volatile ("" : : "m" (URCU_TLS(ust_mutex_nest)));
 395 }
 396
 397 /*
 398  * Fixup urcu bp TLS.
 399  */
 400 static
 401 void lttng_fixup_urcu_bp_tls(void)
 402 {
 403         rcu_read_lock();
 404         rcu_read_unlock();
 405 }
 406
 407 void lttng_ust_fixup_tls(void)
 408 {
 409         lttng_fixup_urcu_bp_tls();
 410         lttng_fixup_ringbuffer_tls();
 411         lttng_fixup_vtid_tls();
 412         lttng_fixup_nest_count_tls();
 413         lttng_fixup_procname_tls();
 414         lttng_fixup_ust_mutex_nest_tls();
 415         lttng_ust_fixup_fd_tracker_tls();
 416 }
 417
 418 int lttng_get_notify_socket(void *owner)
 419 {
 420         struct sock_info *info = owner;
 421
 422         return info->notify_socket;
 423 }
 424
 425 static
 426 void print_cmd(int cmd, int handle)
 427 {
 428         const char *cmd_name = "Unknown";
 429
 430         if (cmd >= 0 && cmd < LTTNG_ARRAY_SIZE(cmd_name_mapping)
 431                         && cmd_name_mapping[cmd]) {
 432                 cmd_name = cmd_name_mapping[cmd];
 433         }
 434         DBG("Message Received \"%s\" (%d), Handle \"%s\" (%d)",
 435                 cmd_name, cmd,
 436                 lttng_ust_obj_get_name(handle), handle);
 437 }
 438
 439 static
 440 int setup_global_apps(void)
 441 {
 442         int ret = 0;
 443         assert(!global_apps.wait_shm_mmap);
 444
 445         global_apps.wait_shm_mmap = get_map_shm(&global_apps);
 446         if (!global_apps.wait_shm_mmap) {
 447                 WARN("Unable to get map shm for global apps. Disabling LTTng-UST global tracing.");
 448                 global_apps.allowed = 0;
 449                 ret = -EIO;
 450                 goto error;
 451         }
 452
 453         global_apps.allowed = 1;
 454 error:
 455         return ret;
 456 }
 457 static
 458 int setup_local_apps(void)
 459 {
 460         int ret = 0;
 461         const char *home_dir;
 462         uid_t uid;
 463
 464         assert(!local_apps.wait_shm_mmap);
 465
 466         uid = getuid();
 467         /*
 468          * Disallow per-user tracing for setuid binaries.
 469          */
 470         if (uid != geteuid()) {
 471                 assert(local_apps.allowed == 0);
 472                 ret = 0;
 473                 goto end;
 474         }
 475         home_dir = get_lttng_home_dir();
 476         if (!home_dir) {
 477                 WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
 478                 assert(local_apps.allowed == 0);
 479                 ret = -ENOENT;
 480                 goto end;
 481         }
 482         local_apps.allowed = 1;
 483         snprintf(local_apps.sock_path, PATH_MAX, "%s/%s/%s",
 484                 home_dir,
 485                 LTTNG_DEFAULT_HOME_RUNDIR,
 486                 LTTNG_UST_SOCK_FILENAME);
 487         snprintf(local_apps.wait_shm_path, PATH_MAX, "/%s-%u",
 488                 LTTNG_UST_WAIT_FILENAME,
 489                 uid);
 490
 491         local_apps.wait_shm_mmap = get_map_shm(&local_apps);
 492         if (!local_apps.wait_shm_mmap) {
 493                 WARN("Unable to get map shm for local apps. Disabling LTTng-UST per-user tracing.");
 494                 local_apps.allowed = 0;
 495                 ret = -EIO;
 496                 goto end;
 497         }
 498 end:
 499         return ret;
 500 }
 501
 502 /*
 503  * Get socket timeout, in ms.
 504  * -1: wait forever. 0: don't wait. >0: timeout, in ms.
 505  */
 506 static
 507 long get_timeout(void)
 508 {
 509         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 510
 511         if (!got_timeout_env) {
 512                 str_timeout = lttng_getenv("LTTNG_UST_REGISTER_TIMEOUT");
 513                 got_timeout_env = 1;
 514         }
 515         if (str_timeout)
 516                 constructor_delay_ms = strtol(str_timeout, NULL, 10);
 517         /* All negative values are considered as "-1". */
 518         if (constructor_delay_ms < -1)
 519                 constructor_delay_ms = -1;
 520         return constructor_delay_ms;
 521 }
 522
 523 /* Timeout for notify socket send and recv. */
 524 static
 525 long get_notify_sock_timeout(void)
 526 {
 527         return get_timeout();
 528 }
 529
 530 /* Timeout for connecting to cmd and notify sockets. */
 531 static
 532 long get_connect_sock_timeout(void)
 533 {
 534         return get_timeout();
 535 }
 536
 537 /*
 538  * Return values: -1: wait forever. 0: don't wait. 1: timeout wait.
 539  */
 540 static
 541 int get_constructor_timeout(struct timespec *constructor_timeout)
 542 {
 543         long constructor_delay_ms;
 544         int ret;
 545
 546         constructor_delay_ms = get_timeout();
 547
 548         switch (constructor_delay_ms) {
 549         case -1:/* fall-through */
 550         case 0:
 551                 return constructor_delay_ms;
 552         default:
 553                 break;
 554         }
 555
 556         /*
 557          * If we are unable to find the current time, don't wait.
 558          */
 559         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 560         if (ret) {
 561                 /* Don't wait. */
 562                 return 0;
 563         }
 564         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 565         constructor_timeout->tv_nsec +=
 566                 (constructor_delay_ms % 1000UL) * 1000000UL;
 567         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 568                 constructor_timeout->tv_sec++;
 569                 constructor_timeout->tv_nsec -= 1000000000UL;
 570         }
 571         /* Timeout wait (constructor_delay_ms). */
 572         return 1;
 573 }
 574
 575 static
 576 void get_allow_blocking(void)
 577 {
 578         const char *str_allow_blocking =
 579                 lttng_getenv("LTTNG_UST_ALLOW_BLOCKING");
 580
 581         if (str_allow_blocking) {
 582                 DBG("%s environment variable is set",
 583                         "LTTNG_UST_ALLOW_BLOCKING");
 584                 lttng_ust_ringbuffer_set_allow_blocking();
 585         }
 586 }
 587
 588 static
 589 int register_to_sessiond(int socket, enum ustctl_socket_type type)
 590 {
 591         return ustcomm_send_reg_msg(socket,
 592                 type,
 593                 CAA_BITS_PER_LONG,
 594                 lttng_alignof(uint8_t) * CHAR_BIT,
 595                 lttng_alignof(uint16_t) * CHAR_BIT,
 596                 lttng_alignof(uint32_t) * CHAR_BIT,
 597                 lttng_alignof(uint64_t) * CHAR_BIT,
 598                 lttng_alignof(unsigned long) * CHAR_BIT);
 599 }
 600
 601 static
 602 int send_reply(int sock, struct ustcomm_ust_reply *lur)
 603 {
 604         ssize_t len;
 605
 606         len = ustcomm_send_unix_sock(sock, lur, sizeof(*lur));
 607         switch (len) {
 608         case sizeof(*lur):
 609                 DBG("message successfully sent");
 610                 return 0;
 611         default:
 612                 if (len == -ECONNRESET) {
 613                         DBG("remote end closed connection");
 614                         return 0;
 615                 }
 616                 if (len < 0)
 617                         return len;
 618                 DBG("incorrect message size: %zd", len);
 619                 return -EINVAL;
 620         }
 621 }
 622
 623 static
 624 int handle_register_done(struct sock_info *sock_info)
 625 {
 626         int ret;
 627
 628         if (sock_info->constructor_sem_posted)
 629                 return 0;
 630         sock_info->constructor_sem_posted = 1;
 631         if (uatomic_read(&sem_count) <= 0) {
 632                 return 0;
 633         }
 634         ret = uatomic_add_return(&sem_count, -1);
 635         if (ret == 0) {
 636                 ret = sem_post(&constructor_wait);
 637                 assert(!ret);
 638         }
 639         return 0;
 640 }
 641
 642 /*
 643  * Only execute pending statedump after the constructor semaphore has
 644  * been posted by each listener thread. This means statedump will only
 645  * be performed after the "registration done" command is received from
 646  * each session daemon the application is connected to.
 647  *
 648  * This ensures we don't run into deadlock issues with the dynamic
 649  * loader mutex, which is held while the constructor is called and
 650  * waiting on the constructor semaphore. All operations requiring this
 651  * dynamic loader lock need to be postponed using this mechanism.
 652  */
 653 static
 654 void handle_pending_statedump(struct sock_info *sock_info)
 655 {
 656         int ctor_passed = sock_info->constructor_sem_posted;
 657
 658         if (ctor_passed && sock_info->statedump_pending) {
 659                 sock_info->statedump_pending = 0;
 660                 pthread_mutex_lock(&ust_fork_mutex);
 661                 lttng_handle_pending_statedump(sock_info);
 662                 pthread_mutex_unlock(&ust_fork_mutex);
 663         }
 664 }
 665
 666 static
 667 int handle_message(struct sock_info *sock_info,
 668                 int sock, struct ustcomm_ust_msg *lum)
 669 {
 670         int ret = 0;
 671         const struct lttng_ust_objd_ops *ops;
 672         struct ustcomm_ust_reply lur;
 673         union ust_args args;
 674         char ctxstr[LTTNG_UST_SYM_NAME_LEN];    /* App context string. */
 675         ssize_t len;
 676
 677         memset(&lur, 0, sizeof(lur));
 678
 679         if (ust_lock()) {
 680                 ret = -LTTNG_UST_ERR_EXITING;
 681                 goto error;
 682         }
 683
 684         ops = objd_ops(lum->handle);
 685         if (!ops) {
 686                 ret = -ENOENT;
 687                 goto error;
 688         }
 689
 690         switch (lum->cmd) {
 691         case LTTNG_UST_REGISTER_DONE:
 692                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 693                         ret = handle_register_done(sock_info);
 694                 else
 695                         ret = -EINVAL;
 696                 break;
 697         case LTTNG_UST_RELEASE:
 698                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 699                         ret = -EPERM;
 700                 else
 701                         ret = lttng_ust_objd_unref(lum->handle, 1);
 702                 break;
 703         case LTTNG_UST_FILTER:
 704         {
 705                 /* Receive filter data */
 706                 struct lttng_ust_filter_bytecode_node *bytecode;
 707
 708                 if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) {
 709                         ERR("Filter data size is too large: %u bytes",
 710                                 lum->u.filter.data_size);
 711                         ret = -EINVAL;
 712                         goto error;
 713                 }
 714
 715                 if (lum->u.filter.reloc_offset > lum->u.filter.data_size) {
 716                         ERR("Filter reloc offset %u is not within data",
 717                                 lum->u.filter.reloc_offset);
 718                         ret = -EINVAL;
 719                         goto error;
 720                 }
 721
 722                 bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size);
 723                 if (!bytecode) {
 724                         ret = -ENOMEM;
 725                         goto error;
 726                 }
 727                 len = ustcomm_recv_unix_sock(sock, bytecode->bc.data,
 728                                 lum->u.filter.data_size);
 729                 switch (len) {
 730                 case 0: /* orderly shutdown */
 731                         ret = 0;
 732                         free(bytecode);
 733                         goto error;
 734                 default:
 735                         if (len == lum->u.filter.data_size) {
 736                                 DBG("filter data received");
 737                                 break;
 738                         } else if (len < 0) {
 739                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 740                                 if (len == -ECONNRESET) {
 741                                         ERR("%s remote end closed connection", sock_info->name);
 742                                         ret = len;
 743                                         free(bytecode);
 744                                         goto error;
 745                                 }
 746                                 ret = len;
 747                                 free(bytecode);
 748                                 goto error;
 749                         } else {
 750                                 DBG("incorrect filter data message size: %zd", len);
 751                                 ret = -EINVAL;
 752                                 free(bytecode);
 753                                 goto error;
 754                         }
 755                 }
 756                 bytecode->bc.len = lum->u.filter.data_size;
 757                 bytecode->bc.reloc_offset = lum->u.filter.reloc_offset;
 758                 bytecode->bc.seqnum = lum->u.filter.seqnum;
 759                 if (ops->cmd) {
 760                         ret = ops->cmd(lum->handle, lum->cmd,
 761                                         (unsigned long) bytecode,
 762                                         &args, sock_info);
 763                         if (ret) {
 764                                 free(bytecode);
 765                         }
 766                         /* don't free bytecode if everything went fine. */
 767                 } else {
 768                         ret = -ENOSYS;
 769                         free(bytecode);
 770                 }
 771                 break;
 772         }
 773         case LTTNG_UST_EXCLUSION:
 774         {
 775                 /* Receive exclusion names */
 776                 struct lttng_ust_excluder_node *node;
 777                 unsigned int count;
 778
 779                 count = lum->u.exclusion.count;
 780                 if (count == 0) {
 781                         /* There are no names to read */
 782                         ret = 0;
 783                         goto error;
 784                 }
 785                 node = zmalloc(sizeof(*node) +
 786                                 count * LTTNG_UST_SYM_NAME_LEN);
 787                 if (!node) {
 788                         ret = -ENOMEM;
 789                         goto error;
 790                 }
 791                 node->excluder.count = count;
 792                 len = ustcomm_recv_unix_sock(sock, node->excluder.names,
 793                                 count * LTTNG_UST_SYM_NAME_LEN);
 794                 switch (len) {
 795                 case 0: /* orderly shutdown */
 796                         ret = 0;
 797                         free(node);
 798                         goto error;
 799                 default:
 800                         if (len == count * LTTNG_UST_SYM_NAME_LEN) {
 801                                 DBG("Exclusion data received");
 802                                 break;
 803                         } else if (len < 0) {
 804                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 805                                 if (len == -ECONNRESET) {
 806                                         ERR("%s remote end closed connection", sock_info->name);
 807                                         ret = len;
 808                                         free(node);
 809                                         goto error;
 810                                 }
 811                                 ret = len;
 812                                 free(node);
 813                                 goto error;
 814                         } else {
 815                                 DBG("Incorrect exclusion data message size: %zd", len);
 816                                 ret = -EINVAL;
 817                                 free(node);
 818                                 goto error;
 819                         }
 820                 }
 821                 if (ops->cmd) {
 822                         ret = ops->cmd(lum->handle, lum->cmd,
 823                                         (unsigned long) node,
 824                                         &args, sock_info);
 825                         if (ret) {
 826                                 free(node);
 827                         }
 828                         /* Don't free exclusion data if everything went fine. */
 829                 } else {
 830                         ret = -ENOSYS;
 831                         free(node);
 832                 }
 833                 break;
 834         }
 835         case LTTNG_UST_CHANNEL:
 836         {
 837                 void *chan_data;
 838                 int wakeup_fd;
 839
 840                 len = ustcomm_recv_channel_from_sessiond(sock,
 841                                 &chan_data, lum->u.channel.len,
 842                                 &wakeup_fd);
 843                 switch (len) {
 844                 case 0: /* orderly shutdown */
 845                         ret = 0;
 846                         goto error;
 847                 default:
 848                         if (len == lum->u.channel.len) {
 849                                 DBG("channel data received");
 850                                 break;
 851                         } else if (len < 0) {
 852                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 853                                 if (len == -ECONNRESET) {
 854                                         ERR("%s remote end closed connection", sock_info->name);
 855                                         ret = len;
 856                                         goto error;
 857                                 }
 858                                 ret = len;
 859                                 goto error;
 860                         } else {
 861                                 DBG("incorrect channel data message size: %zd", len);
 862                                 ret = -EINVAL;
 863                                 goto error;
 864                         }
 865                 }
 866                 args.channel.chan_data = chan_data;
 867                 args.channel.wakeup_fd = wakeup_fd;
 868                 if (ops->cmd)
 869                         ret = ops->cmd(lum->handle, lum->cmd,
 870                                         (unsigned long) &lum->u,
 871                                         &args, sock_info);
 872                 else
 873                         ret = -ENOSYS;
 874                 break;
 875         }
 876         case LTTNG_UST_STREAM:
 877         {
 878                 uint64_t memory_map_size;
 879
 880                 /* Receive shm_fd, wakeup_fd */
 881                 ret = ustcomm_recv_stream_from_sessiond(sock,
 882                         &memory_map_size,
 883                         &args.stream.shm_fd,
 884                         &args.stream.wakeup_fd);
 885                 if (ret) {
 886                         goto error;
 887                 }
 888                 lum->u.stream.len = memory_map_size;
 889
 890                 if (ops->cmd)
 891                         ret = ops->cmd(lum->handle, lum->cmd,
 892                                         (unsigned long) &lum->u,
 893                                         &args, sock_info);
 894                 else
 895                         ret = -ENOSYS;
 896                 break;
 897         }
 898         case LTTNG_UST_CONTEXT:
 899                 switch (lum->u.context.ctx) {
 900                 case LTTNG_UST_CONTEXT_APP_CONTEXT:
 901                 {
 902                         char *p;
 903                         size_t ctxlen, recvlen;
 904
 905                         ctxlen = strlen("$app.") + lum->u.context.u.app_ctx.provider_name_len - 1
 906                                         + strlen(":") + lum->u.context.u.app_ctx.ctx_name_len;
 907                         if (ctxlen >= LTTNG_UST_SYM_NAME_LEN) {
 908                                 ERR("Application context string length size is too large: %zu bytes",
 909                                         ctxlen);
 910                                 ret = -EINVAL;
 911                                 goto error;
 912                         }
 913                         strcpy(ctxstr, "$app.");
 914                         p = &ctxstr[strlen("$app.")];
 915                         recvlen = ctxlen - strlen("$app.");
 916                         len = ustcomm_recv_unix_sock(sock, p, recvlen);
 917                         switch (len) {
 918                         case 0: /* orderly shutdown */
 919                                 ret = 0;
 920                                 goto error;
 921                         default:
 922                                 if (len == recvlen) {
 923                                         DBG("app context data received");
 924                                         break;
 925                                 } else if (len < 0) {
 926                                         DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 927                                         if (len == -ECONNRESET) {
 928                                                 ERR("%s remote end closed connection", sock_info->name);
 929                                                 ret = len;
 930                                                 goto error;
 931                                         }
 932                                         ret = len;
 933                                         goto error;
 934                                 } else {
 935                                         DBG("incorrect app context data message size: %zd", len);
 936                                         ret = -EINVAL;
 937                                         goto error;
 938                                 }
 939                         }
 940                         /* Put : between provider and ctxname. */
 941                         p[lum->u.context.u.app_ctx.provider_name_len - 1] = ':';
 942                         args.app_context.ctxname = ctxstr;
 943                         break;
 944                 }
 945                 default:
 946                         break;
 947                 }
 948                 if (ops->cmd) {
 949                         ret = ops->cmd(lum->handle, lum->cmd,
 950                                         (unsigned long) &lum->u,
 951                                         &args, sock_info);
 952                 } else {
 953                         ret = -ENOSYS;
 954                 }
 955                 break;
 956         default:
 957                 if (ops->cmd)
 958                         ret = ops->cmd(lum->handle, lum->cmd,
 959                                         (unsigned long) &lum->u,
 960                                         &args, sock_info);
 961                 else
 962                         ret = -ENOSYS;
 963                 break;
 964         }
 965
 966         lur.handle = lum->handle;
 967         lur.cmd = lum->cmd;
 968         lur.ret_val = ret;
 969         if (ret >= 0) {
 970                 lur.ret_code = LTTNG_UST_OK;
 971         } else {
 972                 /*
 973                  * Use -LTTNG_UST_ERR as wildcard for UST internal
 974                  * error that are not caused by the transport, except if
 975                  * we already have a more precise error message to
 976                  * report.
 977                  */
 978                 if (ret > -LTTNG_UST_ERR) {
 979                         /* Translate code to UST error. */
 980                         switch (ret) {
 981                         case -EEXIST:
 982                                 lur.ret_code = -LTTNG_UST_ERR_EXIST;
 983                                 break;
 984                         case -EINVAL:
 985                                 lur.ret_code = -LTTNG_UST_ERR_INVAL;
 986                                 break;
 987                         case -ENOENT:
 988                                 lur.ret_code = -LTTNG_UST_ERR_NOENT;
 989                                 break;
 990                         case -EPERM:
 991                                 lur.ret_code = -LTTNG_UST_ERR_PERM;
 992                                 break;
 993                         case -ENOSYS:
 994                                 lur.ret_code = -LTTNG_UST_ERR_NOSYS;
 995                                 break;
 996                         default:
 997                                 lur.ret_code = -LTTNG_UST_ERR;
 998                                 break;
 999                         }
1000                 } else {
1001                         lur.ret_code = ret;
1002                 }
1003         }
1004         if (ret >= 0) {
1005                 switch (lum->cmd) {
1006                 case LTTNG_UST_TRACER_VERSION:
1007                         lur.u.version = lum->u.version;
1008                         break;
1009                 case LTTNG_UST_TRACEPOINT_LIST_GET:
1010                         memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
1011                         break;
1012                 }
1013         }
1014         DBG("Return value: %d", lur.ret_val);
1015
1016         ust_unlock();
1017
1018         /*
1019          * Performed delayed statedump operations outside of the UST
1020          * lock. We need to take the dynamic loader lock before we take
1021          * the UST lock internally within handle_pending_statedump().
1022           */
1023         handle_pending_statedump(sock_info);
1024
1025         if (ust_lock()) {
1026                 ret = -LTTNG_UST_ERR_EXITING;
1027                 goto error;
1028         }
1029
1030         ret = send_reply(sock, &lur);
1031         if (ret < 0) {
1032                 DBG("error sending reply");
1033                 goto error;
1034         }
1035
1036         /*
1037          * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field
1038          * after the reply.
1039          */
1040         if (lur.ret_code == LTTNG_UST_OK) {
1041                 switch (lum->cmd) {
1042                 case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET:
1043                         len = ustcomm_send_unix_sock(sock,
1044                                 &args.field_list.entry,
1045                                 sizeof(args.field_list.entry));
1046                         if (len < 0) {
1047                                 ret = len;
1048                                 goto error;
1049                         }
1050                         if (len != sizeof(args.field_list.entry)) {
1051                                 ret = -EINVAL;
1052                                 goto error;
1053                         }
1054                 }
1055         }
1056
1057 error:
1058         ust_unlock();
1059
1060         return ret;
1061 }
1062
1063 static
1064 void cleanup_sock_info(struct sock_info *sock_info, int exiting)
1065 {
1066         int ret;
1067
1068         if (sock_info->root_handle != -1) {
1069                 ret = lttng_ust_objd_unref(sock_info->root_handle, 1);
1070                 if (ret) {
1071                         ERR("Error unref root handle");
1072                 }
1073                 sock_info->root_handle = -1;
1074         }
1075         sock_info->constructor_sem_posted = 0;
1076
1077         /*
1078          * wait_shm_mmap, socket and notify socket are used by listener
1079          * threads outside of the ust lock, so we cannot tear them down
1080          * ourselves, because we cannot join on these threads. Leave
1081          * responsibility of cleaning up these resources to the OS
1082          * process exit.
1083          */
1084         if (exiting)
1085                 return;
1086
1087         if (sock_info->socket != -1) {
1088                 ret = ustcomm_close_unix_sock(sock_info->socket);
1089                 if (ret) {
1090                         ERR("Error closing ust cmd socket");
1091                 }
1092                 sock_info->socket = -1;
1093         }
1094         if (sock_info->notify_socket != -1) {
1095                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
1096                 if (ret) {
1097                         ERR("Error closing ust notify socket");
1098                 }
1099                 sock_info->notify_socket = -1;
1100         }
1101         if (sock_info->wait_shm_mmap) {
1102                 long page_size;
1103
1104                 page_size = sysconf(_SC_PAGE_SIZE);
1105                 if (page_size <= 0) {
1106                         if (!page_size) {
1107                                 errno = EINVAL;
1108                         }
1109                         PERROR("Error in sysconf(_SC_PAGE_SIZE)");
1110                 } else {
1111                         ret = munmap(sock_info->wait_shm_mmap, page_size);
1112                         if (ret) {
1113                                 ERR("Error unmapping wait shm");
1114                         }
1115                 }
1116                 sock_info->wait_shm_mmap = NULL;
1117         }
1118 }
1119
1120 /*
1121  * Using fork to set umask in the child process (not multi-thread safe).
1122  * We deal with the shm_open vs ftruncate race (happening when the
1123  * sessiond owns the shm and does not let everybody modify it, to ensure
1124  * safety against shm_unlink) by simply letting the mmap fail and
1125  * retrying after a few seconds.
1126  * For global shm, everybody has rw access to it until the sessiond
1127  * starts.
1128  */
1129 static
1130 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
1131 {
1132         int wait_shm_fd, ret;
1133         pid_t pid;
1134
1135         /*
1136          * Try to open read-only.
1137          */
1138         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
1139         if (wait_shm_fd >= 0) {
1140                 int32_t tmp_read;
1141                 ssize_t len;
1142                 size_t bytes_read = 0;
1143
1144                 /*
1145                  * Try to read the fd. If unable to do so, try opening
1146                  * it in write mode.
1147                  */
1148                 do {
1149                         len = read(wait_shm_fd,
1150                                 &((char *) &tmp_read)[bytes_read],
1151                                 sizeof(tmp_read) - bytes_read);
1152                         if (len > 0) {
1153                                 bytes_read += len;
1154                         }
1155                 } while ((len < 0 && errno == EINTR)
1156                         || (len > 0 && bytes_read < sizeof(tmp_read)));
1157                 if (bytes_read != sizeof(tmp_read)) {
1158                         ret = close(wait_shm_fd);
1159                         if (ret) {
1160                                 ERR("close wait_shm_fd");
1161                         }
1162                         goto open_write;
1163                 }
1164                 goto end;
1165         } else if (wait_shm_fd < 0 && errno != ENOENT) {
1166                 /*
1167                  * Real-only open did not work, and it's not because the
1168                  * entry was not present. It's a failure that prohibits
1169                  * using shm.
1170                  */
1171                 ERR("Error opening shm %s", sock_info->wait_shm_path);
1172                 goto end;
1173         }
1174
1175 open_write:
1176         /*
1177          * If the open failed because the file did not exist, or because
1178          * the file was not truncated yet, try creating it ourself.
1179          */
1180         URCU_TLS(lttng_ust_nest_count)++;
1181         pid = fork();
1182         URCU_TLS(lttng_ust_nest_count)--;
1183         if (pid > 0) {
1184                 int status;
1185
1186                 /*
1187                  * Parent: wait for child to return, in which case the
1188                  * shared memory map will have been created.
1189                  */
1190                 pid = wait(&status);
1191                 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
1192                         wait_shm_fd = -1;
1193                         goto end;
1194                 }
1195                 /*
1196                  * Try to open read-only again after creation.
1197                  */
1198                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
1199                 if (wait_shm_fd < 0) {
1200                         /*
1201                          * Real-only open did not work. It's a failure
1202                          * that prohibits using shm.
1203                          */
1204                         ERR("Error opening shm %s", sock_info->wait_shm_path);
1205                         goto end;
1206                 }
1207                 goto end;
1208         } else if (pid == 0) {
1209                 int create_mode;
1210
1211                 /* Child */
1212                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
1213                 if (sock_info->global)
1214                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
1215                 /*
1216                  * We're alone in a child process, so we can modify the
1217                  * process-wide umask.
1218                  */
1219                 umask(~create_mode);
1220                 /*
1221                  * Try creating shm (or get rw access).
1222                  * We don't do an exclusive open, because we allow other
1223                  * processes to create+ftruncate it concurrently.
1224                  */
1225                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
1226                                 O_RDWR | O_CREAT, create_mode);
1227                 if (wait_shm_fd >= 0) {
1228                         ret = ftruncate(wait_shm_fd, mmap_size);
1229                         if (ret) {
1230                                 PERROR("ftruncate");
1231                                 _exit(EXIT_FAILURE);
1232                         }
1233                         _exit(EXIT_SUCCESS);
1234                 }
1235                 /*
1236                  * For local shm, we need to have rw access to accept
1237                  * opening it: this means the local sessiond will be
1238                  * able to wake us up. For global shm, we open it even
1239                  * if rw access is not granted, because the root.root
1240                  * sessiond will be able to override all rights and wake
1241                  * us up.
1242                  */
1243                 if (!sock_info->global && errno != EACCES) {
1244                         ERR("Error opening shm %s", sock_info->wait_shm_path);
1245                         _exit(EXIT_FAILURE);
1246                 }
1247                 /*
1248                  * The shm exists, but we cannot open it RW. Report
1249                  * success.
1250                  */
1251                 _exit(EXIT_SUCCESS);
1252         } else {
1253                 return -1;
1254         }
1255 end:
1256         if (wait_shm_fd >= 0 && !sock_info->global) {
1257                 struct stat statbuf;
1258
1259                 /*
1260                  * Ensure that our user is the owner of the shm file for
1261                  * local shm. If we do not own the file, it means our
1262                  * sessiond will not have access to wake us up (there is
1263                  * probably a rogue process trying to fake our
1264                  * sessiond). Fallback to polling method in this case.
1265                  */
1266                 ret = fstat(wait_shm_fd, &statbuf);
1267                 if (ret) {
1268                         PERROR("fstat");
1269                         goto error_close;
1270                 }
1271                 if (statbuf.st_uid != getuid())
1272                         goto error_close;
1273         }
1274         return wait_shm_fd;
1275
1276 error_close:
1277         ret = close(wait_shm_fd);
1278         if (ret) {
1279                 PERROR("Error closing fd");
1280         }
1281         return -1;
1282 }
1283
1284 static
1285 char *get_map_shm(struct sock_info *sock_info)
1286 {
1287         long page_size;
1288         int wait_shm_fd, ret;
1289         char *wait_shm_mmap;
1290
1291         page_size = sysconf(_SC_PAGE_SIZE);
1292         if (page_size <= 0) {
1293                 if (!page_size) {
1294                         errno = EINVAL;
1295                 }
1296                 PERROR("Error in sysconf(_SC_PAGE_SIZE)");
1297                 goto error;
1298         }
1299
1300         lttng_ust_lock_fd_tracker();
1301         wait_shm_fd = get_wait_shm(sock_info, page_size);
1302         if (wait_shm_fd < 0) {
1303                 lttng_ust_unlock_fd_tracker();
1304                 goto error;
1305         }
1306
1307         ret = lttng_ust_add_fd_to_tracker(wait_shm_fd);
1308         if (ret < 0) {
1309                 ret = close(wait_shm_fd);
1310                 if (!ret) {
1311                         PERROR("Error closing fd");
1312                 }
1313                 lttng_ust_unlock_fd_tracker();
1314                 goto error;
1315         }
1316
1317         wait_shm_fd = ret;
1318         lttng_ust_unlock_fd_tracker();
1319
1320         wait_shm_mmap = mmap(NULL, page_size, PROT_READ,
1321                   MAP_SHARED, wait_shm_fd, 0);
1322
1323         /* close shm fd immediately after taking the mmap reference */
1324         lttng_ust_lock_fd_tracker();
1325         ret = close(wait_shm_fd);
1326         if (!ret) {
1327                 lttng_ust_delete_fd_from_tracker(wait_shm_fd);
1328         } else {
1329                 PERROR("Error closing fd");
1330         }
1331         lttng_ust_unlock_fd_tracker();
1332
1333         if (wait_shm_mmap == MAP_FAILED) {
1334                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
1335                 goto error;
1336         }
1337         return wait_shm_mmap;
1338
1339 error:
1340         return NULL;
1341 }
1342
1343 static
1344 void wait_for_sessiond(struct sock_info *sock_info)
1345 {
1346         /* Use ust_lock to check if we should quit. */
1347         if (ust_lock()) {
1348                 goto quit;
1349         }
1350         if (wait_poll_fallback) {
1351                 goto error;
1352         }
1353         ust_unlock();
1354
1355         assert(sock_info->wait_shm_mmap);
1356
1357         DBG("Waiting for %s apps sessiond", sock_info->name);
1358         /* Wait for futex wakeup */
1359         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap))
1360                 goto end_wait;
1361
1362         while (futex_async((int32_t *) sock_info->wait_shm_mmap,
1363                         FUTEX_WAIT, 0, NULL, NULL, 0)) {
1364                 switch (errno) {
1365                 case EWOULDBLOCK:
1366                         /* Value already changed. */
1367                         goto end_wait;
1368                 case EINTR:
1369                         /* Retry if interrupted by signal. */
1370                         break;  /* Get out of switch. */
1371                 case EFAULT:
1372                         wait_poll_fallback = 1;
1373                         DBG(
1374 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
1375 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
1376 "Please upgrade your kernel "
1377 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
1378 "mainline). LTTng-UST will use polling mode fallback.");
1379                         if (ust_debug())
1380                                 PERROR("futex");
1381                         goto end_wait;
1382                 }
1383         }
1384 end_wait:
1385         return;
1386
1387 quit:
1388         ust_unlock();
1389         return;
1390
1391 error:
1392         ust_unlock();
1393         return;
1394 }
1395
1396 /*
1397  * This thread does not allocate any resource, except within
1398  * handle_message, within mutex protection. This mutex protects against
1399  * fork and exit.
1400  * The other moment it allocates resources is at socket connection, which
1401  * is also protected by the mutex.
1402  */
1403 static
1404 void *ust_listener_thread(void *arg)
1405 {
1406         struct sock_info *sock_info = arg;
1407         int sock, ret, prev_connect_failed = 0, has_waited = 0, fd;
1408         long timeout;
1409
1410         lttng_ust_fixup_tls();
1411         /*
1412          * If available, add '-ust' to the end of this thread's
1413          * process name
1414          */
1415         ret = lttng_ust_setustprocname();
1416         if (ret) {
1417                 ERR("Unable to set UST process name");
1418         }
1419
1420         /* Restart trying to connect to the session daemon */
1421 restart:
1422         if (prev_connect_failed) {
1423                 /* Wait for sessiond availability with pipe */
1424                 wait_for_sessiond(sock_info);
1425                 if (has_waited) {
1426                         has_waited = 0;
1427                         /*
1428                          * Sleep for 5 seconds before retrying after a
1429                          * sequence of failure / wait / failure. This
1430                          * deals with a killed or broken session daemon.
1431                          */
1432                         sleep(5);
1433                 } else {
1434                         has_waited = 1;
1435                 }
1436                 prev_connect_failed = 0;
1437         }
1438
1439         if (ust_lock()) {
1440                 goto quit;
1441         }
1442
1443         if (sock_info->socket != -1) {
1444                 /* FD tracker is updated by ustcomm_close_unix_sock() */
1445                 ret = ustcomm_close_unix_sock(sock_info->socket);
1446                 if (ret) {
1447                         ERR("Error closing %s ust cmd socket",
1448                                 sock_info->name);
1449                 }
1450                 sock_info->socket = -1;
1451         }
1452         if (sock_info->notify_socket != -1) {
1453                 /* FD tracker is updated by ustcomm_close_unix_sock() */
1454                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
1455                 if (ret) {
1456                         ERR("Error closing %s ust notify socket",
1457                                 sock_info->name);
1458                 }
1459                 sock_info->notify_socket = -1;
1460         }
1461
1462
1463         /*
1464          * Register. We need to perform both connect and sending
1465          * registration message before doing the next connect otherwise
1466          * we may reach unix socket connect queue max limits and block
1467          * on the 2nd connect while the session daemon is awaiting the
1468          * first connect registration message.
1469          */
1470         /* Connect cmd socket */
1471         lttng_ust_lock_fd_tracker();
1472         ret = ustcomm_connect_unix_sock(sock_info->sock_path,
1473                 get_connect_sock_timeout());
1474         if (ret < 0) {
1475                 lttng_ust_unlock_fd_tracker();
1476                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1477                 prev_connect_failed = 1;
1478
1479                 /*
1480                  * If we cannot find the sessiond daemon, don't delay
1481                  * constructor execution.
1482                  */
1483                 ret = handle_register_done(sock_info);
1484                 assert(!ret);
1485                 ust_unlock();
1486                 goto restart;
1487         }
1488         fd = ret;
1489         ret = lttng_ust_add_fd_to_tracker(fd);
1490         if (ret < 0) {
1491                 ret = close(fd);
1492                 if (ret) {
1493                         PERROR("close on sock_info->socket");
1494                 }
1495                 ret = -1;
1496                 lttng_ust_unlock_fd_tracker();
1497                 ust_unlock();
1498                 goto quit;
1499         }
1500
1501         sock_info->socket = ret;
1502         lttng_ust_unlock_fd_tracker();
1503
1504         ust_unlock();
1505         /*
1506          * Unlock/relock ust lock because connect is blocking (with
1507          * timeout). Don't delay constructors on the ust lock for too
1508          * long.
1509          */
1510         if (ust_lock()) {
1511                 goto quit;
1512         }
1513
1514         /*
1515          * Create only one root handle per listener thread for the whole
1516          * process lifetime, so we ensure we get ID which is statically
1517          * assigned to the root handle.
1518          */
1519         if (sock_info->root_handle == -1) {
1520                 ret = lttng_abi_create_root_handle();
1521                 if (ret < 0) {
1522                         ERR("Error creating root handle");
1523                         goto quit;
1524                 }
1525                 sock_info->root_handle = ret;
1526         }
1527
1528         ret = register_to_sessiond(sock_info->socket, USTCTL_SOCKET_CMD);
1529         if (ret < 0) {
1530                 ERR("Error registering to %s ust cmd socket",
1531                         sock_info->name);
1532                 prev_connect_failed = 1;
1533                 /*
1534                  * If we cannot register to the sessiond daemon, don't
1535                  * delay constructor execution.
1536                  */
1537                 ret = handle_register_done(sock_info);
1538                 assert(!ret);
1539                 ust_unlock();
1540                 goto restart;
1541         }
1542
1543         ust_unlock();
1544         /*
1545          * Unlock/relock ust lock because connect is blocking (with
1546          * timeout). Don't delay constructors on the ust lock for too
1547          * long.
1548          */
1549         if (ust_lock()) {
1550                 goto quit;
1551         }
1552
1553         /* Connect notify socket */
1554         lttng_ust_lock_fd_tracker();
1555         ret = ustcomm_connect_unix_sock(sock_info->sock_path,
1556                 get_connect_sock_timeout());
1557         if (ret < 0) {
1558                 lttng_ust_unlock_fd_tracker();
1559                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1560                 prev_connect_failed = 1;
1561
1562                 /*
1563                  * If we cannot find the sessiond daemon, don't delay
1564                  * constructor execution.
1565                  */
1566                 ret = handle_register_done(sock_info);
1567                 assert(!ret);
1568                 ust_unlock();
1569                 goto restart;
1570         }
1571
1572         fd = ret;
1573         ret = lttng_ust_add_fd_to_tracker(fd);
1574         if (ret < 0) {
1575                 ret = close(fd);
1576                 if (ret) {
1577                         PERROR("close on sock_info->notify_socket");
1578                 }
1579                 ret = -1;
1580                 lttng_ust_unlock_fd_tracker();
1581                 ust_unlock();
1582                 goto quit;
1583         }
1584
1585         sock_info->notify_socket = ret;
1586         lttng_ust_unlock_fd_tracker();
1587
1588         ust_unlock();
1589         /*
1590          * Unlock/relock ust lock because connect is blocking (with
1591          * timeout). Don't delay constructors on the ust lock for too
1592          * long.
1593          */
1594         if (ust_lock()) {
1595                 goto quit;
1596         }
1597
1598         timeout = get_notify_sock_timeout();
1599         if (timeout >= 0) {
1600                 /*
1601                  * Give at least 10ms to sessiond to reply to
1602                  * notifications.
1603                  */
1604                 if (timeout < 10)
1605                         timeout = 10;
1606                 ret = ustcomm_setsockopt_rcv_timeout(sock_info->notify_socket,
1607                                 timeout);
1608                 if (ret < 0) {
1609                         WARN("Error setting socket receive timeout");
1610                 }
1611                 ret = ustcomm_setsockopt_snd_timeout(sock_info->notify_socket,
1612                                 timeout);
1613                 if (ret < 0) {
1614                         WARN("Error setting socket send timeout");
1615                 }
1616         } else if (timeout < -1) {
1617                 WARN("Unsupported timeout value %ld", timeout);
1618         }
1619
1620         ret = register_to_sessiond(sock_info->notify_socket,
1621                         USTCTL_SOCKET_NOTIFY);
1622         if (ret < 0) {
1623                 ERR("Error registering to %s ust notify socket",
1624                         sock_info->name);
1625                 prev_connect_failed = 1;
1626                 /*
1627                  * If we cannot register to the sessiond daemon, don't
1628                  * delay constructor execution.
1629                  */
1630                 ret = handle_register_done(sock_info);
1631                 assert(!ret);
1632                 ust_unlock();
1633                 goto restart;
1634         }
1635         sock = sock_info->socket;
1636
1637         ust_unlock();
1638
1639         for (;;) {
1640                 ssize_t len;
1641                 struct ustcomm_ust_msg lum;
1642
1643                 len = ustcomm_recv_unix_sock(sock, &lum, sizeof(lum));
1644                 switch (len) {
1645                 case 0: /* orderly shutdown */
1646                         DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
1647                         if (ust_lock()) {
1648                                 goto quit;
1649                         }
1650                         /*
1651                          * Either sessiond has shutdown or refused us by closing the socket.
1652                          * In either case, we don't want to delay construction execution,
1653                          * and we need to wait before retry.
1654                          */
1655                         prev_connect_failed = 1;
1656                         /*
1657                          * If we cannot register to the sessiond daemon, don't
1658                          * delay constructor execution.
1659                          */
1660                         ret = handle_register_done(sock_info);
1661                         assert(!ret);
1662                         ust_unlock();
1663                         goto end;
1664                 case sizeof(lum):
1665                         print_cmd(lum.cmd, lum.handle);
1666                         ret = handle_message(sock_info, sock, &lum);
1667                         if (ret) {
1668                                 ERR("Error handling message for %s socket",
1669                                         sock_info->name);
1670                                 /*
1671                                  * Close socket if protocol error is
1672                                  * detected.
1673                                  */
1674                                 goto end;
1675                         }
1676                         continue;
1677                 default:
1678                         if (len < 0) {
1679                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
1680                         } else {
1681                                 DBG("incorrect message size (%s socket): %zd", sock_info->name, len);
1682                         }
1683                         if (len == -ECONNRESET) {
1684                                 DBG("%s remote end closed connection", sock_info->name);
1685                                 goto end;
1686                         }
1687                         goto end;
1688                 }
1689
1690         }
1691 end:
1692         if (ust_lock()) {
1693                 goto quit;
1694         }
1695         /* Cleanup socket handles before trying to reconnect */
1696         lttng_ust_objd_table_owner_cleanup(sock_info);
1697         ust_unlock();
1698         goto restart;   /* try to reconnect */
1699
1700 quit:
1701         ust_unlock();
1702
1703         pthread_mutex_lock(&ust_exit_mutex);
1704         sock_info->thread_active = 0;
1705         pthread_mutex_unlock(&ust_exit_mutex);
1706         return NULL;
1707 }
1708
1709 /*
1710  * Weak symbol to call when the ust malloc wrapper is not loaded.
1711  */
1712 __attribute__((weak))
1713 void lttng_ust_malloc_wrapper_init(void)
1714 {
1715 }
1716
1717 /*
1718  * sessiond monitoring thread: monitor presence of global and per-user
1719  * sessiond by polling the application common named pipe.
1720  */
1721 void __attribute__((constructor)) lttng_ust_init(void)
1722 {
1723         struct timespec constructor_timeout;
1724         sigset_t sig_all_blocked, orig_parent_mask;
1725         pthread_attr_t thread_attr;
1726         int timeout_mode;
1727         int ret;
1728         void *handle;
1729
1730         if (uatomic_xchg(&initialized, 1) == 1)
1731                 return;
1732
1733         /*
1734          * Fixup interdependency between TLS fixup mutex (which happens
1735          * to be the dynamic linker mutex) and ust_lock, taken within
1736          * the ust lock.
1737          */
1738         lttng_ust_fixup_tls();
1739
1740         lttng_ust_loaded = 1;
1741
1742         /*
1743          * We need to ensure that the liblttng-ust library is not unloaded to avoid
1744          * the unloading of code used by the ust_listener_threads as we can not
1745          * reliably know when they exited. To do that, manually load
1746          * liblttng-ust.so to increment the dynamic loader's internal refcount for
1747          * this library so it never becomes zero, thus never gets unloaded from the
1748          * address space of the process. Since we are already running in the
1749          * constructor of the LTTNG_UST_LIB_SO_NAME library, calling dlopen will
1750          * simply increment the refcount and no additionnal work is needed by the
1751          * dynamic loader as the shared library is already loaded in the address
1752          * space. As a safe guard, we use the RTLD_NODELETE flag to prevent
1753          * unloading of the UST library if its refcount becomes zero (which should
1754          * never happen). Do the return value check but discard the handle at the
1755          * end of the function as it's not needed.
1756          */
1757         handle = dlopen(LTTNG_UST_LIB_SO_NAME, RTLD_LAZY | RTLD_NODELETE);
1758         if (!handle) {
1759                 ERR("dlopen of liblttng-ust shared library (%s).", LTTNG_UST_LIB_SO_NAME);
1760         }
1761
1762         /*
1763          * We want precise control over the order in which we construct
1764          * our sub-libraries vs starting to receive commands from
1765          * sessiond (otherwise leading to errors when trying to create
1766          * sessiond before the init functions are completed).
1767          */
1768         init_usterr();
1769         lttng_ust_getenv_init();        /* Needs init_usterr() to be completed. */
1770         init_tracepoint();
1771         lttng_ust_init_fd_tracker();
1772         lttng_ust_clock_init();
1773         lttng_ust_getcpu_init();
1774         lttng_ust_statedump_init();
1775         lttng_ring_buffer_metadata_client_init();
1776         lttng_ring_buffer_client_overwrite_init();
1777         lttng_ring_buffer_client_overwrite_rt_init();
1778         lttng_ring_buffer_client_discard_init();
1779         lttng_ring_buffer_client_discard_rt_init();
1780         lttng_perf_counter_init();
1781         /*
1782          * Invoke ust malloc wrapper init before starting other threads.
1783          */
1784         lttng_ust_malloc_wrapper_init();
1785
1786         timeout_mode = get_constructor_timeout(&constructor_timeout);
1787
1788         get_allow_blocking();
1789
1790         ret = sem_init(&constructor_wait, 0, 0);
1791         if (ret) {
1792                 PERROR("sem_init");
1793         }
1794
1795         ret = setup_global_apps();
1796         if (ret) {
1797                 assert(global_apps.allowed == 0);
1798                 DBG("global apps setup returned %d", ret);
1799         }
1800
1801         ret = setup_local_apps();
1802         if (ret) {
1803                 assert(local_apps.allowed == 0);
1804                 DBG("local apps setup returned %d", ret);
1805         }
1806
1807         /* A new thread created by pthread_create inherits the signal mask
1808          * from the parent. To avoid any signal being received by the
1809          * listener thread, we block all signals temporarily in the parent,
1810          * while we create the listener thread.
1811          */
1812         sigfillset(&sig_all_blocked);
1813         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
1814         if (ret) {
1815                 ERR("pthread_sigmask: %s", strerror(ret));
1816         }
1817
1818         ret = pthread_attr_init(&thread_attr);
1819         if (ret) {
1820                 ERR("pthread_attr_init: %s", strerror(ret));
1821         }
1822         ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
1823         if (ret) {
1824                 ERR("pthread_attr_setdetachstate: %s", strerror(ret));
1825         }
1826
1827         if (global_apps.allowed) {
1828                 pthread_mutex_lock(&ust_exit_mutex);
1829                 ret = pthread_create(&global_apps.ust_listener, &thread_attr,
1830                                 ust_listener_thread, &global_apps);
1831                 if (ret) {
1832                         ERR("pthread_create global: %s", strerror(ret));
1833                 }
1834                 global_apps.thread_active = 1;
1835                 pthread_mutex_unlock(&ust_exit_mutex);
1836         } else {
1837                 handle_register_done(&global_apps);
1838         }
1839
1840         if (local_apps.allowed) {
1841                 pthread_mutex_lock(&ust_exit_mutex);
1842                 ret = pthread_create(&local_apps.ust_listener, &thread_attr,
1843                                 ust_listener_thread, &local_apps);
1844                 if (ret) {
1845                         ERR("pthread_create local: %s", strerror(ret));
1846                 }
1847                 local_apps.thread_active = 1;
1848                 pthread_mutex_unlock(&ust_exit_mutex);
1849         } else {
1850                 handle_register_done(&local_apps);
1851         }
1852         ret = pthread_attr_destroy(&thread_attr);
1853         if (ret) {
1854                 ERR("pthread_attr_destroy: %s", strerror(ret));
1855         }
1856
1857         /* Restore original signal mask in parent */
1858         ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
1859         if (ret) {
1860                 ERR("pthread_sigmask: %s", strerror(ret));
1861         }
1862
1863         switch (timeout_mode) {
1864         case 1: /* timeout wait */
1865                 do {
1866                         ret = sem_timedwait(&constructor_wait,
1867                                         &constructor_timeout);
1868                 } while (ret < 0 && errno == EINTR);
1869                 if (ret < 0) {
1870                         switch (errno) {
1871                         case ETIMEDOUT:
1872                                 ERR("Timed out waiting for lttng-sessiond");
1873                                 break;
1874                         case EINVAL:
1875                                 PERROR("sem_timedwait");
1876                                 break;
1877                         default:
1878                                 ERR("Unexpected error \"%s\" returned by sem_timedwait",
1879                                         strerror(errno));
1880                         }
1881                 }
1882                 break;
1883         case -1:/* wait forever */
1884                 do {
1885                         ret = sem_wait(&constructor_wait);
1886                 } while (ret < 0 && errno == EINTR);
1887                 if (ret < 0) {
1888                         switch (errno) {
1889                         case EINVAL:
1890                                 PERROR("sem_wait");
1891                                 break;
1892                         default:
1893                                 ERR("Unexpected error \"%s\" returned by sem_wait",
1894                                         strerror(errno));
1895                         }
1896                 }
1897                 break;
1898         case 0: /* no timeout */
1899                 break;
1900         }
1901 }
1902
1903 static
1904 void lttng_ust_cleanup(int exiting)
1905 {
1906         cleanup_sock_info(&global_apps, exiting);
1907         cleanup_sock_info(&local_apps, exiting);
1908         local_apps.allowed = 0;
1909         global_apps.allowed = 0;
1910         /*
1911          * The teardown in this function all affect data structures
1912          * accessed under the UST lock by the listener thread. This
1913          * lock, along with the lttng_ust_comm_should_quit flag, ensure
1914          * that none of these threads are accessing this data at this
1915          * point.
1916          */
1917         lttng_ust_abi_exit();
1918         lttng_ust_events_exit();
1919         lttng_perf_counter_exit();
1920         lttng_ring_buffer_client_discard_rt_exit();
1921         lttng_ring_buffer_client_discard_exit();
1922         lttng_ring_buffer_client_overwrite_rt_exit();
1923         lttng_ring_buffer_client_overwrite_exit();
1924         lttng_ring_buffer_metadata_client_exit();
1925         lttng_ust_statedump_destroy();
1926         exit_tracepoint();
1927         if (!exiting) {
1928                 /* Reinitialize values for fork */
1929                 sem_count = 2;
1930                 lttng_ust_comm_should_quit = 0;
1931                 initialized = 0;
1932         }
1933 }
1934
1935 void __attribute__((destructor)) lttng_ust_exit(void)
1936 {
1937         int ret;
1938
1939         /*
1940          * Using pthread_cancel here because:
1941          * A) we don't want to hang application teardown.
1942          * B) the thread is not allocating any resource.
1943          */
1944
1945         /*
1946          * Require the communication thread to quit. Synchronize with
1947          * mutexes to ensure it is not in a mutex critical section when
1948          * pthread_cancel is later called.
1949          */
1950         ust_lock_nocheck();
1951         lttng_ust_comm_should_quit = 1;
1952         ust_unlock();
1953
1954         pthread_mutex_lock(&ust_exit_mutex);
1955         /* cancel threads */
1956         if (global_apps.thread_active) {
1957                 ret = pthread_cancel(global_apps.ust_listener);
1958                 if (ret) {
1959                         ERR("Error cancelling global ust listener thread: %s",
1960                                 strerror(ret));
1961                 } else {
1962                         global_apps.thread_active = 0;
1963                 }
1964         }
1965         if (local_apps.thread_active) {
1966                 ret = pthread_cancel(local_apps.ust_listener);
1967                 if (ret) {
1968                         ERR("Error cancelling local ust listener thread: %s",
1969                                 strerror(ret));
1970                 } else {
1971                         local_apps.thread_active = 0;
1972                 }
1973         }
1974         pthread_mutex_unlock(&ust_exit_mutex);
1975
1976         /*
1977          * Do NOT join threads: use of sys_futex makes it impossible to
1978          * join the threads without using async-cancel, but async-cancel
1979          * is delivered by a signal, which could hit the target thread
1980          * anywhere in its code path, including while the ust_lock() is
1981          * held, causing a deadlock for the other thread. Let the OS
1982          * cleanup the threads if there are stalled in a syscall.
1983          */
1984         lttng_ust_cleanup(1);
1985 }
1986
1987 /*
1988  * We exclude the worker threads across fork and clone (except
1989  * CLONE_VM), because these system calls only keep the forking thread
1990  * running in the child.  Therefore, we don't want to call fork or clone
1991  * in the middle of an tracepoint or ust tracing state modification.
1992  * Holding this mutex protects these structures across fork and clone.
1993  */
1994 void ust_before_fork(sigset_t *save_sigset)
1995 {
1996         /*
1997          * Disable signals. This is to avoid that the child intervenes
1998          * before it is properly setup for tracing. It is safer to
1999          * disable all signals, because then we know we are not breaking
2000          * anything by restoring the original mask.
2001          */
2002         sigset_t all_sigs;
2003         int ret;
2004
2005         /* Fixup lttng-ust TLS. */
2006         lttng_ust_fixup_tls();
2007
2008         if (URCU_TLS(lttng_ust_nest_count))
2009                 return;
2010         /* Disable signals */
2011         sigfillset(&all_sigs);
2012         ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
2013         if (ret == -1) {
2014                 PERROR("sigprocmask");
2015         }
2016
2017         pthread_mutex_lock(&ust_fork_mutex);
2018
2019         ust_lock_nocheck();
2020         urcu_bp_before_fork();
2021 }
2022
2023 static void ust_after_fork_common(sigset_t *restore_sigset)
2024 {
2025         int ret;
2026
2027         DBG("process %d", getpid());
2028         ust_unlock();
2029
2030         pthread_mutex_unlock(&ust_fork_mutex);
2031
2032         /* Restore signals */
2033         ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
2034         if (ret == -1) {
2035                 PERROR("sigprocmask");
2036         }
2037 }
2038
2039 void ust_after_fork_parent(sigset_t *restore_sigset)
2040 {
2041         if (URCU_TLS(lttng_ust_nest_count))
2042                 return;
2043         DBG("process %d", getpid());
2044         urcu_bp_after_fork_parent();
2045         /* Release mutexes and reenable signals */
2046         ust_after_fork_common(restore_sigset);
2047 }
2048
2049 /*
2050  * After fork, in the child, we need to cleanup all the leftover state,
2051  * except the worker thread which already magically disappeared thanks
2052  * to the weird Linux fork semantics. After tyding up, we call
2053  * lttng_ust_init() again to start over as a new PID.
2054  *
2055  * This is meant for forks() that have tracing in the child between the
2056  * fork and following exec call (if there is any).
2057  */
2058 void ust_after_fork_child(sigset_t *restore_sigset)
2059 {
2060         if (URCU_TLS(lttng_ust_nest_count))
2061                 return;
2062         lttng_context_vpid_reset();
2063         lttng_context_vtid_reset();
2064         lttng_context_procname_reset();
2065         DBG("process %d", getpid());
2066         /* Release urcu mutexes */
2067         urcu_bp_after_fork_child();
2068         lttng_ust_cleanup(0);
2069         /* Release mutexes and reenable signals */
2070         ust_after_fork_common(restore_sigset);
2071         lttng_ust_init();
2072 }
2073
2074 void lttng_ust_sockinfo_session_enabled(void *owner)
2075 {
2076         struct sock_info *sock_info = owner;
2077         sock_info->statedump_pending = 1;
2078 }