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 <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 <limits.h>
  39 #include <urcu/uatomic.h>
  40 #include <urcu/futex.h>
  41 #include <urcu/compiler.h>
  42
  43 #include <lttng/ust-events.h>
  44 #include <lttng/ust-abi.h>
  45 #include <lttng/ust.h>
  46 #include <lttng/ust-error.h>
  47 #include <lttng/ust-ctl.h>
  48 #include <urcu/tls-compat.h>
  49 #include <ust-comm.h>
  50 #include <ust-fd.h>
  51 #include <usterr-signal-safe.h>
  52 #include <helper.h>
  53 #include "tracepoint-internal.h"
  54 #include "lttng-tracer-core.h"
  55 #include "compat.h"
  56 #include "../libringbuffer/rb-init.h"
  57 #include "lttng-ust-statedump.h"
  58 #include "clock.h"
  59 #include "../libringbuffer/getcpu.h"
  60 #include "getenv.h"
  61
  62 /*
  63  * Has lttng ust comm constructor been called ?
  64  */
  65 static int initialized;
  66
  67 /*
  68  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  69  * Held when handling a command, also held by fork() to deal with
  70  * removal of threads, and by exit path.
  71  *
  72  * The UST lock is the centralized mutex across UST tracing control and
  73  * probe registration.
  74  *
  75  * ust_exit_mutex must never nest in ust_mutex.
  76  *
  77  * ust_fork_mutex must never nest in ust_mutex.
  78  *
  79  * ust_mutex_nest is a per-thread nesting counter, allowing the perf
  80  * counter lazy initialization called by events within the statedump,
  81  * which traces while the ust_mutex is held.
  82  *
  83  * ust_lock nests within the dynamic loader lock (within glibc) because
  84  * it is taken within the library constructor.
  85  *
  86  * The ust fd tracker lock nests within the ust_mutex.
  87  */
  88 static pthread_mutex_t ust_mutex = PTHREAD_MUTEX_INITIALIZER;
  89
  90 /* Allow nesting the ust_mutex within the same thread. */
  91 static DEFINE_URCU_TLS(int, ust_mutex_nest);
  92
  93 /*
  94  * ust_exit_mutex protects thread_active variable wrt thread exit. It
  95  * cannot be done by ust_mutex because pthread_cancel(), which takes an
  96  * internal libc lock, cannot nest within ust_mutex.
  97  *
  98  * It never nests within a ust_mutex.
  99  */
 100 static pthread_mutex_t ust_exit_mutex = PTHREAD_MUTEX_INITIALIZER;
 101
 102 /*
 103  * ust_fork_mutex protects base address statedump tracing against forks. It
 104  * prevents the dynamic loader lock to be taken (by base address statedump
 105  * tracing) while a fork is happening, thus preventing deadlock issues with
 106  * the dynamic loader lock.
 107  */
 108 static pthread_mutex_t ust_fork_mutex = PTHREAD_MUTEX_INITIALIZER;
 109
 110 /* Should the ust comm thread quit ? */
 111 static int lttng_ust_comm_should_quit;
 112
 113 /*
 114  * This variable can be tested by applications to check whether
 115  * lttng-ust is loaded. They simply have to define their own
 116  * "lttng_ust_loaded" weak symbol, and test it. It is set to 1 by the
 117  * library constructor.
 118  */
 119 int lttng_ust_loaded __attribute__((weak));
 120
 121 /*
 122  * Return 0 on success, -1 if should quit.
 123  * The lock is taken in both cases.
 124  * Signal-safe.
 125  */
 126 int ust_lock(void)
 127 {
 128         sigset_t sig_all_blocked, orig_mask;
 129         int ret, oldstate;
 130
 131         ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
 132         if (ret) {
 133                 ERR("pthread_setcancelstate: %s", strerror(ret));
 134         }
 135         if (oldstate != PTHREAD_CANCEL_ENABLE) {
 136                 ERR("pthread_setcancelstate: unexpected oldstate");
 137         }
 138         sigfillset(&sig_all_blocked);
 139         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
 140         if (ret) {
 141                 ERR("pthread_sigmask: %s", strerror(ret));
 142         }
 143         if (!URCU_TLS(ust_mutex_nest)++)
 144                 pthread_mutex_lock(&ust_mutex);
 145         ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
 146         if (ret) {
 147                 ERR("pthread_sigmask: %s", strerror(ret));
 148         }
 149         if (lttng_ust_comm_should_quit) {
 150                 return -1;
 151         } else {
 152                 return 0;
 153         }
 154 }
 155
 156 /*
 157  * ust_lock_nocheck() can be used in constructors/destructors, because
 158  * they are already nested within the dynamic loader lock, and therefore
 159  * have exclusive access against execution of liblttng-ust destructor.
 160  * Signal-safe.
 161  */
 162 void ust_lock_nocheck(void)
 163 {
 164         sigset_t sig_all_blocked, orig_mask;
 165         int ret, oldstate;
 166
 167         ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
 168         if (ret) {
 169                 ERR("pthread_setcancelstate: %s", strerror(ret));
 170         }
 171         if (oldstate != PTHREAD_CANCEL_ENABLE) {
 172                 ERR("pthread_setcancelstate: unexpected oldstate");
 173         }
 174         sigfillset(&sig_all_blocked);
 175         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
 176         if (ret) {
 177                 ERR("pthread_sigmask: %s", strerror(ret));
 178         }
 179         if (!URCU_TLS(ust_mutex_nest)++)
 180                 pthread_mutex_lock(&ust_mutex);
 181         ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
 182         if (ret) {
 183                 ERR("pthread_sigmask: %s", strerror(ret));
 184         }
 185 }
 186
 187 /*
 188  * Signal-safe.
 189  */
 190 void ust_unlock(void)
 191 {
 192         sigset_t sig_all_blocked, orig_mask;
 193         int ret, oldstate;
 194
 195         sigfillset(&sig_all_blocked);
 196         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
 197         if (ret) {
 198                 ERR("pthread_sigmask: %s", strerror(ret));
 199         }
 200         if (!--URCU_TLS(ust_mutex_nest))
 201                 pthread_mutex_unlock(&ust_mutex);
 202         ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
 203         if (ret) {
 204                 ERR("pthread_sigmask: %s", strerror(ret));
 205         }
 206         ret = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &oldstate);
 207         if (ret) {
 208                 ERR("pthread_setcancelstate: %s", strerror(ret));
 209         }
 210         if (oldstate != PTHREAD_CANCEL_DISABLE) {
 211                 ERR("pthread_setcancelstate: unexpected oldstate");
 212         }
 213 }
 214
 215 /*
 216  * Wait for either of these before continuing to the main
 217  * program:
 218  * - the register_done message from sessiond daemon
 219  *   (will let the sessiond daemon enable sessions before main
 220  *   starts.)
 221  * - sessiond daemon is not reachable.
 222  * - timeout (ensuring applications are resilient to session
 223  *   daemon problems).
 224  */
 225 static sem_t constructor_wait;
 226 /*
 227  * Doing this for both the global and local sessiond.
 228  */
 229 enum {
 230         sem_count_initial_value = 4,
 231 };
 232
 233 static int sem_count = sem_count_initial_value;
 234
 235 /*
 236  * Counting nesting within lttng-ust. Used to ensure that calling fork()
 237  * from liblttng-ust does not execute the pre/post fork handlers.
 238  */
 239 static DEFINE_URCU_TLS(int, lttng_ust_nest_count);
 240
 241 /*
 242  * Info about socket and associated listener thread.
 243  */
 244 struct sock_info {
 245         const char *name;
 246         pthread_t ust_listener; /* listener thread */
 247         int root_handle;
 248         int registration_done;
 249         int allowed;
 250         int global;
 251         int thread_active;
 252
 253         char sock_path[PATH_MAX];
 254         int socket;
 255         int notify_socket;
 256
 257         char wait_shm_path[PATH_MAX];
 258         char *wait_shm_mmap;
 259         /* Keep track of lazy state dump not performed yet. */
 260         int statedump_pending;
 261         int initial_statedump_done;
 262 };
 263
 264 /* Socket from app (connect) to session daemon (listen) for communication */
 265 struct sock_info global_apps = {
 266         .name = "global",
 267         .global = 1,
 268
 269         .root_handle = -1,
 270         .registration_done = 0,
 271         .allowed = 0,
 272         .thread_active = 0,
 273
 274         .sock_path = LTTNG_DEFAULT_RUNDIR "/" LTTNG_UST_SOCK_FILENAME,
 275         .socket = -1,
 276         .notify_socket = -1,
 277
 278         .wait_shm_path = "/" LTTNG_UST_WAIT_FILENAME,
 279
 280         .statedump_pending = 0,
 281         .initial_statedump_done = 0,
 282 };
 283
 284 /* TODO: allow global_apps_sock_path override */
 285
 286 struct sock_info local_apps = {
 287         .name = "local",
 288         .global = 0,
 289         .root_handle = -1,
 290         .registration_done = 0,
 291         .allowed = 0,   /* Check setuid bit first */
 292         .thread_active = 0,
 293
 294         .socket = -1,
 295         .notify_socket = -1,
 296
 297         .statedump_pending = 0,
 298         .initial_statedump_done = 0,
 299 };
 300
 301 static int wait_poll_fallback;
 302
 303 static const char *cmd_name_mapping[] = {
 304         [ LTTNG_UST_RELEASE ] = "Release",
 305         [ LTTNG_UST_SESSION ] = "Create Session",
 306         [ LTTNG_UST_TRACER_VERSION ] = "Get Tracer Version",
 307
 308         [ LTTNG_UST_TRACEPOINT_LIST ] = "Create Tracepoint List",
 309         [ LTTNG_UST_WAIT_QUIESCENT ] = "Wait for Quiescent State",
 310         [ LTTNG_UST_REGISTER_DONE ] = "Registration Done",
 311         [ LTTNG_UST_TRACEPOINT_FIELD_LIST ] = "Create Tracepoint Field List",
 312
 313         /* Session FD commands */
 314         [ LTTNG_UST_CHANNEL ] = "Create Channel",
 315         [ LTTNG_UST_SESSION_START ] = "Start Session",
 316         [ LTTNG_UST_SESSION_STOP ] = "Stop Session",
 317
 318         /* Channel FD commands */
 319         [ LTTNG_UST_STREAM ] = "Create Stream",
 320         [ LTTNG_UST_EVENT ] = "Create Event",
 321
 322         /* Event and Channel FD commands */
 323         [ LTTNG_UST_CONTEXT ] = "Create Context",
 324         [ LTTNG_UST_FLUSH_BUFFER ] = "Flush Buffer",
 325
 326         /* Event, Channel and Session commands */
 327         [ LTTNG_UST_ENABLE ] = "Enable",
 328         [ LTTNG_UST_DISABLE ] = "Disable",
 329
 330         /* Tracepoint list commands */
 331         [ LTTNG_UST_TRACEPOINT_LIST_GET ] = "List Next Tracepoint",
 332         [ LTTNG_UST_TRACEPOINT_FIELD_LIST_GET ] = "List Next Tracepoint Field",
 333
 334         /* Event FD commands */
 335         [ LTTNG_UST_FILTER ] = "Create Filter",
 336         [ LTTNG_UST_EXCLUSION ] = "Add exclusions to event",
 337 };
 338
 339 static const char *str_timeout;
 340 static int got_timeout_env;
 341
 342 extern void lttng_ring_buffer_client_overwrite_init(void);
 343 extern void lttng_ring_buffer_client_overwrite_rt_init(void);
 344 extern void lttng_ring_buffer_client_discard_init(void);
 345 extern void lttng_ring_buffer_client_discard_rt_init(void);
 346 extern void lttng_ring_buffer_metadata_client_init(void);
 347 extern void lttng_ring_buffer_client_overwrite_exit(void);
 348 extern void lttng_ring_buffer_client_overwrite_rt_exit(void);
 349 extern void lttng_ring_buffer_client_discard_exit(void);
 350 extern void lttng_ring_buffer_client_discard_rt_exit(void);
 351 extern void lttng_ring_buffer_metadata_client_exit(void);
 352
 353 static char *get_map_shm(struct sock_info *sock_info);
 354
 355 ssize_t lttng_ust_read(int fd, void *buf, size_t len)
 356 {
 357         ssize_t ret;
 358         size_t copied = 0, to_copy = len;
 359
 360         do {
 361                 ret = read(fd, buf + copied, to_copy);
 362                 if (ret > 0) {
 363                         copied += ret;
 364                         to_copy -= ret;
 365                 }
 366         } while ((ret > 0 && to_copy > 0)
 367                 || (ret < 0 && errno == EINTR));
 368         if (ret > 0) {
 369                 ret = copied;
 370         }
 371         return ret;
 372 }
 373 /*
 374  * Returns the HOME directory path. Caller MUST NOT free(3) the returned
 375  * pointer.
 376  */
 377 static
 378 const char *get_lttng_home_dir(void)
 379 {
 380        const char *val;
 381
 382        val = (const char *) lttng_getenv("LTTNG_HOME");
 383        if (val != NULL) {
 384                return val;
 385        }
 386        return (const char *) lttng_getenv("HOME");
 387 }
 388
 389 /*
 390  * Force a read (imply TLS fixup for dlopen) of TLS variables.
 391  */
 392 static
 393 void lttng_fixup_nest_count_tls(void)
 394 {
 395         asm volatile ("" : : "m" (URCU_TLS(lttng_ust_nest_count)));
 396 }
 397
 398 static
 399 void lttng_fixup_ust_mutex_nest_tls(void)
 400 {
 401         asm volatile ("" : : "m" (URCU_TLS(ust_mutex_nest)));
 402 }
 403
 404 /*
 405  * Fixup urcu bp TLS.
 406  */
 407 static
 408 void lttng_fixup_urcu_bp_tls(void)
 409 {
 410         rcu_read_lock();
 411         rcu_read_unlock();
 412 }
 413
 414 void lttng_ust_fixup_tls(void)
 415 {
 416         lttng_fixup_urcu_bp_tls();
 417         lttng_fixup_ringbuffer_tls();
 418         lttng_fixup_vtid_tls();
 419         lttng_fixup_nest_count_tls();
 420         lttng_fixup_procname_tls();
 421         lttng_fixup_ust_mutex_nest_tls();
 422         lttng_ust_fixup_perf_counter_tls();
 423         lttng_ust_fixup_fd_tracker_tls();
 424 }
 425
 426 int lttng_get_notify_socket(void *owner)
 427 {
 428         struct sock_info *info = owner;
 429
 430         return info->notify_socket;
 431 }
 432
 433 static
 434 void print_cmd(int cmd, int handle)
 435 {
 436         const char *cmd_name = "Unknown";
 437
 438         if (cmd >= 0 && cmd < LTTNG_ARRAY_SIZE(cmd_name_mapping)
 439                         && cmd_name_mapping[cmd]) {
 440                 cmd_name = cmd_name_mapping[cmd];
 441         }
 442         DBG("Message Received \"%s\" (%d), Handle \"%s\" (%d)",
 443                 cmd_name, cmd,
 444                 lttng_ust_obj_get_name(handle), handle);
 445 }
 446
 447 static
 448 int setup_global_apps(void)
 449 {
 450         int ret = 0;
 451         assert(!global_apps.wait_shm_mmap);
 452
 453         global_apps.wait_shm_mmap = get_map_shm(&global_apps);
 454         if (!global_apps.wait_shm_mmap) {
 455                 WARN("Unable to get map shm for global apps. Disabling LTTng-UST global tracing.");
 456                 global_apps.allowed = 0;
 457                 ret = -EIO;
 458                 goto error;
 459         }
 460
 461         global_apps.allowed = 1;
 462 error:
 463         return ret;
 464 }
 465 static
 466 int setup_local_apps(void)
 467 {
 468         int ret = 0;
 469         const char *home_dir;
 470         uid_t uid;
 471
 472         assert(!local_apps.wait_shm_mmap);
 473
 474         uid = getuid();
 475         /*
 476          * Disallow per-user tracing for setuid binaries.
 477          */
 478         if (uid != geteuid()) {
 479                 assert(local_apps.allowed == 0);
 480                 ret = 0;
 481                 goto end;
 482         }
 483         home_dir = get_lttng_home_dir();
 484         if (!home_dir) {
 485                 WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
 486                 assert(local_apps.allowed == 0);
 487                 ret = -ENOENT;
 488                 goto end;
 489         }
 490         local_apps.allowed = 1;
 491         snprintf(local_apps.sock_path, PATH_MAX, "%s/%s/%s",
 492                 home_dir,
 493                 LTTNG_DEFAULT_HOME_RUNDIR,
 494                 LTTNG_UST_SOCK_FILENAME);
 495         snprintf(local_apps.wait_shm_path, PATH_MAX, "/%s-%u",
 496                 LTTNG_UST_WAIT_FILENAME,
 497                 uid);
 498
 499         local_apps.wait_shm_mmap = get_map_shm(&local_apps);
 500         if (!local_apps.wait_shm_mmap) {
 501                 WARN("Unable to get map shm for local apps. Disabling LTTng-UST per-user tracing.");
 502                 local_apps.allowed = 0;
 503                 ret = -EIO;
 504                 goto end;
 505         }
 506 end:
 507         return ret;
 508 }
 509
 510 /*
 511  * Get socket timeout, in ms.
 512  * -1: wait forever. 0: don't wait. >0: timeout, in ms.
 513  */
 514 static
 515 long get_timeout(void)
 516 {
 517         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 518
 519         if (!got_timeout_env) {
 520                 str_timeout = lttng_getenv("LTTNG_UST_REGISTER_TIMEOUT");
 521                 got_timeout_env = 1;
 522         }
 523         if (str_timeout)
 524                 constructor_delay_ms = strtol(str_timeout, NULL, 10);
 525         /* All negative values are considered as "-1". */
 526         if (constructor_delay_ms < -1)
 527                 constructor_delay_ms = -1;
 528         return constructor_delay_ms;
 529 }
 530
 531 /* Timeout for notify socket send and recv. */
 532 static
 533 long get_notify_sock_timeout(void)
 534 {
 535         return get_timeout();
 536 }
 537
 538 /* Timeout for connecting to cmd and notify sockets. */
 539 static
 540 long get_connect_sock_timeout(void)
 541 {
 542         return get_timeout();
 543 }
 544
 545 /*
 546  * Return values: -1: wait forever. 0: don't wait. 1: timeout wait.
 547  */
 548 static
 549 int get_constructor_timeout(struct timespec *constructor_timeout)
 550 {
 551         long constructor_delay_ms;
 552         int ret;
 553
 554         constructor_delay_ms = get_timeout();
 555
 556         switch (constructor_delay_ms) {
 557         case -1:/* fall-through */
 558         case 0:
 559                 return constructor_delay_ms;
 560         default:
 561                 break;
 562         }
 563
 564         /*
 565          * If we are unable to find the current time, don't wait.
 566          */
 567         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 568         if (ret) {
 569                 /* Don't wait. */
 570                 return 0;
 571         }
 572         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 573         constructor_timeout->tv_nsec +=
 574                 (constructor_delay_ms % 1000UL) * 1000000UL;
 575         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 576                 constructor_timeout->tv_sec++;
 577                 constructor_timeout->tv_nsec -= 1000000000UL;
 578         }
 579         /* Timeout wait (constructor_delay_ms). */
 580         return 1;
 581 }
 582
 583 static
 584 void get_allow_blocking(void)
 585 {
 586         const char *str_allow_blocking =
 587                 lttng_getenv("LTTNG_UST_ALLOW_BLOCKING");
 588
 589         if (str_allow_blocking) {
 590                 DBG("%s environment variable is set",
 591                         "LTTNG_UST_ALLOW_BLOCKING");
 592                 lttng_ust_ringbuffer_set_allow_blocking();
 593         }
 594 }
 595
 596 static
 597 int register_to_sessiond(int socket, enum ustctl_socket_type type)
 598 {
 599         return ustcomm_send_reg_msg(socket,
 600                 type,
 601                 CAA_BITS_PER_LONG,
 602                 lttng_alignof(uint8_t) * CHAR_BIT,
 603                 lttng_alignof(uint16_t) * CHAR_BIT,
 604                 lttng_alignof(uint32_t) * CHAR_BIT,
 605                 lttng_alignof(uint64_t) * CHAR_BIT,
 606                 lttng_alignof(unsigned long) * CHAR_BIT);
 607 }
 608
 609 static
 610 int send_reply(int sock, struct ustcomm_ust_reply *lur)
 611 {
 612         ssize_t len;
 613
 614         len = ustcomm_send_unix_sock(sock, lur, sizeof(*lur));
 615         switch (len) {
 616         case sizeof(*lur):
 617                 DBG("message successfully sent");
 618                 return 0;
 619         default:
 620                 if (len == -ECONNRESET) {
 621                         DBG("remote end closed connection");
 622                         return 0;
 623                 }
 624                 if (len < 0)
 625                         return len;
 626                 DBG("incorrect message size: %zd", len);
 627                 return -EINVAL;
 628         }
 629 }
 630
 631 static
 632 void decrement_sem_count(unsigned int count)
 633 {
 634         int ret;
 635
 636         assert(uatomic_read(&sem_count) >= count);
 637
 638         if (uatomic_read(&sem_count) <= 0) {
 639                 return;
 640         }
 641
 642         ret = uatomic_add_return(&sem_count, -count);
 643         if (ret == 0) {
 644                 ret = sem_post(&constructor_wait);
 645                 assert(!ret);
 646         }
 647 }
 648
 649 static
 650 int handle_register_done(struct sock_info *sock_info)
 651 {
 652         if (sock_info->registration_done)
 653                 return 0;
 654         sock_info->registration_done = 1;
 655
 656         decrement_sem_count(1);
 657         if (!sock_info->statedump_pending) {
 658                 sock_info->initial_statedump_done = 1;
 659                 decrement_sem_count(1);
 660         }
 661
 662         return 0;
 663 }
 664
 665 static
 666 int handle_register_failed(struct sock_info *sock_info)
 667 {
 668         if (sock_info->registration_done)
 669                 return 0;
 670         sock_info->registration_done = 1;
 671         sock_info->initial_statedump_done = 1;
 672
 673         decrement_sem_count(2);
 674
 675         return 0;
 676 }
 677
 678 /*
 679  * Only execute pending statedump after the constructor semaphore has
 680  * been posted by the current listener thread. This means statedump will
 681  * only be performed after the "registration done" command is received
 682  * from this thread's session daemon.
 683  *
 684  * This ensures we don't run into deadlock issues with the dynamic
 685  * loader mutex, which is held while the constructor is called and
 686  * waiting on the constructor semaphore. All operations requiring this
 687  * dynamic loader lock need to be postponed using this mechanism.
 688  *
 689  * In a scenario with two session daemons connected to the application,
 690  * it is possible that the first listener thread which receives the
 691  * registration done command issues its statedump while the dynamic
 692  * loader lock is still held by the application constructor waiting on
 693  * the semaphore. It will however be allowed to proceed when the
 694  * second session daemon sends the registration done command to the
 695  * second listener thread. This situation therefore does not produce
 696  * a deadlock.
 697  */
 698 static
 699 void handle_pending_statedump(struct sock_info *sock_info)
 700 {
 701         if (sock_info->registration_done && sock_info->statedump_pending) {
 702                 sock_info->statedump_pending = 0;
 703                 pthread_mutex_lock(&ust_fork_mutex);
 704                 lttng_handle_pending_statedump(sock_info);
 705                 pthread_mutex_unlock(&ust_fork_mutex);
 706
 707                 if (!sock_info->initial_statedump_done) {
 708                         sock_info->initial_statedump_done = 1;
 709                         decrement_sem_count(1);
 710                 }
 711         }
 712 }
 713
 714 static
 715 int handle_message(struct sock_info *sock_info,
 716                 int sock, struct ustcomm_ust_msg *lum)
 717 {
 718         int ret = 0;
 719         const struct lttng_ust_objd_ops *ops;
 720         struct ustcomm_ust_reply lur;
 721         union ust_args args;
 722         char ctxstr[LTTNG_UST_SYM_NAME_LEN];    /* App context string. */
 723         ssize_t len;
 724
 725         memset(&lur, 0, sizeof(lur));
 726
 727         if (ust_lock()) {
 728                 ret = -LTTNG_UST_ERR_EXITING;
 729                 goto error;
 730         }
 731
 732         ops = objd_ops(lum->handle);
 733         if (!ops) {
 734                 ret = -ENOENT;
 735                 goto error;
 736         }
 737
 738         switch (lum->cmd) {
 739         case LTTNG_UST_REGISTER_DONE:
 740                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 741                         ret = handle_register_done(sock_info);
 742                 else
 743                         ret = -EINVAL;
 744                 break;
 745         case LTTNG_UST_RELEASE:
 746                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 747                         ret = -EPERM;
 748                 else
 749                         ret = lttng_ust_objd_unref(lum->handle, 1);
 750                 break;
 751         case LTTNG_UST_FILTER:
 752         {
 753                 /* Receive filter data */
 754                 struct lttng_ust_filter_bytecode_node *bytecode;
 755
 756                 if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) {
 757                         ERR("Filter data size is too large: %u bytes",
 758                                 lum->u.filter.data_size);
 759                         ret = -EINVAL;
 760                         goto error;
 761                 }
 762
 763                 if (lum->u.filter.reloc_offset > lum->u.filter.data_size) {
 764                         ERR("Filter reloc offset %u is not within data",
 765                                 lum->u.filter.reloc_offset);
 766                         ret = -EINVAL;
 767                         goto error;
 768                 }
 769
 770                 bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size);
 771                 if (!bytecode) {
 772                         ret = -ENOMEM;
 773                         goto error;
 774                 }
 775                 len = ustcomm_recv_unix_sock(sock, bytecode->bc.data,
 776                                 lum->u.filter.data_size);
 777                 switch (len) {
 778                 case 0: /* orderly shutdown */
 779                         ret = 0;
 780                         free(bytecode);
 781                         goto error;
 782                 default:
 783                         if (len == lum->u.filter.data_size) {
 784                                 DBG("filter data received");
 785                                 break;
 786                         } else if (len < 0) {
 787                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 788                                 if (len == -ECONNRESET) {
 789                                         ERR("%s remote end closed connection", sock_info->name);
 790                                         ret = len;
 791                                         free(bytecode);
 792                                         goto error;
 793                                 }
 794                                 ret = len;
 795                                 free(bytecode);
 796                                 goto error;
 797                         } else {
 798                                 DBG("incorrect filter data message size: %zd", len);
 799                                 ret = -EINVAL;
 800                                 free(bytecode);
 801                                 goto error;
 802                         }
 803                 }
 804                 bytecode->bc.len = lum->u.filter.data_size;
 805                 bytecode->bc.reloc_offset = lum->u.filter.reloc_offset;
 806                 bytecode->bc.seqnum = lum->u.filter.seqnum;
 807                 if (ops->cmd) {
 808                         ret = ops->cmd(lum->handle, lum->cmd,
 809                                         (unsigned long) bytecode,
 810                                         &args, sock_info);
 811                         if (ret) {
 812                                 free(bytecode);
 813                         }
 814                         /* don't free bytecode if everything went fine. */
 815                 } else {
 816                         ret = -ENOSYS;
 817                         free(bytecode);
 818                 }
 819                 break;
 820         }
 821         case LTTNG_UST_EXCLUSION:
 822         {
 823                 /* Receive exclusion names */
 824                 struct lttng_ust_excluder_node *node;
 825                 unsigned int count;
 826
 827                 count = lum->u.exclusion.count;
 828                 if (count == 0) {
 829                         /* There are no names to read */
 830                         ret = 0;
 831                         goto error;
 832                 }
 833                 node = zmalloc(sizeof(*node) +
 834                                 count * LTTNG_UST_SYM_NAME_LEN);
 835                 if (!node) {
 836                         ret = -ENOMEM;
 837                         goto error;
 838                 }
 839                 node->excluder.count = count;
 840                 len = ustcomm_recv_unix_sock(sock, node->excluder.names,
 841                                 count * LTTNG_UST_SYM_NAME_LEN);
 842                 switch (len) {
 843                 case 0: /* orderly shutdown */
 844                         ret = 0;
 845                         free(node);
 846                         goto error;
 847                 default:
 848                         if (len == count * LTTNG_UST_SYM_NAME_LEN) {
 849                                 DBG("Exclusion 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                                         free(node);
 857                                         goto error;
 858                                 }
 859                                 ret = len;
 860                                 free(node);
 861                                 goto error;
 862                         } else {
 863                                 DBG("Incorrect exclusion data message size: %zd", len);
 864                                 ret = -EINVAL;
 865                                 free(node);
 866                                 goto error;
 867                         }
 868                 }
 869                 if (ops->cmd) {
 870                         ret = ops->cmd(lum->handle, lum->cmd,
 871                                         (unsigned long) node,
 872                                         &args, sock_info);
 873                         if (ret) {
 874                                 free(node);
 875                         }
 876                         /* Don't free exclusion data if everything went fine. */
 877                 } else {
 878                         ret = -ENOSYS;
 879                         free(node);
 880                 }
 881                 break;
 882         }
 883         case LTTNG_UST_CHANNEL:
 884         {
 885                 void *chan_data;
 886                 int wakeup_fd;
 887
 888                 len = ustcomm_recv_channel_from_sessiond(sock,
 889                                 &chan_data, lum->u.channel.len,
 890                                 &wakeup_fd);
 891                 switch (len) {
 892                 case 0: /* orderly shutdown */
 893                         ret = 0;
 894                         goto error;
 895                 default:
 896                         if (len == lum->u.channel.len) {
 897                                 DBG("channel data received");
 898                                 break;
 899                         } else if (len < 0) {
 900                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 901                                 if (len == -ECONNRESET) {
 902                                         ERR("%s remote end closed connection", sock_info->name);
 903                                         ret = len;
 904                                         goto error;
 905                                 }
 906                                 ret = len;
 907                                 goto error;
 908                         } else {
 909                                 DBG("incorrect channel data message size: %zd", len);
 910                                 ret = -EINVAL;
 911                                 goto error;
 912                         }
 913                 }
 914                 args.channel.chan_data = chan_data;
 915                 args.channel.wakeup_fd = wakeup_fd;
 916                 if (ops->cmd)
 917                         ret = ops->cmd(lum->handle, lum->cmd,
 918                                         (unsigned long) &lum->u,
 919                                         &args, sock_info);
 920                 else
 921                         ret = -ENOSYS;
 922                 break;
 923         }
 924         case LTTNG_UST_STREAM:
 925         {
 926                 /* Receive shm_fd, wakeup_fd */
 927                 ret = ustcomm_recv_stream_from_sessiond(sock,
 928                         NULL,
 929                         &args.stream.shm_fd,
 930                         &args.stream.wakeup_fd);
 931                 if (ret) {
 932                         goto error;
 933                 }
 934
 935                 if (ops->cmd)
 936                         ret = ops->cmd(lum->handle, lum->cmd,
 937                                         (unsigned long) &lum->u,
 938                                         &args, sock_info);
 939                 else
 940                         ret = -ENOSYS;
 941                 break;
 942         }
 943         case LTTNG_UST_CONTEXT:
 944                 switch (lum->u.context.ctx) {
 945                 case LTTNG_UST_CONTEXT_APP_CONTEXT:
 946                 {
 947                         char *p;
 948                         size_t ctxlen, recvlen;
 949
 950                         ctxlen = strlen("$app.") + lum->u.context.u.app_ctx.provider_name_len - 1
 951                                         + strlen(":") + lum->u.context.u.app_ctx.ctx_name_len;
 952                         if (ctxlen >= LTTNG_UST_SYM_NAME_LEN) {
 953                                 ERR("Application context string length size is too large: %zu bytes",
 954                                         ctxlen);
 955                                 ret = -EINVAL;
 956                                 goto error;
 957                         }
 958                         strcpy(ctxstr, "$app.");
 959                         p = &ctxstr[strlen("$app.")];
 960                         recvlen = ctxlen - strlen("$app.");
 961                         len = ustcomm_recv_unix_sock(sock, p, recvlen);
 962                         switch (len) {
 963                         case 0: /* orderly shutdown */
 964                                 ret = 0;
 965                                 goto error;
 966                         default:
 967                                 if (len == recvlen) {
 968                                         DBG("app context data received");
 969                                         break;
 970                                 } else if (len < 0) {
 971                                         DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 972                                         if (len == -ECONNRESET) {
 973                                                 ERR("%s remote end closed connection", sock_info->name);
 974                                                 ret = len;
 975                                                 goto error;
 976                                         }
 977                                         ret = len;
 978                                         goto error;
 979                                 } else {
 980                                         DBG("incorrect app context data message size: %zd", len);
 981                                         ret = -EINVAL;
 982                                         goto error;
 983                                 }
 984                         }
 985                         /* Put : between provider and ctxname. */
 986                         p[lum->u.context.u.app_ctx.provider_name_len - 1] = ':';
 987                         args.app_context.ctxname = ctxstr;
 988                         break;
 989                 }
 990                 default:
 991                         break;
 992                 }
 993                 if (ops->cmd) {
 994                         ret = ops->cmd(lum->handle, lum->cmd,
 995                                         (unsigned long) &lum->u,
 996                                         &args, sock_info);
 997                 } else {
 998                         ret = -ENOSYS;
 999                 }
1000                 break;
1001         default:
1002                 if (ops->cmd)
1003                         ret = ops->cmd(lum->handle, lum->cmd,
1004                                         (unsigned long) &lum->u,
1005                                         &args, sock_info);
1006                 else
1007                         ret = -ENOSYS;
1008                 break;
1009         }
1010
1011         lur.handle = lum->handle;
1012         lur.cmd = lum->cmd;
1013         lur.ret_val = ret;
1014         if (ret >= 0) {
1015                 lur.ret_code = LTTNG_UST_OK;
1016         } else {
1017                 /*
1018                  * Use -LTTNG_UST_ERR as wildcard for UST internal
1019                  * error that are not caused by the transport, except if
1020                  * we already have a more precise error message to
1021                  * report.
1022                  */
1023                 if (ret > -LTTNG_UST_ERR) {
1024                         /* Translate code to UST error. */
1025                         switch (ret) {
1026                         case -EEXIST:
1027                                 lur.ret_code = -LTTNG_UST_ERR_EXIST;
1028                                 break;
1029                         case -EINVAL:
1030                                 lur.ret_code = -LTTNG_UST_ERR_INVAL;
1031                                 break;
1032                         case -ENOENT:
1033                                 lur.ret_code = -LTTNG_UST_ERR_NOENT;
1034                                 break;
1035                         case -EPERM:
1036                                 lur.ret_code = -LTTNG_UST_ERR_PERM;
1037                                 break;
1038                         case -ENOSYS:
1039                                 lur.ret_code = -LTTNG_UST_ERR_NOSYS;
1040                                 break;
1041                         default:
1042                                 lur.ret_code = -LTTNG_UST_ERR;
1043                                 break;
1044                         }
1045                 } else {
1046                         lur.ret_code = ret;
1047                 }
1048         }
1049         if (ret >= 0) {
1050                 switch (lum->cmd) {
1051                 case LTTNG_UST_TRACER_VERSION:
1052                         lur.u.version = lum->u.version;
1053                         break;
1054                 case LTTNG_UST_TRACEPOINT_LIST_GET:
1055                         memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
1056                         break;
1057                 }
1058         }
1059         DBG("Return value: %d", lur.ret_val);
1060
1061         ust_unlock();
1062
1063         /*
1064          * Performed delayed statedump operations outside of the UST
1065          * lock. We need to take the dynamic loader lock before we take
1066          * the UST lock internally within handle_pending_statedump().
1067           */
1068         handle_pending_statedump(sock_info);
1069
1070         if (ust_lock()) {
1071                 ret = -LTTNG_UST_ERR_EXITING;
1072                 goto error;
1073         }
1074
1075         ret = send_reply(sock, &lur);
1076         if (ret < 0) {
1077                 DBG("error sending reply");
1078                 goto error;
1079         }
1080
1081         /*
1082          * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field
1083          * after the reply.
1084          */
1085         if (lur.ret_code == LTTNG_UST_OK) {
1086                 switch (lum->cmd) {
1087                 case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET:
1088                         len = ustcomm_send_unix_sock(sock,
1089                                 &args.field_list.entry,
1090                                 sizeof(args.field_list.entry));
1091                         if (len < 0) {
1092                                 ret = len;
1093                                 goto error;
1094                         }
1095                         if (len != sizeof(args.field_list.entry)) {
1096                                 ret = -EINVAL;
1097                                 goto error;
1098                         }
1099                 }
1100         }
1101
1102 error:
1103         ust_unlock();
1104
1105         return ret;
1106 }
1107
1108 static
1109 void cleanup_sock_info(struct sock_info *sock_info, int exiting)
1110 {
1111         int ret;
1112
1113         if (sock_info->root_handle != -1) {
1114                 ret = lttng_ust_objd_unref(sock_info->root_handle, 1);
1115                 if (ret) {
1116                         ERR("Error unref root handle");
1117                 }
1118                 sock_info->root_handle = -1;
1119         }
1120         sock_info->registration_done = 0;
1121         sock_info->initial_statedump_done = 0;
1122
1123         /*
1124          * wait_shm_mmap, socket and notify socket are used by listener
1125          * threads outside of the ust lock, so we cannot tear them down
1126          * ourselves, because we cannot join on these threads. Leave
1127          * responsibility of cleaning up these resources to the OS
1128          * process exit.
1129          */
1130         if (exiting)
1131                 return;
1132
1133         if (sock_info->socket != -1) {
1134                 ret = ustcomm_close_unix_sock(sock_info->socket);
1135                 if (ret) {
1136                         ERR("Error closing ust cmd socket");
1137                 }
1138                 sock_info->socket = -1;
1139         }
1140         if (sock_info->notify_socket != -1) {
1141                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
1142                 if (ret) {
1143                         ERR("Error closing ust notify socket");
1144                 }
1145                 sock_info->notify_socket = -1;
1146         }
1147         if (sock_info->wait_shm_mmap) {
1148                 long page_size;
1149
1150                 page_size = sysconf(_SC_PAGE_SIZE);
1151                 if (page_size <= 0) {
1152                         if (!page_size) {
1153                                 errno = EINVAL;
1154                         }
1155                         PERROR("Error in sysconf(_SC_PAGE_SIZE)");
1156                 } else {
1157                         ret = munmap(sock_info->wait_shm_mmap, page_size);
1158                         if (ret) {
1159                                 ERR("Error unmapping wait shm");
1160                         }
1161                 }
1162                 sock_info->wait_shm_mmap = NULL;
1163         }
1164 }
1165
1166 /*
1167  * Using fork to set umask in the child process (not multi-thread safe).
1168  * We deal with the shm_open vs ftruncate race (happening when the
1169  * sessiond owns the shm and does not let everybody modify it, to ensure
1170  * safety against shm_unlink) by simply letting the mmap fail and
1171  * retrying after a few seconds.
1172  * For global shm, everybody has rw access to it until the sessiond
1173  * starts.
1174  */
1175 static
1176 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
1177 {
1178         int wait_shm_fd, ret;
1179         pid_t pid;
1180
1181         /*
1182          * Try to open read-only.
1183          */
1184         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
1185         if (wait_shm_fd >= 0) {
1186                 int32_t tmp_read;
1187                 ssize_t len;
1188                 size_t bytes_read = 0;
1189
1190                 /*
1191                  * Try to read the fd. If unable to do so, try opening
1192                  * it in write mode.
1193                  */
1194                 do {
1195                         len = read(wait_shm_fd,
1196                                 &((char *) &tmp_read)[bytes_read],
1197                                 sizeof(tmp_read) - bytes_read);
1198                         if (len > 0) {
1199                                 bytes_read += len;
1200                         }
1201                 } while ((len < 0 && errno == EINTR)
1202                         || (len > 0 && bytes_read < sizeof(tmp_read)));
1203                 if (bytes_read != sizeof(tmp_read)) {
1204                         ret = close(wait_shm_fd);
1205                         if (ret) {
1206                                 ERR("close wait_shm_fd");
1207                         }
1208                         goto open_write;
1209                 }
1210                 goto end;
1211         } else if (wait_shm_fd < 0 && errno != ENOENT) {
1212                 /*
1213                  * Real-only open did not work, and it's not because the
1214                  * entry was not present. It's a failure that prohibits
1215                  * using shm.
1216                  */
1217                 ERR("Error opening shm %s", sock_info->wait_shm_path);
1218                 goto end;
1219         }
1220
1221 open_write:
1222         /*
1223          * If the open failed because the file did not exist, or because
1224          * the file was not truncated yet, try creating it ourself.
1225          */
1226         URCU_TLS(lttng_ust_nest_count)++;
1227         pid = fork();
1228         URCU_TLS(lttng_ust_nest_count)--;
1229         if (pid > 0) {
1230                 int status;
1231
1232                 /*
1233                  * Parent: wait for child to return, in which case the
1234                  * shared memory map will have been created.
1235                  */
1236                 pid = wait(&status);
1237                 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
1238                         wait_shm_fd = -1;
1239                         goto end;
1240                 }
1241                 /*
1242                  * Try to open read-only again after creation.
1243                  */
1244                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
1245                 if (wait_shm_fd < 0) {
1246                         /*
1247                          * Real-only open did not work. It's a failure
1248                          * that prohibits using shm.
1249                          */
1250                         ERR("Error opening shm %s", sock_info->wait_shm_path);
1251                         goto end;
1252                 }
1253                 goto end;
1254         } else if (pid == 0) {
1255                 int create_mode;
1256
1257                 /* Child */
1258                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
1259                 if (sock_info->global)
1260                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
1261                 /*
1262                  * We're alone in a child process, so we can modify the
1263                  * process-wide umask.
1264                  */
1265                 umask(~create_mode);
1266                 /*
1267                  * Try creating shm (or get rw access).
1268                  * We don't do an exclusive open, because we allow other
1269                  * processes to create+ftruncate it concurrently.
1270                  */
1271                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
1272                                 O_RDWR | O_CREAT, create_mode);
1273                 if (wait_shm_fd >= 0) {
1274                         ret = ftruncate(wait_shm_fd, mmap_size);
1275                         if (ret) {
1276                                 PERROR("ftruncate");
1277                                 _exit(EXIT_FAILURE);
1278                         }
1279                         _exit(EXIT_SUCCESS);
1280                 }
1281                 /*
1282                  * For local shm, we need to have rw access to accept
1283                  * opening it: this means the local sessiond will be
1284                  * able to wake us up. For global shm, we open it even
1285                  * if rw access is not granted, because the root.root
1286                  * sessiond will be able to override all rights and wake
1287                  * us up.
1288                  */
1289                 if (!sock_info->global && errno != EACCES) {
1290                         ERR("Error opening shm %s", sock_info->wait_shm_path);
1291                         _exit(EXIT_FAILURE);
1292                 }
1293                 /*
1294                  * The shm exists, but we cannot open it RW. Report
1295                  * success.
1296                  */
1297                 _exit(EXIT_SUCCESS);
1298         } else {
1299                 return -1;
1300         }
1301 end:
1302         if (wait_shm_fd >= 0 && !sock_info->global) {
1303                 struct stat statbuf;
1304
1305                 /*
1306                  * Ensure that our user is the owner of the shm file for
1307                  * local shm. If we do not own the file, it means our
1308                  * sessiond will not have access to wake us up (there is
1309                  * probably a rogue process trying to fake our
1310                  * sessiond). Fallback to polling method in this case.
1311                  */
1312                 ret = fstat(wait_shm_fd, &statbuf);
1313                 if (ret) {
1314                         PERROR("fstat");
1315                         goto error_close;
1316                 }
1317                 if (statbuf.st_uid != getuid())
1318                         goto error_close;
1319         }
1320         return wait_shm_fd;
1321
1322 error_close:
1323         ret = close(wait_shm_fd);
1324         if (ret) {
1325                 PERROR("Error closing fd");
1326         }
1327         return -1;
1328 }
1329
1330 static
1331 char *get_map_shm(struct sock_info *sock_info)
1332 {
1333         long page_size;
1334         int wait_shm_fd, ret;
1335         char *wait_shm_mmap;
1336
1337         page_size = sysconf(_SC_PAGE_SIZE);
1338         if (page_size <= 0) {
1339                 if (!page_size) {
1340                         errno = EINVAL;
1341                 }
1342                 PERROR("Error in sysconf(_SC_PAGE_SIZE)");
1343                 goto error;
1344         }
1345
1346         lttng_ust_lock_fd_tracker();
1347         wait_shm_fd = get_wait_shm(sock_info, page_size);
1348         if (wait_shm_fd < 0) {
1349                 lttng_ust_unlock_fd_tracker();
1350                 goto error;
1351         }
1352
1353         ret = lttng_ust_add_fd_to_tracker(wait_shm_fd);
1354         if (ret < 0) {
1355                 ret = close(wait_shm_fd);
1356                 if (!ret) {
1357                         PERROR("Error closing fd");
1358                 }
1359                 lttng_ust_unlock_fd_tracker();
1360                 goto error;
1361         }
1362
1363         wait_shm_fd = ret;
1364         lttng_ust_unlock_fd_tracker();
1365
1366         wait_shm_mmap = mmap(NULL, page_size, PROT_READ,
1367                   MAP_SHARED, wait_shm_fd, 0);
1368
1369         /* close shm fd immediately after taking the mmap reference */
1370         lttng_ust_lock_fd_tracker();
1371         ret = close(wait_shm_fd);
1372         if (!ret) {
1373                 lttng_ust_delete_fd_from_tracker(wait_shm_fd);
1374         } else {
1375                 PERROR("Error closing fd");
1376         }
1377         lttng_ust_unlock_fd_tracker();
1378
1379         if (wait_shm_mmap == MAP_FAILED) {
1380                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
1381                 goto error;
1382         }
1383         return wait_shm_mmap;
1384
1385 error:
1386         return NULL;
1387 }
1388
1389 static
1390 void wait_for_sessiond(struct sock_info *sock_info)
1391 {
1392         /* Use ust_lock to check if we should quit. */
1393         if (ust_lock()) {
1394                 goto quit;
1395         }
1396         if (wait_poll_fallback) {
1397                 goto error;
1398         }
1399         ust_unlock();
1400
1401         assert(sock_info->wait_shm_mmap);
1402
1403         DBG("Waiting for %s apps sessiond", sock_info->name);
1404         /* Wait for futex wakeup */
1405         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap))
1406                 goto end_wait;
1407
1408         while (futex_async((int32_t *) sock_info->wait_shm_mmap,
1409                         FUTEX_WAIT, 0, NULL, NULL, 0)) {
1410                 switch (errno) {
1411                 case EWOULDBLOCK:
1412                         /* Value already changed. */
1413                         goto end_wait;
1414                 case EINTR:
1415                         /* Retry if interrupted by signal. */
1416                         break;  /* Get out of switch. */
1417                 case EFAULT:
1418                         wait_poll_fallback = 1;
1419                         DBG(
1420 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
1421 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
1422 "Please upgrade your kernel "
1423 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
1424 "mainline). LTTng-UST will use polling mode fallback.");
1425                         if (ust_debug())
1426                                 PERROR("futex");
1427                         goto end_wait;
1428                 }
1429         }
1430 end_wait:
1431         return;
1432
1433 quit:
1434         ust_unlock();
1435         return;
1436
1437 error:
1438         ust_unlock();
1439         return;
1440 }
1441
1442 /*
1443  * This thread does not allocate any resource, except within
1444  * handle_message, within mutex protection. This mutex protects against
1445  * fork and exit.
1446  * The other moment it allocates resources is at socket connection, which
1447  * is also protected by the mutex.
1448  */
1449 static
1450 void *ust_listener_thread(void *arg)
1451 {
1452         struct sock_info *sock_info = arg;
1453         int sock, ret, prev_connect_failed = 0, has_waited = 0, fd;
1454         long timeout;
1455
1456         lttng_ust_fixup_tls();
1457         /*
1458          * If available, add '-ust' to the end of this thread's
1459          * process name
1460          */
1461         ret = lttng_ust_setustprocname();
1462         if (ret) {
1463                 ERR("Unable to set UST process name");
1464         }
1465
1466         /* Restart trying to connect to the session daemon */
1467 restart:
1468         if (prev_connect_failed) {
1469                 /* Wait for sessiond availability with pipe */
1470                 wait_for_sessiond(sock_info);
1471                 if (has_waited) {
1472                         has_waited = 0;
1473                         /*
1474                          * Sleep for 5 seconds before retrying after a
1475                          * sequence of failure / wait / failure. This
1476                          * deals with a killed or broken session daemon.
1477                          */
1478                         sleep(5);
1479                 } else {
1480                         has_waited = 1;
1481                 }
1482                 prev_connect_failed = 0;
1483         }
1484
1485         if (ust_lock()) {
1486                 goto quit;
1487         }
1488
1489         if (sock_info->socket != -1) {
1490                 /* FD tracker is updated by ustcomm_close_unix_sock() */
1491                 ret = ustcomm_close_unix_sock(sock_info->socket);
1492                 if (ret) {
1493                         ERR("Error closing %s ust cmd socket",
1494                                 sock_info->name);
1495                 }
1496                 sock_info->socket = -1;
1497         }
1498         if (sock_info->notify_socket != -1) {
1499                 /* FD tracker is updated by ustcomm_close_unix_sock() */
1500                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
1501                 if (ret) {
1502                         ERR("Error closing %s ust notify socket",
1503                                 sock_info->name);
1504                 }
1505                 sock_info->notify_socket = -1;
1506         }
1507
1508
1509         /*
1510          * Register. We need to perform both connect and sending
1511          * registration message before doing the next connect otherwise
1512          * we may reach unix socket connect queue max limits and block
1513          * on the 2nd connect while the session daemon is awaiting the
1514          * first connect registration message.
1515          */
1516         /* Connect cmd socket */
1517         lttng_ust_lock_fd_tracker();
1518         ret = ustcomm_connect_unix_sock(sock_info->sock_path,
1519                 get_connect_sock_timeout());
1520         if (ret < 0) {
1521                 lttng_ust_unlock_fd_tracker();
1522                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1523                 prev_connect_failed = 1;
1524
1525                 /*
1526                  * If we cannot find the sessiond daemon, don't delay
1527                  * constructor execution.
1528                  */
1529                 ret = handle_register_failed(sock_info);
1530                 assert(!ret);
1531                 ust_unlock();
1532                 goto restart;
1533         }
1534         fd = ret;
1535         ret = lttng_ust_add_fd_to_tracker(fd);
1536         if (ret < 0) {
1537                 ret = close(fd);
1538                 if (ret) {
1539                         PERROR("close on sock_info->socket");
1540                 }
1541                 ret = -1;
1542                 lttng_ust_unlock_fd_tracker();
1543                 ust_unlock();
1544                 goto quit;
1545         }
1546
1547         sock_info->socket = ret;
1548         lttng_ust_unlock_fd_tracker();
1549
1550         ust_unlock();
1551         /*
1552          * Unlock/relock ust lock because connect is blocking (with
1553          * timeout). Don't delay constructors on the ust lock for too
1554          * long.
1555          */
1556         if (ust_lock()) {
1557                 goto quit;
1558         }
1559
1560         /*
1561          * Create only one root handle per listener thread for the whole
1562          * process lifetime, so we ensure we get ID which is statically
1563          * assigned to the root handle.
1564          */
1565         if (sock_info->root_handle == -1) {
1566                 ret = lttng_abi_create_root_handle();
1567                 if (ret < 0) {
1568                         ERR("Error creating root handle");
1569                         goto quit;
1570                 }
1571                 sock_info->root_handle = ret;
1572         }
1573
1574         ret = register_to_sessiond(sock_info->socket, USTCTL_SOCKET_CMD);
1575         if (ret < 0) {
1576                 ERR("Error registering to %s ust cmd socket",
1577                         sock_info->name);
1578                 prev_connect_failed = 1;
1579                 /*
1580                  * If we cannot register to the sessiond daemon, don't
1581                  * delay constructor execution.
1582                  */
1583                 ret = handle_register_failed(sock_info);
1584                 assert(!ret);
1585                 ust_unlock();
1586                 goto restart;
1587         }
1588
1589         ust_unlock();
1590         /*
1591          * Unlock/relock ust lock because connect is blocking (with
1592          * timeout). Don't delay constructors on the ust lock for too
1593          * long.
1594          */
1595         if (ust_lock()) {
1596                 goto quit;
1597         }
1598
1599         /* Connect notify socket */
1600         lttng_ust_lock_fd_tracker();
1601         ret = ustcomm_connect_unix_sock(sock_info->sock_path,
1602                 get_connect_sock_timeout());
1603         if (ret < 0) {
1604                 lttng_ust_unlock_fd_tracker();
1605                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1606                 prev_connect_failed = 1;
1607
1608                 /*
1609                  * If we cannot find the sessiond daemon, don't delay
1610                  * constructor execution.
1611                  */
1612                 ret = handle_register_failed(sock_info);
1613                 assert(!ret);
1614                 ust_unlock();
1615                 goto restart;
1616         }
1617
1618         fd = ret;
1619         ret = lttng_ust_add_fd_to_tracker(fd);
1620         if (ret < 0) {
1621                 ret = close(fd);
1622                 if (ret) {
1623                         PERROR("close on sock_info->notify_socket");
1624                 }
1625                 ret = -1;
1626                 lttng_ust_unlock_fd_tracker();
1627                 ust_unlock();
1628                 goto quit;
1629         }
1630
1631         sock_info->notify_socket = ret;
1632         lttng_ust_unlock_fd_tracker();
1633
1634         ust_unlock();
1635         /*
1636          * Unlock/relock ust lock because connect is blocking (with
1637          * timeout). Don't delay constructors on the ust lock for too
1638          * long.
1639          */
1640         if (ust_lock()) {
1641                 goto quit;
1642         }
1643
1644         timeout = get_notify_sock_timeout();
1645         if (timeout >= 0) {
1646                 /*
1647                  * Give at least 10ms to sessiond to reply to
1648                  * notifications.
1649                  */
1650                 if (timeout < 10)
1651                         timeout = 10;
1652                 ret = ustcomm_setsockopt_rcv_timeout(sock_info->notify_socket,
1653                                 timeout);
1654                 if (ret < 0) {
1655                         WARN("Error setting socket receive timeout");
1656                 }
1657                 ret = ustcomm_setsockopt_snd_timeout(sock_info->notify_socket,
1658                                 timeout);
1659                 if (ret < 0) {
1660                         WARN("Error setting socket send timeout");
1661                 }
1662         } else if (timeout < -1) {
1663                 WARN("Unsupported timeout value %ld", timeout);
1664         }
1665
1666         ret = register_to_sessiond(sock_info->notify_socket,
1667                         USTCTL_SOCKET_NOTIFY);
1668         if (ret < 0) {
1669                 ERR("Error registering to %s ust notify socket",
1670                         sock_info->name);
1671                 prev_connect_failed = 1;
1672                 /*
1673                  * If we cannot register to the sessiond daemon, don't
1674                  * delay constructor execution.
1675                  */
1676                 ret = handle_register_failed(sock_info);
1677                 assert(!ret);
1678                 ust_unlock();
1679                 goto restart;
1680         }
1681         sock = sock_info->socket;
1682
1683         ust_unlock();
1684
1685         for (;;) {
1686                 ssize_t len;
1687                 struct ustcomm_ust_msg lum;
1688
1689                 len = ustcomm_recv_unix_sock(sock, &lum, sizeof(lum));
1690                 switch (len) {
1691                 case 0: /* orderly shutdown */
1692                         DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
1693                         if (ust_lock()) {
1694                                 goto quit;
1695                         }
1696                         /*
1697                          * Either sessiond has shutdown or refused us by closing the socket.
1698                          * In either case, we don't want to delay construction execution,
1699                          * and we need to wait before retry.
1700                          */
1701                         prev_connect_failed = 1;
1702                         /*
1703                          * If we cannot register to the sessiond daemon, don't
1704                          * delay constructor execution.
1705                          */
1706                         ret = handle_register_failed(sock_info);
1707                         assert(!ret);
1708                         ust_unlock();
1709                         goto end;
1710                 case sizeof(lum):
1711                         print_cmd(lum.cmd, lum.handle);
1712                         ret = handle_message(sock_info, sock, &lum);
1713                         if (ret) {
1714                                 ERR("Error handling message for %s socket",
1715                                         sock_info->name);
1716                                 /*
1717                                  * Close socket if protocol error is
1718                                  * detected.
1719                                  */
1720                                 goto end;
1721                         }
1722                         continue;
1723                 default:
1724                         if (len < 0) {
1725                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
1726                         } else {
1727                                 DBG("incorrect message size (%s socket): %zd", sock_info->name, len);
1728                         }
1729                         if (len == -ECONNRESET) {
1730                                 DBG("%s remote end closed connection", sock_info->name);
1731                                 goto end;
1732                         }
1733                         goto end;
1734                 }
1735
1736         }
1737 end:
1738         if (ust_lock()) {
1739                 goto quit;
1740         }
1741         /* Cleanup socket handles before trying to reconnect */
1742         lttng_ust_objd_table_owner_cleanup(sock_info);
1743         ust_unlock();
1744         goto restart;   /* try to reconnect */
1745
1746 quit:
1747         ust_unlock();
1748
1749         pthread_mutex_lock(&ust_exit_mutex);
1750         sock_info->thread_active = 0;
1751         pthread_mutex_unlock(&ust_exit_mutex);
1752         return NULL;
1753 }
1754
1755 /*
1756  * Weak symbol to call when the ust malloc wrapper is not loaded.
1757  */
1758 __attribute__((weak))
1759 void lttng_ust_malloc_wrapper_init(void)
1760 {
1761 }
1762
1763 /*
1764  * sessiond monitoring thread: monitor presence of global and per-user
1765  * sessiond by polling the application common named pipe.
1766  */
1767 void __attribute__((constructor)) lttng_ust_init(void)
1768 {
1769         struct timespec constructor_timeout;
1770         sigset_t sig_all_blocked, orig_parent_mask;
1771         pthread_attr_t thread_attr;
1772         int timeout_mode;
1773         int ret;
1774
1775         if (uatomic_xchg(&initialized, 1) == 1)
1776                 return;
1777
1778         /*
1779          * Fixup interdependency between TLS fixup mutex (which happens
1780          * to be the dynamic linker mutex) and ust_lock, taken within
1781          * the ust lock.
1782          */
1783         lttng_ust_fixup_tls();
1784
1785         lttng_ust_loaded = 1;
1786
1787         /*
1788          * We want precise control over the order in which we construct
1789          * our sub-libraries vs starting to receive commands from
1790          * sessiond (otherwise leading to errors when trying to create
1791          * sessiond before the init functions are completed).
1792          */
1793         init_usterr();
1794         lttng_ust_getenv_init();        /* Needs init_usterr() to be completed. */
1795         init_tracepoint();
1796         lttng_ust_init_fd_tracker();
1797         lttng_ust_clock_init();
1798         lttng_ust_getcpu_init();
1799         lttng_ust_statedump_init();
1800         lttng_ring_buffer_metadata_client_init();
1801         lttng_ring_buffer_client_overwrite_init();
1802         lttng_ring_buffer_client_overwrite_rt_init();
1803         lttng_ring_buffer_client_discard_init();
1804         lttng_ring_buffer_client_discard_rt_init();
1805         lttng_perf_counter_init();
1806         /*
1807          * Invoke ust malloc wrapper init before starting other threads.
1808          */
1809         lttng_ust_malloc_wrapper_init();
1810
1811         timeout_mode = get_constructor_timeout(&constructor_timeout);
1812
1813         get_allow_blocking();
1814
1815         ret = sem_init(&constructor_wait, 0, 0);
1816         if (ret) {
1817                 PERROR("sem_init");
1818         }
1819
1820         ret = setup_global_apps();
1821         if (ret) {
1822                 assert(global_apps.allowed == 0);
1823                 DBG("global apps setup returned %d", ret);
1824         }
1825
1826         ret = setup_local_apps();
1827         if (ret) {
1828                 assert(local_apps.allowed == 0);
1829                 DBG("local apps setup returned %d", ret);
1830         }
1831
1832         /* A new thread created by pthread_create inherits the signal mask
1833          * from the parent. To avoid any signal being received by the
1834          * listener thread, we block all signals temporarily in the parent,
1835          * while we create the listener thread.
1836          */
1837         sigfillset(&sig_all_blocked);
1838         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
1839         if (ret) {
1840                 ERR("pthread_sigmask: %s", strerror(ret));
1841         }
1842
1843         ret = pthread_attr_init(&thread_attr);
1844         if (ret) {
1845                 ERR("pthread_attr_init: %s", strerror(ret));
1846         }
1847         ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
1848         if (ret) {
1849                 ERR("pthread_attr_setdetachstate: %s", strerror(ret));
1850         }
1851
1852         if (global_apps.allowed) {
1853                 pthread_mutex_lock(&ust_exit_mutex);
1854                 ret = pthread_create(&global_apps.ust_listener, &thread_attr,
1855                                 ust_listener_thread, &global_apps);
1856                 if (ret) {
1857                         ERR("pthread_create global: %s", strerror(ret));
1858                 }
1859                 global_apps.thread_active = 1;
1860                 pthread_mutex_unlock(&ust_exit_mutex);
1861         } else {
1862                 handle_register_done(&global_apps);
1863         }
1864
1865         if (local_apps.allowed) {
1866                 pthread_mutex_lock(&ust_exit_mutex);
1867                 ret = pthread_create(&local_apps.ust_listener, &thread_attr,
1868                                 ust_listener_thread, &local_apps);
1869                 if (ret) {
1870                         ERR("pthread_create local: %s", strerror(ret));
1871                 }
1872                 local_apps.thread_active = 1;
1873                 pthread_mutex_unlock(&ust_exit_mutex);
1874         } else {
1875                 handle_register_done(&local_apps);
1876         }
1877         ret = pthread_attr_destroy(&thread_attr);
1878         if (ret) {
1879                 ERR("pthread_attr_destroy: %s", strerror(ret));
1880         }
1881
1882         /* Restore original signal mask in parent */
1883         ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
1884         if (ret) {
1885                 ERR("pthread_sigmask: %s", strerror(ret));
1886         }
1887
1888         switch (timeout_mode) {
1889         case 1: /* timeout wait */
1890                 do {
1891                         ret = sem_timedwait(&constructor_wait,
1892                                         &constructor_timeout);
1893                 } while (ret < 0 && errno == EINTR);
1894                 if (ret < 0) {
1895                         switch (errno) {
1896                         case ETIMEDOUT:
1897                                 ERR("Timed out waiting for lttng-sessiond");
1898                                 break;
1899                         case EINVAL:
1900                                 PERROR("sem_timedwait");
1901                                 break;
1902                         default:
1903                                 ERR("Unexpected error \"%s\" returned by sem_timedwait",
1904                                         strerror(errno));
1905                         }
1906                 }
1907                 break;
1908         case -1:/* wait forever */
1909                 do {
1910                         ret = sem_wait(&constructor_wait);
1911                 } while (ret < 0 && errno == EINTR);
1912                 if (ret < 0) {
1913                         switch (errno) {
1914                         case EINVAL:
1915                                 PERROR("sem_wait");
1916                                 break;
1917                         default:
1918                                 ERR("Unexpected error \"%s\" returned by sem_wait",
1919                                         strerror(errno));
1920                         }
1921                 }
1922                 break;
1923         case 0: /* no timeout */
1924                 break;
1925         }
1926 }
1927
1928 static
1929 void lttng_ust_cleanup(int exiting)
1930 {
1931         cleanup_sock_info(&global_apps, exiting);
1932         cleanup_sock_info(&local_apps, exiting);
1933         local_apps.allowed = 0;
1934         global_apps.allowed = 0;
1935         /*
1936          * The teardown in this function all affect data structures
1937          * accessed under the UST lock by the listener thread. This
1938          * lock, along with the lttng_ust_comm_should_quit flag, ensure
1939          * that none of these threads are accessing this data at this
1940          * point.
1941          */
1942         lttng_ust_abi_exit();
1943         lttng_ust_events_exit();
1944         lttng_perf_counter_exit();
1945         lttng_ring_buffer_client_discard_rt_exit();
1946         lttng_ring_buffer_client_discard_exit();
1947         lttng_ring_buffer_client_overwrite_rt_exit();
1948         lttng_ring_buffer_client_overwrite_exit();
1949         lttng_ring_buffer_metadata_client_exit();
1950         lttng_ust_statedump_destroy();
1951         exit_tracepoint();
1952         if (!exiting) {
1953                 /* Reinitialize values for fork */
1954                 sem_count = sem_count_initial_value;
1955                 lttng_ust_comm_should_quit = 0;
1956                 initialized = 0;
1957         }
1958 }
1959
1960 void __attribute__((destructor)) lttng_ust_exit(void)
1961 {
1962         int ret;
1963
1964         /*
1965          * Using pthread_cancel here because:
1966          * A) we don't want to hang application teardown.
1967          * B) the thread is not allocating any resource.
1968          */
1969
1970         /*
1971          * Require the communication thread to quit. Synchronize with
1972          * mutexes to ensure it is not in a mutex critical section when
1973          * pthread_cancel is later called.
1974          */
1975         ust_lock_nocheck();
1976         lttng_ust_comm_should_quit = 1;
1977         ust_unlock();
1978
1979         pthread_mutex_lock(&ust_exit_mutex);
1980         /* cancel threads */
1981         if (global_apps.thread_active) {
1982                 ret = pthread_cancel(global_apps.ust_listener);
1983                 if (ret) {
1984                         ERR("Error cancelling global ust listener thread: %s",
1985                                 strerror(ret));
1986                 } else {
1987                         global_apps.thread_active = 0;
1988                 }
1989         }
1990         if (local_apps.thread_active) {
1991                 ret = pthread_cancel(local_apps.ust_listener);
1992                 if (ret) {
1993                         ERR("Error cancelling local ust listener thread: %s",
1994                                 strerror(ret));
1995                 } else {
1996                         local_apps.thread_active = 0;
1997                 }
1998         }
1999         pthread_mutex_unlock(&ust_exit_mutex);
2000
2001         /*
2002          * Do NOT join threads: use of sys_futex makes it impossible to
2003          * join the threads without using async-cancel, but async-cancel
2004          * is delivered by a signal, which could hit the target thread
2005          * anywhere in its code path, including while the ust_lock() is
2006          * held, causing a deadlock for the other thread. Let the OS
2007          * cleanup the threads if there are stalled in a syscall.
2008          */
2009         lttng_ust_cleanup(1);
2010 }
2011
2012 /*
2013  * We exclude the worker threads across fork and clone (except
2014  * CLONE_VM), because these system calls only keep the forking thread
2015  * running in the child.  Therefore, we don't want to call fork or clone
2016  * in the middle of an tracepoint or ust tracing state modification.
2017  * Holding this mutex protects these structures across fork and clone.
2018  */
2019 void ust_before_fork(sigset_t *save_sigset)
2020 {
2021         /*
2022          * Disable signals. This is to avoid that the child intervenes
2023          * before it is properly setup for tracing. It is safer to
2024          * disable all signals, because then we know we are not breaking
2025          * anything by restoring the original mask.
2026          */
2027         sigset_t all_sigs;
2028         int ret;
2029
2030         /* Fixup lttng-ust TLS. */
2031         lttng_ust_fixup_tls();
2032
2033         if (URCU_TLS(lttng_ust_nest_count))
2034                 return;
2035         /* Disable signals */
2036         sigfillset(&all_sigs);
2037         ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
2038         if (ret == -1) {
2039                 PERROR("sigprocmask");
2040         }
2041
2042         pthread_mutex_lock(&ust_fork_mutex);
2043
2044         ust_lock_nocheck();
2045         rcu_bp_before_fork();
2046         lttng_ust_lock_fd_tracker();
2047         lttng_perf_lock();
2048 }
2049
2050 static void ust_after_fork_common(sigset_t *restore_sigset)
2051 {
2052         int ret;
2053
2054         DBG("process %d", getpid());
2055         lttng_perf_unlock();
2056         lttng_ust_unlock_fd_tracker();
2057         ust_unlock();
2058
2059         pthread_mutex_unlock(&ust_fork_mutex);
2060
2061         /* Restore signals */
2062         ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
2063         if (ret == -1) {
2064                 PERROR("sigprocmask");
2065         }
2066 }
2067
2068 void ust_after_fork_parent(sigset_t *restore_sigset)
2069 {
2070         if (URCU_TLS(lttng_ust_nest_count))
2071                 return;
2072         DBG("process %d", getpid());
2073         rcu_bp_after_fork_parent();
2074         /* Release mutexes and reenable signals */
2075         ust_after_fork_common(restore_sigset);
2076 }
2077
2078 /*
2079  * After fork, in the child, we need to cleanup all the leftover state,
2080  * except the worker thread which already magically disappeared thanks
2081  * to the weird Linux fork semantics. After tyding up, we call
2082  * lttng_ust_init() again to start over as a new PID.
2083  *
2084  * This is meant for forks() that have tracing in the child between the
2085  * fork and following exec call (if there is any).
2086  */
2087 void ust_after_fork_child(sigset_t *restore_sigset)
2088 {
2089         if (URCU_TLS(lttng_ust_nest_count))
2090                 return;
2091         lttng_context_vpid_reset();
2092         lttng_context_vtid_reset();
2093         lttng_context_procname_reset();
2094         DBG("process %d", getpid());
2095         /* Release urcu mutexes */
2096         rcu_bp_after_fork_child();
2097         lttng_ust_cleanup(0);
2098         /* Release mutexes and reenable signals */
2099         ust_after_fork_common(restore_sigset);
2100         lttng_ust_init();
2101 }
2102
2103 void lttng_ust_sockinfo_session_enabled(void *owner)
2104 {
2105         struct sock_info *sock_info = owner;
2106         sock_info->statedump_pending = 1;
2107 }