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_fd_tracker_tls();
 423 }
 424
 425 int lttng_get_notify_socket(void *owner)
 426 {
 427         struct sock_info *info = owner;
 428
 429         return info->notify_socket;
 430 }
 431
 432 static
 433 void print_cmd(int cmd, int handle)
 434 {
 435         const char *cmd_name = "Unknown";
 436
 437         if (cmd >= 0 && cmd < LTTNG_ARRAY_SIZE(cmd_name_mapping)
 438                         && cmd_name_mapping[cmd]) {
 439                 cmd_name = cmd_name_mapping[cmd];
 440         }
 441         DBG("Message Received \"%s\" (%d), Handle \"%s\" (%d)",
 442                 cmd_name, cmd,
 443                 lttng_ust_obj_get_name(handle), handle);
 444 }
 445
 446 static
 447 int setup_global_apps(void)
 448 {
 449         int ret = 0;
 450         assert(!global_apps.wait_shm_mmap);
 451
 452         global_apps.wait_shm_mmap = get_map_shm(&global_apps);
 453         if (!global_apps.wait_shm_mmap) {
 454                 WARN("Unable to get map shm for global apps. Disabling LTTng-UST global tracing.");
 455                 global_apps.allowed = 0;
 456                 ret = -EIO;
 457                 goto error;
 458         }
 459
 460         global_apps.allowed = 1;
 461 error:
 462         return ret;
 463 }
 464 static
 465 int setup_local_apps(void)
 466 {
 467         int ret = 0;
 468         const char *home_dir;
 469         uid_t uid;
 470
 471         assert(!local_apps.wait_shm_mmap);
 472
 473         uid = getuid();
 474         /*
 475          * Disallow per-user tracing for setuid binaries.
 476          */
 477         if (uid != geteuid()) {
 478                 assert(local_apps.allowed == 0);
 479                 ret = 0;
 480                 goto end;
 481         }
 482         home_dir = get_lttng_home_dir();
 483         if (!home_dir) {
 484                 WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
 485                 assert(local_apps.allowed == 0);
 486                 ret = -ENOENT;
 487                 goto end;
 488         }
 489         local_apps.allowed = 1;
 490         snprintf(local_apps.sock_path, PATH_MAX, "%s/%s/%s",
 491                 home_dir,
 492                 LTTNG_DEFAULT_HOME_RUNDIR,
 493                 LTTNG_UST_SOCK_FILENAME);
 494         snprintf(local_apps.wait_shm_path, PATH_MAX, "/%s-%u",
 495                 LTTNG_UST_WAIT_FILENAME,
 496                 uid);
 497
 498         local_apps.wait_shm_mmap = get_map_shm(&local_apps);
 499         if (!local_apps.wait_shm_mmap) {
 500                 WARN("Unable to get map shm for local apps. Disabling LTTng-UST per-user tracing.");
 501                 local_apps.allowed = 0;
 502                 ret = -EIO;
 503                 goto end;
 504         }
 505 end:
 506         return ret;
 507 }
 508
 509 /*
 510  * Get socket timeout, in ms.
 511  * -1: wait forever. 0: don't wait. >0: timeout, in ms.
 512  */
 513 static
 514 long get_timeout(void)
 515 {
 516         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 517
 518         if (!got_timeout_env) {
 519                 str_timeout = lttng_getenv("LTTNG_UST_REGISTER_TIMEOUT");
 520                 got_timeout_env = 1;
 521         }
 522         if (str_timeout)
 523                 constructor_delay_ms = strtol(str_timeout, NULL, 10);
 524         /* All negative values are considered as "-1". */
 525         if (constructor_delay_ms < -1)
 526                 constructor_delay_ms = -1;
 527         return constructor_delay_ms;
 528 }
 529
 530 /* Timeout for notify socket send and recv. */
 531 static
 532 long get_notify_sock_timeout(void)
 533 {
 534         return get_timeout();
 535 }
 536
 537 /* Timeout for connecting to cmd and notify sockets. */
 538 static
 539 long get_connect_sock_timeout(void)
 540 {
 541         return get_timeout();
 542 }
 543
 544 /*
 545  * Return values: -1: wait forever. 0: don't wait. 1: timeout wait.
 546  */
 547 static
 548 int get_constructor_timeout(struct timespec *constructor_timeout)
 549 {
 550         long constructor_delay_ms;
 551         int ret;
 552
 553         constructor_delay_ms = get_timeout();
 554
 555         switch (constructor_delay_ms) {
 556         case -1:/* fall-through */
 557         case 0:
 558                 return constructor_delay_ms;
 559         default:
 560                 break;
 561         }
 562
 563         /*
 564          * If we are unable to find the current time, don't wait.
 565          */
 566         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 567         if (ret) {
 568                 /* Don't wait. */
 569                 return 0;
 570         }
 571         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 572         constructor_timeout->tv_nsec +=
 573                 (constructor_delay_ms % 1000UL) * 1000000UL;
 574         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 575                 constructor_timeout->tv_sec++;
 576                 constructor_timeout->tv_nsec -= 1000000000UL;
 577         }
 578         /* Timeout wait (constructor_delay_ms). */
 579         return 1;
 580 }
 581
 582 static
 583 void get_allow_blocking(void)
 584 {
 585         const char *str_allow_blocking =
 586                 lttng_getenv("LTTNG_UST_ALLOW_BLOCKING");
 587
 588         if (str_allow_blocking) {
 589                 DBG("%s environment variable is set",
 590                         "LTTNG_UST_ALLOW_BLOCKING");
 591                 lttng_ust_ringbuffer_set_allow_blocking();
 592         }
 593 }
 594
 595 static
 596 int register_to_sessiond(int socket, enum ustctl_socket_type type)
 597 {
 598         return ustcomm_send_reg_msg(socket,
 599                 type,
 600                 CAA_BITS_PER_LONG,
 601                 lttng_alignof(uint8_t) * CHAR_BIT,
 602                 lttng_alignof(uint16_t) * CHAR_BIT,
 603                 lttng_alignof(uint32_t) * CHAR_BIT,
 604                 lttng_alignof(uint64_t) * CHAR_BIT,
 605                 lttng_alignof(unsigned long) * CHAR_BIT);
 606 }
 607
 608 static
 609 int send_reply(int sock, struct ustcomm_ust_reply *lur)
 610 {
 611         ssize_t len;
 612
 613         len = ustcomm_send_unix_sock(sock, lur, sizeof(*lur));
 614         switch (len) {
 615         case sizeof(*lur):
 616                 DBG("message successfully sent");
 617                 return 0;
 618         default:
 619                 if (len == -ECONNRESET) {
 620                         DBG("remote end closed connection");
 621                         return 0;
 622                 }
 623                 if (len < 0)
 624                         return len;
 625                 DBG("incorrect message size: %zd", len);
 626                 return -EINVAL;
 627         }
 628 }
 629
 630 static
 631 void decrement_sem_count(unsigned int count)
 632 {
 633         int ret;
 634
 635         assert(uatomic_read(&sem_count) >= count);
 636
 637         if (uatomic_read(&sem_count) <= 0) {
 638                 return;
 639         }
 640
 641         ret = uatomic_add_return(&sem_count, -count);
 642         if (ret == 0) {
 643                 ret = sem_post(&constructor_wait);
 644                 assert(!ret);
 645         }
 646 }
 647
 648 static
 649 int handle_register_done(struct sock_info *sock_info)
 650 {
 651         if (sock_info->registration_done)
 652                 return 0;
 653         sock_info->registration_done = 1;
 654
 655         decrement_sem_count(1);
 656         if (!sock_info->statedump_pending) {
 657                 sock_info->initial_statedump_done = 1;
 658                 decrement_sem_count(1);
 659         }
 660
 661         return 0;
 662 }
 663
 664 static
 665 int handle_register_failed(struct sock_info *sock_info)
 666 {
 667         if (sock_info->registration_done)
 668                 return 0;
 669         sock_info->registration_done = 1;
 670         sock_info->initial_statedump_done = 1;
 671
 672         decrement_sem_count(2);
 673
 674         return 0;
 675 }
 676
 677 /*
 678  * Only execute pending statedump after the constructor semaphore has
 679  * been posted by the current listener thread. This means statedump will
 680  * only be performed after the "registration done" command is received
 681  * from this thread's session daemon.
 682  *
 683  * This ensures we don't run into deadlock issues with the dynamic
 684  * loader mutex, which is held while the constructor is called and
 685  * waiting on the constructor semaphore. All operations requiring this
 686  * dynamic loader lock need to be postponed using this mechanism.
 687  *
 688  * In a scenario with two session daemons connected to the application,
 689  * it is possible that the first listener thread which receives the
 690  * registration done command issues its statedump while the dynamic
 691  * loader lock is still held by the application constructor waiting on
 692  * the semaphore. It will however be allowed to proceed when the
 693  * second session daemon sends the registration done command to the
 694  * second listener thread. This situation therefore does not produce
 695  * a deadlock.
 696  */
 697 static
 698 void handle_pending_statedump(struct sock_info *sock_info)
 699 {
 700         if (sock_info->registration_done && sock_info->statedump_pending) {
 701                 sock_info->statedump_pending = 0;
 702                 pthread_mutex_lock(&ust_fork_mutex);
 703                 lttng_handle_pending_statedump(sock_info);
 704                 pthread_mutex_unlock(&ust_fork_mutex);
 705
 706                 if (!sock_info->initial_statedump_done) {
 707                         sock_info->initial_statedump_done = 1;
 708                         decrement_sem_count(1);
 709                 }
 710         }
 711 }
 712
 713 static
 714 int handle_message(struct sock_info *sock_info,
 715                 int sock, struct ustcomm_ust_msg *lum)
 716 {
 717         int ret = 0;
 718         const struct lttng_ust_objd_ops *ops;
 719         struct ustcomm_ust_reply lur;
 720         union ust_args args;
 721         char ctxstr[LTTNG_UST_SYM_NAME_LEN];    /* App context string. */
 722         ssize_t len;
 723
 724         memset(&lur, 0, sizeof(lur));
 725
 726         if (ust_lock()) {
 727                 ret = -LTTNG_UST_ERR_EXITING;
 728                 goto error;
 729         }
 730
 731         ops = objd_ops(lum->handle);
 732         if (!ops) {
 733                 ret = -ENOENT;
 734                 goto error;
 735         }
 736
 737         switch (lum->cmd) {
 738         case LTTNG_UST_REGISTER_DONE:
 739                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 740                         ret = handle_register_done(sock_info);
 741                 else
 742                         ret = -EINVAL;
 743                 break;
 744         case LTTNG_UST_RELEASE:
 745                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 746                         ret = -EPERM;
 747                 else
 748                         ret = lttng_ust_objd_unref(lum->handle, 1);
 749                 break;
 750         case LTTNG_UST_FILTER:
 751         {
 752                 /* Receive filter data */
 753                 struct lttng_ust_filter_bytecode_node *bytecode;
 754
 755                 if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) {
 756                         ERR("Filter data size is too large: %u bytes",
 757                                 lum->u.filter.data_size);
 758                         ret = -EINVAL;
 759                         goto error;
 760                 }
 761
 762                 if (lum->u.filter.reloc_offset > lum->u.filter.data_size) {
 763                         ERR("Filter reloc offset %u is not within data",
 764                                 lum->u.filter.reloc_offset);
 765                         ret = -EINVAL;
 766                         goto error;
 767                 }
 768
 769                 bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size);
 770                 if (!bytecode) {
 771                         ret = -ENOMEM;
 772                         goto error;
 773                 }
 774                 len = ustcomm_recv_unix_sock(sock, bytecode->bc.data,
 775                                 lum->u.filter.data_size);
 776                 switch (len) {
 777                 case 0: /* orderly shutdown */
 778                         ret = 0;
 779                         free(bytecode);
 780                         goto error;
 781                 default:
 782                         if (len == lum->u.filter.data_size) {
 783                                 DBG("filter data received");
 784                                 break;
 785                         } else if (len < 0) {
 786                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 787                                 if (len == -ECONNRESET) {
 788                                         ERR("%s remote end closed connection", sock_info->name);
 789                                         ret = len;
 790                                         free(bytecode);
 791                                         goto error;
 792                                 }
 793                                 ret = len;
 794                                 free(bytecode);
 795                                 goto error;
 796                         } else {
 797                                 DBG("incorrect filter data message size: %zd", len);
 798                                 ret = -EINVAL;
 799                                 free(bytecode);
 800                                 goto error;
 801                         }
 802                 }
 803                 bytecode->bc.len = lum->u.filter.data_size;
 804                 bytecode->bc.reloc_offset = lum->u.filter.reloc_offset;
 805                 bytecode->bc.seqnum = lum->u.filter.seqnum;
 806                 if (ops->cmd) {
 807                         ret = ops->cmd(lum->handle, lum->cmd,
 808                                         (unsigned long) bytecode,
 809                                         &args, sock_info);
 810                         if (ret) {
 811                                 free(bytecode);
 812                         }
 813                         /* don't free bytecode if everything went fine. */
 814                 } else {
 815                         ret = -ENOSYS;
 816                         free(bytecode);
 817                 }
 818                 break;
 819         }
 820         case LTTNG_UST_EXCLUSION:
 821         {
 822                 /* Receive exclusion names */
 823                 struct lttng_ust_excluder_node *node;
 824                 unsigned int count;
 825
 826                 count = lum->u.exclusion.count;
 827                 if (count == 0) {
 828                         /* There are no names to read */
 829                         ret = 0;
 830                         goto error;
 831                 }
 832                 node = zmalloc(sizeof(*node) +
 833                                 count * LTTNG_UST_SYM_NAME_LEN);
 834                 if (!node) {
 835                         ret = -ENOMEM;
 836                         goto error;
 837                 }
 838                 node->excluder.count = count;
 839                 len = ustcomm_recv_unix_sock(sock, node->excluder.names,
 840                                 count * LTTNG_UST_SYM_NAME_LEN);
 841                 switch (len) {
 842                 case 0: /* orderly shutdown */
 843                         ret = 0;
 844                         free(node);
 845                         goto error;
 846                 default:
 847                         if (len == count * LTTNG_UST_SYM_NAME_LEN) {
 848                                 DBG("Exclusion data received");
 849                                 break;
 850                         } else if (len < 0) {
 851                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 852                                 if (len == -ECONNRESET) {
 853                                         ERR("%s remote end closed connection", sock_info->name);
 854                                         ret = len;
 855                                         free(node);
 856                                         goto error;
 857                                 }
 858                                 ret = len;
 859                                 free(node);
 860                                 goto error;
 861                         } else {
 862                                 DBG("Incorrect exclusion data message size: %zd", len);
 863                                 ret = -EINVAL;
 864                                 free(node);
 865                                 goto error;
 866                         }
 867                 }
 868                 if (ops->cmd) {
 869                         ret = ops->cmd(lum->handle, lum->cmd,
 870                                         (unsigned long) node,
 871                                         &args, sock_info);
 872                         if (ret) {
 873                                 free(node);
 874                         }
 875                         /* Don't free exclusion data if everything went fine. */
 876                 } else {
 877                         ret = -ENOSYS;
 878                         free(node);
 879                 }
 880                 break;
 881         }
 882         case LTTNG_UST_CHANNEL:
 883         {
 884                 void *chan_data;
 885                 int wakeup_fd;
 886
 887                 len = ustcomm_recv_channel_from_sessiond(sock,
 888                                 &chan_data, lum->u.channel.len,
 889                                 &wakeup_fd);
 890                 switch (len) {
 891                 case 0: /* orderly shutdown */
 892                         ret = 0;
 893                         goto error;
 894                 default:
 895                         if (len == lum->u.channel.len) {
 896                                 DBG("channel data received");
 897                                 break;
 898                         } else if (len < 0) {
 899                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 900                                 if (len == -ECONNRESET) {
 901                                         ERR("%s remote end closed connection", sock_info->name);
 902                                         ret = len;
 903                                         goto error;
 904                                 }
 905                                 ret = len;
 906                                 goto error;
 907                         } else {
 908                                 DBG("incorrect channel data message size: %zd", len);
 909                                 ret = -EINVAL;
 910                                 goto error;
 911                         }
 912                 }
 913                 args.channel.chan_data = chan_data;
 914                 args.channel.wakeup_fd = wakeup_fd;
 915                 if (ops->cmd)
 916                         ret = ops->cmd(lum->handle, lum->cmd,
 917                                         (unsigned long) &lum->u,
 918                                         &args, sock_info);
 919                 else
 920                         ret = -ENOSYS;
 921                 break;
 922         }
 923         case LTTNG_UST_STREAM:
 924         {
 925                 /* Receive shm_fd, wakeup_fd */
 926                 ret = ustcomm_recv_stream_from_sessiond(sock,
 927                         NULL,
 928                         &args.stream.shm_fd,
 929                         &args.stream.wakeup_fd);
 930                 if (ret) {
 931                         goto error;
 932                 }
 933
 934                 if (ops->cmd)
 935                         ret = ops->cmd(lum->handle, lum->cmd,
 936                                         (unsigned long) &lum->u,
 937                                         &args, sock_info);
 938                 else
 939                         ret = -ENOSYS;
 940                 break;
 941         }
 942         case LTTNG_UST_CONTEXT:
 943                 switch (lum->u.context.ctx) {
 944                 case LTTNG_UST_CONTEXT_APP_CONTEXT:
 945                 {
 946                         char *p;
 947                         size_t ctxlen, recvlen;
 948
 949                         ctxlen = strlen("$app.") + lum->u.context.u.app_ctx.provider_name_len - 1
 950                                         + strlen(":") + lum->u.context.u.app_ctx.ctx_name_len;
 951                         if (ctxlen >= LTTNG_UST_SYM_NAME_LEN) {
 952                                 ERR("Application context string length size is too large: %zu bytes",
 953                                         ctxlen);
 954                                 ret = -EINVAL;
 955                                 goto error;
 956                         }
 957                         strcpy(ctxstr, "$app.");
 958                         p = &ctxstr[strlen("$app.")];
 959                         recvlen = ctxlen - strlen("$app.");
 960                         len = ustcomm_recv_unix_sock(sock, p, recvlen);
 961                         switch (len) {
 962                         case 0: /* orderly shutdown */
 963                                 ret = 0;
 964                                 goto error;
 965                         default:
 966                                 if (len == recvlen) {
 967                                         DBG("app context data received");
 968                                         break;
 969                                 } else if (len < 0) {
 970                                         DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 971                                         if (len == -ECONNRESET) {
 972                                                 ERR("%s remote end closed connection", sock_info->name);
 973                                                 ret = len;
 974                                                 goto error;
 975                                         }
 976                                         ret = len;
 977                                         goto error;
 978                                 } else {
 979                                         DBG("incorrect app context data message size: %zd", len);
 980                                         ret = -EINVAL;
 981                                         goto error;
 982                                 }
 983                         }
 984                         /* Put : between provider and ctxname. */
 985                         p[lum->u.context.u.app_ctx.provider_name_len - 1] = ':';
 986                         args.app_context.ctxname = ctxstr;
 987                         break;
 988                 }
 989                 default:
 990                         break;
 991                 }
 992                 if (ops->cmd) {
 993                         ret = ops->cmd(lum->handle, lum->cmd,
 994                                         (unsigned long) &lum->u,
 995                                         &args, sock_info);
 996                 } else {
 997                         ret = -ENOSYS;
 998                 }
 999                 break;
1000         default:
1001                 if (ops->cmd)
1002                         ret = ops->cmd(lum->handle, lum->cmd,
1003                                         (unsigned long) &lum->u,
1004                                         &args, sock_info);
1005                 else
1006                         ret = -ENOSYS;
1007                 break;
1008         }
1009
1010         lur.handle = lum->handle;
1011         lur.cmd = lum->cmd;
1012         lur.ret_val = ret;
1013         if (ret >= 0) {
1014                 lur.ret_code = LTTNG_UST_OK;
1015         } else {
1016                 /*
1017                  * Use -LTTNG_UST_ERR as wildcard for UST internal
1018                  * error that are not caused by the transport, except if
1019                  * we already have a more precise error message to
1020                  * report.
1021                  */
1022                 if (ret > -LTTNG_UST_ERR) {
1023                         /* Translate code to UST error. */
1024                         switch (ret) {
1025                         case -EEXIST:
1026                                 lur.ret_code = -LTTNG_UST_ERR_EXIST;
1027                                 break;
1028                         case -EINVAL:
1029                                 lur.ret_code = -LTTNG_UST_ERR_INVAL;
1030                                 break;
1031                         case -ENOENT:
1032                                 lur.ret_code = -LTTNG_UST_ERR_NOENT;
1033                                 break;
1034                         case -EPERM:
1035                                 lur.ret_code = -LTTNG_UST_ERR_PERM;
1036                                 break;
1037                         case -ENOSYS:
1038                                 lur.ret_code = -LTTNG_UST_ERR_NOSYS;
1039                                 break;
1040                         default:
1041                                 lur.ret_code = -LTTNG_UST_ERR;
1042                                 break;
1043                         }
1044                 } else {
1045                         lur.ret_code = ret;
1046                 }
1047         }
1048         if (ret >= 0) {
1049                 switch (lum->cmd) {
1050                 case LTTNG_UST_TRACER_VERSION:
1051                         lur.u.version = lum->u.version;
1052                         break;
1053                 case LTTNG_UST_TRACEPOINT_LIST_GET:
1054                         memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
1055                         break;
1056                 }
1057         }
1058         DBG("Return value: %d", lur.ret_val);
1059
1060         ust_unlock();
1061
1062         /*
1063          * Performed delayed statedump operations outside of the UST
1064          * lock. We need to take the dynamic loader lock before we take
1065          * the UST lock internally within handle_pending_statedump().
1066           */
1067         handle_pending_statedump(sock_info);
1068
1069         if (ust_lock()) {
1070                 ret = -LTTNG_UST_ERR_EXITING;
1071                 goto error;
1072         }
1073
1074         ret = send_reply(sock, &lur);
1075         if (ret < 0) {
1076                 DBG("error sending reply");
1077                 goto error;
1078         }
1079
1080         /*
1081          * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field
1082          * after the reply.
1083          */
1084         if (lur.ret_code == LTTNG_UST_OK) {
1085                 switch (lum->cmd) {
1086                 case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET:
1087                         len = ustcomm_send_unix_sock(sock,
1088                                 &args.field_list.entry,
1089                                 sizeof(args.field_list.entry));
1090                         if (len < 0) {
1091                                 ret = len;
1092                                 goto error;
1093                         }
1094                         if (len != sizeof(args.field_list.entry)) {
1095                                 ret = -EINVAL;
1096                                 goto error;
1097                         }
1098                 }
1099         }
1100
1101 error:
1102         ust_unlock();
1103
1104         return ret;
1105 }
1106
1107 static
1108 void cleanup_sock_info(struct sock_info *sock_info, int exiting)
1109 {
1110         int ret;
1111
1112         if (sock_info->root_handle != -1) {
1113                 ret = lttng_ust_objd_unref(sock_info->root_handle, 1);
1114                 if (ret) {
1115                         ERR("Error unref root handle");
1116                 }
1117                 sock_info->root_handle = -1;
1118         }
1119         sock_info->registration_done = 0;
1120         sock_info->initial_statedump_done = 0;
1121
1122         /*
1123          * wait_shm_mmap, socket and notify socket are used by listener
1124          * threads outside of the ust lock, so we cannot tear them down
1125          * ourselves, because we cannot join on these threads. Leave
1126          * responsibility of cleaning up these resources to the OS
1127          * process exit.
1128          */
1129         if (exiting)
1130                 return;
1131
1132         if (sock_info->socket != -1) {
1133                 ret = ustcomm_close_unix_sock(sock_info->socket);
1134                 if (ret) {
1135                         ERR("Error closing ust cmd socket");
1136                 }
1137                 sock_info->socket = -1;
1138         }
1139         if (sock_info->notify_socket != -1) {
1140                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
1141                 if (ret) {
1142                         ERR("Error closing ust notify socket");
1143                 }
1144                 sock_info->notify_socket = -1;
1145         }
1146         if (sock_info->wait_shm_mmap) {
1147                 long page_size;
1148
1149                 page_size = sysconf(_SC_PAGE_SIZE);
1150                 if (page_size <= 0) {
1151                         if (!page_size) {
1152                                 errno = EINVAL;
1153                         }
1154                         PERROR("Error in sysconf(_SC_PAGE_SIZE)");
1155                 } else {
1156                         ret = munmap(sock_info->wait_shm_mmap, page_size);
1157                         if (ret) {
1158                                 ERR("Error unmapping wait shm");
1159                         }
1160                 }
1161                 sock_info->wait_shm_mmap = NULL;
1162         }
1163 }
1164
1165 /*
1166  * Using fork to set umask in the child process (not multi-thread safe).
1167  * We deal with the shm_open vs ftruncate race (happening when the
1168  * sessiond owns the shm and does not let everybody modify it, to ensure
1169  * safety against shm_unlink) by simply letting the mmap fail and
1170  * retrying after a few seconds.
1171  * For global shm, everybody has rw access to it until the sessiond
1172  * starts.
1173  */
1174 static
1175 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
1176 {
1177         int wait_shm_fd, ret;
1178         pid_t pid;
1179
1180         /*
1181          * Try to open read-only.
1182          */
1183         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
1184         if (wait_shm_fd >= 0) {
1185                 int32_t tmp_read;
1186                 ssize_t len;
1187                 size_t bytes_read = 0;
1188
1189                 /*
1190                  * Try to read the fd. If unable to do so, try opening
1191                  * it in write mode.
1192                  */
1193                 do {
1194                         len = read(wait_shm_fd,
1195                                 &((char *) &tmp_read)[bytes_read],
1196                                 sizeof(tmp_read) - bytes_read);
1197                         if (len > 0) {
1198                                 bytes_read += len;
1199                         }
1200                 } while ((len < 0 && errno == EINTR)
1201                         || (len > 0 && bytes_read < sizeof(tmp_read)));
1202                 if (bytes_read != sizeof(tmp_read)) {
1203                         ret = close(wait_shm_fd);
1204                         if (ret) {
1205                                 ERR("close wait_shm_fd");
1206                         }
1207                         goto open_write;
1208                 }
1209                 goto end;
1210         } else if (wait_shm_fd < 0 && errno != ENOENT) {
1211                 /*
1212                  * Real-only open did not work, and it's not because the
1213                  * entry was not present. It's a failure that prohibits
1214                  * using shm.
1215                  */
1216                 ERR("Error opening shm %s", sock_info->wait_shm_path);
1217                 goto end;
1218         }
1219
1220 open_write:
1221         /*
1222          * If the open failed because the file did not exist, or because
1223          * the file was not truncated yet, try creating it ourself.
1224          */
1225         URCU_TLS(lttng_ust_nest_count)++;
1226         pid = fork();
1227         URCU_TLS(lttng_ust_nest_count)--;
1228         if (pid > 0) {
1229                 int status;
1230
1231                 /*
1232                  * Parent: wait for child to return, in which case the
1233                  * shared memory map will have been created.
1234                  */
1235                 pid = wait(&status);
1236                 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
1237                         wait_shm_fd = -1;
1238                         goto end;
1239                 }
1240                 /*
1241                  * Try to open read-only again after creation.
1242                  */
1243                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
1244                 if (wait_shm_fd < 0) {
1245                         /*
1246                          * Real-only open did not work. It's a failure
1247                          * that prohibits using shm.
1248                          */
1249                         ERR("Error opening shm %s", sock_info->wait_shm_path);
1250                         goto end;
1251                 }
1252                 goto end;
1253         } else if (pid == 0) {
1254                 int create_mode;
1255
1256                 /* Child */
1257                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
1258                 if (sock_info->global)
1259                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
1260                 /*
1261                  * We're alone in a child process, so we can modify the
1262                  * process-wide umask.
1263                  */
1264                 umask(~create_mode);
1265                 /*
1266                  * Try creating shm (or get rw access).
1267                  * We don't do an exclusive open, because we allow other
1268                  * processes to create+ftruncate it concurrently.
1269                  */
1270                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
1271                                 O_RDWR | O_CREAT, create_mode);
1272                 if (wait_shm_fd >= 0) {
1273                         ret = ftruncate(wait_shm_fd, mmap_size);
1274                         if (ret) {
1275                                 PERROR("ftruncate");
1276                                 _exit(EXIT_FAILURE);
1277                         }
1278                         _exit(EXIT_SUCCESS);
1279                 }
1280                 /*
1281                  * For local shm, we need to have rw access to accept
1282                  * opening it: this means the local sessiond will be
1283                  * able to wake us up. For global shm, we open it even
1284                  * if rw access is not granted, because the root.root
1285                  * sessiond will be able to override all rights and wake
1286                  * us up.
1287                  */
1288                 if (!sock_info->global && errno != EACCES) {
1289                         ERR("Error opening shm %s", sock_info->wait_shm_path);
1290                         _exit(EXIT_FAILURE);
1291                 }
1292                 /*
1293                  * The shm exists, but we cannot open it RW. Report
1294                  * success.
1295                  */
1296                 _exit(EXIT_SUCCESS);
1297         } else {
1298                 return -1;
1299         }
1300 end:
1301         if (wait_shm_fd >= 0 && !sock_info->global) {
1302                 struct stat statbuf;
1303
1304                 /*
1305                  * Ensure that our user is the owner of the shm file for
1306                  * local shm. If we do not own the file, it means our
1307                  * sessiond will not have access to wake us up (there is
1308                  * probably a rogue process trying to fake our
1309                  * sessiond). Fallback to polling method in this case.
1310                  */
1311                 ret = fstat(wait_shm_fd, &statbuf);
1312                 if (ret) {
1313                         PERROR("fstat");
1314                         goto error_close;
1315                 }
1316                 if (statbuf.st_uid != getuid())
1317                         goto error_close;
1318         }
1319         return wait_shm_fd;
1320
1321 error_close:
1322         ret = close(wait_shm_fd);
1323         if (ret) {
1324                 PERROR("Error closing fd");
1325         }
1326         return -1;
1327 }
1328
1329 static
1330 char *get_map_shm(struct sock_info *sock_info)
1331 {
1332         long page_size;
1333         int wait_shm_fd, ret;
1334         char *wait_shm_mmap;
1335
1336         page_size = sysconf(_SC_PAGE_SIZE);
1337         if (page_size <= 0) {
1338                 if (!page_size) {
1339                         errno = EINVAL;
1340                 }
1341                 PERROR("Error in sysconf(_SC_PAGE_SIZE)");
1342                 goto error;
1343         }
1344
1345         lttng_ust_lock_fd_tracker();
1346         wait_shm_fd = get_wait_shm(sock_info, page_size);
1347         if (wait_shm_fd < 0) {
1348                 lttng_ust_unlock_fd_tracker();
1349                 goto error;
1350         }
1351
1352         ret = lttng_ust_add_fd_to_tracker(wait_shm_fd);
1353         if (ret < 0) {
1354                 ret = close(wait_shm_fd);
1355                 if (!ret) {
1356                         PERROR("Error closing fd");
1357                 }
1358                 lttng_ust_unlock_fd_tracker();
1359                 goto error;
1360         }
1361
1362         wait_shm_fd = ret;
1363         lttng_ust_unlock_fd_tracker();
1364
1365         wait_shm_mmap = mmap(NULL, page_size, PROT_READ,
1366                   MAP_SHARED, wait_shm_fd, 0);
1367
1368         /* close shm fd immediately after taking the mmap reference */
1369         lttng_ust_lock_fd_tracker();
1370         ret = close(wait_shm_fd);
1371         if (!ret) {
1372                 lttng_ust_delete_fd_from_tracker(wait_shm_fd);
1373         } else {
1374                 PERROR("Error closing fd");
1375         }
1376         lttng_ust_unlock_fd_tracker();
1377
1378         if (wait_shm_mmap == MAP_FAILED) {
1379                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
1380                 goto error;
1381         }
1382         return wait_shm_mmap;
1383
1384 error:
1385         return NULL;
1386 }
1387
1388 static
1389 void wait_for_sessiond(struct sock_info *sock_info)
1390 {
1391         /* Use ust_lock to check if we should quit. */
1392         if (ust_lock()) {
1393                 goto quit;
1394         }
1395         if (wait_poll_fallback) {
1396                 goto error;
1397         }
1398         ust_unlock();
1399
1400         assert(sock_info->wait_shm_mmap);
1401
1402         DBG("Waiting for %s apps sessiond", sock_info->name);
1403         /* Wait for futex wakeup */
1404         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap))
1405                 goto end_wait;
1406
1407         while (futex_async((int32_t *) sock_info->wait_shm_mmap,
1408                         FUTEX_WAIT, 0, NULL, NULL, 0)) {
1409                 switch (errno) {
1410                 case EWOULDBLOCK:
1411                         /* Value already changed. */
1412                         goto end_wait;
1413                 case EINTR:
1414                         /* Retry if interrupted by signal. */
1415                         break;  /* Get out of switch. */
1416                 case EFAULT:
1417                         wait_poll_fallback = 1;
1418                         DBG(
1419 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
1420 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
1421 "Please upgrade your kernel "
1422 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
1423 "mainline). LTTng-UST will use polling mode fallback.");
1424                         if (ust_debug())
1425                                 PERROR("futex");
1426                         goto end_wait;
1427                 }
1428         }
1429 end_wait:
1430         return;
1431
1432 quit:
1433         ust_unlock();
1434         return;
1435
1436 error:
1437         ust_unlock();
1438         return;
1439 }
1440
1441 /*
1442  * This thread does not allocate any resource, except within
1443  * handle_message, within mutex protection. This mutex protects against
1444  * fork and exit.
1445  * The other moment it allocates resources is at socket connection, which
1446  * is also protected by the mutex.
1447  */
1448 static
1449 void *ust_listener_thread(void *arg)
1450 {
1451         struct sock_info *sock_info = arg;
1452         int sock, ret, prev_connect_failed = 0, has_waited = 0, fd;
1453         long timeout;
1454
1455         lttng_ust_fixup_tls();
1456         lttng_ust_fd_tracker_register_thread();
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 }
2048
2049 static void ust_after_fork_common(sigset_t *restore_sigset)
2050 {
2051         int ret;
2052
2053         DBG("process %d", getpid());
2054         lttng_ust_unlock_fd_tracker();
2055         ust_unlock();
2056
2057         pthread_mutex_unlock(&ust_fork_mutex);
2058
2059         /* Restore signals */
2060         ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
2061         if (ret == -1) {
2062                 PERROR("sigprocmask");
2063         }
2064 }
2065
2066 void ust_after_fork_parent(sigset_t *restore_sigset)
2067 {
2068         if (URCU_TLS(lttng_ust_nest_count))
2069                 return;
2070         DBG("process %d", getpid());
2071         rcu_bp_after_fork_parent();
2072         /* Release mutexes and reenable signals */
2073         ust_after_fork_common(restore_sigset);
2074 }
2075
2076 /*
2077  * After fork, in the child, we need to cleanup all the leftover state,
2078  * except the worker thread which already magically disappeared thanks
2079  * to the weird Linux fork semantics. After tyding up, we call
2080  * lttng_ust_init() again to start over as a new PID.
2081  *
2082  * This is meant for forks() that have tracing in the child between the
2083  * fork and following exec call (if there is any).
2084  */
2085 void ust_after_fork_child(sigset_t *restore_sigset)
2086 {
2087         if (URCU_TLS(lttng_ust_nest_count))
2088                 return;
2089         lttng_context_vpid_reset();
2090         lttng_context_vtid_reset();
2091         lttng_context_procname_reset();
2092         DBG("process %d", getpid());
2093         /* Release urcu mutexes */
2094         rcu_bp_after_fork_child();
2095         lttng_ust_cleanup(0);
2096         /* Release mutexes and reenable signals */
2097         ust_after_fork_common(restore_sigset);
2098         lttng_ust_init();
2099 }
2100
2101 void lttng_ust_sockinfo_session_enabled(void *owner)
2102 {
2103         struct sock_info *sock_info = owner;
2104         sock_info->statedump_pending = 1;
2105 }