liblttng-ust/lttng-ust-comm.c

   1 /*
   2  * lttng-ust-comm.c
   3  *
   4  * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
   5  * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; only
  10  * version 2.1 of the License.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with this library; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #define _LGPL_SOURCE
  23 #include <sys/types.h>
  24 #include <sys/socket.h>
  25 #include <sys/mman.h>
  26 #include <sys/stat.h>
  27 #include <sys/types.h>
  28 #include <sys/wait.h>
  29 #include <fcntl.h>
  30 #include <unistd.h>
  31 #include <errno.h>
  32 #include <pthread.h>
  33 #include <semaphore.h>
  34 #include <time.h>
  35 #include <assert.h>
  36 #include <signal.h>
  37 #include <urcu/uatomic.h>
  38 #include <urcu/futex.h>
  39 #include <urcu/compiler.h>
  40
  41 #include <lttng/ust-events.h>
  42 #include <lttng/ust-abi.h>
  43 #include <lttng/ust.h>
  44 #include <lttng/ust-error.h>
  45 #include <lttng/ust-ctl.h>
  46 #include <urcu/tls-compat.h>
  47 #include <ust-comm.h>
  48 #include <usterr-signal-safe.h>
  49 #include <helper.h>
  50 #include "tracepoint-internal.h"
  51 #include "lttng-tracer-core.h"
  52 #include "compat.h"
  53 #include "../libringbuffer/tlsfixup.h"
  54
  55 /*
  56  * Has lttng ust comm constructor been called ?
  57  */
  58 static int initialized;
  59
  60 /*
  61  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  62  * Held when handling a command, also held by fork() to deal with
  63  * removal of threads, and by exit path.
  64  */
  65
  66 /* Should the ust comm thread quit ? */
  67 static int lttng_ust_comm_should_quit;
  68
  69 /*
  70  * Wait for either of these before continuing to the main
  71  * program:
  72  * - the register_done message from sessiond daemon
  73  *   (will let the sessiond daemon enable sessions before main
  74  *   starts.)
  75  * - sessiond daemon is not reachable.
  76  * - timeout (ensuring applications are resilient to session
  77  *   daemon problems).
  78  */
  79 static sem_t constructor_wait;
  80 /*
  81  * Doing this for both the global and local sessiond.
  82  */
  83 static int sem_count = { 2 };
  84
  85 /*
  86  * Counting nesting within lttng-ust. Used to ensure that calling fork()
  87  * from liblttng-ust does not execute the pre/post fork handlers.
  88  */
  89 static DEFINE_URCU_TLS(int, lttng_ust_nest_count);
  90
  91 /*
  92  * Info about socket and associated listener thread.
  93  */
  94 struct sock_info {
  95         const char *name;
  96         pthread_t ust_listener; /* listener thread */
  97         int root_handle;
  98         int constructor_sem_posted;
  99         int allowed;
 100         int global;
 101         int thread_active;
 102
 103         char sock_path[PATH_MAX];
 104         int socket;
 105         int notify_socket;
 106
 107         char wait_shm_path[PATH_MAX];
 108         char *wait_shm_mmap;
 109 };
 110
 111 /* Socket from app (connect) to session daemon (listen) for communication */
 112 struct sock_info global_apps = {
 113         .name = "global",
 114         .global = 1,
 115
 116         .root_handle = -1,
 117         .allowed = 1,
 118         .thread_active = 0,
 119
 120         .sock_path = LTTNG_DEFAULT_RUNDIR "/" LTTNG_UST_SOCK_FILENAME,
 121         .socket = -1,
 122         .notify_socket = -1,
 123
 124         .wait_shm_path = "/" LTTNG_UST_WAIT_FILENAME,
 125 };
 126
 127 /* TODO: allow global_apps_sock_path override */
 128
 129 struct sock_info local_apps = {
 130         .name = "local",
 131         .global = 0,
 132         .root_handle = -1,
 133         .allowed = 0,   /* Check setuid bit first */
 134         .thread_active = 0,
 135
 136         .socket = -1,
 137         .notify_socket = -1,
 138 };
 139
 140 static int wait_poll_fallback;
 141
 142 static const char *cmd_name_mapping[] = {
 143         [ LTTNG_UST_RELEASE ] = "Release",
 144         [ LTTNG_UST_SESSION ] = "Create Session",
 145         [ LTTNG_UST_TRACER_VERSION ] = "Get Tracer Version",
 146
 147         [ LTTNG_UST_TRACEPOINT_LIST ] = "Create Tracepoint List",
 148         [ LTTNG_UST_WAIT_QUIESCENT ] = "Wait for Quiescent State",
 149         [ LTTNG_UST_REGISTER_DONE ] = "Registration Done",
 150         [ LTTNG_UST_TRACEPOINT_FIELD_LIST ] = "Create Tracepoint Field List",
 151
 152         /* Session FD commands */
 153         [ LTTNG_UST_CHANNEL ] = "Create Channel",
 154         [ LTTNG_UST_SESSION_START ] = "Start Session",
 155         [ LTTNG_UST_SESSION_STOP ] = "Stop Session",
 156
 157         /* Channel FD commands */
 158         [ LTTNG_UST_STREAM ] = "Create Stream",
 159         [ LTTNG_UST_EVENT ] = "Create Event",
 160
 161         /* Event and Channel FD commands */
 162         [ LTTNG_UST_CONTEXT ] = "Create Context",
 163         [ LTTNG_UST_FLUSH_BUFFER ] = "Flush Buffer",
 164
 165         /* Event, Channel and Session commands */
 166         [ LTTNG_UST_ENABLE ] = "Enable",
 167         [ LTTNG_UST_DISABLE ] = "Disable",
 168
 169         /* Tracepoint list commands */
 170         [ LTTNG_UST_TRACEPOINT_LIST_GET ] = "List Next Tracepoint",
 171         [ LTTNG_UST_TRACEPOINT_FIELD_LIST_GET ] = "List Next Tracepoint Field",
 172
 173         /* Event FD commands */
 174         [ LTTNG_UST_FILTER ] = "Create Filter",
 175 };
 176
 177 static const char *str_timeout;
 178 static int got_timeout_env;
 179
 180 extern void lttng_ring_buffer_client_overwrite_init(void);
 181 extern void lttng_ring_buffer_client_overwrite_rt_init(void);
 182 extern void lttng_ring_buffer_client_discard_init(void);
 183 extern void lttng_ring_buffer_client_discard_rt_init(void);
 184 extern void lttng_ring_buffer_metadata_client_init(void);
 185 extern void lttng_ring_buffer_client_overwrite_exit(void);
 186 extern void lttng_ring_buffer_client_overwrite_rt_exit(void);
 187 extern void lttng_ring_buffer_client_discard_exit(void);
 188 extern void lttng_ring_buffer_client_discard_rt_exit(void);
 189 extern void lttng_ring_buffer_metadata_client_exit(void);
 190
 191 /*
 192  * Returns the HOME directory path. Caller MUST NOT free(3) the returned
 193  * pointer.
 194  */
 195 static
 196 const char *get_lttng_home_dir(void)
 197 {
 198        const char *val;
 199
 200        val = (const char *) getenv("LTTNG_HOME");
 201        if (val != NULL) {
 202                return val;
 203        }
 204        return (const char *) getenv("HOME");
 205 }
 206
 207 /*
 208  * Force a read (imply TLS fixup for dlopen) of TLS variables.
 209  */
 210 static
 211 void lttng_fixup_nest_count_tls(void)
 212 {
 213         asm volatile ("" : : "m" (URCU_TLS(lttng_ust_nest_count)));
 214 }
 215
 216 int lttng_get_notify_socket(void *owner)
 217 {
 218         struct sock_info *info = owner;
 219
 220         return info->notify_socket;
 221 }
 222
 223 static
 224 void print_cmd(int cmd, int handle)
 225 {
 226         const char *cmd_name = "Unknown";
 227
 228         if (cmd >= 0 && cmd < LTTNG_ARRAY_SIZE(cmd_name_mapping)
 229                         && cmd_name_mapping[cmd]) {
 230                 cmd_name = cmd_name_mapping[cmd];
 231         }
 232         DBG("Message Received \"%s\" (%d), Handle \"%s\" (%d)",
 233                 cmd_name, cmd,
 234                 lttng_ust_obj_get_name(handle), handle);
 235 }
 236
 237 static
 238 int setup_local_apps(void)
 239 {
 240         const char *home_dir;
 241         uid_t uid;
 242
 243         uid = getuid();
 244         /*
 245          * Disallow per-user tracing for setuid binaries.
 246          */
 247         if (uid != geteuid()) {
 248                 assert(local_apps.allowed == 0);
 249                 return 0;
 250         }
 251         home_dir = get_lttng_home_dir();
 252         if (!home_dir) {
 253                 WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
 254                 assert(local_apps.allowed == 0);
 255                 return -ENOENT;
 256         }
 257         local_apps.allowed = 1;
 258         snprintf(local_apps.sock_path, PATH_MAX, "%s/%s/%s",
 259                 home_dir,
 260                 LTTNG_DEFAULT_HOME_RUNDIR,
 261                 LTTNG_UST_SOCK_FILENAME);
 262         snprintf(local_apps.wait_shm_path, PATH_MAX, "/%s-%u",
 263                 LTTNG_UST_WAIT_FILENAME,
 264                 uid);
 265         return 0;
 266 }
 267
 268 /*
 269  * Get notify_sock timeout, in ms.
 270  * -1: don't wait. 0: wait forever. >0: timeout, in ms.
 271  */
 272 static
 273 long get_timeout(void)
 274 {
 275         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 276
 277         if (!got_timeout_env) {
 278                 str_timeout = getenv("LTTNG_UST_REGISTER_TIMEOUT");
 279                 got_timeout_env = 1;
 280         }
 281         if (str_timeout)
 282                 constructor_delay_ms = strtol(str_timeout, NULL, 10);
 283         return constructor_delay_ms;
 284 }
 285
 286 static
 287 long get_notify_sock_timeout(void)
 288 {
 289         return get_timeout();
 290 }
 291
 292 /*
 293  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 294  */
 295 static
 296 int get_constructor_timeout(struct timespec *constructor_timeout)
 297 {
 298         long constructor_delay_ms;
 299         int ret;
 300
 301         constructor_delay_ms = get_timeout();
 302
 303         switch (constructor_delay_ms) {
 304         case -1:/* fall-through */
 305         case 0:
 306                 return constructor_delay_ms;
 307         default:
 308                 break;
 309         }
 310
 311         /*
 312          * If we are unable to find the current time, don't wait.
 313          */
 314         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 315         if (ret) {
 316                 return -1;
 317         }
 318         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 319         constructor_timeout->tv_nsec +=
 320                 (constructor_delay_ms % 1000UL) * 1000000UL;
 321         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 322                 constructor_timeout->tv_sec++;
 323                 constructor_timeout->tv_nsec -= 1000000000UL;
 324         }
 325         return 1;
 326 }
 327
 328 static
 329 int register_to_sessiond(int socket, enum ustctl_socket_type type)
 330 {
 331         return ustcomm_send_reg_msg(socket,
 332                 type,
 333                 CAA_BITS_PER_LONG,
 334                 lttng_alignof(uint8_t) * CHAR_BIT,
 335                 lttng_alignof(uint16_t) * CHAR_BIT,
 336                 lttng_alignof(uint32_t) * CHAR_BIT,
 337                 lttng_alignof(uint64_t) * CHAR_BIT,
 338                 lttng_alignof(unsigned long) * CHAR_BIT);
 339 }
 340
 341 static
 342 int send_reply(int sock, struct ustcomm_ust_reply *lur)
 343 {
 344         ssize_t len;
 345
 346         len = ustcomm_send_unix_sock(sock, lur, sizeof(*lur));
 347         switch (len) {
 348         case sizeof(*lur):
 349                 DBG("message successfully sent");
 350                 return 0;
 351         default:
 352                 if (len == -ECONNRESET) {
 353                         DBG("remote end closed connection");
 354                         return 0;
 355                 }
 356                 if (len < 0)
 357                         return len;
 358                 DBG("incorrect message size: %zd", len);
 359                 return -EINVAL;
 360         }
 361 }
 362
 363 static
 364 int handle_register_done(struct sock_info *sock_info)
 365 {
 366         int ret;
 367
 368         if (sock_info->constructor_sem_posted)
 369                 return 0;
 370         sock_info->constructor_sem_posted = 1;
 371         if (uatomic_read(&sem_count) <= 0) {
 372                 return 0;
 373         }
 374         ret = uatomic_add_return(&sem_count, -1);
 375         if (ret == 0) {
 376                 ret = sem_post(&constructor_wait);
 377                 assert(!ret);
 378         }
 379         return 0;
 380 }
 381
 382 static
 383 int handle_message(struct sock_info *sock_info,
 384                 int sock, struct ustcomm_ust_msg *lum)
 385 {
 386         int ret = 0;
 387         const struct lttng_ust_objd_ops *ops;
 388         struct ustcomm_ust_reply lur;
 389         union ust_args args;
 390         ssize_t len;
 391
 392         ust_lock();
 393
 394         memset(&lur, 0, sizeof(lur));
 395
 396         if (lttng_ust_comm_should_quit) {
 397                 ret = -LTTNG_UST_ERR_EXITING;
 398                 goto end;
 399         }
 400
 401         ops = objd_ops(lum->handle);
 402         if (!ops) {
 403                 ret = -ENOENT;
 404                 goto end;
 405         }
 406
 407         switch (lum->cmd) {
 408         case LTTNG_UST_REGISTER_DONE:
 409                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 410                         ret = handle_register_done(sock_info);
 411                 else
 412                         ret = -EINVAL;
 413                 break;
 414         case LTTNG_UST_RELEASE:
 415                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 416                         ret = -EPERM;
 417                 else
 418                         ret = lttng_ust_objd_unref(lum->handle, 1);
 419                 break;
 420         case LTTNG_UST_FILTER:
 421         {
 422                 /* Receive filter data */
 423                 struct lttng_ust_filter_bytecode_node *bytecode;
 424
 425                 if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) {
 426                         ERR("Filter data size is too large: %u bytes",
 427                                 lum->u.filter.data_size);
 428                         ret = -EINVAL;
 429                         goto error;
 430                 }
 431
 432                 if (lum->u.filter.reloc_offset > lum->u.filter.data_size) {
 433                         ERR("Filter reloc offset %u is not within data",
 434                                 lum->u.filter.reloc_offset);
 435                         ret = -EINVAL;
 436                         goto error;
 437                 }
 438
 439                 bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size);
 440                 if (!bytecode) {
 441                         ret = -ENOMEM;
 442                         goto error;
 443                 }
 444                 len = ustcomm_recv_unix_sock(sock, bytecode->bc.data,
 445                                 lum->u.filter.data_size);
 446                 switch (len) {
 447                 case 0: /* orderly shutdown */
 448                         ret = 0;
 449                         free(bytecode);
 450                         goto error;
 451                 default:
 452                         if (len == lum->u.filter.data_size) {
 453                                 DBG("filter data received");
 454                                 break;
 455                         } else if (len < 0) {
 456                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 457                                 if (len == -ECONNRESET) {
 458                                         ERR("%s remote end closed connection", sock_info->name);
 459                                         ret = len;
 460                                         free(bytecode);
 461                                         goto error;
 462                                 }
 463                                 ret = len;
 464                                 free(bytecode);
 465                                 goto end;
 466                         } else {
 467                                 DBG("incorrect filter data message size: %zd", len);
 468                                 ret = -EINVAL;
 469                                 free(bytecode);
 470                                 goto end;
 471                         }
 472                 }
 473                 bytecode->bc.len = lum->u.filter.data_size;
 474                 bytecode->bc.reloc_offset = lum->u.filter.reloc_offset;
 475                 bytecode->bc.seqnum = lum->u.filter.seqnum;
 476                 if (ops->cmd) {
 477                         ret = ops->cmd(lum->handle, lum->cmd,
 478                                         (unsigned long) bytecode,
 479                                         &args, sock_info);
 480                         if (ret) {
 481                                 free(bytecode);
 482                         }
 483                         /* don't free bytecode if everything went fine. */
 484                 } else {
 485                         ret = -ENOSYS;
 486                         free(bytecode);
 487                 }
 488                 break;
 489         }
 490         case LTTNG_UST_CHANNEL:
 491         {
 492                 void *chan_data;
 493                 int wakeup_fd;
 494
 495                 len = ustcomm_recv_channel_from_sessiond(sock,
 496                                 &chan_data, lum->u.channel.len,
 497                                 &wakeup_fd);
 498                 switch (len) {
 499                 case 0: /* orderly shutdown */
 500                         ret = 0;
 501                         goto error;
 502                 default:
 503                         if (len == lum->u.channel.len) {
 504                                 DBG("channel data received");
 505                                 break;
 506                         } else if (len < 0) {
 507                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 508                                 if (len == -ECONNRESET) {
 509                                         ERR("%s remote end closed connection", sock_info->name);
 510                                         ret = len;
 511                                         goto error;
 512                                 }
 513                                 ret = len;
 514                                 goto end;
 515                         } else {
 516                                 DBG("incorrect channel data message size: %zd", len);
 517                                 ret = -EINVAL;
 518                                 goto end;
 519                         }
 520                 }
 521                 args.channel.chan_data = chan_data;
 522                 args.channel.wakeup_fd = wakeup_fd;
 523                 if (ops->cmd)
 524                         ret = ops->cmd(lum->handle, lum->cmd,
 525                                         (unsigned long) &lum->u,
 526                                         &args, sock_info);
 527                 else
 528                         ret = -ENOSYS;
 529                 break;
 530         }
 531         case LTTNG_UST_STREAM:
 532         {
 533                 /* Receive shm_fd, wakeup_fd */
 534                 ret = ustcomm_recv_stream_from_sessiond(sock,
 535                         &lum->u.stream.len,
 536                         &args.stream.shm_fd,
 537                         &args.stream.wakeup_fd);
 538                 if (ret) {
 539                         goto end;
 540                 }
 541                 if (ops->cmd)
 542                         ret = ops->cmd(lum->handle, lum->cmd,
 543                                         (unsigned long) &lum->u,
 544                                         &args, sock_info);
 545                 else
 546                         ret = -ENOSYS;
 547                 break;
 548         }
 549         default:
 550                 if (ops->cmd)
 551                         ret = ops->cmd(lum->handle, lum->cmd,
 552                                         (unsigned long) &lum->u,
 553                                         &args, sock_info);
 554                 else
 555                         ret = -ENOSYS;
 556                 break;
 557         }
 558
 559 end:
 560         lur.handle = lum->handle;
 561         lur.cmd = lum->cmd;
 562         lur.ret_val = ret;
 563         if (ret >= 0) {
 564                 lur.ret_code = LTTNG_UST_OK;
 565         } else {
 566                 /*
 567                  * Use -LTTNG_UST_ERR as wildcard for UST internal
 568                  * error that are not caused by the transport, except if
 569                  * we already have a more precise error message to
 570                  * report.
 571                  */
 572                 if (ret > -LTTNG_UST_ERR) {
 573                         /* Translate code to UST error. */
 574                         switch (ret) {
 575                         case -EEXIST:
 576                                 lur.ret_code = -LTTNG_UST_ERR_EXIST;
 577                                 break;
 578                         case -EINVAL:
 579                                 lur.ret_code = -LTTNG_UST_ERR_INVAL;
 580                                 break;
 581                         case -ENOENT:
 582                                 lur.ret_code = -LTTNG_UST_ERR_NOENT;
 583                                 break;
 584                         case -EPERM:
 585                                 lur.ret_code = -LTTNG_UST_ERR_PERM;
 586                                 break;
 587                         case -ENOSYS:
 588                                 lur.ret_code = -LTTNG_UST_ERR_NOSYS;
 589                                 break;
 590                         default:
 591                                 lur.ret_code = -LTTNG_UST_ERR;
 592                                 break;
 593                         }
 594                 } else {
 595                         lur.ret_code = ret;
 596                 }
 597         }
 598         if (ret >= 0) {
 599                 switch (lum->cmd) {
 600                 case LTTNG_UST_TRACER_VERSION:
 601                         lur.u.version = lum->u.version;
 602                         break;
 603                 case LTTNG_UST_TRACEPOINT_LIST_GET:
 604                         memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
 605                         break;
 606                 }
 607         }
 608         DBG("Return value: %d", lur.ret_val);
 609         ret = send_reply(sock, &lur);
 610         if (ret < 0) {
 611                 DBG("error sending reply");
 612                 goto error;
 613         }
 614
 615         /*
 616          * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field
 617          * after the reply.
 618          */
 619         if (lur.ret_code == LTTNG_UST_OK) {
 620                 switch (lum->cmd) {
 621                 case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET:
 622                         len = ustcomm_send_unix_sock(sock,
 623                                 &args.field_list.entry,
 624                                 sizeof(args.field_list.entry));
 625                         if (len < 0) {
 626                                 ret = len;
 627                                 goto error;
 628                         }
 629                         if (len != sizeof(args.field_list.entry)) {
 630                                 ret = -EINVAL;
 631                                 goto error;
 632                         }
 633                 }
 634         }
 635
 636 error:
 637         ust_unlock();
 638         return ret;
 639 }
 640
 641 static
 642 void cleanup_sock_info(struct sock_info *sock_info, int exiting)
 643 {
 644         int ret;
 645
 646         if (sock_info->root_handle != -1) {
 647                 ret = lttng_ust_objd_unref(sock_info->root_handle, 1);
 648                 if (ret) {
 649                         ERR("Error unref root handle");
 650                 }
 651                 sock_info->root_handle = -1;
 652         }
 653         sock_info->constructor_sem_posted = 0;
 654
 655         /*
 656          * wait_shm_mmap, socket and notify socket are used by listener
 657          * threads outside of the ust lock, so we cannot tear them down
 658          * ourselves, because we cannot join on these threads. Leave
 659          * responsibility of cleaning up these resources to the OS
 660          * process exit.
 661          */
 662         if (exiting)
 663                 return;
 664
 665         if (sock_info->socket != -1) {
 666                 ret = ustcomm_close_unix_sock(sock_info->socket);
 667                 if (ret) {
 668                         ERR("Error closing ust cmd socket");
 669                 }
 670                 sock_info->socket = -1;
 671         }
 672         if (sock_info->notify_socket != -1) {
 673                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
 674                 if (ret) {
 675                         ERR("Error closing ust notify socket");
 676                 }
 677                 sock_info->notify_socket = -1;
 678         }
 679         if (sock_info->wait_shm_mmap) {
 680                 ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
 681                 if (ret) {
 682                         ERR("Error unmapping wait shm");
 683                 }
 684                 sock_info->wait_shm_mmap = NULL;
 685         }
 686 }
 687
 688 /*
 689  * Using fork to set umask in the child process (not multi-thread safe).
 690  * We deal with the shm_open vs ftruncate race (happening when the
 691  * sessiond owns the shm and does not let everybody modify it, to ensure
 692  * safety against shm_unlink) by simply letting the mmap fail and
 693  * retrying after a few seconds.
 694  * For global shm, everybody has rw access to it until the sessiond
 695  * starts.
 696  */
 697 static
 698 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 699 {
 700         int wait_shm_fd, ret;
 701         pid_t pid;
 702
 703         /*
 704          * Try to open read-only.
 705          */
 706         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 707         if (wait_shm_fd >= 0) {
 708                 goto end;
 709         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 710                 /*
 711                  * Real-only open did not work, and it's not because the
 712                  * entry was not present. It's a failure that prohibits
 713                  * using shm.
 714                  */
 715                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 716                 goto end;
 717         }
 718         /*
 719          * If the open failed because the file did not exist, try
 720          * creating it ourself.
 721          */
 722         URCU_TLS(lttng_ust_nest_count)++;
 723         pid = fork();
 724         URCU_TLS(lttng_ust_nest_count)--;
 725         if (pid > 0) {
 726                 int status;
 727
 728                 /*
 729                  * Parent: wait for child to return, in which case the
 730                  * shared memory map will have been created.
 731                  */
 732                 pid = wait(&status);
 733                 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 734                         wait_shm_fd = -1;
 735                         goto end;
 736                 }
 737                 /*
 738                  * Try to open read-only again after creation.
 739                  */
 740                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 741                 if (wait_shm_fd < 0) {
 742                         /*
 743                          * Real-only open did not work. It's a failure
 744                          * that prohibits using shm.
 745                          */
 746                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 747                         goto end;
 748                 }
 749                 goto end;
 750         } else if (pid == 0) {
 751                 int create_mode;
 752
 753                 /* Child */
 754                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
 755                 if (sock_info->global)
 756                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
 757                 /*
 758                  * We're alone in a child process, so we can modify the
 759                  * process-wide umask.
 760                  */
 761                 umask(~create_mode);
 762                 /*
 763                  * Try creating shm (or get rw access).
 764                  * We don't do an exclusive open, because we allow other
 765                  * processes to create+ftruncate it concurrently.
 766                  */
 767                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 768                                 O_RDWR | O_CREAT, create_mode);
 769                 if (wait_shm_fd >= 0) {
 770                         ret = ftruncate(wait_shm_fd, mmap_size);
 771                         if (ret) {
 772                                 PERROR("ftruncate");
 773                                 _exit(EXIT_FAILURE);
 774                         }
 775                         _exit(EXIT_SUCCESS);
 776                 }
 777                 /*
 778                  * For local shm, we need to have rw access to accept
 779                  * opening it: this means the local sessiond will be
 780                  * able to wake us up. For global shm, we open it even
 781                  * if rw access is not granted, because the root.root
 782                  * sessiond will be able to override all rights and wake
 783                  * us up.
 784                  */
 785                 if (!sock_info->global && errno != EACCES) {
 786                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 787                         _exit(EXIT_FAILURE);
 788                 }
 789                 /*
 790                  * The shm exists, but we cannot open it RW. Report
 791                  * success.
 792                  */
 793                 _exit(EXIT_SUCCESS);
 794         } else {
 795                 return -1;
 796         }
 797 end:
 798         if (wait_shm_fd >= 0 && !sock_info->global) {
 799                 struct stat statbuf;
 800
 801                 /*
 802                  * Ensure that our user is the owner of the shm file for
 803                  * local shm. If we do not own the file, it means our
 804                  * sessiond will not have access to wake us up (there is
 805                  * probably a rogue process trying to fake our
 806                  * sessiond). Fallback to polling method in this case.
 807                  */
 808                 ret = fstat(wait_shm_fd, &statbuf);
 809                 if (ret) {
 810                         PERROR("fstat");
 811                         goto error_close;
 812                 }
 813                 if (statbuf.st_uid != getuid())
 814                         goto error_close;
 815         }
 816         return wait_shm_fd;
 817
 818 error_close:
 819         ret = close(wait_shm_fd);
 820         if (ret) {
 821                 PERROR("Error closing fd");
 822         }
 823         return -1;
 824 }
 825
 826 static
 827 char *get_map_shm(struct sock_info *sock_info)
 828 {
 829         size_t mmap_size = sysconf(_SC_PAGE_SIZE);
 830         int wait_shm_fd, ret;
 831         char *wait_shm_mmap;
 832
 833         wait_shm_fd = get_wait_shm(sock_info, mmap_size);
 834         if (wait_shm_fd < 0) {
 835                 goto error;
 836         }
 837         wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
 838                   MAP_SHARED, wait_shm_fd, 0);
 839         /* close shm fd immediately after taking the mmap reference */
 840         ret = close(wait_shm_fd);
 841         if (ret) {
 842                 PERROR("Error closing fd");
 843         }
 844         if (wait_shm_mmap == MAP_FAILED) {
 845                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
 846                 goto error;
 847         }
 848         return wait_shm_mmap;
 849
 850 error:
 851         return NULL;
 852 }
 853
 854 static
 855 void wait_for_sessiond(struct sock_info *sock_info)
 856 {
 857         int ret;
 858
 859         ust_lock();
 860         if (lttng_ust_comm_should_quit) {
 861                 goto quit;
 862         }
 863         if (wait_poll_fallback) {
 864                 goto error;
 865         }
 866         if (!sock_info->wait_shm_mmap) {
 867                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
 868                 if (!sock_info->wait_shm_mmap)
 869                         goto error;
 870         }
 871         ust_unlock();
 872
 873         DBG("Waiting for %s apps sessiond", sock_info->name);
 874         /* Wait for futex wakeup */
 875         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
 876                 ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
 877                         FUTEX_WAIT, 0, NULL, NULL, 0);
 878                 if (ret < 0) {
 879                         if (errno == EFAULT) {
 880                                 wait_poll_fallback = 1;
 881                                 DBG(
 882 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
 883 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
 884 "Please upgrade your kernel "
 885 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
 886 "mainline). LTTng-UST will use polling mode fallback.");
 887                                 if (ust_debug())
 888                                         PERROR("futex");
 889                         }
 890                 }
 891         }
 892         return;
 893
 894 quit:
 895         ust_unlock();
 896         return;
 897
 898 error:
 899         ust_unlock();
 900         return;
 901 }
 902
 903 /*
 904  * This thread does not allocate any resource, except within
 905  * handle_message, within mutex protection. This mutex protects against
 906  * fork and exit.
 907  * The other moment it allocates resources is at socket connection, which
 908  * is also protected by the mutex.
 909  */
 910 static
 911 void *ust_listener_thread(void *arg)
 912 {
 913         struct sock_info *sock_info = arg;
 914         int sock, ret, prev_connect_failed = 0, has_waited = 0;
 915         int open_sock[2];
 916         int i;
 917         long timeout;
 918
 919         /* Restart trying to connect to the session daemon */
 920 restart:
 921         if (prev_connect_failed) {
 922                 /* Wait for sessiond availability with pipe */
 923                 wait_for_sessiond(sock_info);
 924                 if (has_waited) {
 925                         has_waited = 0;
 926                         /*
 927                          * Sleep for 5 seconds before retrying after a
 928                          * sequence of failure / wait / failure. This
 929                          * deals with a killed or broken session daemon.
 930                          */
 931                         sleep(5);
 932                 }
 933                 has_waited = 1;
 934                 prev_connect_failed = 0;
 935         }
 936
 937         if (sock_info->socket != -1) {
 938                 ret = ustcomm_close_unix_sock(sock_info->socket);
 939                 if (ret) {
 940                         ERR("Error closing %s ust cmd socket",
 941                                 sock_info->name);
 942                 }
 943                 sock_info->socket = -1;
 944         }
 945         if (sock_info->notify_socket != -1) {
 946                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
 947                 if (ret) {
 948                         ERR("Error closing %s ust notify socket",
 949                                 sock_info->name);
 950                 }
 951                 sock_info->notify_socket = -1;
 952         }
 953
 954         /* Register */
 955         for (i = 0; i < 2; i++) {
 956                 ret = ustcomm_connect_unix_sock(sock_info->sock_path);
 957                 if (ret < 0) {
 958                         DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
 959                         prev_connect_failed = 1;
 960
 961                         ust_lock();
 962
 963                         if (lttng_ust_comm_should_quit) {
 964                                 goto quit;
 965                         }
 966
 967                         /*
 968                          * If we cannot find the sessiond daemon, don't delay
 969                          * constructor execution.
 970                          */
 971                         ret = handle_register_done(sock_info);
 972                         assert(!ret);
 973                         ust_unlock();
 974                         goto restart;
 975                 }
 976                 open_sock[i] = ret;
 977         }
 978
 979         sock_info->socket = open_sock[0];
 980         sock_info->notify_socket = open_sock[1];
 981
 982         timeout = get_notify_sock_timeout();
 983         if (timeout >= 0) {
 984                 /*
 985                  * Give at least 10ms to sessiond to reply to
 986                  * notifications.
 987                  */
 988                 if (timeout < 10)
 989                         timeout = 10;
 990                 ret = ustcomm_setsockopt_rcv_timeout(sock_info->notify_socket,
 991                                 timeout);
 992                 if (ret < 0) {
 993                         WARN("Error setting socket receive timeout");
 994                 }
 995                 ret = ustcomm_setsockopt_snd_timeout(sock_info->notify_socket,
 996                                 timeout);
 997                 if (ret < 0) {
 998                         WARN("Error setting socket send timeout");
 999                 }
1000         } else if (timeout < -1) {
1001                 WARN("Unsupported timeout value %ld", timeout);
1002         }
1003
1004         ust_lock();
1005
1006         if (lttng_ust_comm_should_quit) {
1007                 goto quit;
1008         }
1009
1010         /*
1011          * Create only one root handle per listener thread for the whole
1012          * process lifetime, so we ensure we get ID which is statically
1013          * assigned to the root handle.
1014          */
1015         if (sock_info->root_handle == -1) {
1016                 ret = lttng_abi_create_root_handle();
1017                 if (ret < 0) {
1018                         ERR("Error creating root handle");
1019                         goto quit;
1020                 }
1021                 sock_info->root_handle = ret;
1022         }
1023
1024         ret = register_to_sessiond(sock_info->socket, USTCTL_SOCKET_CMD);
1025         if (ret < 0) {
1026                 ERR("Error registering to %s ust cmd socket",
1027                         sock_info->name);
1028                 prev_connect_failed = 1;
1029                 /*
1030                  * If we cannot register to the sessiond daemon, don't
1031                  * delay constructor execution.
1032                  */
1033                 ret = handle_register_done(sock_info);
1034                 assert(!ret);
1035                 ust_unlock();
1036                 goto restart;
1037         }
1038         ret = register_to_sessiond(sock_info->notify_socket,
1039                         USTCTL_SOCKET_NOTIFY);
1040         if (ret < 0) {
1041                 ERR("Error registering to %s ust notify socket",
1042                         sock_info->name);
1043                 prev_connect_failed = 1;
1044                 /*
1045                  * If we cannot register to the sessiond daemon, don't
1046                  * delay constructor execution.
1047                  */
1048                 ret = handle_register_done(sock_info);
1049                 assert(!ret);
1050                 ust_unlock();
1051                 goto restart;
1052         }
1053         sock = sock_info->socket;
1054
1055         ust_unlock();
1056
1057         for (;;) {
1058                 ssize_t len;
1059                 struct ustcomm_ust_msg lum;
1060
1061                 len = ustcomm_recv_unix_sock(sock, &lum, sizeof(lum));
1062                 switch (len) {
1063                 case 0: /* orderly shutdown */
1064                         DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
1065                         ust_lock();
1066                         if (lttng_ust_comm_should_quit) {
1067                                 goto quit;
1068                         }
1069                         /*
1070                          * Either sessiond has shutdown or refused us by closing the socket.
1071                          * In either case, we don't want to delay construction execution,
1072                          * and we need to wait before retry.
1073                          */
1074                         prev_connect_failed = 1;
1075                         /*
1076                          * If we cannot register to the sessiond daemon, don't
1077                          * delay constructor execution.
1078                          */
1079                         ret = handle_register_done(sock_info);
1080                         assert(!ret);
1081                         ust_unlock();
1082                         goto end;
1083                 case sizeof(lum):
1084                         print_cmd(lum.cmd, lum.handle);
1085                         ret = handle_message(sock_info, sock, &lum);
1086                         if (ret) {
1087                                 ERR("Error handling message for %s socket", sock_info->name);
1088                         }
1089                         continue;
1090                 default:
1091                         if (len < 0) {
1092                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
1093                         } else {
1094                                 DBG("incorrect message size (%s socket): %zd", sock_info->name, len);
1095                         }
1096                         if (len == -ECONNRESET) {
1097                                 DBG("%s remote end closed connection", sock_info->name);
1098                                 goto end;
1099                         }
1100                         goto end;
1101                 }
1102
1103         }
1104 end:
1105         ust_lock();
1106         if (lttng_ust_comm_should_quit) {
1107                 goto quit;
1108         }
1109         /* Cleanup socket handles before trying to reconnect */
1110         lttng_ust_objd_table_owner_cleanup(sock_info);
1111         ust_unlock();
1112         goto restart;   /* try to reconnect */
1113
1114 quit:
1115         sock_info->thread_active = 0;
1116         ust_unlock();
1117         return NULL;
1118 }
1119
1120 /*
1121  * sessiond monitoring thread: monitor presence of global and per-user
1122  * sessiond by polling the application common named pipe.
1123  */
1124 void __attribute__((constructor)) lttng_ust_init(void)
1125 {
1126         struct timespec constructor_timeout;
1127         sigset_t sig_all_blocked, orig_parent_mask;
1128         pthread_attr_t thread_attr;
1129         int timeout_mode;
1130         int ret;
1131
1132         if (uatomic_xchg(&initialized, 1) == 1)
1133                 return;
1134
1135         /*
1136          * Fixup interdependency between TLS fixup mutex (which happens
1137          * to be the dynamic linker mutex) and ust_lock, taken within
1138          * the ust lock.
1139          */
1140         lttng_fixup_ringbuffer_tls();
1141         lttng_fixup_vtid_tls();
1142         lttng_fixup_nest_count_tls();
1143         lttng_fixup_procname_tls();
1144
1145         /*
1146          * We want precise control over the order in which we construct
1147          * our sub-libraries vs starting to receive commands from
1148          * sessiond (otherwise leading to errors when trying to create
1149          * sessiond before the init functions are completed).
1150          */
1151         init_usterr();
1152         init_tracepoint();
1153         lttng_ring_buffer_metadata_client_init();
1154         lttng_ring_buffer_client_overwrite_init();
1155         lttng_ring_buffer_client_overwrite_rt_init();
1156         lttng_ring_buffer_client_discard_init();
1157         lttng_ring_buffer_client_discard_rt_init();
1158         lttng_context_init();
1159
1160         timeout_mode = get_constructor_timeout(&constructor_timeout);
1161
1162         ret = sem_init(&constructor_wait, 0, 0);
1163         assert(!ret);
1164
1165         ret = setup_local_apps();
1166         if (ret) {
1167                 DBG("local apps setup returned %d", ret);
1168         }
1169
1170         /* A new thread created by pthread_create inherits the signal mask
1171          * from the parent. To avoid any signal being received by the
1172          * listener thread, we block all signals temporarily in the parent,
1173          * while we create the listener thread.
1174          */
1175         sigfillset(&sig_all_blocked);
1176         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
1177         if (ret) {
1178                 ERR("pthread_sigmask: %s", strerror(ret));
1179         }
1180
1181         ret = pthread_attr_init(&thread_attr);
1182         if (ret) {
1183                 ERR("pthread_attr_init: %s", strerror(ret));
1184         }
1185         ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
1186         if (ret) {
1187                 ERR("pthread_attr_setdetachstate: %s", strerror(ret));
1188         }
1189
1190         ust_lock();
1191         ret = pthread_create(&global_apps.ust_listener, &thread_attr,
1192                         ust_listener_thread, &global_apps);
1193         if (ret) {
1194                 ERR("pthread_create global: %s", strerror(ret));
1195         }
1196         global_apps.thread_active = 1;
1197         ust_unlock();
1198
1199         if (local_apps.allowed) {
1200                 ust_lock();
1201                 ret = pthread_create(&local_apps.ust_listener, &thread_attr,
1202                                 ust_listener_thread, &local_apps);
1203                 if (ret) {
1204                         ERR("pthread_create local: %s", strerror(ret));
1205                 }
1206                 local_apps.thread_active = 1;
1207                 ust_unlock();
1208         } else {
1209                 handle_register_done(&local_apps);
1210         }
1211         ret = pthread_attr_destroy(&thread_attr);
1212         if (ret) {
1213                 ERR("pthread_attr_destroy: %s", strerror(ret));
1214         }
1215
1216         /* Restore original signal mask in parent */
1217         ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
1218         if (ret) {
1219                 ERR("pthread_sigmask: %s", strerror(ret));
1220         }
1221
1222         switch (timeout_mode) {
1223         case 1: /* timeout wait */
1224                 do {
1225                         ret = sem_timedwait(&constructor_wait,
1226                                         &constructor_timeout);
1227                 } while (ret < 0 && errno == EINTR);
1228                 if (ret < 0 && errno == ETIMEDOUT) {
1229                         ERR("Timed out waiting for lttng-sessiond");
1230                 } else {
1231                         assert(!ret);
1232                 }
1233                 break;
1234         case -1:/* wait forever */
1235                 do {
1236                         ret = sem_wait(&constructor_wait);
1237                 } while (ret < 0 && errno == EINTR);
1238                 assert(!ret);
1239                 break;
1240         case 0: /* no timeout */
1241                 break;
1242         }
1243 }
1244
1245 static
1246 void lttng_ust_cleanup(int exiting)
1247 {
1248         cleanup_sock_info(&global_apps, exiting);
1249         if (local_apps.allowed) {
1250                 cleanup_sock_info(&local_apps, exiting);
1251         }
1252         /*
1253          * The teardown in this function all affect data structures
1254          * accessed under the UST lock by the listener thread. This
1255          * lock, along with the lttng_ust_comm_should_quit flag, ensure
1256          * that none of these threads are accessing this data at this
1257          * point.
1258          */
1259         lttng_ust_abi_exit();
1260         lttng_ust_events_exit();
1261         lttng_context_exit();
1262         lttng_ring_buffer_client_discard_rt_exit();
1263         lttng_ring_buffer_client_discard_exit();
1264         lttng_ring_buffer_client_overwrite_rt_exit();
1265         lttng_ring_buffer_client_overwrite_exit();
1266         lttng_ring_buffer_metadata_client_exit();
1267         exit_tracepoint();
1268         if (!exiting) {
1269                 /* Reinitialize values for fork */
1270                 sem_count = 2;
1271                 lttng_ust_comm_should_quit = 0;
1272                 initialized = 0;
1273         }
1274 }
1275
1276 void __attribute__((destructor)) lttng_ust_exit(void)
1277 {
1278         int ret;
1279
1280         /*
1281          * Using pthread_cancel here because:
1282          * A) we don't want to hang application teardown.
1283          * B) the thread is not allocating any resource.
1284          */
1285
1286         /*
1287          * Require the communication thread to quit. Synchronize with
1288          * mutexes to ensure it is not in a mutex critical section when
1289          * pthread_cancel is later called.
1290          */
1291         ust_lock();
1292         lttng_ust_comm_should_quit = 1;
1293
1294         /* cancel threads */
1295         if (global_apps.thread_active) {
1296                 ret = pthread_cancel(global_apps.ust_listener);
1297                 if (ret) {
1298                         ERR("Error cancelling global ust listener thread: %s",
1299                                 strerror(ret));
1300                 } else {
1301                         global_apps.thread_active = 0;
1302                 }
1303         }
1304         if (local_apps.thread_active) {
1305                 ret = pthread_cancel(local_apps.ust_listener);
1306                 if (ret) {
1307                         ERR("Error cancelling local ust listener thread: %s",
1308                                 strerror(ret));
1309                 } else {
1310                         local_apps.thread_active = 0;
1311                 }
1312         }
1313         ust_unlock();
1314
1315         /*
1316          * Do NOT join threads: use of sys_futex makes it impossible to
1317          * join the threads without using async-cancel, but async-cancel
1318          * is delivered by a signal, which could hit the target thread
1319          * anywhere in its code path, including while the ust_lock() is
1320          * held, causing a deadlock for the other thread. Let the OS
1321          * cleanup the threads if there are stalled in a syscall.
1322          */
1323         lttng_ust_cleanup(1);
1324 }
1325
1326 /*
1327  * We exclude the worker threads across fork and clone (except
1328  * CLONE_VM), because these system calls only keep the forking thread
1329  * running in the child.  Therefore, we don't want to call fork or clone
1330  * in the middle of an tracepoint or ust tracing state modification.
1331  * Holding this mutex protects these structures across fork and clone.
1332  */
1333 void ust_before_fork(sigset_t *save_sigset)
1334 {
1335         /*
1336          * Disable signals. This is to avoid that the child intervenes
1337          * before it is properly setup for tracing. It is safer to
1338          * disable all signals, because then we know we are not breaking
1339          * anything by restoring the original mask.
1340          */
1341         sigset_t all_sigs;
1342         int ret;
1343
1344         if (URCU_TLS(lttng_ust_nest_count))
1345                 return;
1346         /* Disable signals */
1347         sigfillset(&all_sigs);
1348         ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
1349         if (ret == -1) {
1350                 PERROR("sigprocmask");
1351         }
1352         ust_lock();
1353         rcu_bp_before_fork();
1354 }
1355
1356 static void ust_after_fork_common(sigset_t *restore_sigset)
1357 {
1358         int ret;
1359
1360         DBG("process %d", getpid());
1361         ust_unlock();
1362         /* Restore signals */
1363         ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
1364         if (ret == -1) {
1365                 PERROR("sigprocmask");
1366         }
1367 }
1368
1369 void ust_after_fork_parent(sigset_t *restore_sigset)
1370 {
1371         if (URCU_TLS(lttng_ust_nest_count))
1372                 return;
1373         DBG("process %d", getpid());
1374         rcu_bp_after_fork_parent();
1375         /* Release mutexes and reenable signals */
1376         ust_after_fork_common(restore_sigset);
1377 }
1378
1379 /*
1380  * After fork, in the child, we need to cleanup all the leftover state,
1381  * except the worker thread which already magically disappeared thanks
1382  * to the weird Linux fork semantics. After tyding up, we call
1383  * lttng_ust_init() again to start over as a new PID.
1384  *
1385  * This is meant for forks() that have tracing in the child between the
1386  * fork and following exec call (if there is any).
1387  */
1388 void ust_after_fork_child(sigset_t *restore_sigset)
1389 {
1390         if (URCU_TLS(lttng_ust_nest_count))
1391                 return;
1392         DBG("process %d", getpid());
1393         /* Release urcu mutexes */
1394         rcu_bp_after_fork_child();
1395         lttng_ust_cleanup(0);
1396         lttng_context_vtid_reset();
1397         /* Release mutexes and reenable signals */
1398         ust_after_fork_common(restore_sigset);
1399         lttng_ust_init();
1400 }