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