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                 long page_size;
 681
 682                 page_size = sysconf(_SC_PAGE_SIZE);
 683                 if (page_size > 0) {
 684                         ret = munmap(sock_info->wait_shm_mmap, page_size);
 685                         if (ret) {
 686                                 ERR("Error unmapping wait shm");
 687                         }
 688                 }
 689                 sock_info->wait_shm_mmap = NULL;
 690         }
 691 }
 692
 693 /*
 694  * Using fork to set umask in the child process (not multi-thread safe).
 695  * We deal with the shm_open vs ftruncate race (happening when the
 696  * sessiond owns the shm and does not let everybody modify it, to ensure
 697  * safety against shm_unlink) by simply letting the mmap fail and
 698  * retrying after a few seconds.
 699  * For global shm, everybody has rw access to it until the sessiond
 700  * starts.
 701  */
 702 static
 703 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 704 {
 705         int wait_shm_fd, ret;
 706         pid_t pid;
 707
 708         /*
 709          * Try to open read-only.
 710          */
 711         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 712         if (wait_shm_fd >= 0) {
 713                 int32_t tmp_read;
 714                 ssize_t len;
 715                 size_t bytes_read = 0;
 716
 717                 /*
 718                  * Try to read the fd. If unable to do so, try opening
 719                  * it in write mode.
 720                  */
 721                 do {
 722                         len = read(wait_shm_fd,
 723                                 &((char *) &tmp_read)[bytes_read],
 724                                 sizeof(tmp_read) - bytes_read);
 725                         if (len > 0) {
 726                                 bytes_read += len;
 727                         }
 728                 } while ((len < 0 && errno == EINTR)
 729                         || (len > 0 && bytes_read < sizeof(tmp_read)));
 730                 if (bytes_read != sizeof(tmp_read)) {
 731                         ret = close(wait_shm_fd);
 732                         if (ret) {
 733                                 ERR("close wait_shm_fd");
 734                         }
 735                         goto open_write;
 736                 }
 737                 goto end;
 738         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 739                 /*
 740                  * Real-only open did not work, and it's not because the
 741                  * entry was not present. It's a failure that prohibits
 742                  * using shm.
 743                  */
 744                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 745                 goto end;
 746         }
 747
 748 open_write:
 749         /*
 750          * If the open failed because the file did not exist, or because
 751          * the file was not truncated yet, try creating it ourself.
 752          */
 753         URCU_TLS(lttng_ust_nest_count)++;
 754         pid = fork();
 755         URCU_TLS(lttng_ust_nest_count)--;
 756         if (pid > 0) {
 757                 int status;
 758
 759                 /*
 760                  * Parent: wait for child to return, in which case the
 761                  * shared memory map will have been created.
 762                  */
 763                 pid = wait(&status);
 764                 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 765                         wait_shm_fd = -1;
 766                         goto end;
 767                 }
 768                 /*
 769                  * Try to open read-only again after creation.
 770                  */
 771                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 772                 if (wait_shm_fd < 0) {
 773                         /*
 774                          * Real-only open did not work. It's a failure
 775                          * that prohibits using shm.
 776                          */
 777                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 778                         goto end;
 779                 }
 780                 goto end;
 781         } else if (pid == 0) {
 782                 int create_mode;
 783
 784                 /* Child */
 785                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
 786                 if (sock_info->global)
 787                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
 788                 /*
 789                  * We're alone in a child process, so we can modify the
 790                  * process-wide umask.
 791                  */
 792                 umask(~create_mode);
 793                 /*
 794                  * Try creating shm (or get rw access).
 795                  * We don't do an exclusive open, because we allow other
 796                  * processes to create+ftruncate it concurrently.
 797                  */
 798                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 799                                 O_RDWR | O_CREAT, create_mode);
 800                 if (wait_shm_fd >= 0) {
 801                         ret = ftruncate(wait_shm_fd, mmap_size);
 802                         if (ret) {
 803                                 PERROR("ftruncate");
 804                                 _exit(EXIT_FAILURE);
 805                         }
 806                         _exit(EXIT_SUCCESS);
 807                 }
 808                 /*
 809                  * For local shm, we need to have rw access to accept
 810                  * opening it: this means the local sessiond will be
 811                  * able to wake us up. For global shm, we open it even
 812                  * if rw access is not granted, because the root.root
 813                  * sessiond will be able to override all rights and wake
 814                  * us up.
 815                  */
 816                 if (!sock_info->global && errno != EACCES) {
 817                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 818                         _exit(EXIT_FAILURE);
 819                 }
 820                 /*
 821                  * The shm exists, but we cannot open it RW. Report
 822                  * success.
 823                  */
 824                 _exit(EXIT_SUCCESS);
 825         } else {
 826                 return -1;
 827         }
 828 end:
 829         if (wait_shm_fd >= 0 && !sock_info->global) {
 830                 struct stat statbuf;
 831
 832                 /*
 833                  * Ensure that our user is the owner of the shm file for
 834                  * local shm. If we do not own the file, it means our
 835                  * sessiond will not have access to wake us up (there is
 836                  * probably a rogue process trying to fake our
 837                  * sessiond). Fallback to polling method in this case.
 838                  */
 839                 ret = fstat(wait_shm_fd, &statbuf);
 840                 if (ret) {
 841                         PERROR("fstat");
 842                         goto error_close;
 843                 }
 844                 if (statbuf.st_uid != getuid())
 845                         goto error_close;
 846         }
 847         return wait_shm_fd;
 848
 849 error_close:
 850         ret = close(wait_shm_fd);
 851         if (ret) {
 852                 PERROR("Error closing fd");
 853         }
 854         return -1;
 855 }
 856
 857 static
 858 char *get_map_shm(struct sock_info *sock_info)
 859 {
 860         long page_size;
 861         int wait_shm_fd, ret;
 862         char *wait_shm_mmap;
 863
 864         page_size = sysconf(_SC_PAGE_SIZE);
 865         if (page_size < 0) {
 866                 goto error;
 867         }
 868
 869         wait_shm_fd = get_wait_shm(sock_info, page_size);
 870         if (wait_shm_fd < 0) {
 871                 goto error;
 872         }
 873         wait_shm_mmap = mmap(NULL, page_size, PROT_READ,
 874                   MAP_SHARED, wait_shm_fd, 0);
 875         /* close shm fd immediately after taking the mmap reference */
 876         ret = close(wait_shm_fd);
 877         if (ret) {
 878                 PERROR("Error closing fd");
 879         }
 880         if (wait_shm_mmap == MAP_FAILED) {
 881                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
 882                 goto error;
 883         }
 884         return wait_shm_mmap;
 885
 886 error:
 887         return NULL;
 888 }
 889
 890 static
 891 void wait_for_sessiond(struct sock_info *sock_info)
 892 {
 893         int ret;
 894
 895         ust_lock();
 896         if (lttng_ust_comm_should_quit) {
 897                 goto quit;
 898         }
 899         if (wait_poll_fallback) {
 900                 goto error;
 901         }
 902         if (!sock_info->wait_shm_mmap) {
 903                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
 904                 if (!sock_info->wait_shm_mmap)
 905                         goto error;
 906         }
 907         ust_unlock();
 908
 909         DBG("Waiting for %s apps sessiond", sock_info->name);
 910         /* Wait for futex wakeup */
 911         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
 912                 ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
 913                         FUTEX_WAIT, 0, NULL, NULL, 0);
 914                 if (ret < 0) {
 915                         if (errno == EFAULT) {
 916                                 wait_poll_fallback = 1;
 917                                 DBG(
 918 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
 919 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
 920 "Please upgrade your kernel "
 921 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
 922 "mainline). LTTng-UST will use polling mode fallback.");
 923                                 if (ust_debug())
 924                                         PERROR("futex");
 925                         }
 926                 }
 927         }
 928         return;
 929
 930 quit:
 931         ust_unlock();
 932         return;
 933
 934 error:
 935         ust_unlock();
 936         return;
 937 }
 938
 939 /*
 940  * This thread does not allocate any resource, except within
 941  * handle_message, within mutex protection. This mutex protects against
 942  * fork and exit.
 943  * The other moment it allocates resources is at socket connection, which
 944  * is also protected by the mutex.
 945  */
 946 static
 947 void *ust_listener_thread(void *arg)
 948 {
 949         struct sock_info *sock_info = arg;
 950         int sock, ret, prev_connect_failed = 0, has_waited = 0;
 951         long timeout;
 952
 953         /* Restart trying to connect to the session daemon */
 954 restart:
 955         if (prev_connect_failed) {
 956                 /* Wait for sessiond availability with pipe */
 957                 wait_for_sessiond(sock_info);
 958                 if (has_waited) {
 959                         has_waited = 0;
 960                         /*
 961                          * Sleep for 5 seconds before retrying after a
 962                          * sequence of failure / wait / failure. This
 963                          * deals with a killed or broken session daemon.
 964                          */
 965                         sleep(5);
 966                 }
 967                 has_waited = 1;
 968                 prev_connect_failed = 0;
 969         }
 970
 971         if (sock_info->socket != -1) {
 972                 ret = ustcomm_close_unix_sock(sock_info->socket);
 973                 if (ret) {
 974                         ERR("Error closing %s ust cmd socket",
 975                                 sock_info->name);
 976                 }
 977                 sock_info->socket = -1;
 978         }
 979         if (sock_info->notify_socket != -1) {
 980                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
 981                 if (ret) {
 982                         ERR("Error closing %s ust notify socket",
 983                                 sock_info->name);
 984                 }
 985                 sock_info->notify_socket = -1;
 986         }
 987
 988         /*
 989          * Register. We need to perform both connect and sending
 990          * registration message before doing the next connect otherwise
 991          * we may reach unix socket connect queue max limits and block
 992          * on the 2nd connect while the session daemon is awaiting the
 993          * first connect registration message.
 994          */
 995         /* Connect cmd socket */
 996         ret = ustcomm_connect_unix_sock(sock_info->sock_path);
 997         if (ret < 0) {
 998                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
 999                 prev_connect_failed = 1;
1000
1001                 ust_lock();
1002
1003                 if (lttng_ust_comm_should_quit) {
1004                         goto quit;
1005                 }
1006
1007                 /*
1008                  * If we cannot find the sessiond daemon, don't delay
1009                  * constructor execution.
1010                  */
1011                 ret = handle_register_done(sock_info);
1012                 assert(!ret);
1013                 ust_unlock();
1014                 goto restart;
1015         }
1016         sock_info->socket = ret;
1017
1018         ust_lock();
1019
1020         if (lttng_ust_comm_should_quit) {
1021                 goto quit;
1022         }
1023
1024         /*
1025          * Create only one root handle per listener thread for the whole
1026          * process lifetime, so we ensure we get ID which is statically
1027          * assigned to the root handle.
1028          */
1029         if (sock_info->root_handle == -1) {
1030                 ret = lttng_abi_create_root_handle();
1031                 if (ret < 0) {
1032                         ERR("Error creating root handle");
1033                         goto quit;
1034                 }
1035                 sock_info->root_handle = ret;
1036         }
1037
1038         ret = register_to_sessiond(sock_info->socket, USTCTL_SOCKET_CMD);
1039         if (ret < 0) {
1040                 ERR("Error registering to %s ust cmd socket",
1041                         sock_info->name);
1042                 prev_connect_failed = 1;
1043                 /*
1044                  * If we cannot register to the sessiond daemon, don't
1045                  * delay constructor execution.
1046                  */
1047                 ret = handle_register_done(sock_info);
1048                 assert(!ret);
1049                 ust_unlock();
1050                 goto restart;
1051         }
1052
1053         ust_unlock();
1054
1055         /* Connect notify socket */
1056         ret = ustcomm_connect_unix_sock(sock_info->sock_path);
1057         if (ret < 0) {
1058                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1059                 prev_connect_failed = 1;
1060
1061                 ust_lock();
1062
1063                 if (lttng_ust_comm_should_quit) {
1064                         goto quit;
1065                 }
1066
1067                 /*
1068                  * If we cannot find the sessiond daemon, don't delay
1069                  * constructor execution.
1070                  */
1071                 ret = handle_register_done(sock_info);
1072                 assert(!ret);
1073                 ust_unlock();
1074                 goto restart;
1075         }
1076         sock_info->notify_socket = ret;
1077
1078         timeout = get_notify_sock_timeout();
1079         if (timeout >= 0) {
1080                 /*
1081                  * Give at least 10ms to sessiond to reply to
1082                  * notifications.
1083                  */
1084                 if (timeout < 10)
1085                         timeout = 10;
1086                 ret = ustcomm_setsockopt_rcv_timeout(sock_info->notify_socket,
1087                                 timeout);
1088                 if (ret < 0) {
1089                         WARN("Error setting socket receive timeout");
1090                 }
1091                 ret = ustcomm_setsockopt_snd_timeout(sock_info->notify_socket,
1092                                 timeout);
1093                 if (ret < 0) {
1094                         WARN("Error setting socket send timeout");
1095                 }
1096         } else if (timeout < -1) {
1097                 WARN("Unsupported timeout value %ld", timeout);
1098         }
1099
1100         ust_lock();
1101
1102         if (lttng_ust_comm_should_quit) {
1103                 goto quit;
1104         }
1105
1106         ret = register_to_sessiond(sock_info->notify_socket,
1107                         USTCTL_SOCKET_NOTIFY);
1108         if (ret < 0) {
1109                 ERR("Error registering to %s ust notify socket",
1110                         sock_info->name);
1111                 prev_connect_failed = 1;
1112                 /*
1113                  * If we cannot register to the sessiond daemon, don't
1114                  * delay constructor execution.
1115                  */
1116                 ret = handle_register_done(sock_info);
1117                 assert(!ret);
1118                 ust_unlock();
1119                 goto restart;
1120         }
1121         sock = sock_info->socket;
1122
1123         ust_unlock();
1124
1125         for (;;) {
1126                 ssize_t len;
1127                 struct ustcomm_ust_msg lum;
1128
1129                 len = ustcomm_recv_unix_sock(sock, &lum, sizeof(lum));
1130                 switch (len) {
1131                 case 0: /* orderly shutdown */
1132                         DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
1133                         ust_lock();
1134                         if (lttng_ust_comm_should_quit) {
1135                                 goto quit;
1136                         }
1137                         /*
1138                          * Either sessiond has shutdown or refused us by closing the socket.
1139                          * In either case, we don't want to delay construction execution,
1140                          * and we need to wait before retry.
1141                          */
1142                         prev_connect_failed = 1;
1143                         /*
1144                          * If we cannot register to the sessiond daemon, don't
1145                          * delay constructor execution.
1146                          */
1147                         ret = handle_register_done(sock_info);
1148                         assert(!ret);
1149                         ust_unlock();
1150                         goto end;
1151                 case sizeof(lum):
1152                         print_cmd(lum.cmd, lum.handle);
1153                         ret = handle_message(sock_info, sock, &lum);
1154                         if (ret) {
1155                                 ERR("Error handling message for %s socket", sock_info->name);
1156                         }
1157                         continue;
1158                 default:
1159                         if (len < 0) {
1160                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
1161                         } else {
1162                                 DBG("incorrect message size (%s socket): %zd", sock_info->name, len);
1163                         }
1164                         if (len == -ECONNRESET) {
1165                                 DBG("%s remote end closed connection", sock_info->name);
1166                                 goto end;
1167                         }
1168                         goto end;
1169                 }
1170
1171         }
1172 end:
1173         ust_lock();
1174         if (lttng_ust_comm_should_quit) {
1175                 goto quit;
1176         }
1177         /* Cleanup socket handles before trying to reconnect */
1178         lttng_ust_objd_table_owner_cleanup(sock_info);
1179         ust_unlock();
1180         goto restart;   /* try to reconnect */
1181
1182 quit:
1183         sock_info->thread_active = 0;
1184         ust_unlock();
1185         return NULL;
1186 }
1187
1188 /*
1189  * sessiond monitoring thread: monitor presence of global and per-user
1190  * sessiond by polling the application common named pipe.
1191  */
1192 void __attribute__((constructor)) lttng_ust_init(void)
1193 {
1194         struct timespec constructor_timeout;
1195         sigset_t sig_all_blocked, orig_parent_mask;
1196         pthread_attr_t thread_attr;
1197         int timeout_mode;
1198         int ret;
1199
1200         if (uatomic_xchg(&initialized, 1) == 1)
1201                 return;
1202
1203         /*
1204          * Fixup interdependency between TLS fixup mutex (which happens
1205          * to be the dynamic linker mutex) and ust_lock, taken within
1206          * the ust lock.
1207          */
1208         lttng_fixup_ringbuffer_tls();
1209         lttng_fixup_vtid_tls();
1210         lttng_fixup_nest_count_tls();
1211         lttng_fixup_procname_tls();
1212
1213         /*
1214          * We want precise control over the order in which we construct
1215          * our sub-libraries vs starting to receive commands from
1216          * sessiond (otherwise leading to errors when trying to create
1217          * sessiond before the init functions are completed).
1218          */
1219         init_usterr();
1220         init_tracepoint();
1221         lttng_ring_buffer_metadata_client_init();
1222         lttng_ring_buffer_client_overwrite_init();
1223         lttng_ring_buffer_client_overwrite_rt_init();
1224         lttng_ring_buffer_client_discard_init();
1225         lttng_ring_buffer_client_discard_rt_init();
1226         lttng_context_init();
1227
1228         timeout_mode = get_constructor_timeout(&constructor_timeout);
1229
1230         ret = sem_init(&constructor_wait, 0, 0);
1231         assert(!ret);
1232
1233         ret = setup_local_apps();
1234         if (ret) {
1235                 DBG("local apps setup returned %d", ret);
1236         }
1237
1238         /* A new thread created by pthread_create inherits the signal mask
1239          * from the parent. To avoid any signal being received by the
1240          * listener thread, we block all signals temporarily in the parent,
1241          * while we create the listener thread.
1242          */
1243         sigfillset(&sig_all_blocked);
1244         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
1245         if (ret) {
1246                 ERR("pthread_sigmask: %s", strerror(ret));
1247         }
1248
1249         ret = pthread_attr_init(&thread_attr);
1250         if (ret) {
1251                 ERR("pthread_attr_init: %s", strerror(ret));
1252         }
1253         ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
1254         if (ret) {
1255                 ERR("pthread_attr_setdetachstate: %s", strerror(ret));
1256         }
1257
1258         ust_lock();
1259         ret = pthread_create(&global_apps.ust_listener, &thread_attr,
1260                         ust_listener_thread, &global_apps);
1261         if (ret) {
1262                 ERR("pthread_create global: %s", strerror(ret));
1263         }
1264         global_apps.thread_active = 1;
1265         ust_unlock();
1266
1267         if (local_apps.allowed) {
1268                 ust_lock();
1269                 ret = pthread_create(&local_apps.ust_listener, &thread_attr,
1270                                 ust_listener_thread, &local_apps);
1271                 if (ret) {
1272                         ERR("pthread_create local: %s", strerror(ret));
1273                 }
1274                 local_apps.thread_active = 1;
1275                 ust_unlock();
1276         } else {
1277                 handle_register_done(&local_apps);
1278         }
1279         ret = pthread_attr_destroy(&thread_attr);
1280         if (ret) {
1281                 ERR("pthread_attr_destroy: %s", strerror(ret));
1282         }
1283
1284         /* Restore original signal mask in parent */
1285         ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
1286         if (ret) {
1287                 ERR("pthread_sigmask: %s", strerror(ret));
1288         }
1289
1290         switch (timeout_mode) {
1291         case 1: /* timeout wait */
1292                 do {
1293                         ret = sem_timedwait(&constructor_wait,
1294                                         &constructor_timeout);
1295                 } while (ret < 0 && errno == EINTR);
1296                 if (ret < 0 && errno == ETIMEDOUT) {
1297                         ERR("Timed out waiting for lttng-sessiond");
1298                 } else {
1299                         assert(!ret);
1300                 }
1301                 break;
1302         case -1:/* wait forever */
1303                 do {
1304                         ret = sem_wait(&constructor_wait);
1305                 } while (ret < 0 && errno == EINTR);
1306                 assert(!ret);
1307                 break;
1308         case 0: /* no timeout */
1309                 break;
1310         }
1311 }
1312
1313 static
1314 void lttng_ust_cleanup(int exiting)
1315 {
1316         cleanup_sock_info(&global_apps, exiting);
1317         if (local_apps.allowed) {
1318                 cleanup_sock_info(&local_apps, exiting);
1319         }
1320         /*
1321          * The teardown in this function all affect data structures
1322          * accessed under the UST lock by the listener thread. This
1323          * lock, along with the lttng_ust_comm_should_quit flag, ensure
1324          * that none of these threads are accessing this data at this
1325          * point.
1326          */
1327         lttng_ust_abi_exit();
1328         lttng_ust_events_exit();
1329         lttng_context_exit();
1330         lttng_ring_buffer_client_discard_rt_exit();
1331         lttng_ring_buffer_client_discard_exit();
1332         lttng_ring_buffer_client_overwrite_rt_exit();
1333         lttng_ring_buffer_client_overwrite_exit();
1334         lttng_ring_buffer_metadata_client_exit();
1335         exit_tracepoint();
1336         if (!exiting) {
1337                 /* Reinitialize values for fork */
1338                 sem_count = 2;
1339                 lttng_ust_comm_should_quit = 0;
1340                 initialized = 0;
1341         }
1342 }
1343
1344 void __attribute__((destructor)) lttng_ust_exit(void)
1345 {
1346         int ret;
1347
1348         /*
1349          * Using pthread_cancel here because:
1350          * A) we don't want to hang application teardown.
1351          * B) the thread is not allocating any resource.
1352          */
1353
1354         /*
1355          * Require the communication thread to quit. Synchronize with
1356          * mutexes to ensure it is not in a mutex critical section when
1357          * pthread_cancel is later called.
1358          */
1359         ust_lock();
1360         lttng_ust_comm_should_quit = 1;
1361
1362         /* cancel threads */
1363         if (global_apps.thread_active) {
1364                 ret = pthread_cancel(global_apps.ust_listener);
1365                 if (ret) {
1366                         ERR("Error cancelling global ust listener thread: %s",
1367                                 strerror(ret));
1368                 } else {
1369                         global_apps.thread_active = 0;
1370                 }
1371         }
1372         if (local_apps.thread_active) {
1373                 ret = pthread_cancel(local_apps.ust_listener);
1374                 if (ret) {
1375                         ERR("Error cancelling local ust listener thread: %s",
1376                                 strerror(ret));
1377                 } else {
1378                         local_apps.thread_active = 0;
1379                 }
1380         }
1381         ust_unlock();
1382
1383         /*
1384          * Do NOT join threads: use of sys_futex makes it impossible to
1385          * join the threads without using async-cancel, but async-cancel
1386          * is delivered by a signal, which could hit the target thread
1387          * anywhere in its code path, including while the ust_lock() is
1388          * held, causing a deadlock for the other thread. Let the OS
1389          * cleanup the threads if there are stalled in a syscall.
1390          */
1391         lttng_ust_cleanup(1);
1392 }
1393
1394 /*
1395  * We exclude the worker threads across fork and clone (except
1396  * CLONE_VM), because these system calls only keep the forking thread
1397  * running in the child.  Therefore, we don't want to call fork or clone
1398  * in the middle of an tracepoint or ust tracing state modification.
1399  * Holding this mutex protects these structures across fork and clone.
1400  */
1401 void ust_before_fork(sigset_t *save_sigset)
1402 {
1403         /*
1404          * Disable signals. This is to avoid that the child intervenes
1405          * before it is properly setup for tracing. It is safer to
1406          * disable all signals, because then we know we are not breaking
1407          * anything by restoring the original mask.
1408          */
1409         sigset_t all_sigs;
1410         int ret;
1411
1412         if (URCU_TLS(lttng_ust_nest_count))
1413                 return;
1414         /* Disable signals */
1415         sigfillset(&all_sigs);
1416         ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
1417         if (ret == -1) {
1418                 PERROR("sigprocmask");
1419         }
1420         ust_lock();
1421         rcu_bp_before_fork();
1422 }
1423
1424 static void ust_after_fork_common(sigset_t *restore_sigset)
1425 {
1426         int ret;
1427
1428         DBG("process %d", getpid());
1429         ust_unlock();
1430         /* Restore signals */
1431         ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
1432         if (ret == -1) {
1433                 PERROR("sigprocmask");
1434         }
1435 }
1436
1437 void ust_after_fork_parent(sigset_t *restore_sigset)
1438 {
1439         if (URCU_TLS(lttng_ust_nest_count))
1440                 return;
1441         DBG("process %d", getpid());
1442         rcu_bp_after_fork_parent();
1443         /* Release mutexes and reenable signals */
1444         ust_after_fork_common(restore_sigset);
1445 }
1446
1447 /*
1448  * After fork, in the child, we need to cleanup all the leftover state,
1449  * except the worker thread which already magically disappeared thanks
1450  * to the weird Linux fork semantics. After tyding up, we call
1451  * lttng_ust_init() again to start over as a new PID.
1452  *
1453  * This is meant for forks() that have tracing in the child between the
1454  * fork and following exec call (if there is any).
1455  */
1456 void ust_after_fork_child(sigset_t *restore_sigset)
1457 {
1458         if (URCU_TLS(lttng_ust_nest_count))
1459                 return;
1460         DBG("process %d", getpid());
1461         /* Release urcu mutexes */
1462         rcu_bp_after_fork_child();
1463         lttng_ust_cleanup(0);
1464         lttng_context_vtid_reset();
1465         /* Release mutexes and reenable signals */
1466         ust_after_fork_common(restore_sigset);
1467         lttng_ust_init();
1468 }