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 <dlfcn.h>
  38 #include <urcu/uatomic.h>
  39 #include <urcu/futex.h>
  40 #include <urcu/compiler.h>
  41
  42 #include <lttng/ust-events.h>
  43 #include <lttng/ust-abi.h>
  44 #include <lttng/ust.h>
  45 #include <lttng/ust-error.h>
  46 #include <lttng/ust-ctl.h>
  47 #include <urcu/tls-compat.h>
  48 #include <ust-comm.h>
  49 #include <usterr-signal-safe.h>
  50 #include <helper.h>
  51 #include "tracepoint-internal.h"
  52 #include "lttng-tracer-core.h"
  53 #include "compat.h"
  54 #include "../libringbuffer/tlsfixup.h"
  55 #include "lttng-ust-baddr.h"
  56
  57 /*
  58  * Has lttng ust comm constructor been called ?
  59  */
  60 static int initialized;
  61
  62 /*
  63  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  64  * Held when handling a command, also held by fork() to deal with
  65  * removal of threads, and by exit path.
  66  */
  67
  68 /* Should the ust comm thread quit ? */
  69 static int lttng_ust_comm_should_quit;
  70
  71 /*
  72  * Wait for either of these before continuing to the main
  73  * program:
  74  * - the register_done message from sessiond daemon
  75  *   (will let the sessiond daemon enable sessions before main
  76  *   starts.)
  77  * - sessiond daemon is not reachable.
  78  * - timeout (ensuring applications are resilient to session
  79  *   daemon problems).
  80  */
  81 static sem_t constructor_wait;
  82 /*
  83  * Doing this for both the global and local sessiond.
  84  */
  85 static int sem_count = { 2 };
  86
  87 /*
  88  * Counting nesting within lttng-ust. Used to ensure that calling fork()
  89  * from liblttng-ust does not execute the pre/post fork handlers.
  90  */
  91 static DEFINE_URCU_TLS(int, lttng_ust_nest_count);
  92
  93 /*
  94  * Info about socket and associated listener thread.
  95  */
  96 struct sock_info {
  97         const char *name;
  98         pthread_t ust_listener; /* listener thread */
  99         int root_handle;
 100         int constructor_sem_posted;
 101         int allowed;
 102         int global;
 103         int thread_active;
 104
 105         char sock_path[PATH_MAX];
 106         int socket;
 107         int notify_socket;
 108
 109         char wait_shm_path[PATH_MAX];
 110         char *wait_shm_mmap;
 111         /* Keep track of lazy state dump not performed yet. */
 112         int statedump_pending;
 113 };
 114
 115 /* Socket from app (connect) to session daemon (listen) for communication */
 116 struct sock_info global_apps = {
 117         .name = "global",
 118         .global = 1,
 119
 120         .root_handle = -1,
 121         .allowed = 1,
 122         .thread_active = 0,
 123
 124         .sock_path = LTTNG_DEFAULT_RUNDIR "/" LTTNG_UST_SOCK_FILENAME,
 125         .socket = -1,
 126         .notify_socket = -1,
 127
 128         .wait_shm_path = "/" LTTNG_UST_WAIT_FILENAME,
 129
 130         .statedump_pending = 0,
 131 };
 132
 133 /* TODO: allow global_apps_sock_path override */
 134
 135 struct sock_info local_apps = {
 136         .name = "local",
 137         .global = 0,
 138         .root_handle = -1,
 139         .allowed = 0,   /* Check setuid bit first */
 140         .thread_active = 0,
 141
 142         .socket = -1,
 143         .notify_socket = -1,
 144
 145         .statedump_pending = 0,
 146 };
 147
 148 static int wait_poll_fallback;
 149
 150 static const char *cmd_name_mapping[] = {
 151         [ LTTNG_UST_RELEASE ] = "Release",
 152         [ LTTNG_UST_SESSION ] = "Create Session",
 153         [ LTTNG_UST_TRACER_VERSION ] = "Get Tracer Version",
 154
 155         [ LTTNG_UST_TRACEPOINT_LIST ] = "Create Tracepoint List",
 156         [ LTTNG_UST_WAIT_QUIESCENT ] = "Wait for Quiescent State",
 157         [ LTTNG_UST_REGISTER_DONE ] = "Registration Done",
 158         [ LTTNG_UST_TRACEPOINT_FIELD_LIST ] = "Create Tracepoint Field List",
 159
 160         /* Session FD commands */
 161         [ LTTNG_UST_CHANNEL ] = "Create Channel",
 162         [ LTTNG_UST_SESSION_START ] = "Start Session",
 163         [ LTTNG_UST_SESSION_STOP ] = "Stop Session",
 164
 165         /* Channel FD commands */
 166         [ LTTNG_UST_STREAM ] = "Create Stream",
 167         [ LTTNG_UST_EVENT ] = "Create Event",
 168
 169         /* Event and Channel FD commands */
 170         [ LTTNG_UST_CONTEXT ] = "Create Context",
 171         [ LTTNG_UST_FLUSH_BUFFER ] = "Flush Buffer",
 172
 173         /* Event, Channel and Session commands */
 174         [ LTTNG_UST_ENABLE ] = "Enable",
 175         [ LTTNG_UST_DISABLE ] = "Disable",
 176
 177         /* Tracepoint list commands */
 178         [ LTTNG_UST_TRACEPOINT_LIST_GET ] = "List Next Tracepoint",
 179         [ LTTNG_UST_TRACEPOINT_FIELD_LIST_GET ] = "List Next Tracepoint Field",
 180
 181         /* Event FD commands */
 182         [ LTTNG_UST_FILTER ] = "Create Filter",
 183         [ LTTNG_UST_EXCLUSION ] = "Add exclusions to event",
 184 };
 185
 186 static const char *str_timeout;
 187 static int got_timeout_env;
 188
 189 extern void lttng_ring_buffer_client_overwrite_init(void);
 190 extern void lttng_ring_buffer_client_overwrite_rt_init(void);
 191 extern void lttng_ring_buffer_client_discard_init(void);
 192 extern void lttng_ring_buffer_client_discard_rt_init(void);
 193 extern void lttng_ring_buffer_metadata_client_init(void);
 194 extern void lttng_ring_buffer_client_overwrite_exit(void);
 195 extern void lttng_ring_buffer_client_overwrite_rt_exit(void);
 196 extern void lttng_ring_buffer_client_discard_exit(void);
 197 extern void lttng_ring_buffer_client_discard_rt_exit(void);
 198 extern void lttng_ring_buffer_metadata_client_exit(void);
 199
 200 /*
 201  * Returns the HOME directory path. Caller MUST NOT free(3) the returned
 202  * pointer.
 203  */
 204 static
 205 const char *get_lttng_home_dir(void)
 206 {
 207        const char *val;
 208
 209        val = (const char *) getenv("LTTNG_HOME");
 210        if (val != NULL) {
 211                return val;
 212        }
 213        return (const char *) getenv("HOME");
 214 }
 215
 216 /*
 217  * Force a read (imply TLS fixup for dlopen) of TLS variables.
 218  */
 219 static
 220 void lttng_fixup_nest_count_tls(void)
 221 {
 222         asm volatile ("" : : "m" (URCU_TLS(lttng_ust_nest_count)));
 223 }
 224
 225 int lttng_get_notify_socket(void *owner)
 226 {
 227         struct sock_info *info = owner;
 228
 229         return info->notify_socket;
 230 }
 231
 232 static
 233 void print_cmd(int cmd, int handle)
 234 {
 235         const char *cmd_name = "Unknown";
 236
 237         if (cmd >= 0 && cmd < LTTNG_ARRAY_SIZE(cmd_name_mapping)
 238                         && cmd_name_mapping[cmd]) {
 239                 cmd_name = cmd_name_mapping[cmd];
 240         }
 241         DBG("Message Received \"%s\" (%d), Handle \"%s\" (%d)",
 242                 cmd_name, cmd,
 243                 lttng_ust_obj_get_name(handle), handle);
 244 }
 245
 246 static
 247 int setup_local_apps(void)
 248 {
 249         const char *home_dir;
 250         uid_t uid;
 251
 252         uid = getuid();
 253         /*
 254          * Disallow per-user tracing for setuid binaries.
 255          */
 256         if (uid != geteuid()) {
 257                 assert(local_apps.allowed == 0);
 258                 return 0;
 259         }
 260         home_dir = get_lttng_home_dir();
 261         if (!home_dir) {
 262                 WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
 263                 assert(local_apps.allowed == 0);
 264                 return -ENOENT;
 265         }
 266         local_apps.allowed = 1;
 267         snprintf(local_apps.sock_path, PATH_MAX, "%s/%s/%s",
 268                 home_dir,
 269                 LTTNG_DEFAULT_HOME_RUNDIR,
 270                 LTTNG_UST_SOCK_FILENAME);
 271         snprintf(local_apps.wait_shm_path, PATH_MAX, "/%s-%u",
 272                 LTTNG_UST_WAIT_FILENAME,
 273                 uid);
 274         return 0;
 275 }
 276
 277 /*
 278  * Get notify_sock timeout, in ms.
 279  * -1: don't wait. 0: wait forever. >0: timeout, in ms.
 280  */
 281 static
 282 long get_timeout(void)
 283 {
 284         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 285
 286         if (!got_timeout_env) {
 287                 str_timeout = getenv("LTTNG_UST_REGISTER_TIMEOUT");
 288                 got_timeout_env = 1;
 289         }
 290         if (str_timeout)
 291                 constructor_delay_ms = strtol(str_timeout, NULL, 10);
 292         return constructor_delay_ms;
 293 }
 294
 295 static
 296 long get_notify_sock_timeout(void)
 297 {
 298         return get_timeout();
 299 }
 300
 301 /*
 302  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 303  */
 304 static
 305 int get_constructor_timeout(struct timespec *constructor_timeout)
 306 {
 307         long constructor_delay_ms;
 308         int ret;
 309
 310         constructor_delay_ms = get_timeout();
 311
 312         switch (constructor_delay_ms) {
 313         case -1:/* fall-through */
 314         case 0:
 315                 return constructor_delay_ms;
 316         default:
 317                 break;
 318         }
 319
 320         /*
 321          * If we are unable to find the current time, don't wait.
 322          */
 323         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 324         if (ret) {
 325                 return -1;
 326         }
 327         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 328         constructor_timeout->tv_nsec +=
 329                 (constructor_delay_ms % 1000UL) * 1000000UL;
 330         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 331                 constructor_timeout->tv_sec++;
 332                 constructor_timeout->tv_nsec -= 1000000000UL;
 333         }
 334         return 1;
 335 }
 336
 337 static
 338 int register_to_sessiond(int socket, enum ustctl_socket_type type)
 339 {
 340         return ustcomm_send_reg_msg(socket,
 341                 type,
 342                 CAA_BITS_PER_LONG,
 343                 lttng_alignof(uint8_t) * CHAR_BIT,
 344                 lttng_alignof(uint16_t) * CHAR_BIT,
 345                 lttng_alignof(uint32_t) * CHAR_BIT,
 346                 lttng_alignof(uint64_t) * CHAR_BIT,
 347                 lttng_alignof(unsigned long) * CHAR_BIT);
 348 }
 349
 350 static
 351 int send_reply(int sock, struct ustcomm_ust_reply *lur)
 352 {
 353         ssize_t len;
 354
 355         len = ustcomm_send_unix_sock(sock, lur, sizeof(*lur));
 356         switch (len) {
 357         case sizeof(*lur):
 358                 DBG("message successfully sent");
 359                 return 0;
 360         default:
 361                 if (len == -ECONNRESET) {
 362                         DBG("remote end closed connection");
 363                         return 0;
 364                 }
 365                 if (len < 0)
 366                         return len;
 367                 DBG("incorrect message size: %zd", len);
 368                 return -EINVAL;
 369         }
 370 }
 371
 372 static
 373 int handle_register_done(struct sock_info *sock_info)
 374 {
 375         int ret;
 376
 377         if (sock_info->constructor_sem_posted)
 378                 return 0;
 379         sock_info->constructor_sem_posted = 1;
 380         if (uatomic_read(&sem_count) <= 0) {
 381                 return 0;
 382         }
 383         ret = uatomic_add_return(&sem_count, -1);
 384         if (ret == 0) {
 385                 ret = sem_post(&constructor_wait);
 386                 assert(!ret);
 387         }
 388         return 0;
 389 }
 390
 391 /*
 392  * Only execute pending statedump after the constructor semaphore has
 393  * been posted by each listener thread. This means statedump will only
 394  * be performed after the "registration done" command is received from
 395  * each session daemon the application is connected to.
 396  *
 397  * This ensures we don't run into deadlock issues with the dynamic
 398  * loader mutex, which is held while the constructor is called and
 399  * waiting on the constructor semaphore. All operations requiring this
 400  * dynamic loader lock need to be postponed using this mechanism.
 401  */
 402 static
 403 void handle_pending_statedump(struct sock_info *sock_info)
 404 {
 405         int ctor_passed = sock_info->constructor_sem_posted;
 406
 407         if (ctor_passed && sock_info->statedump_pending) {
 408                 sock_info->statedump_pending = 0;
 409                 lttng_handle_pending_statedump(sock_info);
 410         }
 411 }
 412
 413 static
 414 int handle_message(struct sock_info *sock_info,
 415                 int sock, struct ustcomm_ust_msg *lum)
 416 {
 417         int ret = 0;
 418         const struct lttng_ust_objd_ops *ops;
 419         struct ustcomm_ust_reply lur;
 420         union ust_args args;
 421         ssize_t len;
 422
 423         ust_lock();
 424
 425         memset(&lur, 0, sizeof(lur));
 426
 427         if (lttng_ust_comm_should_quit) {
 428                 ret = -LTTNG_UST_ERR_EXITING;
 429                 goto end;
 430         }
 431
 432         ops = objd_ops(lum->handle);
 433         if (!ops) {
 434                 ret = -ENOENT;
 435                 goto end;
 436         }
 437
 438         switch (lum->cmd) {
 439         case LTTNG_UST_REGISTER_DONE:
 440                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 441                         ret = handle_register_done(sock_info);
 442                 else
 443                         ret = -EINVAL;
 444                 break;
 445         case LTTNG_UST_RELEASE:
 446                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 447                         ret = -EPERM;
 448                 else
 449                         ret = lttng_ust_objd_unref(lum->handle, 1);
 450                 break;
 451         case LTTNG_UST_FILTER:
 452         {
 453                 /* Receive filter data */
 454                 struct lttng_ust_filter_bytecode_node *bytecode;
 455
 456                 if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) {
 457                         ERR("Filter data size is too large: %u bytes",
 458                                 lum->u.filter.data_size);
 459                         ret = -EINVAL;
 460                         goto error;
 461                 }
 462
 463                 if (lum->u.filter.reloc_offset > lum->u.filter.data_size) {
 464                         ERR("Filter reloc offset %u is not within data",
 465                                 lum->u.filter.reloc_offset);
 466                         ret = -EINVAL;
 467                         goto error;
 468                 }
 469
 470                 bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size);
 471                 if (!bytecode) {
 472                         ret = -ENOMEM;
 473                         goto error;
 474                 }
 475                 len = ustcomm_recv_unix_sock(sock, bytecode->bc.data,
 476                                 lum->u.filter.data_size);
 477                 switch (len) {
 478                 case 0: /* orderly shutdown */
 479                         ret = 0;
 480                         free(bytecode);
 481                         goto error;
 482                 default:
 483                         if (len == lum->u.filter.data_size) {
 484                                 DBG("filter data received");
 485                                 break;
 486                         } else if (len < 0) {
 487                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 488                                 if (len == -ECONNRESET) {
 489                                         ERR("%s remote end closed connection", sock_info->name);
 490                                         ret = len;
 491                                         free(bytecode);
 492                                         goto error;
 493                                 }
 494                                 ret = len;
 495                                 free(bytecode);
 496                                 goto end;
 497                         } else {
 498                                 DBG("incorrect filter data message size: %zd", len);
 499                                 ret = -EINVAL;
 500                                 free(bytecode);
 501                                 goto end;
 502                         }
 503                 }
 504                 bytecode->bc.len = lum->u.filter.data_size;
 505                 bytecode->bc.reloc_offset = lum->u.filter.reloc_offset;
 506                 bytecode->bc.seqnum = lum->u.filter.seqnum;
 507                 if (ops->cmd) {
 508                         ret = ops->cmd(lum->handle, lum->cmd,
 509                                         (unsigned long) bytecode,
 510                                         &args, sock_info);
 511                         if (ret) {
 512                                 free(bytecode);
 513                         }
 514                         /* don't free bytecode if everything went fine. */
 515                 } else {
 516                         ret = -ENOSYS;
 517                         free(bytecode);
 518                 }
 519                 break;
 520         }
 521         case LTTNG_UST_EXCLUSION:
 522         {
 523                 /* Receive exclusion names */
 524                 struct lttng_ust_excluder_node *node;
 525                 unsigned int count;
 526
 527                 count = lum->u.exclusion.count;
 528                 if (count == 0) {
 529                         /* There are no names to read */
 530                         ret = 0;
 531                         goto error;
 532                 }
 533                 node = zmalloc(sizeof(*node) +
 534                                 count * LTTNG_UST_SYM_NAME_LEN);
 535                 if (!node) {
 536                         ret = -ENOMEM;
 537                         goto error;
 538                 }
 539                 node->excluder.count = count;
 540                 len = ustcomm_recv_unix_sock(sock, node->excluder.names,
 541                                 count * LTTNG_UST_SYM_NAME_LEN);
 542                 switch (len) {
 543                 case 0: /* orderly shutdown */
 544                         ret = 0;
 545                         free(node);
 546                         goto error;
 547                 default:
 548                         if (len == count * LTTNG_UST_SYM_NAME_LEN) {
 549                                 DBG("Exclusion data received");
 550                                 break;
 551                         } else if (len < 0) {
 552                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 553                                 if (len == -ECONNRESET) {
 554                                         ERR("%s remote end closed connection", sock_info->name);
 555                                         ret = len;
 556                                         free(node);
 557                                         goto error;
 558                                 }
 559                                 ret = len;
 560                                 free(node);
 561                                 goto end;
 562                         } else {
 563                                 DBG("Incorrect exclusion data message size: %zd", len);
 564                                 ret = -EINVAL;
 565                                 free(node);
 566                                 goto end;
 567                         }
 568                 }
 569                 if (ops->cmd) {
 570                         ret = ops->cmd(lum->handle, lum->cmd,
 571                                         (unsigned long) node,
 572                                         &args, sock_info);
 573                         if (ret) {
 574                                 free(node);
 575                         }
 576                         /* Don't free exclusion data if everything went fine. */
 577                 } else {
 578                         ret = -ENOSYS;
 579                         free(node);
 580                 }
 581                 break;
 582         }
 583         case LTTNG_UST_CHANNEL:
 584         {
 585                 void *chan_data;
 586                 int wakeup_fd;
 587
 588                 len = ustcomm_recv_channel_from_sessiond(sock,
 589                                 &chan_data, lum->u.channel.len,
 590                                 &wakeup_fd);
 591                 switch (len) {
 592                 case 0: /* orderly shutdown */
 593                         ret = 0;
 594                         goto error;
 595                 default:
 596                         if (len == lum->u.channel.len) {
 597                                 DBG("channel data received");
 598                                 break;
 599                         } else if (len < 0) {
 600                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 601                                 if (len == -ECONNRESET) {
 602                                         ERR("%s remote end closed connection", sock_info->name);
 603                                         ret = len;
 604                                         goto error;
 605                                 }
 606                                 ret = len;
 607                                 goto end;
 608                         } else {
 609                                 DBG("incorrect channel data message size: %zd", len);
 610                                 ret = -EINVAL;
 611                                 goto end;
 612                         }
 613                 }
 614                 args.channel.chan_data = chan_data;
 615                 args.channel.wakeup_fd = wakeup_fd;
 616                 if (ops->cmd)
 617                         ret = ops->cmd(lum->handle, lum->cmd,
 618                                         (unsigned long) &lum->u,
 619                                         &args, sock_info);
 620                 else
 621                         ret = -ENOSYS;
 622                 break;
 623         }
 624         case LTTNG_UST_STREAM:
 625         {
 626                 /* Receive shm_fd, wakeup_fd */
 627                 ret = ustcomm_recv_stream_from_sessiond(sock,
 628                         &lum->u.stream.len,
 629                         &args.stream.shm_fd,
 630                         &args.stream.wakeup_fd);
 631                 if (ret) {
 632                         goto end;
 633                 }
 634                 if (ops->cmd)
 635                         ret = ops->cmd(lum->handle, lum->cmd,
 636                                         (unsigned long) &lum->u,
 637                                         &args, sock_info);
 638                 else
 639                         ret = -ENOSYS;
 640                 break;
 641         }
 642         default:
 643                 if (ops->cmd)
 644                         ret = ops->cmd(lum->handle, lum->cmd,
 645                                         (unsigned long) &lum->u,
 646                                         &args, sock_info);
 647                 else
 648                         ret = -ENOSYS;
 649                 break;
 650         }
 651
 652 end:
 653         lur.handle = lum->handle;
 654         lur.cmd = lum->cmd;
 655         lur.ret_val = ret;
 656         if (ret >= 0) {
 657                 lur.ret_code = LTTNG_UST_OK;
 658         } else {
 659                 /*
 660                  * Use -LTTNG_UST_ERR as wildcard for UST internal
 661                  * error that are not caused by the transport, except if
 662                  * we already have a more precise error message to
 663                  * report.
 664                  */
 665                 if (ret > -LTTNG_UST_ERR) {
 666                         /* Translate code to UST error. */
 667                         switch (ret) {
 668                         case -EEXIST:
 669                                 lur.ret_code = -LTTNG_UST_ERR_EXIST;
 670                                 break;
 671                         case -EINVAL:
 672                                 lur.ret_code = -LTTNG_UST_ERR_INVAL;
 673                                 break;
 674                         case -ENOENT:
 675                                 lur.ret_code = -LTTNG_UST_ERR_NOENT;
 676                                 break;
 677                         case -EPERM:
 678                                 lur.ret_code = -LTTNG_UST_ERR_PERM;
 679                                 break;
 680                         case -ENOSYS:
 681                                 lur.ret_code = -LTTNG_UST_ERR_NOSYS;
 682                                 break;
 683                         default:
 684                                 lur.ret_code = -LTTNG_UST_ERR;
 685                                 break;
 686                         }
 687                 } else {
 688                         lur.ret_code = ret;
 689                 }
 690         }
 691         if (ret >= 0) {
 692                 switch (lum->cmd) {
 693                 case LTTNG_UST_TRACER_VERSION:
 694                         lur.u.version = lum->u.version;
 695                         break;
 696                 case LTTNG_UST_TRACEPOINT_LIST_GET:
 697                         memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
 698                         break;
 699                 }
 700         }
 701         DBG("Return value: %d", lur.ret_val);
 702         ret = send_reply(sock, &lur);
 703         if (ret < 0) {
 704                 DBG("error sending reply");
 705                 goto error;
 706         }
 707
 708         /*
 709          * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field
 710          * after the reply.
 711          */
 712         if (lur.ret_code == LTTNG_UST_OK) {
 713                 switch (lum->cmd) {
 714                 case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET:
 715                         len = ustcomm_send_unix_sock(sock,
 716                                 &args.field_list.entry,
 717                                 sizeof(args.field_list.entry));
 718                         if (len < 0) {
 719                                 ret = len;
 720                                 goto error;
 721                         }
 722                         if (len != sizeof(args.field_list.entry)) {
 723                                 ret = -EINVAL;
 724                                 goto error;
 725                         }
 726                 }
 727         }
 728
 729 error:
 730         ust_unlock();
 731
 732         /*
 733          * Performed delayed statedump operations outside of the UST
 734          * lock. We need to take the dynamic loader lock before we take
 735          * the UST lock internally within handle_pending_statedump().
 736           */
 737         handle_pending_statedump(sock_info);
 738
 739         return ret;
 740 }
 741
 742 static
 743 void cleanup_sock_info(struct sock_info *sock_info, int exiting)
 744 {
 745         int ret;
 746
 747         if (sock_info->root_handle != -1) {
 748                 ret = lttng_ust_objd_unref(sock_info->root_handle, 1);
 749                 if (ret) {
 750                         ERR("Error unref root handle");
 751                 }
 752                 sock_info->root_handle = -1;
 753         }
 754         sock_info->constructor_sem_posted = 0;
 755
 756         /*
 757          * wait_shm_mmap, socket and notify socket are used by listener
 758          * threads outside of the ust lock, so we cannot tear them down
 759          * ourselves, because we cannot join on these threads. Leave
 760          * responsibility of cleaning up these resources to the OS
 761          * process exit.
 762          */
 763         if (exiting)
 764                 return;
 765
 766         if (sock_info->socket != -1) {
 767                 ret = ustcomm_close_unix_sock(sock_info->socket);
 768                 if (ret) {
 769                         ERR("Error closing ust cmd socket");
 770                 }
 771                 sock_info->socket = -1;
 772         }
 773         if (sock_info->notify_socket != -1) {
 774                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
 775                 if (ret) {
 776                         ERR("Error closing ust notify socket");
 777                 }
 778                 sock_info->notify_socket = -1;
 779         }
 780         if (sock_info->wait_shm_mmap) {
 781                 ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
 782                 if (ret) {
 783                         ERR("Error unmapping wait shm");
 784                 }
 785                 sock_info->wait_shm_mmap = NULL;
 786         }
 787 }
 788
 789 /*
 790  * Using fork to set umask in the child process (not multi-thread safe).
 791  * We deal with the shm_open vs ftruncate race (happening when the
 792  * sessiond owns the shm and does not let everybody modify it, to ensure
 793  * safety against shm_unlink) by simply letting the mmap fail and
 794  * retrying after a few seconds.
 795  * For global shm, everybody has rw access to it until the sessiond
 796  * starts.
 797  */
 798 static
 799 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 800 {
 801         int wait_shm_fd, ret;
 802         pid_t pid;
 803
 804         /*
 805          * Try to open read-only.
 806          */
 807         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 808         if (wait_shm_fd >= 0) {
 809                 int32_t tmp_read;
 810                 ssize_t len;
 811                 size_t bytes_read = 0;
 812
 813                 /*
 814                  * Try to read the fd. If unable to do so, try opening
 815                  * it in write mode.
 816                  */
 817                 do {
 818                         len = read(wait_shm_fd,
 819                                 &((char *) &tmp_read)[bytes_read],
 820                                 sizeof(tmp_read) - bytes_read);
 821                         if (len > 0) {
 822                                 bytes_read += len;
 823                         }
 824                 } while ((len < 0 && errno == EINTR)
 825                         || (len > 0 && bytes_read < sizeof(tmp_read)));
 826                 if (bytes_read != sizeof(tmp_read)) {
 827                         ret = close(wait_shm_fd);
 828                         if (ret) {
 829                                 ERR("close wait_shm_fd");
 830                         }
 831                         goto open_write;
 832                 }
 833                 goto end;
 834         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 835                 /*
 836                  * Real-only open did not work, and it's not because the
 837                  * entry was not present. It's a failure that prohibits
 838                  * using shm.
 839                  */
 840                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 841                 goto end;
 842         }
 843
 844 open_write:
 845         /*
 846          * If the open failed because the file did not exist, or because
 847          * the file was not truncated yet, try creating it ourself.
 848          */
 849         URCU_TLS(lttng_ust_nest_count)++;
 850         pid = fork();
 851         URCU_TLS(lttng_ust_nest_count)--;
 852         if (pid > 0) {
 853                 int status;
 854
 855                 /*
 856                  * Parent: wait for child to return, in which case the
 857                  * shared memory map will have been created.
 858                  */
 859                 pid = wait(&status);
 860                 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 861                         wait_shm_fd = -1;
 862                         goto end;
 863                 }
 864                 /*
 865                  * Try to open read-only again after creation.
 866                  */
 867                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 868                 if (wait_shm_fd < 0) {
 869                         /*
 870                          * Real-only open did not work. It's a failure
 871                          * that prohibits using shm.
 872                          */
 873                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 874                         goto end;
 875                 }
 876                 goto end;
 877         } else if (pid == 0) {
 878                 int create_mode;
 879
 880                 /* Child */
 881                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
 882                 if (sock_info->global)
 883                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
 884                 /*
 885                  * We're alone in a child process, so we can modify the
 886                  * process-wide umask.
 887                  */
 888                 umask(~create_mode);
 889                 /*
 890                  * Try creating shm (or get rw access).
 891                  * We don't do an exclusive open, because we allow other
 892                  * processes to create+ftruncate it concurrently.
 893                  */
 894                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 895                                 O_RDWR | O_CREAT, create_mode);
 896                 if (wait_shm_fd >= 0) {
 897                         ret = ftruncate(wait_shm_fd, mmap_size);
 898                         if (ret) {
 899                                 PERROR("ftruncate");
 900                                 _exit(EXIT_FAILURE);
 901                         }
 902                         _exit(EXIT_SUCCESS);
 903                 }
 904                 /*
 905                  * For local shm, we need to have rw access to accept
 906                  * opening it: this means the local sessiond will be
 907                  * able to wake us up. For global shm, we open it even
 908                  * if rw access is not granted, because the root.root
 909                  * sessiond will be able to override all rights and wake
 910                  * us up.
 911                  */
 912                 if (!sock_info->global && errno != EACCES) {
 913                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 914                         _exit(EXIT_FAILURE);
 915                 }
 916                 /*
 917                  * The shm exists, but we cannot open it RW. Report
 918                  * success.
 919                  */
 920                 _exit(EXIT_SUCCESS);
 921         } else {
 922                 return -1;
 923         }
 924 end:
 925         if (wait_shm_fd >= 0 && !sock_info->global) {
 926                 struct stat statbuf;
 927
 928                 /*
 929                  * Ensure that our user is the owner of the shm file for
 930                  * local shm. If we do not own the file, it means our
 931                  * sessiond will not have access to wake us up (there is
 932                  * probably a rogue process trying to fake our
 933                  * sessiond). Fallback to polling method in this case.
 934                  */
 935                 ret = fstat(wait_shm_fd, &statbuf);
 936                 if (ret) {
 937                         PERROR("fstat");
 938                         goto error_close;
 939                 }
 940                 if (statbuf.st_uid != getuid())
 941                         goto error_close;
 942         }
 943         return wait_shm_fd;
 944
 945 error_close:
 946         ret = close(wait_shm_fd);
 947         if (ret) {
 948                 PERROR("Error closing fd");
 949         }
 950         return -1;
 951 }
 952
 953 static
 954 char *get_map_shm(struct sock_info *sock_info)
 955 {
 956         size_t mmap_size = sysconf(_SC_PAGE_SIZE);
 957         int wait_shm_fd, ret;
 958         char *wait_shm_mmap;
 959
 960         wait_shm_fd = get_wait_shm(sock_info, mmap_size);
 961         if (wait_shm_fd < 0) {
 962                 goto error;
 963         }
 964         wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
 965                   MAP_SHARED, wait_shm_fd, 0);
 966         /* close shm fd immediately after taking the mmap reference */
 967         ret = close(wait_shm_fd);
 968         if (ret) {
 969                 PERROR("Error closing fd");
 970         }
 971         if (wait_shm_mmap == MAP_FAILED) {
 972                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
 973                 goto error;
 974         }
 975         return wait_shm_mmap;
 976
 977 error:
 978         return NULL;
 979 }
 980
 981 static
 982 void wait_for_sessiond(struct sock_info *sock_info)
 983 {
 984         int ret;
 985
 986         ust_lock();
 987         if (lttng_ust_comm_should_quit) {
 988                 goto quit;
 989         }
 990         if (wait_poll_fallback) {
 991                 goto error;
 992         }
 993         if (!sock_info->wait_shm_mmap) {
 994                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
 995                 if (!sock_info->wait_shm_mmap)
 996                         goto error;
 997         }
 998         ust_unlock();
 999
1000         DBG("Waiting for %s apps sessiond", sock_info->name);
1001         /* Wait for futex wakeup */
1002         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
1003                 ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
1004                         FUTEX_WAIT, 0, NULL, NULL, 0);
1005                 if (ret < 0) {
1006                         if (errno == EFAULT) {
1007                                 wait_poll_fallback = 1;
1008                                 DBG(
1009 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
1010 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
1011 "Please upgrade your kernel "
1012 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
1013 "mainline). LTTng-UST will use polling mode fallback.");
1014                                 if (ust_debug())
1015                                         PERROR("futex");
1016                         }
1017                 }
1018         }
1019         return;
1020
1021 quit:
1022         ust_unlock();
1023         return;
1024
1025 error:
1026         ust_unlock();
1027         return;
1028 }
1029
1030 /*
1031  * This thread does not allocate any resource, except within
1032  * handle_message, within mutex protection. This mutex protects against
1033  * fork and exit.
1034  * The other moment it allocates resources is at socket connection, which
1035  * is also protected by the mutex.
1036  */
1037 static
1038 void *ust_listener_thread(void *arg)
1039 {
1040         struct sock_info *sock_info = arg;
1041         int sock, ret, prev_connect_failed = 0, has_waited = 0;
1042         long timeout;
1043
1044         /* Restart trying to connect to the session daemon */
1045 restart:
1046         if (prev_connect_failed) {
1047                 /* Wait for sessiond availability with pipe */
1048                 wait_for_sessiond(sock_info);
1049                 if (has_waited) {
1050                         has_waited = 0;
1051                         /*
1052                          * Sleep for 5 seconds before retrying after a
1053                          * sequence of failure / wait / failure. This
1054                          * deals with a killed or broken session daemon.
1055                          */
1056                         sleep(5);
1057                 }
1058                 has_waited = 1;
1059                 prev_connect_failed = 0;
1060         }
1061
1062         if (sock_info->socket != -1) {
1063                 ret = ustcomm_close_unix_sock(sock_info->socket);
1064                 if (ret) {
1065                         ERR("Error closing %s ust cmd socket",
1066                                 sock_info->name);
1067                 }
1068                 sock_info->socket = -1;
1069         }
1070         if (sock_info->notify_socket != -1) {
1071                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
1072                 if (ret) {
1073                         ERR("Error closing %s ust notify socket",
1074                                 sock_info->name);
1075                 }
1076                 sock_info->notify_socket = -1;
1077         }
1078
1079         /*
1080          * Register. We need to perform both connect and sending
1081          * registration message before doing the next connect otherwise
1082          * we may reach unix socket connect queue max limits and block
1083          * on the 2nd connect while the session daemon is awaiting the
1084          * first connect registration message.
1085          */
1086         /* Connect cmd socket */
1087         ret = ustcomm_connect_unix_sock(sock_info->sock_path);
1088         if (ret < 0) {
1089                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1090                 prev_connect_failed = 1;
1091
1092                 ust_lock();
1093
1094                 if (lttng_ust_comm_should_quit) {
1095                         goto quit;
1096                 }
1097
1098                 /*
1099                  * If we cannot find the sessiond daemon, don't delay
1100                  * constructor execution.
1101                  */
1102                 ret = handle_register_done(sock_info);
1103                 assert(!ret);
1104                 ust_unlock();
1105                 goto restart;
1106         }
1107         sock_info->socket = ret;
1108
1109         ust_lock();
1110
1111         if (lttng_ust_comm_should_quit) {
1112                 goto quit;
1113         }
1114
1115         /*
1116          * Create only one root handle per listener thread for the whole
1117          * process lifetime, so we ensure we get ID which is statically
1118          * assigned to the root handle.
1119          */
1120         if (sock_info->root_handle == -1) {
1121                 ret = lttng_abi_create_root_handle();
1122                 if (ret < 0) {
1123                         ERR("Error creating root handle");
1124                         goto quit;
1125                 }
1126                 sock_info->root_handle = ret;
1127         }
1128
1129         ret = register_to_sessiond(sock_info->socket, USTCTL_SOCKET_CMD);
1130         if (ret < 0) {
1131                 ERR("Error registering to %s ust cmd socket",
1132                         sock_info->name);
1133                 prev_connect_failed = 1;
1134                 /*
1135                  * If we cannot register to the sessiond daemon, don't
1136                  * delay constructor execution.
1137                  */
1138                 ret = handle_register_done(sock_info);
1139                 assert(!ret);
1140                 ust_unlock();
1141                 goto restart;
1142         }
1143
1144         ust_unlock();
1145
1146         /* Connect notify socket */
1147         ret = ustcomm_connect_unix_sock(sock_info->sock_path);
1148         if (ret < 0) {
1149                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1150                 prev_connect_failed = 1;
1151
1152                 ust_lock();
1153
1154                 if (lttng_ust_comm_should_quit) {
1155                         goto quit;
1156                 }
1157
1158                 /*
1159                  * If we cannot find the sessiond daemon, don't delay
1160                  * constructor execution.
1161                  */
1162                 ret = handle_register_done(sock_info);
1163                 assert(!ret);
1164                 ust_unlock();
1165                 goto restart;
1166         }
1167         sock_info->notify_socket = ret;
1168
1169         timeout = get_notify_sock_timeout();
1170         if (timeout >= 0) {
1171                 /*
1172                  * Give at least 10ms to sessiond to reply to
1173                  * notifications.
1174                  */
1175                 if (timeout < 10)
1176                         timeout = 10;
1177                 ret = ustcomm_setsockopt_rcv_timeout(sock_info->notify_socket,
1178                                 timeout);
1179                 if (ret < 0) {
1180                         WARN("Error setting socket receive timeout");
1181                 }
1182                 ret = ustcomm_setsockopt_snd_timeout(sock_info->notify_socket,
1183                                 timeout);
1184                 if (ret < 0) {
1185                         WARN("Error setting socket send timeout");
1186                 }
1187         } else if (timeout < -1) {
1188                 WARN("Unsupported timeout value %ld", timeout);
1189         }
1190
1191         ust_lock();
1192
1193         if (lttng_ust_comm_should_quit) {
1194                 goto quit;
1195         }
1196
1197         ret = register_to_sessiond(sock_info->notify_socket,
1198                         USTCTL_SOCKET_NOTIFY);
1199         if (ret < 0) {
1200                 ERR("Error registering to %s ust notify socket",
1201                         sock_info->name);
1202                 prev_connect_failed = 1;
1203                 /*
1204                  * If we cannot register to the sessiond daemon, don't
1205                  * delay constructor execution.
1206                  */
1207                 ret = handle_register_done(sock_info);
1208                 assert(!ret);
1209                 ust_unlock();
1210                 goto restart;
1211         }
1212         sock = sock_info->socket;
1213
1214         ust_unlock();
1215
1216         for (;;) {
1217                 ssize_t len;
1218                 struct ustcomm_ust_msg lum;
1219
1220                 len = ustcomm_recv_unix_sock(sock, &lum, sizeof(lum));
1221                 switch (len) {
1222                 case 0: /* orderly shutdown */
1223                         DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
1224                         ust_lock();
1225                         if (lttng_ust_comm_should_quit) {
1226                                 goto quit;
1227                         }
1228                         /*
1229                          * Either sessiond has shutdown or refused us by closing the socket.
1230                          * In either case, we don't want to delay construction execution,
1231                          * and we need to wait before retry.
1232                          */
1233                         prev_connect_failed = 1;
1234                         /*
1235                          * If we cannot register to the sessiond daemon, don't
1236                          * delay constructor execution.
1237                          */
1238                         ret = handle_register_done(sock_info);
1239                         assert(!ret);
1240                         ust_unlock();
1241                         goto end;
1242                 case sizeof(lum):
1243                         print_cmd(lum.cmd, lum.handle);
1244                         ret = handle_message(sock_info, sock, &lum);
1245                         if (ret) {
1246                                 ERR("Error handling message for %s socket", sock_info->name);
1247                         }
1248                         continue;
1249                 default:
1250                         if (len < 0) {
1251                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
1252                         } else {
1253                                 DBG("incorrect message size (%s socket): %zd", sock_info->name, len);
1254                         }
1255                         if (len == -ECONNRESET) {
1256                                 DBG("%s remote end closed connection", sock_info->name);
1257                                 goto end;
1258                         }
1259                         goto end;
1260                 }
1261
1262         }
1263 end:
1264         ust_lock();
1265         if (lttng_ust_comm_should_quit) {
1266                 goto quit;
1267         }
1268         /* Cleanup socket handles before trying to reconnect */
1269         lttng_ust_objd_table_owner_cleanup(sock_info);
1270         ust_unlock();
1271         goto restart;   /* try to reconnect */
1272
1273 quit:
1274         sock_info->thread_active = 0;
1275         ust_unlock();
1276         return NULL;
1277 }
1278
1279 /*
1280  * sessiond monitoring thread: monitor presence of global and per-user
1281  * sessiond by polling the application common named pipe.
1282  */
1283 void __attribute__((constructor)) lttng_ust_init(void)
1284 {
1285         struct timespec constructor_timeout;
1286         sigset_t sig_all_blocked, orig_parent_mask;
1287         pthread_attr_t thread_attr;
1288         int timeout_mode;
1289         int ret;
1290
1291         if (uatomic_xchg(&initialized, 1) == 1)
1292                 return;
1293
1294         /*
1295          * Fixup interdependency between TLS fixup mutex (which happens
1296          * to be the dynamic linker mutex) and ust_lock, taken within
1297          * the ust lock.
1298          */
1299         lttng_fixup_ringbuffer_tls();
1300         lttng_fixup_vtid_tls();
1301         lttng_fixup_nest_count_tls();
1302         lttng_fixup_procname_tls();
1303
1304         /*
1305          * We want precise control over the order in which we construct
1306          * our sub-libraries vs starting to receive commands from
1307          * sessiond (otherwise leading to errors when trying to create
1308          * sessiond before the init functions are completed).
1309          */
1310         init_usterr();
1311         init_tracepoint();
1312         lttng_ring_buffer_metadata_client_init();
1313         lttng_ring_buffer_client_overwrite_init();
1314         lttng_ring_buffer_client_overwrite_rt_init();
1315         lttng_ring_buffer_client_discard_init();
1316         lttng_ring_buffer_client_discard_rt_init();
1317         lttng_context_init();
1318
1319         timeout_mode = get_constructor_timeout(&constructor_timeout);
1320
1321         ret = sem_init(&constructor_wait, 0, 0);
1322         assert(!ret);
1323
1324         ret = setup_local_apps();
1325         if (ret) {
1326                 DBG("local apps setup returned %d", ret);
1327         }
1328
1329         /* A new thread created by pthread_create inherits the signal mask
1330          * from the parent. To avoid any signal being received by the
1331          * listener thread, we block all signals temporarily in the parent,
1332          * while we create the listener thread.
1333          */
1334         sigfillset(&sig_all_blocked);
1335         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
1336         if (ret) {
1337                 ERR("pthread_sigmask: %s", strerror(ret));
1338         }
1339
1340         ret = pthread_attr_init(&thread_attr);
1341         if (ret) {
1342                 ERR("pthread_attr_init: %s", strerror(ret));
1343         }
1344         ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
1345         if (ret) {
1346                 ERR("pthread_attr_setdetachstate: %s", strerror(ret));
1347         }
1348
1349         ust_lock();
1350         ret = pthread_create(&global_apps.ust_listener, &thread_attr,
1351                         ust_listener_thread, &global_apps);
1352         if (ret) {
1353                 ERR("pthread_create global: %s", strerror(ret));
1354         }
1355         global_apps.thread_active = 1;
1356         ust_unlock();
1357
1358         if (local_apps.allowed) {
1359                 ust_lock();
1360                 ret = pthread_create(&local_apps.ust_listener, &thread_attr,
1361                                 ust_listener_thread, &local_apps);
1362                 if (ret) {
1363                         ERR("pthread_create local: %s", strerror(ret));
1364                 }
1365                 local_apps.thread_active = 1;
1366                 ust_unlock();
1367         } else {
1368                 handle_register_done(&local_apps);
1369         }
1370         ret = pthread_attr_destroy(&thread_attr);
1371         if (ret) {
1372                 ERR("pthread_attr_destroy: %s", strerror(ret));
1373         }
1374
1375         /* Restore original signal mask in parent */
1376         ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
1377         if (ret) {
1378                 ERR("pthread_sigmask: %s", strerror(ret));
1379         }
1380
1381         switch (timeout_mode) {
1382         case 1: /* timeout wait */
1383                 do {
1384                         ret = sem_timedwait(&constructor_wait,
1385                                         &constructor_timeout);
1386                 } while (ret < 0 && errno == EINTR);
1387                 if (ret < 0 && errno == ETIMEDOUT) {
1388                         ERR("Timed out waiting for lttng-sessiond");
1389                 } else {
1390                         assert(!ret);
1391                 }
1392                 break;
1393         case -1:/* wait forever */
1394                 do {
1395                         ret = sem_wait(&constructor_wait);
1396                 } while (ret < 0 && errno == EINTR);
1397                 assert(!ret);
1398                 break;
1399         case 0: /* no timeout */
1400                 break;
1401         }
1402 }
1403
1404 static
1405 void lttng_ust_cleanup(int exiting)
1406 {
1407         cleanup_sock_info(&global_apps, exiting);
1408         if (local_apps.allowed) {
1409                 cleanup_sock_info(&local_apps, exiting);
1410         }
1411         /*
1412          * The teardown in this function all affect data structures
1413          * accessed under the UST lock by the listener thread. This
1414          * lock, along with the lttng_ust_comm_should_quit flag, ensure
1415          * that none of these threads are accessing this data at this
1416          * point.
1417          */
1418         lttng_ust_abi_exit();
1419         lttng_ust_events_exit();
1420         lttng_context_exit();
1421         lttng_ring_buffer_client_discard_rt_exit();
1422         lttng_ring_buffer_client_discard_exit();
1423         lttng_ring_buffer_client_overwrite_rt_exit();
1424         lttng_ring_buffer_client_overwrite_exit();
1425         lttng_ring_buffer_metadata_client_exit();
1426         exit_tracepoint();
1427         if (!exiting) {
1428                 /* Reinitialize values for fork */
1429                 sem_count = 2;
1430                 lttng_ust_comm_should_quit = 0;
1431                 initialized = 0;
1432         }
1433 }
1434
1435 void __attribute__((destructor)) lttng_ust_exit(void)
1436 {
1437         int ret;
1438
1439         /*
1440          * Using pthread_cancel here because:
1441          * A) we don't want to hang application teardown.
1442          * B) the thread is not allocating any resource.
1443          */
1444
1445         /*
1446          * Require the communication thread to quit. Synchronize with
1447          * mutexes to ensure it is not in a mutex critical section when
1448          * pthread_cancel is later called.
1449          */
1450         ust_lock();
1451         lttng_ust_comm_should_quit = 1;
1452
1453         /* cancel threads */
1454         if (global_apps.thread_active) {
1455                 ret = pthread_cancel(global_apps.ust_listener);
1456                 if (ret) {
1457                         ERR("Error cancelling global ust listener thread: %s",
1458                                 strerror(ret));
1459                 } else {
1460                         global_apps.thread_active = 0;
1461                 }
1462         }
1463         if (local_apps.thread_active) {
1464                 ret = pthread_cancel(local_apps.ust_listener);
1465                 if (ret) {
1466                         ERR("Error cancelling local ust listener thread: %s",
1467                                 strerror(ret));
1468                 } else {
1469                         local_apps.thread_active = 0;
1470                 }
1471         }
1472         ust_unlock();
1473
1474         /*
1475          * Do NOT join threads: use of sys_futex makes it impossible to
1476          * join the threads without using async-cancel, but async-cancel
1477          * is delivered by a signal, which could hit the target thread
1478          * anywhere in its code path, including while the ust_lock() is
1479          * held, causing a deadlock for the other thread. Let the OS
1480          * cleanup the threads if there are stalled in a syscall.
1481          */
1482         lttng_ust_cleanup(1);
1483 }
1484
1485 /*
1486  * We exclude the worker threads across fork and clone (except
1487  * CLONE_VM), because these system calls only keep the forking thread
1488  * running in the child.  Therefore, we don't want to call fork or clone
1489  * in the middle of an tracepoint or ust tracing state modification.
1490  * Holding this mutex protects these structures across fork and clone.
1491  */
1492 void ust_before_fork(sigset_t *save_sigset)
1493 {
1494         /*
1495          * Disable signals. This is to avoid that the child intervenes
1496          * before it is properly setup for tracing. It is safer to
1497          * disable all signals, because then we know we are not breaking
1498          * anything by restoring the original mask.
1499          */
1500         sigset_t all_sigs;
1501         int ret;
1502
1503         if (URCU_TLS(lttng_ust_nest_count))
1504                 return;
1505         /* Disable signals */
1506         sigfillset(&all_sigs);
1507         ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
1508         if (ret == -1) {
1509                 PERROR("sigprocmask");
1510         }
1511         ust_lock();
1512         rcu_bp_before_fork();
1513 }
1514
1515 static void ust_after_fork_common(sigset_t *restore_sigset)
1516 {
1517         int ret;
1518
1519         DBG("process %d", getpid());
1520         ust_unlock();
1521         /* Restore signals */
1522         ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
1523         if (ret == -1) {
1524                 PERROR("sigprocmask");
1525         }
1526 }
1527
1528 void ust_after_fork_parent(sigset_t *restore_sigset)
1529 {
1530         if (URCU_TLS(lttng_ust_nest_count))
1531                 return;
1532         DBG("process %d", getpid());
1533         rcu_bp_after_fork_parent();
1534         /* Release mutexes and reenable signals */
1535         ust_after_fork_common(restore_sigset);
1536 }
1537
1538 /*
1539  * After fork, in the child, we need to cleanup all the leftover state,
1540  * except the worker thread which already magically disappeared thanks
1541  * to the weird Linux fork semantics. After tyding up, we call
1542  * lttng_ust_init() again to start over as a new PID.
1543  *
1544  * This is meant for forks() that have tracing in the child between the
1545  * fork and following exec call (if there is any).
1546  */
1547 void ust_after_fork_child(sigset_t *restore_sigset)
1548 {
1549         if (URCU_TLS(lttng_ust_nest_count))
1550                 return;
1551         DBG("process %d", getpid());
1552         /* Release urcu mutexes */
1553         rcu_bp_after_fork_child();
1554         lttng_ust_cleanup(0);
1555         lttng_context_vtid_reset();
1556         /* Release mutexes and reenable signals */
1557         ust_after_fork_common(restore_sigset);
1558         lttng_ust_init();
1559 }
1560
1561 void lttng_ust_sockinfo_session_enabled(void *owner)
1562 {
1563         struct sock_info *sock_info = owner;
1564         sock_info->statedump_pending = 1;
1565 }