libust/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 #include <sys/types.h>
  23 #include <sys/socket.h>
  24 #include <sys/prctl.h>
  25 #include <unistd.h>
  26 #include <errno.h>
  27 #include <pthread.h>
  28 #include <semaphore.h>
  29 #include <time.h>
  30 #include <assert.h>
  31 #include <urcu/uatomic.h>
  32
  33 #include <lttng-ust-comm.h>
  34 #include <ust/usterr-signal-safe.h>
  35 #include <ust/lttng-ust-abi.h>
  36 #include <ust/tracepoint.h>
  37
  38 /*
  39  * Has lttng ust comm constructor been called ?
  40  */
  41 static int initialized;
  42
  43 /*
  44  * communication thread mutex. Held when handling a command, also held
  45  * by fork() to deal with removal of threads, and by exit path.
  46  */
  47 static pthread_mutex_t lttng_ust_comm_mutex = PTHREAD_MUTEX_INITIALIZER;
  48
  49 /* Should the ust comm thread quit ? */
  50 static int lttng_ust_comm_should_quit;
  51
  52 /*
  53  * Wait for either of these before continuing to the main
  54  * program:
  55  * - the register_done message from sessiond daemon
  56  *   (will let the sessiond daemon enable sessions before main
  57  *   starts.)
  58  * - sessiond daemon is not reachable.
  59  * - timeout (ensuring applications are resilient to session
  60  *   daemon problems).
  61  */
  62 static sem_t constructor_wait;
  63 /*
  64  * Doing this for both the global and local sessiond.
  65  */
  66 static int sem_count = { 2 };
  67
  68 /*
  69  * Info about socket and associated listener thread.
  70  */
  71 struct sock_info {
  72         const char *name;
  73         char sock_path[PATH_MAX];
  74         int socket;
  75         pthread_t ust_listener; /* listener thread */
  76         int root_handle;
  77         int constructor_sem_posted;;
  78 };
  79
  80 /* Socket from app (connect) to session daemon (listen) for communication */
  81 struct sock_info global_apps = {
  82         .name = "global",
  83         .sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
  84         .socket = -1,
  85         .root_handle = -1,
  86 };
  87
  88 /* TODO: allow global_apps_sock_path override */
  89
  90 struct sock_info local_apps = {
  91         .name = "local",
  92         .socket = -1,
  93         .root_handle = -1,
  94 };
  95
  96 extern void ltt_ring_buffer_client_overwrite_init(void);
  97 extern void ltt_ring_buffer_client_discard_init(void);
  98 extern void ltt_ring_buffer_metadata_client_init(void);
  99 extern void ltt_ring_buffer_client_overwrite_exit(void);
 100 extern void ltt_ring_buffer_client_discard_exit(void);
 101 extern void ltt_ring_buffer_metadata_client_exit(void);
 102
 103 static
 104 int setup_local_apps_socket(void)
 105 {
 106         const char *home_dir;
 107
 108         home_dir = (const char *) getenv("HOME");
 109         if (!home_dir)
 110                 return -ENOENT;
 111         snprintf(local_apps.sock_path, PATH_MAX,
 112                  DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
 113         return 0;
 114 }
 115
 116 static
 117 int register_app_to_sessiond(int socket)
 118 {
 119         ssize_t ret;
 120         int prctl_ret;
 121         struct {
 122                 uint32_t major;
 123                 uint32_t minor;
 124                 pid_t pid;
 125                 pid_t ppid;
 126                 uid_t uid;
 127                 gid_t gid;
 128                 char name[16];  /* process name */
 129         } reg_msg;
 130
 131         reg_msg.major = LTTNG_UST_COMM_VERSION_MAJOR;
 132         reg_msg.minor = LTTNG_UST_COMM_VERSION_MINOR;
 133         reg_msg.pid = getpid();
 134         reg_msg.ppid = getppid();
 135         reg_msg.uid = getuid();
 136         reg_msg.gid = getgid();
 137         prctl_ret = prctl(PR_GET_NAME, (unsigned long) reg_msg.name, 0, 0, 0);
 138         if (prctl_ret) {
 139                 ERR("Error executing prctl");
 140                 return -errno;
 141         }
 142
 143         ret = lttcomm_send_unix_sock(socket, &reg_msg, sizeof(reg_msg));
 144         if (ret >= 0 && ret != sizeof(reg_msg))
 145                 return -EIO;
 146         return ret;
 147 }
 148
 149 static
 150 int send_reply(int sock, struct lttcomm_ust_reply *lur)
 151 {
 152         ssize_t len;
 153
 154         len = lttcomm_send_unix_sock(sock, lur, sizeof(*lur));
 155         switch (len) {
 156         case sizeof(*lur):
 157                 DBG("message successfully sent");
 158                 return 0;
 159         case -1:
 160                 if (errno == ECONNRESET) {
 161                         printf("remote end closed connection\n");
 162                         return 0;
 163                 }
 164                 return -1;
 165         default:
 166                 printf("incorrect message size: %zd\n", len);
 167                 return -1;
 168         }
 169 }
 170
 171 static
 172 int handle_register_done(struct sock_info *sock_info)
 173 {
 174         int ret;
 175
 176         if (sock_info->constructor_sem_posted)
 177                 return 0;
 178         sock_info->constructor_sem_posted = 1;
 179         ret = uatomic_add_return(&sem_count, -1);
 180         if (ret == 0) {
 181                 ret = sem_post(&constructor_wait);
 182                 assert(!ret);
 183         }
 184         return 0;
 185 }
 186
 187 static
 188 int handle_message(struct sock_info *sock_info,
 189                 int sock, struct lttcomm_ust_msg *lum)
 190 {
 191         int ret = 0;
 192         const struct objd_ops *ops;
 193         struct lttcomm_ust_reply lur;
 194
 195         pthread_mutex_lock(&lttng_ust_comm_mutex);
 196
 197         memset(&lur, 0, sizeof(lur));
 198
 199         if (lttng_ust_comm_should_quit) {
 200                 ret = -EPERM;
 201                 goto end;
 202         }
 203
 204         ops = objd_ops(lum->handle);
 205         if (!ops) {
 206                 ret = -ENOENT;
 207                 goto end;
 208         }
 209
 210         switch (lum->cmd) {
 211         case LTTNG_UST_REGISTER_DONE:
 212                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 213                         ret = handle_register_done(sock_info);
 214                 else
 215                         ret = -EINVAL;
 216                 break;
 217         case LTTNG_UST_RELEASE:
 218                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 219                         ret = -EPERM;
 220                 else
 221                         ret = objd_unref(lum->handle);
 222                 break;
 223         default:
 224                 if (ops->cmd)
 225                         ret = ops->cmd(lum->handle, lum->cmd,
 226                                         (unsigned long) &lum->u);
 227                 else
 228                         ret = -ENOSYS;
 229                 break;
 230         }
 231
 232 end:
 233         lur.handle = lum->handle;
 234         lur.cmd = lum->cmd;
 235         lur.ret_val = ret;
 236         if (ret >= 0) {
 237                 lur.ret_code = LTTCOMM_OK;
 238         } else {
 239                 lur.ret_code = LTTCOMM_SESSION_FAIL;
 240         }
 241         ret = send_reply(sock, &lur);
 242
 243         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 244         return ret;
 245 }
 246
 247 static
 248 void cleanup_sock_info(struct sock_info *sock_info)
 249 {
 250         int ret;
 251
 252         if (sock_info->socket != -1) {
 253                 ret = close(sock_info->socket);
 254                 if (ret) {
 255                         ERR("Error closing local apps socket");
 256                 }
 257                 sock_info->socket = -1;
 258         }
 259         if (sock_info->root_handle != -1) {
 260                 ret = objd_unref(sock_info->root_handle);
 261                 if (ret) {
 262                         ERR("Error unref root handle");
 263                 }
 264                 sock_info->root_handle = -1;
 265         }
 266 }
 267
 268 /*
 269  * This thread does not allocate any resource, except within
 270  * handle_message, within mutex protection. This mutex protects against
 271  * fork and exit.
 272  * The other moment it allocates resources is at socket connexion, which
 273  * is also protected by the mutex.
 274  */
 275 static
 276 void *ust_listener_thread(void *arg)
 277 {
 278         struct sock_info *sock_info = arg;
 279         int sock, ret;
 280
 281         /* Restart trying to connect to the session daemon */
 282 restart:
 283         pthread_mutex_lock(&lttng_ust_comm_mutex);
 284
 285         if (lttng_ust_comm_should_quit) {
 286                 pthread_mutex_unlock(&lttng_ust_comm_mutex);
 287                 goto quit;
 288         }
 289
 290         if (sock_info->socket != -1) {
 291                 ret = close(sock_info->socket);
 292                 if (ret) {
 293                         ERR("Error closing %s apps socket", sock_info->name);
 294                 }
 295                 sock_info->socket = -1;
 296         }
 297
 298         /* Check for sessiond availability with pipe TODO */
 299
 300         /* Register */
 301         ret = lttcomm_connect_unix_sock(sock_info->sock_path);
 302         if (ret < 0) {
 303                 ERR("Error connecting to %s apps socket", sock_info->name);
 304                 /*
 305                  * If we cannot find the sessiond daemon, don't delay
 306                  * constructor execution.
 307                  */
 308                 ret = handle_register_done(sock_info);
 309                 assert(!ret);
 310                 pthread_mutex_unlock(&lttng_ust_comm_mutex);
 311                 sleep(5);
 312                 goto restart;
 313         }
 314
 315         sock_info->socket = sock = ret;
 316
 317         /*
 318          * Create only one root handle per listener thread for the whole
 319          * process lifetime.
 320          */
 321         if (sock_info->root_handle == -1) {
 322                 ret = lttng_abi_create_root_handle();
 323                 if (ret) {
 324                         ERR("Error creating root handle");
 325                         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 326                         goto quit;
 327                 }
 328                 sock_info->root_handle = ret;
 329         }
 330
 331         ret = register_app_to_sessiond(sock);
 332         if (ret < 0) {
 333                 ERR("Error registering to %s apps socket", sock_info->name);
 334                 /*
 335                  * If we cannot register to the sessiond daemon, don't
 336                  * delay constructor execution.
 337                  */
 338                 ret = handle_register_done(sock_info);
 339                 assert(!ret);
 340                 pthread_mutex_unlock(&lttng_ust_comm_mutex);
 341                 sleep(5);
 342                 goto restart;
 343         }
 344         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 345
 346         for (;;) {
 347                 ssize_t len;
 348                 struct lttcomm_ust_msg lum;
 349
 350                 len = lttcomm_recv_unix_sock(sock, &lum, sizeof(lum));
 351                 switch (len) {
 352                 case 0: /* orderly shutdown */
 353                         DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
 354                         goto end;
 355                 case sizeof(lum):
 356                         DBG("message received\n");
 357                         ret = handle_message(sock_info, sock, &lum);
 358                         if (ret < 0) {
 359                                 ERR("Error handling message for %s socket", sock_info->name);
 360                         }
 361                         continue;
 362                 case -1:
 363                         if (errno == ECONNRESET) {
 364                                 ERR("%s remote end closed connection\n", sock_info->name);
 365                                 goto end;
 366                         }
 367                         goto end;
 368                 default:
 369                         ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
 370                         continue;
 371                 }
 372
 373         }
 374 end:
 375         goto restart;   /* try to reconnect */
 376 quit:
 377         return NULL;
 378 }
 379
 380 /*
 381  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 382  */
 383 static
 384 int get_timeout(struct timespec *constructor_timeout)
 385 {
 386         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 387         char *str_delay;
 388         int ret;
 389
 390         str_delay = getenv("UST_REGISTER_TIMEOUT");
 391         if (str_delay) {
 392                 constructor_delay_ms = strtol(str_delay, NULL, 10);
 393         }
 394
 395         switch (constructor_delay_ms) {
 396         case -1:/* fall-through */
 397         case 0:
 398                 return constructor_delay_ms;
 399         default:
 400                 break;
 401         }
 402
 403         /*
 404          * If we are unable to find the current time, don't wait.
 405          */
 406         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 407         if (ret) {
 408                 return -1;
 409         }
 410         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 411         constructor_timeout->tv_nsec +=
 412                 (constructor_delay_ms % 1000UL) * 1000000UL;
 413         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 414                 constructor_timeout->tv_sec++;
 415                 constructor_timeout->tv_nsec -= 1000000000UL;
 416         }
 417         return 1;
 418 }
 419
 420 /*
 421  * sessiond monitoring thread: monitor presence of global and per-user
 422  * sessiond by polling the application common named pipe.
 423  */
 424 /* TODO */
 425
 426 void __attribute__((constructor)) lttng_ust_init(void)
 427 {
 428         struct timespec constructor_timeout;
 429         int timeout_mode;
 430         int ret;
 431
 432         if (uatomic_xchg(&initialized, 1) == 1)
 433                 return;
 434
 435         /*
 436          * We want precise control over the order in which we construct
 437          * our sub-libraries vs starting to receive commands from
 438          * sessiond (otherwise leading to errors when trying to create
 439          * sessiond before the init functions are completed).
 440          */
 441         init_usterr();
 442         init_tracepoint();
 443         ltt_ring_buffer_metadata_client_init();
 444         ltt_ring_buffer_client_overwrite_init();
 445         ltt_ring_buffer_client_discard_init();
 446
 447         timeout_mode = get_timeout(&constructor_timeout);
 448
 449         ret = sem_init(&constructor_wait, 0, 0);
 450         assert(!ret);
 451
 452         ret = setup_local_apps_socket();
 453         if (ret) {
 454                 ERR("Error setting up to local apps socket");
 455         }
 456
 457         ret = pthread_create(&global_apps.ust_listener, NULL,
 458                         ust_listener_thread, &global_apps);
 459         ret = pthread_create(&local_apps.ust_listener, NULL,
 460                         ust_listener_thread, &local_apps);
 461
 462         switch (timeout_mode) {
 463         case 1: /* timeout wait */
 464                 do {
 465                         ret = sem_timedwait(&constructor_wait,
 466                                         &constructor_timeout);
 467                 } while (ret < 0 && errno == EINTR);
 468                 if (ret < 0 && errno == ETIMEDOUT) {
 469                         ERR("Timed out waiting for ltt-sessiond");
 470                 } else {
 471                         assert(!ret);
 472                 }
 473                 break;
 474         case -1:/* wait forever */
 475                 do {
 476                         ret = sem_wait(&constructor_wait);
 477                 } while (ret < 0 && errno == EINTR);
 478                 assert(!ret);
 479                 break;
 480         case 0: /* no timeout */
 481                 break;
 482         }
 483 }
 484
 485 void __attribute__((destructor)) lttng_ust_exit(void)
 486 {
 487         int ret;
 488
 489         /*
 490          * Using pthread_cancel here because:
 491          * A) we don't want to hang application teardown.
 492          * B) the thread is not allocating any resource.
 493          */
 494
 495         /*
 496          * Require the communication thread to quit. Synchronize with
 497          * mutexes to ensure it is not in a mutex critical section when
 498          * pthread_cancel is later called.
 499          */
 500         pthread_mutex_lock(&lttng_ust_comm_mutex);
 501         lttng_ust_comm_should_quit = 1;
 502         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 503
 504         ret = pthread_cancel(global_apps.ust_listener);
 505         if (ret) {
 506                 ERR("Error cancelling global ust listener thread");
 507         }
 508
 509         cleanup_sock_info(&global_apps);
 510
 511         ret = pthread_cancel(local_apps.ust_listener);
 512         if (ret) {
 513                 ERR("Error cancelling local ust listener thread");
 514         }
 515
 516         cleanup_sock_info(&local_apps);
 517
 518         lttng_ust_abi_exit();
 519         ltt_events_exit();
 520         ltt_ring_buffer_client_discard_exit();
 521         ltt_ring_buffer_client_overwrite_exit();
 522         ltt_ring_buffer_metadata_client_exit();
 523         exit_tracepoint();
 524 }