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                 char name[16];  /* process name */
 128         } reg_msg;
 129
 130         reg_msg.major = LTTNG_UST_COMM_VERSION_MAJOR;
 131         reg_msg.minor = LTTNG_UST_COMM_VERSION_MINOR;
 132         reg_msg.pid = getpid();
 133         reg_msg.ppid = getppid();
 134         reg_msg.uid = getuid();
 135         prctl_ret = prctl(PR_GET_NAME, (unsigned long) reg_msg.name, 0, 0, 0);
 136         if (prctl_ret) {
 137                 ERR("Error executing prctl");
 138                 return -errno;
 139         }
 140
 141         ret = lttcomm_send_unix_sock(socket, &reg_msg, sizeof(reg_msg));
 142         if (ret >= 0 && ret != sizeof(reg_msg))
 143                 return -EIO;
 144         return ret;
 145 }
 146
 147 static
 148 int send_reply(int sock, struct lttcomm_ust_reply *lur)
 149 {
 150         ssize_t len;
 151
 152         len = lttcomm_send_unix_sock(sock, lur, sizeof(*lur));
 153         switch (len) {
 154         case sizeof(*lur):
 155                 DBG("message successfully sent");
 156                 return 0;
 157         case -1:
 158                 if (errno == ECONNRESET) {
 159                         printf("remote end closed connection\n");
 160                         return 0;
 161                 }
 162                 return -1;
 163         default:
 164                 printf("incorrect message size: %zd\n", len);
 165                 return -1;
 166         }
 167 }
 168
 169 static
 170 int handle_register_done(struct sock_info *sock_info)
 171 {
 172         int ret;
 173
 174         if (sock_info->constructor_sem_posted)
 175                 return 0;
 176         sock_info->constructor_sem_posted = 1;
 177         ret = uatomic_add_return(&sem_count, -1);
 178         if (ret == 0) {
 179                 ret = sem_post(&constructor_wait);
 180                 assert(!ret);
 181         }
 182         return 0;
 183 }
 184
 185 static
 186 int handle_message(struct sock_info *sock_info,
 187                 int sock, struct lttcomm_ust_msg *lum)
 188 {
 189         int ret = 0;
 190         const struct objd_ops *ops;
 191         struct lttcomm_ust_reply lur;
 192
 193         pthread_mutex_lock(&lttng_ust_comm_mutex);
 194
 195         memset(&lur, 0, sizeof(lur));
 196
 197         if (lttng_ust_comm_should_quit) {
 198                 ret = -EPERM;
 199                 goto end;
 200         }
 201
 202         ops = objd_ops(lum->handle);
 203         if (!ops) {
 204                 ret = -ENOENT;
 205                 goto end;
 206         }
 207
 208         switch (lum->cmd) {
 209         case LTTNG_UST_REGISTER_DONE:
 210                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 211                         ret = handle_register_done(sock_info);
 212                 else
 213                         ret = -EINVAL;
 214                 break;
 215         case LTTNG_UST_RELEASE:
 216                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 217                         ret = -EPERM;
 218                 else
 219                         ret = objd_unref(lum->handle);
 220                 break;
 221         default:
 222                 if (ops->cmd)
 223                         ret = ops->cmd(lum->handle, lum->cmd,
 224                                         (unsigned long) &lum->u);
 225                 else
 226                         ret = -ENOSYS;
 227                 break;
 228         }
 229
 230 end:
 231         lur.handle = lum->handle;
 232         lur.cmd = lum->cmd;
 233         lur.ret_val = ret;
 234         if (ret >= 0) {
 235                 lur.ret_code = LTTCOMM_OK;
 236         } else {
 237                 lur.ret_code = LTTCOMM_SESSION_FAIL;
 238         }
 239         ret = send_reply(sock, &lur);
 240
 241         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 242         return ret;
 243 }
 244
 245 static
 246 void cleanup_sock_info(struct sock_info *sock_info)
 247 {
 248         int ret;
 249
 250         if (sock_info->socket != -1) {
 251                 ret = close(sock_info->socket);
 252                 if (ret) {
 253                         ERR("Error closing local apps socket");
 254                 }
 255                 sock_info->socket = -1;
 256         }
 257         if (sock_info->root_handle != -1) {
 258                 ret = objd_unref(sock_info->root_handle);
 259                 if (ret) {
 260                         ERR("Error unref root handle");
 261                 }
 262                 sock_info->root_handle = -1;
 263         }
 264 }
 265
 266 /*
 267  * This thread does not allocate any resource, except within
 268  * handle_message, within mutex protection. This mutex protects against
 269  * fork and exit.
 270  * The other moment it allocates resources is at socket connexion, which
 271  * is also protected by the mutex.
 272  */
 273 static
 274 void *ust_listener_thread(void *arg)
 275 {
 276         struct sock_info *sock_info = arg;
 277         int sock, ret;
 278
 279         /* Restart trying to connect to the session daemon */
 280 restart:
 281         pthread_mutex_lock(&lttng_ust_comm_mutex);
 282
 283         if (lttng_ust_comm_should_quit) {
 284                 pthread_mutex_unlock(&lttng_ust_comm_mutex);
 285                 goto quit;
 286         }
 287
 288         if (sock_info->socket != -1) {
 289                 ret = close(sock_info->socket);
 290                 if (ret) {
 291                         ERR("Error closing %s apps socket", sock_info->name);
 292                 }
 293                 sock_info->socket = -1;
 294         }
 295
 296         /* Check for sessiond availability with pipe TODO */
 297
 298         /* Register */
 299         ret = lttcomm_connect_unix_sock(sock_info->sock_path);
 300         if (ret < 0) {
 301                 ERR("Error connecting to %s apps socket", sock_info->name);
 302                 /*
 303                  * If we cannot find the sessiond daemon, don't delay
 304                  * constructor execution.
 305                  */
 306                 ret = handle_register_done(sock_info);
 307                 assert(!ret);
 308                 pthread_mutex_unlock(&lttng_ust_comm_mutex);
 309                 sleep(5);
 310                 goto restart;
 311         }
 312
 313         sock_info->socket = sock = ret;
 314
 315         /*
 316          * Create only one root handle per listener thread for the whole
 317          * process lifetime.
 318          */
 319         if (sock_info->root_handle == -1) {
 320                 ret = lttng_abi_create_root_handle();
 321                 if (ret) {
 322                         ERR("Error creating root handle");
 323                         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 324                         goto quit;
 325                 }
 326                 sock_info->root_handle = ret;
 327         }
 328
 329         ret = register_app_to_sessiond(sock);
 330         if (ret < 0) {
 331                 ERR("Error registering to %s apps socket", sock_info->name);
 332                 /*
 333                  * If we cannot register to the sessiond daemon, don't
 334                  * delay constructor execution.
 335                  */
 336                 ret = handle_register_done(sock_info);
 337                 assert(!ret);
 338                 pthread_mutex_unlock(&lttng_ust_comm_mutex);
 339                 sleep(5);
 340                 goto restart;
 341         }
 342         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 343
 344         for (;;) {
 345                 ssize_t len;
 346                 struct lttcomm_ust_msg lum;
 347
 348                 len = lttcomm_recv_unix_sock(sock, &lum, sizeof(lum));
 349                 switch (len) {
 350                 case 0: /* orderly shutdown */
 351                         DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
 352                         goto end;
 353                 case sizeof(lum):
 354                         DBG("message received\n");
 355                         ret = handle_message(sock_info, sock, &lum);
 356                         if (ret < 0) {
 357                                 ERR("Error handling message for %s socket", sock_info->name);
 358                         }
 359                         continue;
 360                 case -1:
 361                         if (errno == ECONNRESET) {
 362                                 ERR("%s remote end closed connection\n", sock_info->name);
 363                                 goto end;
 364                         }
 365                         goto end;
 366                 default:
 367                         ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
 368                         continue;
 369                 }
 370
 371         }
 372 end:
 373         goto restart;   /* try to reconnect */
 374 quit:
 375         return NULL;
 376 }
 377
 378 /*
 379  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 380  */
 381 static
 382 int get_timeout(struct timespec *constructor_timeout)
 383 {
 384         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 385         char *str_delay;
 386         int ret;
 387
 388         str_delay = getenv("UST_REGISTER_TIMEOUT");
 389         if (str_delay) {
 390                 constructor_delay_ms = strtol(str_delay, NULL, 10);
 391         }
 392
 393         switch (constructor_delay_ms) {
 394         case -1:/* fall-through */
 395         case 0:
 396                 return constructor_delay_ms;
 397         default:
 398                 break;
 399         }
 400
 401         /*
 402          * If we are unable to find the current time, don't wait.
 403          */
 404         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 405         if (ret) {
 406                 return -1;
 407         }
 408         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 409         constructor_timeout->tv_nsec +=
 410                 (constructor_delay_ms % 1000UL) * 1000000UL;
 411         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 412                 constructor_timeout->tv_sec++;
 413                 constructor_timeout->tv_nsec -= 1000000000UL;
 414         }
 415         return 1;
 416 }
 417
 418 /*
 419  * sessiond monitoring thread: monitor presence of global and per-user
 420  * sessiond by polling the application common named pipe.
 421  */
 422 /* TODO */
 423
 424 void __attribute__((constructor)) lttng_ust_init(void)
 425 {
 426         struct timespec constructor_timeout;
 427         int timeout_mode;
 428         int ret;
 429
 430         if (uatomic_xchg(&initialized, 1) == 1)
 431                 return;
 432
 433         /*
 434          * We want precise control over the order in which we construct
 435          * our sub-libraries vs starting to receive commands from
 436          * sessiond (otherwise leading to errors when trying to create
 437          * sessiond before the init functions are completed).
 438          */
 439         init_usterr();
 440         init_tracepoint();
 441         ltt_ring_buffer_metadata_client_init();
 442         ltt_ring_buffer_client_overwrite_init();
 443         ltt_ring_buffer_client_discard_init();
 444
 445         timeout_mode = get_timeout(&constructor_timeout);
 446
 447         ret = sem_init(&constructor_wait, 0, 0);
 448         assert(!ret);
 449
 450         ret = setup_local_apps_socket();
 451         if (ret) {
 452                 ERR("Error setting up to local apps socket");
 453         }
 454
 455         ret = pthread_create(&global_apps.ust_listener, NULL,
 456                         ust_listener_thread, &global_apps);
 457         ret = pthread_create(&local_apps.ust_listener, NULL,
 458                         ust_listener_thread, &local_apps);
 459
 460         switch (timeout_mode) {
 461         case 1: /* timeout wait */
 462                 do {
 463                         ret = sem_timedwait(&constructor_wait,
 464                                         &constructor_timeout);
 465                 } while (ret < 0 && errno == EINTR);
 466                 if (ret < 0 && errno == ETIMEDOUT) {
 467                         ERR("Timed out waiting for ltt-sessiond");
 468                 } else {
 469                         assert(!ret);
 470                 }
 471                 break;
 472         case -1:/* wait forever */
 473                 do {
 474                         ret = sem_wait(&constructor_wait);
 475                 } while (ret < 0 && errno == EINTR);
 476                 assert(!ret);
 477                 break;
 478         case 0: /* no timeout */
 479                 break;
 480         }
 481 }
 482
 483 void __attribute__((destructor)) lttng_ust_exit(void)
 484 {
 485         int ret;
 486
 487         /*
 488          * Using pthread_cancel here because:
 489          * A) we don't want to hang application teardown.
 490          * B) the thread is not allocating any resource.
 491          */
 492
 493         /*
 494          * Require the communication thread to quit. Synchronize with
 495          * mutexes to ensure it is not in a mutex critical section when
 496          * pthread_cancel is later called.
 497          */
 498         pthread_mutex_lock(&lttng_ust_comm_mutex);
 499         lttng_ust_comm_should_quit = 1;
 500         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 501
 502 #if 0
 503         ret = pthread_cancel(global_apps.ust_listener);
 504         if (ret) {
 505                 ERR("Error cancelling global ust listener thread");
 506         }
 507 #endif //0
 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 }