src/bin/lttng-sessiond/ust-thread.c

   1 /*
   2  * Copyright (C) 2013 - David Goulet <dgoulet@efficios.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License, version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  11  * more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along with
  14  * this program; if not, write to the Free Software Foundation, Inc., 51
  15  * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17 #define _GNU_SOURCE
  18 #include <assert.h>
  19
  20 #include <common/common.h>
  21 #include <common/utils.h>
  22
  23 #include "fd-limit.h"
  24 #include "lttng-sessiond.h"
  25 #include "ust-thread.h"
  26
  27 /*
  28  * This thread manage application notify communication.
  29  */
  30 void *ust_thread_manage_notify(void *data)
  31 {
  32         int i, ret, pollfd;
  33         uint32_t revents, nb_fd;
  34         struct lttng_poll_event events;
  35
  36         DBG("[ust-thread] Manage application notify command");
  37
  38         rcu_register_thread();
  39         rcu_thread_online();
  40
  41         ret = sessiond_set_thread_pollset(&events, 2);
  42         if (ret < 0) {
  43                 goto error_poll_create;
  44         }
  45
  46         /* Add notify pipe to the pollset. */
  47         ret = lttng_poll_add(&events, apps_cmd_notify_pipe[0], LPOLLIN | LPOLLERR);
  48         if (ret < 0) {
  49                 goto error;
  50         }
  51
  52         while (1) {
  53                 DBG3("[ust-thread] Manage notify polling on %d fds",
  54                                 LTTNG_POLL_GETNB(&events));
  55
  56                 /* Inifinite blocking call, waiting for transmission */
  57 restart:
  58                 ret = lttng_poll_wait(&events, -1);
  59                 if (ret < 0) {
  60                         /*
  61                          * Restart interrupted system call.
  62                          */
  63                         if (errno == EINTR) {
  64                                 goto restart;
  65                         }
  66                         goto error;
  67                 }
  68
  69                 nb_fd = ret;
  70
  71                 for (i = 0; i < nb_fd; i++) {
  72                         /* Fetch once the poll data */
  73                         revents = LTTNG_POLL_GETEV(&events, i);
  74                         pollfd = LTTNG_POLL_GETFD(&events, i);
  75
  76                         /* Thread quit pipe has been closed. Killing thread. */
  77                         ret = sessiond_check_thread_quit_pipe(pollfd, revents);
  78                         if (ret) {
  79                                 goto exit;
  80                         }
  81
  82                         /* Inspect the apps cmd pipe */
  83                         if (pollfd == apps_cmd_notify_pipe[0]) {
  84                                 int sock;
  85
  86                                 if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
  87                                         ERR("Apps notify command pipe error");
  88                                         goto error;
  89                                 } else if (!(revents & LPOLLIN)) {
  90                                         /* No POLLIN and not a catched error, stop the thread. */
  91                                         ERR("Notify command pipe failed. revent: %u", revents);
  92                                         goto error;
  93                                 }
  94
  95                                 do {
  96                                         /* Get socket from dispatch thread. */
  97                                         ret = read(apps_cmd_notify_pipe[0], &sock, sizeof(sock));
  98                                 } while (ret < 0 && errno == EINTR);
  99                                 if (ret < 0 || ret < sizeof(sock)) {
 100                                         PERROR("read apps notify pipe");
 101                                         goto error;
 102                                 }
 103
 104                                 ret = lttng_poll_add(&events, sock,
 105                                                 LPOLLIN | LPOLLERR | LPOLLHUP | LPOLLRDHUP);
 106                                 if (ret < 0) {
 107                                         /*
 108                                          * It's possible we've reached the max poll fd allowed.
 109                                          * Let's close the socket but continue normal execution.
 110                                          */
 111                                         ret = close(sock);
 112                                         if (ret) {
 113                                                 PERROR("close notify socket %d", sock);
 114                                         }
 115                                         lttng_fd_put(LTTNG_FD_APPS, 1);
 116                                         continue;
 117                                 }
 118                                 DBG3("UST thread notify added sock %d to pollset", sock);
 119                         } else {
 120                                 /*
 121                                  * At this point, we know that a registered application
 122                                  * triggered the event.
 123                                  */
 124                                 if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
 125                                         /* Removing from the poll set */
 126                                         ret = lttng_poll_del(&events, pollfd);
 127                                         if (ret < 0) {
 128                                                 goto error;
 129                                         }
 130
 131                                         /* The socket is closed after a grace period here. */
 132                                         ust_app_notify_sock_unregister(pollfd);
 133                                 } else if (revents & (LPOLLIN | LPOLLPRI)) {
 134                                         ret = ust_app_recv_notify(pollfd);
 135                                         if (ret < 0) {
 136                                                 /*
 137                                                  * If the notification failed either the application is
 138                                                  * dead or an internal error happened. In both cases,
 139                                                  * we can only continue here. If the application is
 140                                                  * dead, an unregistration will follow or else the
 141                                                  * application will notice that we are not responding
 142                                                  * on that socket and will close it.
 143                                                  */
 144                                                 continue;
 145                                         }
 146                                 } else {
 147                                         ERR("Unknown poll events %u for sock %d", revents, pollfd);
 148                                         continue;
 149                                 }
 150                         }
 151                 }
 152         }
 153
 154 exit:
 155 error:
 156         lttng_poll_clean(&events);
 157 error_poll_create:
 158         utils_close_pipe(apps_cmd_notify_pipe);
 159         apps_cmd_notify_pipe[0] = apps_cmd_notify_pipe[1] = -1;
 160         DBG("Application notify communication apps thread cleanup complete");
 161         rcu_thread_offline();
 162         rcu_unregister_thread();
 163         return NULL;
 164 }