src/bin/lttng-sessiond/thread-utils.cpp

   1 /*
   2  * Copyright (C) 2011 EfficiOS Inc.
   3  * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  * Copyright (C) 2013 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   5  *
   6  * SPDX-License-Identifier: GPL-2.0-only
   7  *
   8  */
   9
  10 #include "lttng-sessiond.hpp"
  11 #include "utils.hpp"
  12 #include <common/utils.hpp>
  13 #include <pthread.h>
  14
  15 /*
  16  * Quit pipe for the main thread. This is used by signal handlers to start the
  17  * shutdown sequence of the main thread which will tear down the other threads
  18  * in the appropriate order.
  19  */
  20 static int main_quit_pipe[2] = { -1, -1 };
  21
  22 /*
  23  * Init main quit pipe.
  24  *
  25  * Return -1 on error or 0 if all pipes are created.
  26  */
  27 int sessiond_init_main_quit_pipe(void)
  28 {
  29         int ret, i;
  30
  31         ret = pipe(main_quit_pipe);
  32         if (ret < 0) {
  33                 PERROR("main quit pipe");
  34                 goto error;
  35         }
  36
  37         for (i = 0; i < 2; i++) {
  38                 ret = fcntl(main_quit_pipe[i], F_SETFD, FD_CLOEXEC);
  39                 if (ret < 0) {
  40                         PERROR("fcntl main_quit_pipe");
  41                         goto error;
  42                 }
  43         }
  44
  45 error:
  46         return ret;
  47 }
  48
  49 /*
  50  * Wait for a notification on the main quit pipe (with a timeout).
  51  *
  52  * A timeout value of -1U means no timeout.
  53  *
  54  * Returns 1 if the caller should quit, 0 if the timeout was reached, and
  55  * -1 if an error was encountered.
  56  */
  57 int sessiond_wait_for_main_quit_pipe(int timeout_ms)
  58 {
  59         int ret;
  60         struct lttng_poll_event events;
  61
  62         ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
  63         if (ret < 0) {
  64                 PERROR("Failed to initialize poll/epoll set");
  65                 ret = -1;
  66                 goto end;
  67         }
  68         ret = lttng_poll_add(&events, main_quit_pipe[0], LPOLLIN | LPOLLERR);
  69         if (ret < 0) {
  70                 PERROR("Failed to add file descriptor to poll/epoll set");
  71                 ret = -1;
  72                 goto end_clean_poll;
  73         }
  74         ret = lttng_poll_wait(&events, timeout_ms);
  75         if (ret > 0) {
  76                 /* Should quit. */
  77                 ret = 1;
  78         } else if (ret < 0 && errno != EINTR) {
  79                 /* Unknown error. */
  80                 PERROR("Failed to epoll()/poll() main quit pipe");
  81                 ret = -1;
  82         } else {
  83                 /* Timeout reached. */
  84                 ret = 0;
  85         }
  86 end_clean_poll:
  87         lttng_poll_clean(&events);
  88 end:
  89         return ret;
  90 }
  91
  92 int sessiond_notify_main_quit_pipe(void)
  93 {
  94         return notify_thread_pipe(main_quit_pipe[1]);
  95 }
  96
  97 void sessiond_close_main_quit_pipe(void)
  98 {
  99         utils_close_pipe(main_quit_pipe);
 100 }
 101
 102 /*
 103  * Create a poll set with O_CLOEXEC and add the main quit pipe to the set.
 104  */
 105 int sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size)
 106 {
 107         int ret;
 108
 109         LTTNG_ASSERT(events);
 110
 111         ret = lttng_poll_create(events, size, LTTNG_CLOEXEC);
 112         if (ret < 0) {
 113                 goto error;
 114         }
 115
 116         /* Add main quit pipe */
 117         ret = lttng_poll_add(events, main_quit_pipe[0], LPOLLIN | LPOLLERR);
 118         if (ret < 0) {
 119                 goto error;
 120         }
 121
 122         return 0;
 123
 124 error:
 125         return ret;
 126 }