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
  13 #include <common/utils.hpp>
  14
  15 #include <pthread.h>
  16
  17 /*
  18  * Quit pipe for the main thread. This is used by signal handlers to start the
  19  * shutdown sequence of the main thread which will tear down the other threads
  20  * in the appropriate order.
  21  */
  22 static int main_quit_pipe[2] = { -1, -1 };
  23
  24 /*
  25  * Init main quit pipe.
  26  *
  27  * Return -1 on error or 0 if all pipes are created.
  28  */
  29 int sessiond_init_main_quit_pipe()
  30 {
  31         int ret, i;
  32
  33         ret = pipe(main_quit_pipe);
  34         if (ret < 0) {
  35                 PERROR("main quit pipe");
  36                 goto error;
  37         }
  38
  39         for (i = 0; i < 2; i++) {
  40                 ret = fcntl(main_quit_pipe[i], F_SETFD, FD_CLOEXEC);
  41                 if (ret < 0) {
  42                         PERROR("fcntl main_quit_pipe");
  43                         goto error;
  44                 }
  45         }
  46
  47 error:
  48         return ret;
  49 }
  50
  51 /*
  52  * Wait for a notification on the main quit pipe (with a timeout).
  53  *
  54  * A timeout value of -1U means no timeout.
  55  *
  56  * Returns 1 if the caller should quit, 0 if the timeout was reached, and
  57  * -1 if an error was encountered.
  58  */
  59 int sessiond_wait_for_main_quit_pipe(int timeout_ms)
  60 {
  61         int ret;
  62         struct lttng_poll_event events;
  63
  64         ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
  65         if (ret < 0) {
  66                 PERROR("Failed to initialize poll/epoll set");
  67                 ret = -1;
  68                 goto end;
  69         }
  70         ret = lttng_poll_add(&events, main_quit_pipe[0], LPOLLIN);
  71         if (ret < 0) {
  72                 PERROR("Failed to add file descriptor to poll/epoll set");
  73                 ret = -1;
  74                 goto end_clean_poll;
  75         }
  76         ret = lttng_poll_wait(&events, timeout_ms);
  77         if (ret > 0) {
  78                 /* Should quit. */
  79                 ret = 1;
  80         } else if (ret < 0 && errno != EINTR) {
  81                 /* Unknown error. */
  82                 PERROR("Failed to epoll()/poll() main quit pipe");
  83                 ret = -1;
  84         } else {
  85                 /* Timeout reached. */
  86                 ret = 0;
  87         }
  88 end_clean_poll:
  89         lttng_poll_clean(&events);
  90 end:
  91         return ret;
  92 }
  93
  94 int sessiond_notify_main_quit_pipe()
  95 {
  96         return notify_thread_pipe(main_quit_pipe[1]);
  97 }
  98
  99 void sessiond_close_main_quit_pipe()
 100 {
 101         utils_close_pipe(main_quit_pipe);
 102 }
 103
 104 /*
 105  * Create a poll set with O_CLOEXEC and add the main quit pipe to the set.
 106  */
 107 int sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size)
 108 {
 109         int ret;
 110
 111         LTTNG_ASSERT(events);
 112
 113         ret = lttng_poll_create(events, size, LTTNG_CLOEXEC);
 114         if (ret < 0) {
 115                 goto error;
 116         }
 117
 118         /* Add main quit pipe */
 119         ret = lttng_poll_add(events, main_quit_pipe[0], LPOLLIN);
 120         if (ret < 0) {
 121                 goto error;
 122         }
 123
 124         return 0;
 125
 126 error:
 127         return ret;
 128 }