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 all threads. This permits a single cancellation point
  17  * for all threads when receiving an event on the pipe.
  18  */
  19 static int thread_quit_pipe[2] = { -1, -1 };
  20
  21 /*
  22  * Init thread quit pipe.
  23  *
  24  * Return -1 on error or 0 if all pipes are created.
  25  */
  26 static int __init_thread_quit_pipe(int *a_pipe)
  27 {
  28         int ret, i;
  29
  30         ret = pipe(a_pipe);
  31         if (ret < 0) {
  32                 PERROR("thread quit pipe");
  33                 goto error;
  34         }
  35
  36         for (i = 0; i < 2; i++) {
  37                 ret = fcntl(a_pipe[i], F_SETFD, FD_CLOEXEC);
  38                 if (ret < 0) {
  39                         PERROR("fcntl");
  40                         goto error;
  41                 }
  42         }
  43
  44 error:
  45         return ret;
  46 }
  47
  48 int sessiond_init_thread_quit_pipe(void)
  49 {
  50         return __init_thread_quit_pipe(thread_quit_pipe);
  51 }
  52
  53 int sessiond_check_thread_quit_pipe(int fd, uint32_t events)
  54 {
  55         return (fd == thread_quit_pipe[0] && (events & LPOLLIN));
  56 }
  57
  58 /*
  59  * Wait for a notification on the quit pipe (with a timeout).
  60  *
  61  * A timeout value of -1U means no timeout.
  62  *
  63  * Returns 1 if the caller should quit, 0 if the timeout was reached, and
  64  * -1 if an error was encountered.
  65  */
  66 int sessiond_wait_for_quit_pipe(int timeout_ms)
  67 {
  68         int ret;
  69         struct lttng_poll_event events;
  70
  71         ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
  72         if (ret < 0) {
  73                 PERROR("Failed to initialize poll/epoll set");
  74                 ret = -1;
  75                 goto end;
  76         }
  77         ret = lttng_poll_add(&events, thread_quit_pipe[0], LPOLLIN | LPOLLERR);
  78         if (ret < 0) {
  79                 PERROR("Failed to add file descriptor to poll/epoll set");
  80                 ret = -1;
  81                 goto end_clean_poll;
  82         }
  83         ret = lttng_poll_wait(&events, timeout_ms);
  84         if (ret > 0) {
  85                 /* Should quit. */
  86                 ret = 1;
  87         } else if (ret < 0 && errno != EINTR) {
  88                 /* Unknown error. */
  89                 PERROR("Failed to epoll()/poll() thread quit pipe");
  90                 ret = -1;
  91         } else {
  92                 /* Timeout reached. */
  93                 ret = 0;
  94         }
  95 end_clean_poll:
  96         lttng_poll_clean(&events);
  97 end:
  98         return ret;
  99 }
 100
 101 int sessiond_notify_quit_pipe(void)
 102 {
 103         return notify_thread_pipe(thread_quit_pipe[1]);
 104 }
 105
 106 void sessiond_close_quit_pipe(void)
 107 {
 108         utils_close_pipe(thread_quit_pipe);
 109 }
 110
 111 static
 112 int __sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size,
 113                 int *a_pipe)
 114 {
 115         int ret;
 116
 117         LTTNG_ASSERT(events);
 118
 119         ret = lttng_poll_create(events, size, LTTNG_CLOEXEC);
 120         if (ret < 0) {
 121                 goto error;
 122         }
 123
 124         /* Add quit pipe */
 125         ret = lttng_poll_add(events, a_pipe[0], LPOLLIN | LPOLLERR);
 126         if (ret < 0) {
 127                 goto error;
 128         }
 129
 130         return 0;
 131
 132 error:
 133         return ret;
 134 }
 135
 136 /*
 137  * Create a poll set with O_CLOEXEC and add the thread quit pipe to the set.
 138  */
 139 int sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size)
 140 {
 141         return __sessiond_set_thread_pollset(events, size, thread_quit_pipe);
 142 }