sessiond: use epoll()/poll() instead of select()
[lttng-tools.git] / src / bin / lttng-sessiond / thread-utils.c
1 /*
2 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
3 * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
4 * 2013 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License, version 2 only,
8 * as published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License along
16 * with this program; if not, write to the Free Software Foundation, Inc.,
17 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
18 */
19
20 #include "lttng-sessiond.h"
21 #include "utils.h"
22 #include <common/utils.h>
23 #include <pthread.h>
24
25 /*
26 * Quit pipe for all threads. This permits a single cancellation point
27 * for all threads when receiving an event on the pipe.
28 */
29 static int thread_quit_pipe[2] = { -1, -1 };
30
31 /*
32 * Init thread quit pipe.
33 *
34 * Return -1 on error or 0 if all pipes are created.
35 */
36 static int __init_thread_quit_pipe(int *a_pipe)
37 {
38 int ret, i;
39
40 ret = pipe(a_pipe);
41 if (ret < 0) {
42 PERROR("thread quit pipe");
43 goto error;
44 }
45
46 for (i = 0; i < 2; i++) {
47 ret = fcntl(a_pipe[i], F_SETFD, FD_CLOEXEC);
48 if (ret < 0) {
49 PERROR("fcntl");
50 goto error;
51 }
52 }
53
54 error:
55 return ret;
56 }
57
58 int sessiond_init_thread_quit_pipe(void)
59 {
60 return __init_thread_quit_pipe(thread_quit_pipe);
61 }
62
63 int sessiond_check_thread_quit_pipe(int fd, uint32_t events)
64 {
65 return (fd == thread_quit_pipe[0] && (events & LPOLLIN));
66 }
67
68 /*
69 * Wait for a notification on the quit pipe (with a timeout).
70 *
71 * A timeout value of -1U means no timeout.
72 *
73 * Returns 1 if the caller should quit, 0 if the timeout was reached, and
74 * -1 if an error was encountered.
75 */
76 int sessiond_wait_for_quit_pipe(int timeout_ms)
77 {
78 int ret;
79 struct lttng_poll_event events;
80
81 ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
82 if (ret < 0) {
83 PERROR("Failed to initialize poll/epoll set");
84 ret = -1;
85 goto end;
86 }
87 ret = lttng_poll_add(&events, thread_quit_pipe[0], LPOLLIN | LPOLLERR);
88 if (ret < 0) {
89 PERROR("Failed to add file descriptor to poll/epoll set");
90 ret = -1;
91 goto end_clean_poll;
92 }
93 ret = lttng_poll_wait(&events, timeout_ms);
94 if (ret > 0) {
95 /* Should quit. */
96 ret = 1;
97 } else if (ret < 0 && errno != EINTR) {
98 /* Unknown error. */
99 PERROR("Failed to epoll()/poll() thread quit pipe");
100 ret = -1;
101 } else {
102 /* Timeout reached. */
103 ret = 0;
104 }
105 end_clean_poll:
106 lttng_poll_clean(&events);
107 end:
108 return ret;
109 }
110
111 int sessiond_notify_quit_pipe(void)
112 {
113 return notify_thread_pipe(thread_quit_pipe[1]);
114 }
115
116 void sessiond_close_quit_pipe(void)
117 {
118 utils_close_pipe(thread_quit_pipe);
119 }
120
121 static
122 int __sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size,
123 int *a_pipe)
124 {
125 int ret;
126
127 assert(events);
128
129 ret = lttng_poll_create(events, size, LTTNG_CLOEXEC);
130 if (ret < 0) {
131 goto error;
132 }
133
134 /* Add quit pipe */
135 ret = lttng_poll_add(events, a_pipe[0], LPOLLIN | LPOLLERR);
136 if (ret < 0) {
137 goto error;
138 }
139
140 return 0;
141
142 error:
143 return ret;
144 }
145
146 /*
147 * Create a poll set with O_CLOEXEC and add the thread quit pipe to the set.
148 */
149 int sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size)
150 {
151 return __sessiond_set_thread_pollset(events, size, thread_quit_pipe);
152 }
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