549cd69f867e23998220f01e5e80174520b83014
[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 #define USEC_PER_SEC 1000000
26
27 /*
28 * Quit pipe for all threads. This permits a single cancellation point
29 * for all threads when receiving an event on the pipe.
30 */
31 static int thread_quit_pipe[2] = { -1, -1 };
32
33 /*
34 * Init thread quit pipe.
35 *
36 * Return -1 on error or 0 if all pipes are created.
37 */
38 static int __init_thread_quit_pipe(int *a_pipe)
39 {
40 int ret, i;
41
42 ret = pipe(a_pipe);
43 if (ret < 0) {
44 PERROR("thread quit pipe");
45 goto error;
46 }
47
48 for (i = 0; i < 2; i++) {
49 ret = fcntl(a_pipe[i], F_SETFD, FD_CLOEXEC);
50 if (ret < 0) {
51 PERROR("fcntl");
52 goto error;
53 }
54 }
55
56 error:
57 return ret;
58 }
59
60 int sessiond_init_thread_quit_pipe(void)
61 {
62 return __init_thread_quit_pipe(thread_quit_pipe);
63 }
64
65 int sessiond_check_thread_quit_pipe(int fd, uint32_t events)
66 {
67 return (fd == thread_quit_pipe[0] && (events & LPOLLIN));
68 }
69
70 /*
71 * Wait for a notification on the quit pipe (with a timeout).
72 *
73 * A timeout value of -1U means no timeout.
74 *
75 * Returns 1 if the caller should quit, 0 if the timeout was reached, and
76 * -1 if an error was encountered.
77 */
78 int sessiond_wait_for_quit_pipe(unsigned int timeout_us)
79 {
80 int ret;
81 fd_set read_fds;
82 struct timeval timeout;
83
84 FD_ZERO(&read_fds);
85 FD_SET(thread_quit_pipe[0], &read_fds);
86 memset(&timeout, 0, sizeof(timeout));
87 timeout.tv_sec = timeout_us / USEC_PER_SEC;
88 timeout.tv_usec = timeout_us % USEC_PER_SEC;
89
90 while (true) {
91 ret = select(thread_quit_pipe[0] + 1, &read_fds, NULL, NULL,
92 timeout_us != -1U ? &timeout : NULL);
93 if (ret < 0 && errno == EINTR) {
94 /* Retry on interrupt. */
95 continue;
96 } else {
97 break;
98 }
99 }
100
101 if (ret > 0) {
102 /* Should quit. */
103 ret = 1;
104 } else if (ret < 0 && errno != EINTR) {
105 /* Unknown error. */
106 PERROR("Failed to select() thread quit pipe");
107 ret = -1;
108 } else {
109 /* Timeout reached. */
110 ret = 0;
111 }
112
113 return ret;
114 }
115
116 int sessiond_notify_quit_pipe(void)
117 {
118 return notify_thread_pipe(thread_quit_pipe[1]);
119 }
120
121 void sessiond_close_quit_pipe(void)
122 {
123 utils_close_pipe(thread_quit_pipe);
124 }
125
126 static
127 int __sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size,
128 int *a_pipe)
129 {
130 int ret;
131
132 assert(events);
133
134 ret = lttng_poll_create(events, size, LTTNG_CLOEXEC);
135 if (ret < 0) {
136 goto error;
137 }
138
139 /* Add quit pipe */
140 ret = lttng_poll_add(events, a_pipe[0], LPOLLIN | LPOLLERR);
141 if (ret < 0) {
142 goto error;
143 }
144
145 return 0;
146
147 error:
148 return ret;
149 }
150
151 /*
152 * Create a poll set with O_CLOEXEC and add the thread quit pipe to the set.
153 */
154 int sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size)
155 {
156 return __sessiond_set_thread_pollset(events, size, thread_quit_pipe);
157 }
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