2 * Copyright (c) 2008, 2009, 2011 Nicira Networks.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
24 #include "poll-loop.h"
25 #include "socket-util.h"
26 #include "type-props.h"
30 VLOG_DEFINE_THIS_MODULE(signals);
33 #define N_SIGNALS _NSIG
35 #define N_SIGNALS NSIG
37 /* We could try harder to get the maximum signal number, but in practice we
38 * only care about SIGHUP, which is normally signal 1 anyway. */
46 static volatile sig_atomic_t signaled[N_SIGNALS];
50 static void signal_handler(int signr);
52 /* Initializes the signals subsystem (if it is not already initialized). Calls
53 * exit() if initialization fails.
55 * Calling this function is optional; it will be called automatically by
56 * signal_start() if necessary. Calling it explicitly allows the client to
57 * prevent the process from exiting at an unexpected time. */
65 set_nonblocking(fds[0]);
66 set_nonblocking(fds[1]);
70 /* Sets up a handler for 'signr' and returns a structure that represents it.
72 * Only one handler for a given signal may be registered at a time. */
74 signal_register(int signr)
81 /* Set up signal handler. */
82 assert(signr >= 1 && signr < N_SIGNALS);
83 memset(&sa, 0, sizeof sa);
84 sa.sa_handler = signal_handler;
85 sigemptyset(&sa.sa_mask);
86 sa.sa_flags = SA_RESTART;
87 xsigaction(signr, &sa, NULL);
89 /* Return structure. */
90 s = xmalloc(sizeof *s);
95 /* Returns true if signal 's' has been received since the last call to this
96 * function with argument 's'. */
98 signal_poll(struct signal *s)
100 char buf[_POSIX_PIPE_BUF];
101 ignore(read(fds[0], buf, sizeof buf));
102 if (signaled[s->signr]) {
103 signaled[s->signr] = 0;
109 /* Causes the next call to poll_block() to wake up when signal_poll(s) would
112 signal_wait(struct signal *s)
114 if (signaled[s->signr]) {
115 poll_immediate_wake();
117 poll_fd_wait(fds[0], POLLIN);
122 signal_handler(int signr)
124 if (signr >= 1 && signr < N_SIGNALS) {
125 ignore(write(fds[1], "", 1));
126 signaled[signr] = true;
130 /* Returns the name of signal 'signum' as a string. The string may be in a
131 * static buffer that is reused from one call to the next.
133 * The string is probably a (possibly multi-word) description of the signal
134 * (e.g. "Hangup") instead of just the stringified version of the macro
135 * (e.g. "SIGHUP"). */
137 signal_name(int signum)
139 const char *name = NULL;
140 #ifdef HAVE_STRSIGNAL
141 name = strsignal(signum);
144 static char buffer[7 + INT_STRLEN(int) + 1];
145 sprintf(buffer, "signal %d", signum);
152 xsigaction(int signum, const struct sigaction *new, struct sigaction *old)
154 if (sigaction(signum, new, old)) {
155 VLOG_FATAL("sigaction(%s) failed (%s)",
156 signal_name(signum), strerror(errno));
161 xsigprocmask(int how, const sigset_t *new, sigset_t *old)
163 if (sigprocmask(how, new, old)) {
164 VLOG_FATAL("sigprocmask failed (%s)", strerror(errno));