2 * Copyright (c) 2008, 2009, 2011, 2012 Nicira, Inc.
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.
25 #include "poll-loop.h"
26 #include "socket-util.h"
27 #include "type-props.h"
31 VLOG_DEFINE_THIS_MODULE(signals);
34 #define N_SIGNALS _NSIG
36 #define N_SIGNALS NSIG
38 /* We could try harder to get the maximum signal number, but in practice we
39 * only care about SIGHUP, which is normally signal 1 anyway. */
44 struct sigaction saved_sa;
48 static volatile sig_atomic_t signaled[N_SIGNALS];
52 static void signal_handler(int signr);
54 /* Initializes the signals subsystem (if it is not already initialized). Calls
55 * exit() if initialization fails.
57 * Calling this function is optional; it will be called automatically by
58 * signal_start() if necessary. Calling it explicitly allows the client to
59 * prevent the process from exiting at an unexpected time. */
67 xset_nonblocking(fds[0]);
68 xset_nonblocking(fds[1]);
72 /* Sets up a handler for 'signr' and returns a structure that represents it.
74 * Only one handler for a given signal may be registered at a time. */
76 signal_register(int signr)
83 s = xmalloc(sizeof *s);
86 /* Set up signal handler. */
87 assert(signr >= 1 && signr < N_SIGNALS);
88 memset(&sa, 0, sizeof sa);
89 sa.sa_handler = signal_handler;
90 sigemptyset(&sa.sa_mask);
91 sa.sa_flags = SA_RESTART;
92 xsigaction(signr, &sa, &s->saved_sa);
97 /* Unregisters the handler for 's', restores the signal handler that was in
98 * effect before signal_register() was called, and frees 's'. */
100 signal_unregister(struct signal *s)
103 xsigaction(s->signr, &s->saved_sa, NULL);
108 /* Returns true if signal 's' has been received since the last call to this
109 * function with argument 's'. */
111 signal_poll(struct signal *s)
113 char buf[_POSIX_PIPE_BUF];
114 ignore(read(fds[0], buf, sizeof buf));
115 if (signaled[s->signr]) {
116 signaled[s->signr] = 0;
122 /* Causes the next call to poll_block() to wake up when signal_poll(s) would
125 signal_wait(struct signal *s)
127 if (signaled[s->signr]) {
128 poll_immediate_wake();
130 poll_fd_wait(fds[0], POLLIN);
135 signal_handler(int signr)
137 if (signr >= 1 && signr < N_SIGNALS) {
138 ignore(write(fds[1], "", 1));
139 signaled[signr] = true;
143 /* Returns the name of signal 'signum' as a string. The string may be in a
144 * static buffer that is reused from one call to the next.
146 * The string is probably a (possibly multi-word) description of the signal
147 * (e.g. "Hangup") instead of just the stringified version of the macro
148 * (e.g. "SIGHUP"). */
150 signal_name(int signum)
152 const char *name = NULL;
153 #ifdef HAVE_STRSIGNAL
154 name = strsignal(signum);
157 static char buffer[7 + INT_STRLEN(int) + 1];
158 sprintf(buffer, "signal %d", signum);
165 xsigaction(int signum, const struct sigaction *new, struct sigaction *old)
167 if (sigaction(signum, new, old)) {
168 VLOG_FATAL("sigaction(%s) failed (%s)",
169 signal_name(signum), strerror(errno));
174 xsigprocmask(int how, const sigset_t *new, sigset_t *old)
176 if (sigprocmask(how, new, old)) {
177 VLOG_FATAL("sigprocmask failed (%s)", strerror(errno));