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/*
* Copyright (c) 2008, 2009, 2011, 2012 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "signals.h"
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include "poll-loop.h"
#include "socket-util.h"
#include "type-props.h"
#include "util.h"
#include "vlog.h"
VLOG_DEFINE_THIS_MODULE(signals);
#if defined(_NSIG)
#define N_SIGNALS _NSIG
#elif defined(NSIG)
#define N_SIGNALS NSIG
#else
/* We could try harder to get the maximum signal number, but in practice we
* only care about SIGHUP, which is normally signal 1 anyway. */
#define N_SIGNALS 32
#endif
struct signal {
struct sigaction saved_sa;
int signr;
};
static volatile sig_atomic_t signaled[N_SIGNALS];
static int fds[2];
static void signal_handler(int signr);
/* Initializes the signals subsystem (if it is not already initialized). Calls
* exit() if initialization fails.
*
* Calling this function is optional; it will be called automatically by
* signal_start() if necessary. Calling it explicitly allows the client to
* prevent the process from exiting at an unexpected time. */
void
signal_init(void)
{
static bool inited;
if (!inited) {
inited = true;
xpipe(fds);
xset_nonblocking(fds[0]);
xset_nonblocking(fds[1]);
}
}
/* Sets up a handler for 'signr' and returns a structure that represents it.
*
* Only one handler for a given signal may be registered at a time. */
struct signal *
signal_register(int signr)
{
struct sigaction sa;
struct signal *s;
signal_init();
s = xmalloc(sizeof *s);
s->signr = signr;
/* Set up signal handler. */
assert(signr >= 1 && signr < N_SIGNALS);
memset(&sa, 0, sizeof sa);
sa.sa_handler = signal_handler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
xsigaction(signr, &sa, &s->saved_sa);
return s;
}
/* Unregisters the handler for 's', restores the signal handler that was in
* effect before signal_register() was called, and frees 's'. */
void
signal_unregister(struct signal *s)
{
if (s) {
xsigaction(s->signr, &s->saved_sa, NULL);
free(s);
}
}
/* Returns true if signal 's' has been received since the last call to this
* function with argument 's'. */
bool
signal_poll(struct signal *s)
{
char buf[_POSIX_PIPE_BUF];
ignore(read(fds[0], buf, sizeof buf));
if (signaled[s->signr]) {
signaled[s->signr] = 0;
return true;
}
return false;
}
/* Causes the next call to poll_block() to wake up when signal_poll(s) would
* return true. */
void
signal_wait(struct signal *s)
{
if (signaled[s->signr]) {
poll_immediate_wake();
} else {
poll_fd_wait(fds[0], POLLIN);
}
}
static void
signal_handler(int signr)
{
if (signr >= 1 && signr < N_SIGNALS) {
ignore(write(fds[1], "", 1));
signaled[signr] = true;
}
}
/* Returns the name of signal 'signum' as a string. The string may be in a
* static buffer that is reused from one call to the next.
*
* The string is probably a (possibly multi-word) description of the signal
* (e.g. "Hangup") instead of just the stringified version of the macro
* (e.g. "SIGHUP"). */
const char *
signal_name(int signum)
{
const char *name = NULL;
#ifdef HAVE_STRSIGNAL
name = strsignal(signum);
#endif
if (!name) {
static char buffer[7 + INT_STRLEN(int) + 1];
sprintf(buffer, "signal %d", signum);
name = buffer;
}
return name;
}
void
xsigaction(int signum, const struct sigaction *new, struct sigaction *old)
{
if (sigaction(signum, new, old)) {
VLOG_FATAL("sigaction(%s) failed (%s)",
signal_name(signum), strerror(errno));
}
}
void
xsigprocmask(int how, const sigset_t *new, sigset_t *old)
{
if (sigprocmask(how, new, old)) {
VLOG_FATAL("sigprocmask failed (%s)", strerror(errno));
}
}
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