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/*
* Copyright (c) 2008, 2009 Nicira Networks.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <config.h>
#include "signals.h"
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <unistd.h>
#include "poll-loop.h"
#include "socket-util.h"
#include "util.h"
#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 {
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;
if (pipe(fds)) {
ovs_fatal(errno, "could not create pipe");
}
set_nonblocking(fds[0]);
set_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();
/* 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;
if (sigaction(signr, &sa, NULL)) {
ovs_fatal(errno, "sigaction(%d) failed", signr);
}
/* Return structure. */
s = xmalloc(sizeof *s);
s->signr = signr;
return 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];
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) {
write(fds[1], "", 1);
signaled[signr] = true;
}
}
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