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/* $OpenBSD: sigsuspend.c,v 1.2 2010/06/20 17:57:09 phessler Exp $ */
/*
* Written by Artur Grabowski <art@openbsd.org> 2005, Public domain.
*/
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <err.h>
#include <sys/types.h>
#include <sys/wait.h>
sig_atomic_t gotusr1;
sig_atomic_t gotusr2;
void
usr1handler(int signo)
{
gotusr1 = 1;
}
void
usr2handler(int signo)
{
gotusr2 = 1;
}
int
main()
{
sigset_t set, oset;
struct sigaction sa;
pid_t pid, ppid;
int status;
ppid = getpid();
memset(&sa, 0, sizeof(sa));
sigemptyset(&sa.sa_mask);
sa.sa_handler = usr1handler;
if (sigaction(SIGUSR1, &sa, NULL))
err(1, "sigaction(USR1)");
sa.sa_handler = usr2handler;
if (sigaction(SIGUSR2, &sa, NULL))
err(1, "sigaction(USR2)");
/*
* Set the procmask to mask the early USR1 the child will send us.
*/
sigemptyset(&set);
sigaddset(&set, SIGUSR1);
sigaddset(&set, SIGUSR2);
if (sigprocmask(SIG_BLOCK, &set, &oset))
err(1, "sigprocmask");
switch((pid = fork())) {
case 0:
/*
* In the child.
*/
kill(ppid, SIGUSR1); /* Tell the parent we're ready. */
sigemptyset(&set);
sigaddset(&set, SIGUSR2);
sigsuspend(&set);
/*
* Check that sigsuspend didn't change the signal mask.
*/
if (sigprocmask(SIG_SETMASK, NULL, &oset))
err(1, "sigprocmask");
if (!sigismember(&oset, SIGUSR1) ||
!sigismember(&oset, SIGUSR2))
errx(1, "sigprocmask is bad");
/* Check that we got the sigusr1 that we expected. */
if (!gotusr1)
errx(1, "didn't get usr1");
if (gotusr2)
errx(1, "got incorrect usr2");
sigemptyset(&set);
sigaddset(&set, SIGUSR1);
sigsuspend(&set);
if (!gotusr2)
errx(1, "didn't get usr2");
_exit(0);
case -1:
err(1, "fork");
default:
/*
* In the parent.
* Waiting for the initial USR1 that tells us the child
* is ready.
*/
while (gotusr1 == 0)
sigsuspend(&oset);
/*
* Check that sigsuspend didn't change the signal mask.
*/
if (sigprocmask(SIG_SETMASK, NULL, &oset))
err(1, "sigprocmask");
if (!sigismember(&oset, SIGUSR1) ||
!sigismember(&oset, SIGUSR2))
errx(1, "sigprocmask is bad");
/*
* Deliberately send USR2 first to confuse.
*/
kill(pid, SIGUSR2);
kill(pid, SIGUSR1);
if (waitpid(pid, &status, 0) != pid)
err(1, "waitpid");
if (WIFEXITED(status))
exit(WEXITSTATUS(status));
exit(1);
}
/* NOTREACHED */
}
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