int
main(int argc, char *argv[])
{
int loopNum;
time_t startTime;
sigset_t origMask, blockMask;
struct sigaction sa;
printSigMask(stdout, "Initial signal mask is:\n");
sigemptyset(&blockMask);
sigaddset(&blockMask, SIGINT);
sigaddset(&blockMask, SIGQUIT);
if (sigprocmask(SIG_BLOCK, &blockMask, &origMask) == -1)
errExit("sigprocmask - SIG_BLOCK");
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_handler = handler;
if (sigaction(SIGINT, &sa, NULL) == -1)
errExit("sigaction");
if (sigaction(SIGQUIT, &sa, NULL) == -1)
errExit("sigaction");
for (loopNum = 1; !gotSigquit; loopNum++) {
printf("=== LOOP %d\n", loopNum);
/* Simulate a critical section by delaying a few seconds */
printSigMask(stdout, "Starting critical section, signal mask is:\n");
for (startTime = time(NULL); time(NULL) < startTime + 4; )
continue; /* Run for a few seconds elapsed time */
printPendingSigs(stdout,
"Before sigsuspend() - pending signals:\n");
if (sigsuspend(&origMask) == -1 && errno != EINTR)
errExit("sigsuspend");
}
if (sigprocmask(SIG_SETMASK, &origMask, NULL) == -1)
errExit("sigprocmask - SIG_SETMASK");
printSigMask(stdout, "=== Exited loop\nRestored signal mask to:\n");
/* Do other processing... */
exit(EXIT_SUCCESS);
}
int
main(int argc, char *argv[])
{
int loopNum;
#ifdef USE_PAUSE
int sleepTime;
#endif
time_t startTime;
sigset_t origMask, blockMask;
struct sigaction sa;
printSigMask(stdout, "Initial signal mask is:\n");
sigemptyset(&blockMask);
sigaddset(&blockMask, SIGINT);
sigaddset(&blockMask, SIGQUIT);
#ifdef USE_PAUSE
sleepTime = (argc > 1) ? getInt(argv[1], GN_NONNEG, NULL) : 0;
#endif
/* Block SIGINT and SIGQUIT - at this point we assume that these signals
are not already blocked (obviously true in this simple program) so that
'origMask' will not contain either of these signals after the call. */
if (sigprocmask(SIG_BLOCK, &blockMask, &origMask) == -1)
errExit("sigprocmask - SIG_BLOCK");
/* Set up handlers for SIGINT and SIGQUIT */
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_handler = handler;
if (sigaction(SIGINT, &sa, NULL) == -1)
errExit("sigaction");
if (sigaction(SIGQUIT, &sa, NULL) == -1)
errExit("sigaction");
/* Loop until SIGQUIT received */
for (loopNum = 1; !gotSigquit; loopNum++) {
printf("=== LOOP %d\n", loopNum);
/* Simulate a critical section by delaying a few seconds */
printSigMask(stdout, "Starting critical section, signal mask is:\n");
for (startTime = time(NULL); time(NULL) < startTime + 4; )
continue; /* Run for a few seconds elapsed time */
#ifndef USE_PAUSE
/* The right way: use sigsuspend() to atomically unblock
signals and pause waiting for signal */
printPendingSigs(stdout,
"Before sigsuspend() - pending signals:\n");
if (sigsuspend(&origMask) == -1 && errno != EINTR)
errExit("sigsuspend");
#else
/* The wrong way: unblock signal using sigprocmask(),
then pause() */
if (sigprocmask(SIG_SETMASK, &origMask, NULL) == -1)
errExit("sigprocmask - SIG_SETMASK");
/* At this point, if SIGINT arrives, it will be caught and
handled before the pause() call and, in consequence,
pause() will block. (And thus only another SIGINT signal
AFTER the pause call() will actually cause the pause()
call to be interrupted.) Here we make the window between
the two calls a bit larger so that we have a better
chance of sending the signal. */
if (sleepTime > 0) {
printf("Unblocked SIGINT, now waiting for %d seconds\n", sleepTime);
for (startTime = time(NULL);
time(NULL) < startTime + sleepTime; )
continue;
printf("Finished waiting - now going to pause()\n");
}
/* And now wait for the signal */
pause();
printf("Signal count = %d\n", sigintCnt);
sigintCnt = 0;
#endif
}
/* Restore signal mask so that signals are unblocked */
if (sigprocmask(SIG_SETMASK, &origMask, NULL) == -1)
errExit("sigprocmask - SIG_SETMASK");
printSigMask(stdout, "=== Exited loop\nRestored signal mask to:\n");
/* Do other processing... */
exit(EXIT_SUCCESS);
}
