Date: Fri, 7 Nov 1997 21:47:08 -0500 From: Jim Carroll <jim@carroll.com> To: freebsd-questions@freebsd.org Subject: wait not interrupted on signal Message-ID: <Pine.BSD.3.91.971107213028.20097L-100000@apollo.carroll.com>
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I have a piece of code that depends on being notified when a child process
sends it a signal. The parent spends most of it's life waiting for this
signal.
The mechanism I have tried to use is to trap SIGUSR1 in the parent, then
execute a wait() system call. From my reading of the wait(2) man pages and
the sigaction(2) pages, the wait call in the parent should be interrupted
when the child task posts SIGUSR1.
I'm not sure what I'm doing wrong, but I cannot get the wait() call to
interrupt. I had print routines that seem to indicate that the signal was
caught, but the wait refuses to return to the parent until the child dies.
I have narrowed the problem down to the smallest piece of code I could
develope, and included it below. In the example below, I would expect to
see:
wait for child
SIGUSR1 caught
errno: 4
The last line indicates that an errno 4 (EINTR) was received.
Instead, we are seeing:
wait for child
SIGUSR1 caught
errno: 0
We are running FreeBSD 2.2.1
Any assistance would be appreciated.
Thanks in advance
=-=-=-=-= SAMPLE CODE -=-=-=-=-=-=-=
#include <sys/errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>
void sigreset(int s) {
fprintf(stderr,"SIGUSR1 caught\n");
}
void main(int argc, char* argv[]) {
int p, s;
signal(SIGUSR1, sigreset); /* prepare to catch signal */
if ((p = fork()) == 0) { /* in child */
sleep(2);
kill(getppid(), SIGUSR1); /* post signal to parent */
sleep(5);
return;
}
/* in parent */
fprintf(stderr, "wait for child\n");
wait(&s); /* wait for EINTR or child dealth */
fprintf(stderr, "errno: %d\n", errno);
}
---
Jim C., President | C A R R O L L - N E T, Inc.
201-488-1332 | New Jersey's Premier Internet Service Provider
www.carroll.com |
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