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Message-ID: <6DED3619289CD311BCEB00508B8E1336ACF397@nt-server2.antwerp.seagha.com>
From: Karl Vogel <karl DOT vogel AT seagha DOT com>
To: "'Mak, Ryan'" <RMak AT wmsgaming DOT com>,
   "'cygwin AT cygwin DOT com'"
	 <cygwin AT cygwin DOT com>
Subject: RE: pthread signal handling bug?
Date: Wed, 7 Aug 2002 17:21:54 +0200 
MIME-Version: 1.0
Content-Type: text/plain;
	charset="iso-8859-1"

Nope.. That works without a problem (as it should)

From the pthread_mutex_init manpages:

" If attr is set to
  NULL, the default mutex attributes are used. "

Just tried it with gdb and that also works.

> -----Original Message-----
> From: Mak, Ryan [mailto:RMak AT wmsgaming DOT com]
> Sent: Wednesday, August 07, 2002 17:14
> To: 'Karl Vogel'; 'cygwin AT cygwin DOT com'
> Subject: RE: pthread signal handling bug?
> 
> 
> Hi Karl.
> 
> When you use gdb to step through your program, does it give you a
> segmentation fault
> on the pthread_mutex_init(&mux,NULL) line??
> 
> Thanx.
> -Ryan
> 
> 
> -----Original Message-----
> From: Karl Vogel [mailto:karl DOT vogel AT seagha DOT com]
> Sent: Wednesday, August 07, 2002 10:12 AM
> To: 'cygwin AT cygwin DOT com'
> Subject: pthread signal handling bug?
> 
> 
> [NOTE: I'm not subscribed to this list, so please add me in Cc: if you
> reply]
> 
> I have a problem with signal delivery when using POSIX threads. If you
> start 2 threads and sleep in both, but 1 has an alarm() defined, then
> when the signal is delivered it also cancels the other thread.
> 
> My knowledge of pthreads is limited, so I don't know if this is an
> expected result, but I tried the same program on Linux & 
> Digital UNIX V4.0b
> and got a different result.
> 
> Pseudo code:
> 
> 	thread 1
> 
> 		repeat
> 			print message
> 			sleep
> 
> 	thread 2
> 		set alarm
> 		sleep
> 		exit
> 
> What I expected was that thread 1 would keep on running and 
> not get any
> signals
> delivered, while thread 2 would just cancel the sleep and 
> exit. However what
> I got was that the sleep from thread 1 fails after the signal 
> got delivered.
> 
> Included is the test case source. Following version numbers 
> might be useful:
> 
> cygwin              1.3.12-4 
> gcc                 3.1.1-4      
> 
> On Windows 2000 SP1.
> 
> 
> ---- test case -----
> #include <pthread.h>
> #include <stdio.h>
> #include <signal.h>
> #include <time.h>
> #include <unistd.h>
> #include <string.h>
> #include <errno.h>
> 
> pthread_mutex_t mux;
> 
> void *func(void *x)
> {
> 	int *p = (int *)x;
> 	time_t t;
> 	int r;
> 
> 	/* Print time every 5 seconds */
> 	while(1) {
> 		time(&t);
> 		pthread_mutex_lock(&mux);
> 		printf("thread %d - %s",*p,ctime(&t)); 
> 		pthread_mutex_unlock(&mux);
> 		r= sleep(5);
> 		if (r) {
> 			pthread_mutex_lock(&mux);
> 			printf("Remaining %d\n", r);
> 			pthread_mutex_unlock(&mux);
> 		}
> 	}
> 	return NULL;
> }
> 
> void *func2(void *x)
> {
> 	int *p = (int *)x;
> 	time_t t;
> 
> 	/* Trigger SIGALRM after 7 seconds */
> 	time(&t);
> 	pthread_mutex_lock(&mux);
> 	printf("thread %d - %s",*p,ctime(&t)); 
> 	pthread_mutex_unlock(&mux);
> 	alarm(7);
> 	sleep(60*60);
> 	alarm(0);
> 
> 	time(&t);
> 	pthread_mutex_lock(&mux);
> 	printf("exit thread %d - %s",*p,ctime(&t)); 
> 	pthread_mutex_unlock(&mux);
> 	return NULL;
> }
> 
> void sighandler(int sig)
> {
> 	printf("Caught signal\n");
> 	return;
> }
> 
> int main()
> {
> 	pthread_t t;
> 	pthread_t t2;
> 	pthread_attr_t attr;
> 	int i;
> 	int p;
> 	void *result;
> 
> 	struct sigaction actions;
> 
> 	memset((char *)&actions, 0, sizeof(actions));
> 	sigemptyset(&actions.sa_mask);
> 	actions.sa_flags = 0;
> 	actions.sa_handler = sighandler;
> 	sigaction(SIGALRM, &actions, NULL);
> 
> 	pthread_mutex_init(&mux, NULL);
> 	pthread_mutex_lock(&mux);
> 
> 	pthread_attr_init(&attr);
> 	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
> 
> 	i= 1;
> 	if (pthread_create(&t, &attr, func, &i)!=0) {
> 		perror("pthread_create t1");
> 	}
> 	p= 2;
> 	if (pthread_create(&t2, &attr, func2, &p)!=0) {
> 		perror("pthread_create t2");
> 	}
> 
> 	printf("Main thread\n");
> 	pthread_mutex_unlock(&mux);
> 
> 	pthread_join(t, &result);
> 	pthread_join(t2, &result);
> 	pthread_mutex_destroy(&mux);
> 	return 0;
> }
> --------------------
> 
> Compile with:
> 	gcc -o tester tester.c -lpthread
> 
> 
> Output on cygwin:
> 
> $ ./tester
> Main thread
> thread 1 - Wed Aug  7 17:00:55 2002
> thread 2 - Wed Aug  7 17:00:55 2002
> thread 1 - Wed Aug  7 17:01:00 2002
> exit thread 2 - Wed Aug  7 17:01:02 2002
> Remaining 3
> thread 1 - Wed Aug  7 17:01:02 2002
> Remaining 5
> thread 1 - Wed Aug  7 17:01:02 2002
> Remaining 5
> thread 1 - Wed Aug  7 17:01:02 2002
> Remaining 5
> thread 1 - Wed Aug  7 17:01:02 2002
> Remaining 5
> thread 1 - Wed Aug  7 17:01:02 2002
> 
> 
> Output on Linux & Digital UNIX:
> 
> $ ./tester
> Main thread
> thread 1 - Wed Aug  7 17:00:02 2002
> thread 2 - Wed Aug  7 17:00:02 2002
> thread 1 - Wed Aug  7 17:00:07 2002
> Caught signal
> exit thread 2 - Wed Aug  7 17:00:09 2002
> thread 1 - Wed Aug  7 17:00:12 2002
> thread 1 - Wed Aug  7 17:00:17 2002
> thread 1 - Wed Aug  7 17:00:22 2002
> 
> 
> 
> Am I making a gross mistake here?! Or is there a problem with cygwin?
> 
> 
> Rgrds,
> 
> Karl Vogel
> ----------
> Violence in reality is quite different from theory.
> 		-- Spock, "The Cloud Minders", stardate 5818.4
> 
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