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From:	"Mark Pizzolato" <list-cygwin AT subscriptions DOT pizzolato DOT net>
To:	<cygwin AT cygwin DOT com>
Subject:	gdb threading troubles
Date:	Wed, 8 Jun 2005 09:19:33 -0700
MIME-Version:	1.0
X-IsSubscribed:	yes

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The attached example test program runs to completion when run directly, but 
spins infinitely when run under gdb.

I'm compiling with:

gcc -g -O0 mutexttest.c -o mutexttest

running under:
    cygwin    1.5.17-1
    gdb         20041228-3 

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	filename="mutextest.c"

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <stdarg.h>

pthread_mutex_t log_mutex =3D PTHREAD_MUTEX_INITIALIZER;

void
logit(const char *fmt, ...) {
	va_list args;
	char buf[1024];
	int bytes;
=09
	buf[sizeof(buf)-1] =3D '\0';
	va_start(args, fmt);
	bytes =3D vsnprintf(buf, sizeof(buf)-1, fmt, args);
	va_end(args);
	pthread_mutex_lock(&log_mutex);
	printf("%s", buf);
	pthread_mutex_unlock(&log_mutex);
}

pthread_mutex_t mutex =3D PTHREAD_MUTEX_INITIALIZER;

struct TestInfo {
	void (*Lock)(void);
	void (*Unlock)(void);
	int Iterations;
	int Data;
	int Increment;
};

void
NoLock(void) {
}

void
NoUnlock(void) {
}

void
PthreadLock(void) {
	pthread_mutex_lock(&mutex);
}

void
PthreadUnlock(void) {
	pthread_mutex_unlock(&mutex);
}

void *
TestThread (void *arg) {
	struct TestInfo *t =3D (struct TestInfo *)arg;
	int i;
	int *pData =3D &t->Data;
=09
	logit("Thread %d starting...\n", pthread_self());
	sleep(1);
	for (i=3D0; i<t->Iterations; ++i) {
		int tmp;
		int trand;
		t->Lock();
		srand(46);
		trand =3D rand();
		srand(46);
		tmp =3D t->Data;
		tmp =3D tmp + trand - rand();
		tmp =3D tmp + t->Increment;
		t->Data =3D tmp;
		t->Unlock();
	}
	logit("Thread %d done.\n", pthread_self());
	return NULL;
}

main (int argc, char ** argv) {
	int threadcount =3D 10;
	pthread_t tid[10];
	int i;
	struct TestInfo Info;

	Info.Iterations =3D 500000;
	Info.Increment =3D 3;
=09
	Info.Data =3D 0;
	Info.Unlock =3D &NoUnlock;
	Info.Lock =3D &NoLock;
	for (i=3D0; i<threadcount; ++i) {
		pthread_create(&tid[i], NULL, TestThread, &Info);
	}
	for (i=3D0; i<threadcount; ++i)
		pthread_join(tid[i], NULL);
	logit("NoLock Data           =3D %d\n", Info.Data);
	logit("Expected              =3D %d\n", Info.Iterations*Info.Increment*thr=
eadcount);
	Info.Data =3D 0;
	Info.Unlock =3D &PthreadUnlock;
	Info.Lock =3D &PthreadLock;
	for (i=3D0; i<threadcount; ++i) {
		pthread_create(&tid[i], NULL, TestThread, &Info);
	}
	for (i=3D0; i<threadcount; ++i)
		pthread_join(tid[i], NULL);
	logit("pthreads Locking Data =3D %d\n", Info.Data);
	logit("Expected              =3D %d\n", Info.Iterations*Info.Increment*thr=
eadcount);
}


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