Re: The perl 5.10.0 headache

[Petr Salinger <Petr.Salinger@seznam.cz>]

Hi from GNU/kFreeBSD porter.

> After talking it over with stephen and arranging perl 5.10 to be built on
> real metal vs aranym, we are pleased to report that perl passes its test
> suite with the exception of one test, a threading stress test which 
> launchs multiple threads, and then tries to make sure that they close in 
> order.

> It appears its caused by the antique version of glibc we use, and the 
> fact that we are using the old linuxthreads package vs. nptl.

The test passes even under linuxthreads, but real-time variant of
signals have to be used, i.e. they should properly queue in kernel.
I know it, because on GNU/kFreeBSD it needs 7.x kernel.

You can use attached code to perform the same test in C.
Problem would be rather missing memory barier, or non-atomic operation.
This should be fixable even with 2.5 glibc and linuxthreads.

Petr

#include <sys/time.h>
#include <time.h>
#include <errno.h>
#include <pthread.h>
#include <stdlib.h>


int x,y;
pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

void * job(void * arg)
{
	int a = (int) arg;

	struct timeval now;
	struct timespec timeout;
	
	int retcode;
	printf("Started %d\n", a);
	usleep((rand() % 32777));

	pthread_mutex_lock(&mut);
	while (x != a) 
        {
        	printf("wait %d %d\n", x, a);
		gettimeofday(&now,NULL);
		timeout.tv_sec = now.tv_sec + 1;
		timeout.tv_nsec = now.tv_usec * 1000;
        	retcode = pthread_cond_timedwait(&cond, &mut, &timeout);
		if (retcode == ETIMEDOUT)
			printf("Timeout %d\n", a);
	}
	
	x++;
        printf("exit a %d %d\n", x, a);
	pthread_cond_broadcast(&cond);
        printf("exit b %d %d\n", x, a);
	pthread_mutex_unlock(&mut);
        printf("exit c %d %d\n", x, a);
}

int main()
{
	pthread_t t;
	int i;
	for (i = 0; i < 50; i++)
		pthread_create(&t, NULL, job, (void *) i);
	sleep (10);
        printf("FINAL %d %d\n", x, i);
	
}