Re: [PATCH] fix de_thread() vs do_coredump() deadlock

[Oleg Nesterov <oleg@tv-sign.ru>]

On 04/11, Roland McGrath wrote:
>
> > So, de_thread() sets SIGNAL_GROUP_EXEC and sends SIGKILL to other thereads.
> > 
> > Sub-thread receives the signal, and calls get_signal_to_deliver->do_group_exit.
> > do_group_exit() calls zap_other_threads(SIGNAL_GROUP_EXIT) because there is no
> > SIGNAL_GROUP_EXIT set. zap_other_threads() notices SIGNAL_GROUP_EXEC, wakes up
> > execer, and changes ->signal->flags to SIGNAL_GROUP_EXIT.
> > 
> > de_thread() re-locks sighand, sees !SIGNAL_GROUP_EXEC and goes to 'dying:'.
> 
> That is what I intend.  The exec'ing thread backs out and processes its SIGKILL.
> It sounds like you are calling this scenario a problem, but I don't know why.

Ok, here is the test:

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

static void *tfunc(void *arg)
{
	pause();
	return NULL;
}

int main(int argc, const char *argv[])
{
	pthread_t thread;

	if (!argv[0]) {
		printf("--------- SUCCESS ----------\n");
		exit(0);
	}

	if (pthread_create(&thread, NULL, tfunc, NULL)) {
		perror ("pthread_create");
		exit (1);
	}

	execl("/proc/self/exe", NULL);

	return pause();
}


	$ ./test
	--------- SUCCESS ----------

With this patch applied I have:

	$ ./test
	Killed

Oleg.