Re: futex wait failure

[John David Anglin <dave@xxxxxxxxxxxxxxxxxx>]

On Thu, 11 Mar 2010, John David Anglin wrote:

> I am 95% certain that the bug has to do with the clone implementation
> and scheduling.  I have attached another version of the minifail test.
> The loops after the fork and pthread_create calls are to isolate these
> syscalls.  Typically, I see something like:

Attached.

Dave
-- 
J. David Anglin                                  dave.anglin@xxxxxxxxxxxxxx
National Research Council of Canada              (613) 990-0752 (FAX: 952-6602)

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

/*
  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=561203

  clone(child_stack=0x4088d040, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x4108c4e8, tls=0x4108c900, child_tidptr=0x4108c4e8) = 14819
[pid 14819] set_robust_list(0x4108c4f0, 0xc) = 0
[pid 14818] clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x40002028) = 14820

 g++  minifail.cpp -o minifail -O0 -pthread -g

 i=0; while true; do i=$(($i+1)); echo Run $i; ./minifail; done;

 */

static volatile int run = 1;

void* thread_run(void* arg) {
	static long status;
	int i;
        
	run = 1;
	pthread_yield();
	for (i = 10000000; i; i--)
	   continue;
	write(1,"Thread OK.\n",11);
	return (void *)&status;
}

int pure_test() {
	int i;
	pthread_t thread;
	pthread_create(&thread, NULL, thread_run, NULL);

	while (!run)
	  pthread_yield();
	switch (fork()) {
		case -1:
			perror("fork() failed");
		case 0:
			write(1,"Child OK.\n",10);
			_exit(0);
		default:
			break;
		
	}
	pthread_yield();
	for (i = 20000000; i; i--)
	  continue;
	write(1,"Fork done\n",10);
	pthread_join(thread, NULL);
	return 0;
}

int main(int argc, char** argv) {
	return pure_test();
}