Re: [PATCH fs/locks 2 of 3] Use proper tgid in locks_remove_posix

[Olaf Kirch <okir@suse.de>]

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On Mon, Jul 11, 2005 at 09:52:17AM -0400, Trond Myklebust wrote:
> In the case of NLM, we use the function nlm_find_lockowner() to create a
> mapping between fl_owner and a 32-bit numerical value which we call
> "pid", but which is really just a unique number. This mapping is
> preserved at least for the lifetime of the lock, and is shared between
> all locks that reference the same fl_owner.
> The "pid" of this mapping is the number that is seen by the server.

Alright. I stand corrected.

I originally reproduced this problem on SLES (ie 2.6.5), where the
lockowner stuff didn't exist yet. I then retested on 2.6.12, and found
the same problem - but didn't notice the mechanism is entirely different.
So whatever I'm seeing on 2.6.12 is different from what I saw on 2.6.5.

I'll do some more testing - in case anyone else would like to do so, too,
the test app is attached.

Olaf
-- 
Olaf Kirch   |  --- o --- Nous sommes du soleil we love when we play
okir@suse.de |    / | \   sol.dhoop.naytheet.ah kin.ir.samse.qurax

[-- Attachment #2: two-thread-unlock.c --]
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#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/param.h>
#include <fcntl.h>
#include <pthread.h>
#include <string.h>

int	fd;
int	running = 1;
int	locked = 0;

int
get_lock (int fd)
{
	struct flock    lock_it;
	int		res = 0;

	lock_it.l_type = F_WRLCK;
	lock_it.l_whence = SEEK_SET;
	lock_it.l_start = 0;
	lock_it.l_len = 0;

	if (fcntl (fd, F_SETLK, &lock_it) < 0) {
		perror ("fcntl(F_WRLCK)");
		res = -1;
	}

	return res;
}


void *
do_lock(void *arg)
{
	if (get_lock(fd) >= 0) {
		printf("Locked file\n");
		sleep(1);
		locked = 1;
	}

	while (running)
		sleep(1);
	return NULL;
}

void *
do_close(void *arg)
{
	int i;

	for (i = 0; !locked && i < 10; ++i)
		sleep(1);
	if (locked)
		close(fd);
	else
		printf("Never obtained the lock\n");
	running = 0;
	return NULL;
}

int
main(int argc, char** argv)
{
#define THREADS 1

	pthread_t	locker_thread;
	pthread_t	close_thread;

	if (argc != 2) {
		fprintf(stderr, "%s <path>\n", argv[0]);
		exit(-1);
	}

	if ((fd = open (argv[1], O_RDWR | O_CREAT, S_IRUSR | S_IWUSR)) < 0) {
		perror ("open");
		return 1;
	}

	pthread_create(&locker_thread, NULL, do_lock, NULL);
	pthread_create(&close_thread, NULL, do_close, NULL);
	sleep(2);

	running = 0;
	pthread_join(locker_thread, NULL);
	pthread_join(close_thread, NULL);

	return 0;
}