lkml.org 
[lkml]   [2007]   [Mar]   [25]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
DateSun, 25 Mar 2007 09:46:02 +0530
FromSrivatsa Vaddagiri <>
SubjectRe: [ckrm-tech] [PATCH 1/7] containers (V7): Generic container system abstracted from cpusets code
On Sun, Mar 25, 2007 at 07:58:16AM +0530, Srivatsa Vaddagiri wrote:
> Not just this, continuing further we have more trouble:
> > --------------------------------------------------------------------
> CPU0 (attach_task T1 to CS2)			CPU1 (T1 is exiting)
> --------------------------------------------------------------------
> > synchronize_rcu()> 						    atomic_dec(&CS1->count);
> 						    [CS1->count = 0]
> 
> if atomic_dec_and_test(&oldcs->count))
> 	[CS1->count = -1]
> 
> 
> 
> We now have CS1->count negative. Is that good? I am uncomfortable ..
> 
> We need a task_lock() in cpuset_exit to avoid this race.

2nd race is tricky. We probably need to do this to avoid it:

	task_lock(tsk);

	/* Check if tsk->cpuset is still same. We may have raced with 
	 * cpuset_exit changing tsk->cpuset again under our feet.
	 */
	if (tsk->cpuset == cs && atomic_dec_and_test(&oldcs->count)) {
		task_unlock(tsk);
                check_for_release(oldcs, ppathbuf);
		goto done;
	}
	task_unlock(tsk);

done:
	return 0;



-- 
Regards,
vatsa
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-03-25 06:11    [from the cache]
©2003-2008