lkml.org 
[lkml]   [2007]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
DateSat, 6 Jan 2007 19:30:35 +0300
FromOleg Nesterov <>
SubjectRe: [PATCH] fix-flush_workqueue-vs-cpu_dead-race-update
On 01/06, Srivatsa Vaddagiri wrote:
>
> On Sat, Jan 06, 2007 at 06:10:36PM +0300, Oleg Nesterov wrote:
> > Increment hotplug_sequence earlier, under CPU_DOWN_PREPARE. We can't
> > miss the event, the task running flush_workqueue() will be re-scheduled
> > at least once before CPU actually disappears from cpu_online_map.
>
> Eww ..what happens if flush_workqueue() starts after CPU_DOWN_PREPARE?
^^^^^
Stupid me. Thanks.

> CPU_DOWN_PREPARE(8)
> hotplug_sequence++ = 10
>
> flush_workqueue()
> sequence = 10
> flush cpus 1 ....7
>
> CPU_DEAD(8)
> take_over_work(8->1)
>
> return not flushing dead cpu8 (=BUG)

I'll try to do something else tomorrow. Do you see a simple soulution?

The current usage of workqueue_mutex (I mean stable kernel) is broken
and deadlockable. We really need to change it.

Oleg.

-
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: 2007-01-06 17:33    [from the cache]
©2003-2010