lkml.org 
[lkml]   [2006]   [Dec]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: workqueue deadlock
On Thu, Dec 07, 2006 at 11:37:00AM -0800, Andrew Morton wrote:
> -static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
> +/*
> + * If cpu == -1 it's a single-threaded workqueue and the caller does not hold
> + * workqueue_mutex
> + */
> +static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq, int cpu)

Lets say @cpu = 4

> {
> if (cwq->thread == current) {
> /*
> * Probably keventd trying to flush its own queue. So simply run
> * it by hand rather than deadlocking.
> */
> + if (cpu != -1)
> + mutex_unlock(&workqueue_mutex);

Lets say we release the workqueue mutex here (events/4 is trying to
flush its own workqueue). Immediately another CPU takes this mutex
(in CPU_DOWN_PREPARE) and brings down CPU4. In CPU_DEAD handling we now wait
on events/4 thread to exit (cleanup_workqueue_thread).

Couldnt this wait deadlock on :

> run_workqueue(cwq);

> + if (cpu != -1)
> + mutex_lock(&workqueue_mutex);

events/4 thread itself wanting the same mutex above?

What am I missing?


--
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: 2006-12-08 03:59    [W:0.048 / U:1.224 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site