linux-kernel - Re: [PATCH v2 1/2] workqueue: add quiescent state between work items

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Date:	Sun, 5 Oct 2014 15:47:48 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Joe Lawrence <joe.lawrence@...atus.com>
Cc:	linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
	jiri@...nulli.us, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/2] workqueue: add quiescent state between work items

On Sun, Oct 05, 2014 at 03:21:19PM -0400, Tejun Heo wrote:
> On Sun, Oct 05, 2014 at 01:24:21PM -0400, Joe Lawrence wrote:
> > Similar to the stop_machine deadlock scenario on !PREEMPT kernels
> > addressed in b22ce2785d97 "workqueue: cond_resched() after processing
> > each work item", kworker threads requeueing back-to-back with zero jiffy
> > delay can stall RCU. The cond_resched call introduced in that fix will
> > yield only iff there are other higher priority tasks to run, so force a
> > quiescent RCU state between work items.
> > 
> > Signed-off-by: Joe Lawrence <joe.lawrence@...atus.com>
> > Link: https://lkml.kernel.org/r/20140926105227.01325697@jlaw-desktop.mno.stratus.com
> > Link: https://lkml.kernel.org/r/20140929115445.40221d8e@jlaw-desktop.mno.stratus.com
> > Fixes: b22ce2785d97 ("workqueue: cond_resched() after processing each work item")
> > Cc: <stable@...r.kernel.org>
> 
> Applied to wq/for-3.17-fixes.  If 3.17 comes out before this gets
> merged, I'll send it as for-3.18.

Oops, the rcu calls aren't in mainline yet.  I think it'd be best to
route these through the RCU tree.  Paul, can you please route these
two patches?

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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