linux-kernel - Re: mlockall triggred rcu

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Date:	Tue, 30 Jul 2013 14:05:04 -0400
From:	Dave Jones <davej@...hat.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	kosaki.motohiro@...il.com, walken@...gle.com,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org
Subject: Re: mlockall triggred rcu_preempt stall.

On Tue, Jul 30, 2013 at 10:57:18AM -0700, Paul E. McKenney wrote:
 > On Fri, Jul 19, 2013 at 08:32:12PM -0400, Dave Jones wrote:
 > > On Fri, Jul 19, 2013 at 03:15:39PM -0700, Paul E. McKenney wrote:
 > >  > On Fri, Jul 19, 2013 at 10:53:23AM -0400, Dave Jones wrote:
 > >  > > My fuzz tester keeps hitting this. Every instance shows the non-irq stack
 > >  > > came in from mlockall.  I'm only seeing this on one box, but that has more
 > >  > > ram (8gb) than my other machines, which might explain it.
 > >  > 
 > >  > Are you building CONFIG_PREEMPT=n?  I don't see any preemption points in
 > >  > do_mlockall(), so a range containing enough vmas might well stall the
 > >  > CPU in that case.  
 > > 
 > > That was with full preempt.
 > > 
 > >  > Does the patch below help?  If so, we probably need others, but let's
 > >  > first see if this one helps.  ;-)
 > > 
 > > I'll try it on Monday.
 > 
 > Any news?  If I don't hear otherwise, I will assume that the patch did
 > not help, and will therefore drop it.

I wasn't able to do any tests yesterday, because I kept hitting other oopses.
I've got patches for the more obvious ones now, so I'll start testing rc3 this
afternoon.

	Dave


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