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Date: Sun, 2 Feb 2014 14:02:58 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Jason Low <jason.low2@...com>, Ingo Molnar <mingo@...hat.com>,
Waiman Long <Waiman.Long@...com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Rik van Riel <riel@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Davidlohr Bueso <davidlohr@...com>,
"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
"Chandramouleeswaran, Aswin" <aswin@...com>,
"Norton, Scott J" <scott.norton@...com>, chegu_vinod@...com
Subject: Re: [RFC][PATCH v2 5/5] mutex: Give spinners a chance to
spin_on_owner if need_resched() triggered while queued
On Fri, Jan 31, 2014 at 09:08:25PM +0100, Peter Zijlstra wrote:
> On Fri, Jan 31, 2014 at 12:01:37PM -0800, Jason Low wrote:
> > On Fri, Jan 31, 2014 at 6:09 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > > I've downloaded AIM7 from sf.net and I hope I'm running it with 100+
> > > loads but I'm not entirely sure I got this thing right, its not really
> > > making progress with or without patch :/
> >
> > Ingo's program http://lkml.org/lkml/2006/1/8/50 using the V option may
> > be able to generate similar mutex contention.
> >
> > Currently still getting soft lockups with the updated version.
>
> Bugger.. ok clearly I need to think harder still. I'm fairly sure this
> cancelation can work though, just seems tricky to get right :-)
We used to do something similar to avoid passing locks off to tasks that
had been interrupted while spinning, and it was a bit tricky. But we
had it a bit easier, because we didn't actually have to remove the element
from the queue, just bypass it at lock-grant time.
Thanx, Paul
> I'll give that proglet from Ingo a go, although that might be Monday ere
> I get to it.
>
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