linux-kernel - Re: [PATCHSET] timer: clean up initializers and implement irqsafe timers

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Message-ID: <alpine.LFD.2.02.1208141031180.32033@ionos>
Date:	Tue, 14 Aug 2012 10:32:06 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Tejun Heo <tj@...nel.org>
cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	mingo@...hat.com, akpm@...ux-foundation.org, peterz@...radead.org
Subject: Re: [PATCHSET] timer: clean up initializers and implement irqsafe
 timers

On Mon, 13 Aug 2012, Tejun Heo wrote:
> Hello,
> 
> On Wed, Aug 08, 2012 at 11:10:24AM -0700, Tejun Heo wrote:
> > Timer internals are protected by irqsafe lock but the lock is
> > naturally dropped and irq enabled while a timer is executed.  This
> > makes dequeueing timer for execution and the actual execution
> > non-atomic against IRQs.  No matter what the timer function does, IRQs
> > can occur between timer dispatch and execution.  This means that an
> > IRQ handler could interrupt any timer in progress and it's impossible
> > for an IRQ handler to cancel and drain a timer.
> 
> If nobody objects, I'll route this through wq/for-3.7 together with
> "workqueue: use irqsafe timer in delayed_work" patchset.  If you
> object, please scream.

SCREAM!

I'll reply to the original posting later - still processing my
vacation backlog.

Thanks,

	tglx
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