linux-kernel - Re: [this_cpu_xx V5 19/19] SLUB: Experimental new fastpath w/o interrupt disable

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Message-ID: <alpine.DEB.1.10.0910121122400.21558@gentwo.org>
Date:	Mon, 12 Oct 2009 11:23:23 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
cc:	Peter Zijlstra <peterz@...radead.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	Tejun Heo <tj@...nel.org>, Mel Gorman <mel@....ul.ie>,
	mingo@...e.hu
Subject: Re: [this_cpu_xx V5 19/19] SLUB: Experimental new fastpath w/o
 interrupt disable

On Mon, 12 Oct 2009, Mathieu Desnoyers wrote:

> > If I just enable interrupts there then the preempt check will not be
> > done and we may miss a scheduling point.
> >
>
> That's why you should do:
>
> local_irq_save()
> preempt_enable_no_resched()
> ...
> local_irq_restore()
> preempt_check_resched()

What is the difference then to

local_irq_save()

...

local_irq_enable();
preempt_enable();

?
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