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Date: Tue, 14 Aug 2007 22:44:54 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Christoph Lameter <clameter@sgi.com>
Cc: Andi Kleen <andi@firstfloor.org>, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org
Subject: Re: [RFC 4/9] Atomic reclaim: Save irq flags in vmscan.c
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References: <20070814153021.446917377@sgi.com> <20070814153501.766137366@sgi.com> <p73vebhnauo.fsf@bingen.suse.de> <Pine.LNX.4.64.0708141209270.29498@schroedinger.engr.sgi.com> <20070814203329.GA22202@one.firstfloor.org> <Pine.LNX.4.64.0708141341120.31513@schroedinger.engr.sgi.com>
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> Hmmmm... The spinlock is its own flag.

Yes, but it's not CPU local. Taking the spinlock from another CPU's
interrupt handler is perfectly safe, just not from the local CPU.
If you use the spinlock as flag you would need to lock out everybody.

-Andi