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Subject: Re: [RFC][PATCH 2/6] mm: stack based kmap_atomic
From: Peter Zijlstra <peterz@infradead.org>
In-Reply-To: <20100824163545.052e44fd.kamezawa.hiroyu@jp.fujitsu.com>
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	 <20100824162427.58e2eb88.kamezawa.hiroyu@jp.fujitsu.com>
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Date: Tue, 24 Aug 2010 10:04:23 +0200
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To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>
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On Tue, 2010-08-24 at 16:35 +0900, KAMEZAWA Hiroyuki wrote:
> On Tue, 24 Aug 2010 16:24:27 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>=20
> > And Is it documented that kmap_atomic shouln't be used under NMI or som=
ething
> > special interrupts ?
> >=20
> Sorry, I missed something..Maybe not trouble.

In particular, we actually do use kmap_atomic from NMI context ;-)

It only relies on preempt_disable(), which for now is implied by
pagefault_disable(), if at some point those get split kmap_atomic will
need to do both (currently only PREEMPT_RT splits it, but then that has
a totally different kmap implementation too).

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