Date: Mon, 4 Feb 2008 11:13:53 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
To: Andrea Arcangeli <andrea@qumranet.com>
cc: Robin Holt <holt@sgi.com>, Avi Kivity <avi@qumranet.com>,
       Izik Eidus <izike@qumranet.com>, kvm-devel@lists.sourceforge.net,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, steiner@sgi.com,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       daniel.blueman@quadrics.com
Subject: Re: [patch 1/3] mmu_notifier: Core code
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On Sun, 3 Feb 2008, Andrea Arcangeli wrote:

> On Thu, Jan 31, 2008 at 07:58:40PM -0800, Christoph Lameter wrote:
> > Ok. Andrea wanted the same because then he can void the begin callouts.
> 
> Exactly. I hope the page-pin will avoid me having to serialize the KVM
> page fault against the start/end critical section.
> 
> BTW, I wonder if the start/end critical section API is intended to
> forbid scheduling inside it. In short I wonder if GRU can is allowed
> to take a spinlock in _range_start as last thing before returning, and
> to release that same spinlock in _range_end as first thing, and not to
> be forced to use a mutex.

_begin/end encloses code that may sleep and _begin/_end itself may sleep. 
So a semaphore may work but not a spinlock.
 
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