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Date: Thu, 7 Jan 2010 12:08:25 -0800 (PST)
From: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()
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To: Christoph Lameter <cl@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>, Arjan van de Ven <arjan@infradead.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "minchan.kim@gmail.com" <minchan.kim@gmail.com>, "hugh.dickins" <hugh.dickins@tiscali.co.uk>, Nick Piggin <nickpiggin@yahoo.com.au>, Ingo Molnar <mingo@elte.hu>
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On Thu, 7 Jan 2010, Christoph Lameter wrote:
> 
> page_table_lock used to serialize multiple fast brks?
> 
> CONFIG_SPLIT_PTLOCK implies that code will not use this lock in fault
> handling. So no serialization with faults.

Correct. The faults we do not need to serialize with. It doesn't matter 
whether they see the old or the new end. 

> Also the current code assumes vm_end and so on to be stable if mmap_sem is
> held. F.e. find_vma() from do_fault is now running while vm_end may be changing
> under it.

Again, it doesn't matter. Old or new - if some other thread looks up the 
vma, either is fine.

			Linus

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