linux-kernel - Re: [RFC][PATCH 6/8] mm: handle_speculative

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Date:	Thu, 7 Jan 2010 12:08:25 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Christoph Lameter <cl@...ux-foundation.org>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Arjan van de Ven <arjan@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>,
	"hugh.dickins" <hugh.dickins@...cali.co.uk>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()



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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