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

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Message-ID: <alpine.LFD.2.00.1001071634500.7821@localhost.localdomain>
Date:	Thu, 7 Jan 2010 16:39:27 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.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 Fri, 8 Jan 2010, KAMEZAWA Hiroyuki wrote:
> 
> Hmm, do_brk() sometimes unmap conflicting mapping. Isn't it be a problem ?

No. For two reasons:

 - sys_brk() doesn't actually do that (see the "find_vma_intersection()" 
   call). I'm not sure why do_brk() does, but it might have to do with 
   execve().

 - the patch I sent out just falls back to the old code if it finds 
   something fishy, so it will do whatever do_brk() does regardless.

(Yes, brk() does unmap the old brk for the _shrinking_ case, of course. 
Again, the patch I sent just falls back to the old behavior in that case)

		Linus

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