linux-kernel - Re: [PATCH 01/13] powerpc: Add rcu_read_lock() to gup

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Message-ID: <4BBE3D2F.6030609@redhat.com>
Date:	Thu, 08 Apr 2010 16:31:43 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Andrea Arcangeli <aarcange@...hat.com>,
	Avi Kivity <avi@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Miller <davem@...emloft.net>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Mel Gorman <mel@....ul.ie>, Nick Piggin <npiggin@...e.de>
Subject: Re: [PATCH 01/13] powerpc: Add rcu_read_lock() to gup_fast() implementation

On 04/08/2010 03:17 PM, Peter Zijlstra wrote:
> The powerpc page table freeing relies on the fact that IRQs hold off
> an RCU grace period, this is currently true for all existing RCU
> implementations but is not an assumption Paul wants to support.
>
> Therefore, also take the RCU read lock along with disabling IRQs to
> ensure the RCU grace period does at least cover these lookups.
>
> Requested-by: Paul E. McKenney<paulmck@...ux.vnet.ibm.com>
> Signed-off-by: Peter Zijlstra<a.p.zijlstra@...llo.nl>
> Cc: Nick Piggin<npiggin@...e.de>
> Cc: Benjamin Herrenschmidt<benh@...nel.crashing.org>

Reviewed-by: Rik van Riel <riel@...hat.com>
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