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

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Message-ID: <1271253110.32749.47.camel@laptop>
Date:	Wed, 14 Apr 2010 15:51:50 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Avi Kivity <avi@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rik van Riel <riel@...hat.com>, 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,
	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 Mon, 2010-04-12 at 20:43 -0700, Paul E. McKenney wrote:
> > So we might have to support the interrupt assumption, at least in some
> > form, with those guys...
> 
> One way to make the interrupt assumption official is to use
> synchronize_sched() rather than synchronize_rcu().

Well, call_rcu_sched() then, because the current usage is to use
call_rcu() to free the page directories.

Paul, here is a call_rcu_sched() available in kernel/rcutree.c, but am I
right in reading that code that that would not be available for
preemptible RCU?


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