From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 01/13] powerpc: Add rcu_read_lock() to gup_fast()
 implementation
Date: Fri, 16 Apr 2010 16:54:51 +1000
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Cc: Peter Zijlstra <peterz@infradead.org>, Andrea Arcangeli <aarcange@redhat.com>, Avi Kivity <avi@redhat.com>, Thomas Gleixner <tglx@linutronix.de>, Rik van Riel <riel@redhat.com>, Ingo Molnar <mingo@elte.hu>, akpm@linux-foundation.org, Linus Torvalds <torvalds@linux-foundation.org>, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, David Miller <davem@davemloft.net>, Hugh Dickins <hugh.dickins@tiscali.co.uk>, Mel Gorman <mel@csn.ul.ie>, Nick Piggin <npiggin@suse.de>

On Thu, 2010-04-15 at 07:28 -0700, Paul E. McKenney wrote:
> 
> Of course, with call_rcu_sched(), the corresponding RCU read-side
> critical
> sections are non-preemptible.  Therefore, in CONFIG_PREEMPT_RT, these
> read-side critical sections must use raw spinlocks.
> 
> Can the code in question accommodate these restrictions? 

What we protect against is always code that hard-disable IRQs (though
there seem to be a bug in the hugepages code there...). Would that
work ?

Cheers,
Ben.