Date: Fri, 6 Jun 2008 18:27:55 +0200
From: Nick Piggin <npiggin@suse.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org,
       linux-mm@kvack.org, linux-kernel@vger.kernel.org,
       benh@kernel.crashing.org, paulus@samba.org,
       Paul E McKenney <paulmck@linux.vnet.ibm.com>
Subject: Re: [patch 3/7] mm: speculative page references
Message-ID: <20080606162754.GC23939@wotan.suse.de>
References: <20080605094300.295184000@nick.local0.net> <20080605094825.699347000@nick.local0.net> <1212762004.23439.119.camel@twins>
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On Fri, Jun 06, 2008 at 04:20:04PM +0200, Peter Zijlstra wrote:
> On Thu, 2008-06-05 at 19:43 +1000, npiggin@suse.de wrote:
> > plain text document attachment (mm-speculative-get_page-hugh.patch)
> 
> > +static inline int page_cache_get_speculative(struct page *page)
> > +{
> > +	VM_BUG_ON(in_interrupt());
> > +
> > +#ifndef CONFIG_SMP
> > +# ifdef CONFIG_PREEMPT
> > +	VM_BUG_ON(!in_atomic());
> > +# endif
> > +	/*
> > +	 * Preempt must be disabled here - we rely on rcu_read_lock doing
> > +	 * this for us.
> 
> Preemptible RCU is already in the tree, so I guess you'll have to
> explcitly disable preemption if you require it.
> 

And here is the fix for patch 7/7

--
Index: linux-2.6/include/linux/pagemap.h
===================================================================
--- linux-2.6.orig/include/linux/pagemap.h
+++ linux-2.6/include/linux/pagemap.h
@@ -149,7 +149,7 @@ static inline int page_cache_add_specula
 {
 	VM_BUG_ON(in_interrupt());
 
-#ifndef CONFIG_SMP
+#if !defined(CONFIG_SMP) && defined(CONFIG_CLASSIC_RCU)
 # ifdef CONFIG_PREEMPT
 	VM_BUG_ON(!in_atomic());
 # endif
--
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