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Message-ID: <d120d5000709190717y69dca8b3tf4a17b920267806b@mail.gmail.com>
Date: Wed, 19 Sep 2007 10:17:25 -0400
From: "Dmitry Torokhov" <dmitry.torokhov@gmail.com>
To: "Peter Zijlstra" <a.p.zijlstra@chello.nl>
Subject: Re: [RFC][PATCH 2/6] lockdep: validate rcu_dereference() vs rcu_read_lock()
Cc: linux-kernel@vger.kernel.org,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       "Ingo Molnar" <mingo@elte.hu>,
       "Andrew Morton" <akpm@linux-foundation.org>,
       "Nick Piggin" <nickpiggin@yahoo.com.au>
In-Reply-To: <20070919105054.332308000@chello.nl>
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Hi Peter,

On 9/19/07, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> Warn when rcu_dereference() is not used in combination with rcu_read_lock()
>

According to Paul it is fine to use RCU primitives (when accompanied
with proper comments) when the read-size critical section is guarded
by spin_lock_irqsave()/spin_lock_irqsrestore() instead of
rcu_read_lock()/rcu_read_unlock() and writers synchronize with
synchronize_sched(), not synchronize_rcu(). Your patch will trigger
warnign on such valid usages.

-- 
Dmitry