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Date: Fri, 10 Oct 2008 09:35:21 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] markers: bit-field is not thread-safe nor smp-safe
Message-ID: <20081010073520.GC16016@elte.hu>
References: <48EEF9AD.9040401@cn.fujitsu.com> <20081010073136.GC23247@Krystal>
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* Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> * Lai Jiangshan (laijs@cn.fujitsu.com) wrote:
> > 
> > bit-field is not thread-safe nor smp-safe.
> > 
> > struct marker_entry.rcu_pending is not protected by any lock
> > in rcu-callback free_old_closure().
> > so we must turn it into a safe type.
> > 
> 
> 
> hrm, yes, you are right. I first test for 
> 
>         if (entry->rcu_pending)
>            rcu_barrier_sched();
> 
> To check if I must execute the rcu callback, and _this_ races against
> the entry->rcu_pending = 0; within the callback.
> 
> Your fix is therefore needed.
> 
> Thanks !
> 
> Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>

applied to tip/tracing/markers, thanks guys!

	Ingo