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Date: Tue, 1 Jul 2008 11:58:54 +0530
From: Dhaval Giani <dhaval@linux.vnet.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Gautham R Shenoy <ego@in.ibm.com>,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       Dipankar Sarma <dipankar@in.ibm.com>, laijs@cn.fujitsu.com,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       lkml <linux-kernel@vger.kernel.org>,
       Rusty Russel <rusty@rustcorp.com.au>
Subject: Re: [PATCH] fix rcu vs hotplug race
Message-ID: <20080701062854.GD6131@linux.vnet.ibm.com>
Reply-To: Dhaval Giani <dhaval@linux.vnet.ibm.com>
References: <20080623105844.GC28192@elte.hu> <20080623114941.GB3160@in.ibm.com> <20080624110144.GA8695@elte.hu> <20080626152728.GA24972@linux.vnet.ibm.com> <20080627044738.GC3419@in.ibm.com> <20080627051855.GD26167@in.ibm.com> <20080627054959.GB3309@linux.vnet.ibm.com> <20080627145845.GA9229@linux.vnet.ibm.com> <20080701053900.GB8205@in.ibm.com> <20080701061600.GF14658@elte.hu>
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On Tue, Jul 01, 2008 at 08:16:01AM +0200, Ingo Molnar wrote:
> 
> * Gautham R Shenoy <ego@in.ibm.com> wrote:
> 
> > So, it's the design of stop_machine() that's preventing someone from 
> > updating the cpu_online_map while force_quiescent_state() is 
> > performing the cpu_is_online() check. Becase we always call 
> > force_quiescent_state() with irqs disabled :)
> 
> Paul, do you concur? I'll apply the commit in the form below to 
> tip/core/urgent if Paul agrees.
> 
> 	Ingo

Ingo,

I believe Gautham's fix at http://lkml.org/lkml/2008/6/27/9 is better
and also explains it better.

Thanks.
-- 
regards,
Dhaval