linux-kernel - Re: [PATCH -v5 6/5] context_tracking: fix exception_enter when already in IN

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Date:	Thu, 12 Feb 2015 12:48:51 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	paulmck@...ux.vnet.ibm.com, luto@...capital.net,
	will.deacon@....com, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, mtosatti@...hat.com, borntraeger@...ibm.com,
	lcapitulino@...hat.com, pbonzini@...hat.com
Subject: Re: [PATCH -v5 6/5] context_tracking: fix exception_enter when already
 in IN_KERNEL

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On 02/12/2015 12:00 PM, Frederic Weisbecker wrote:
> On Thu, Feb 12, 2015 at 10:47:10AM -0500, Rik van Riel wrote:
>> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
>> 
>> On 02/12/2015 10:42 AM, Frederic Weisbecker wrote:
>>> On Wed, Feb 11, 2015 at 02:43:19PM -0500, Rik van Riel wrote:
>>>> If exception_enter happens when already in IN_KERNEL state,
>>>> the code still calls context_tracking_exit, which ends up in
>>>>  rcu_eqs_exit_common, which explodes with a WARN_ON when it
>>>> is called in a situation where dynticks are not enabled.
>>> 
>>> Fortunately context_tracking_exit() already has a current_state
>>> == IN_KERNEL check so this shouldn't be a problem.
>> 
>> No, it had a hard-coded "current_state == IN_USER" check, which
>> is very close, but ...
>> 
>> ... I replaced that with a state argument, and forgot to ensure
>> that it never gets called with state == IN_KERNEL. This patch
>> fixes that.
> 
> Ah that's right! Well I'm going to merge this patch to 1/5 then to 
> avoid breaking bisection.

Thank you, Frederic!

- -- 
All rights reversed
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