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

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Message-ID: <54DCCAFE.7080206@redhat.com>
Date:	Thu, 12 Feb 2015 10:47:10 -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 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.

> Meanwhile I'll still take the patch, it's better to handle that 
> from the caller.

Thanks.

- -- 
All rights reversed
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