linux-kernel - Re: [PATCH V2 1/1] lib/atomic64 using raw_spin_lock

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Message-ID: <4E6027E1.1090905@gmail.com>
Date:	Fri, 02 Sep 2011 08:48:33 +0800
From:	Shan Hai <haishan.bai@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	akpm@...ux-foundation.org, eric.dumazet@...il.com,
	vapier@...too.org, asharma@...com, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org
Subject: Re: [PATCH V2 1/1] lib/atomic64 using raw_spin_lock_irq[save|resotre]
 for atomicity

On 09/01/2011 06:11 PM, Thomas Gleixner wrote:
> On Thu, 1 Sep 2011, Thomas Gleixner wrote:
>
>> On Thu, 1 Sep 2011, Shan Hai wrote:
>>
>>> The spin_lock_irq[save|restore] could break the atomicity of the
>>> atomic64_* operations in the PREEMPT-RT configuration, because
>>> the spin_lock_irq[save|restore] themselves are preemptable in the
>>> PREEMPT-RT, using raw variant of the spin lock could provide the
>>> atomicity that atomic64_* need.
>> Good catch. Queued for the next release.
> Though the changelog is misleading. The reason is not that they are
> preemtible.
>
> The reason for your OOPs is that the sleeping locks are not IRQ
> safe. And your system simply deadlocked due to that.
>

Will correct it in the V3 patch, thanks for the advice.

Cheers
Shan Hai

> Thanks,
>
> 	tglx
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