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	Wed, 8 Aug 2012 11:19:09 -0400
Date: Wed, 8 Aug 2012 20:50:46 +0530
From: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
To: Felix Fietkau <nbd@openwrt.org>
CC: <linux-wireless@vger.kernel.org>, <linville@tuxdriver.com>,
	<rodrigue@qca.qualcomm.com>, <c_manoha@qca.qualcomm.com>
Subject: Re: [PATCH v2 3.6] ath9k: fix interrupt storms on queued hardware
 reset
Message-ID: <20120808152045.GC2041@vmraj-lnx.qualcomm.com> (sfid-20120808_171914_769445_971A01A0)
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On Wed, Aug 08, 2012 at 05:00:39PM +0200, Felix Fietkau wrote:
> On 2012-08-08 4:43 PM, Rajkumar Manoharan wrote:
> > On Wed, Aug 08, 2012 at 04:25:03PM +0200, Felix Fietkau wrote:
> >> commit b74713d04effbacd3d126ce94cec18742187b6ce
> >> "ath9k: Handle fatal interrupts properly" introduced a race condition, where
> >> IRQs are being left enabled, however the irq handler returns IRQ_HANDLED
> >> while the reset is still queued without addressing the IRQ cause.
> >> This leads to an IRQ storm that prevents the system from even getting to
> >> the reset code.
> >> 
> >> Fix this by disabling IRQs in the handler without touching intr_ref_cnt.
> >>
> > It is safer not to re-enable interrupts on FATAL errors rather than enabling
> > it and then checking it on irq for bailing out. It would be better if you kill
> > the interrupts on processing fatal interrupts.
> A fatal interrupt isn't the only place where this is race shows up.
> Anything that queues a reset is affected, so skipping the interrupt
> enable in the IRQ handler is not enough (aside from the fact that it
> would mess up irq disable refcounting).
> 
> Also, how is it safer? It's not like the interrupt handler does any real
> processing before running into that check.
> 
Agree. I confused with the mentioned commit subject. Sorry for the noise.

-Rajkumar