linux-kernel - Re: [PATCH] rtc: max77686: fix irqf

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Message-ID: <56C584CC.2000104@posteo.net>
Date:	Thu, 18 Feb 2016 09:46:04 +0100
From:	Valentin Rothberg <valentin.rothberg@...teo.net>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>, ldewangan@...dia.com
Cc:	kbuild-all@...org, alexandre.belloni@...e-electrons.com,
	javier@....samsung.com, cw00.choi@...sung.com,
	a.zummo@...ertech.it, linux-kernel@...r.kernel.org,
	rtc-linux@...glegroups.com,
	kbuild test robot <fengguang.wu@...el.com>
Subject: Re: [PATCH] rtc: max77686: fix irqf_oneshot.cocci warnings



Hi Krzysztof,

On 2/18/16 9:13 AM, Krzysztof Kozlowski wrote:
> On 18.02.2016 17:06, Valentin Rothberg wrote:
>> From: kbuild test robot <fengguang.wu@...el.com>
>>
>>  Since commit 1c6c69525b40 ("genirq: Reject bogus threaded irq requests")
>>  threaded IRQs without a primary handler need to be requested with
>>  IRQF_ONESHOT, otherwise the request will fail.
>>
>>  So pass the IRQF_ONESHOT flag in this case.
>>
>> Generated by: scripts/coccinelle/misc/irqf_oneshot.cocci
>>
>> CC: Laxman Dewangan <ldewangan@...dia.com>
>> Signed-off-by: Fengguang Wu <fengguang.wu@...el.com>
>> Signed-off-by: Valentin Rothberg <valentin.rothberg@...teo.net>
>> ---
>>  drivers/rtc/rtc-max77686.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
> 
> Nack, because:
> 1. AFAIR this is a false positive.

Looking at kernel/irq/manage.c +1250 such requests will be rejected
unconditionally when the primary handler is NULL, except when the chip
is marked to be oneshot safe.

Is there another semantic that I am not aware of?  In case the script
produces false positives, I will change it immediately.

> 2. Was it tested? Was it reproduced? Was the bug actually spotted or
> just coccicheck pointed this and you assumed that "request will fail"?
> 
> Coccicheck is a great tool... but not necessarily for pointing run-time
> bugs.

I did not test it.  To me the issue rather seems seems like something
where Coccinelle is really good at, static analysis.

Kind regards,
 Valentin