Re: [PATCH] rtc: max77686: fix irqf_oneshot.cocci warnings

[Valentin Rothberg]

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@xxxxxxxxx>
>>
>>  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@xxxxxxxxxx>
>> Signed-off-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
>> Signed-off-by: Valentin Rothberg <valentin.rothberg@xxxxxxxxxx>
>> ---
>>  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