[ldv-project] [PATCH] drivers/dma/dma-jz4780: Fix race condition between probe and irq handler
Paul Cercueil
paul at crapouillou.net
Thu Aug 20 21:46:43 MSK 2020
Le jeu. 20 août 2020 à 20:23, Lars-Peter Clausen <lars at metafoo.de> a
écrit :
> On 8/20/20 1:59 PM, Paul Cercueil wrote:
>> Hi,
>>
>> Le dim. 16 août 2020 à 12:52, madhuparnabhowmik10 at gmail.com a
>> écrit :
>>> From: Madhuparna Bhowmik <madhuparnabhowmik10 at gmail.com>
>>>
>>> In probe IRQ is requested before zchan->id is initialized which can
>>> be
>>> read in the irq handler. Hence, shift request irq and enable clock
>>> after
>>> other initializations complete. Here, enable clock part is not part
>>> of
>>> the race, it is just shifted down after request_irq to keep the
>>> error
>>> path same as before.
>>>
>>> Found by Linux Driver Verification project (linuxtesting.org).
>>>
>>> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10 at gmail.com>
>>
>> I don't think there is a race at all, the interrupt handler won't be
>> called before the DMA is registered.
>>
> From a purely formal verification perspective there is a bug. The
> interrupt could fire if i.e. the hardware is buggy or something. In
> general it is a good idea to not request the IRQ until all the
> resources that are used in the interrupt handler are properly set up.
> Even if you know that in practice the interrupt will never fire this
> early.
>
Fair enough, I'm fine with that, but the patch should be reworked so
that the clk_prepare_enable() call is not moved.
Cheers,
-Paul
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