Messages in this thread | | | Date | Thu, 20 Aug 2020 20:46:43 +0200 | From | Paul Cercueil <> | Subject | Re: [PATCH] drivers/dma/dma-jz4780: Fix race condition between probe and irq handler |
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Le jeu. 20 août 2020 à 20:23, Lars-Peter Clausen <lars@metafoo.de> a écrit : > On 8/20/20 1:59 PM, Paul Cercueil wrote: >> Hi, >> >> Le dim. 16 août 2020 à 12:52, madhuparnabhowmik10@gmail.com a >> écrit : >>> From: Madhuparna Bhowmik <madhuparnabhowmik10@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@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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