linux-kernel - Re: [PATCH v2 2/4] dmaengine: Add STM32 DMA driver

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Message-ID: <561E7497.1050105@linaro.org>
Date:	Wed, 14 Oct 2015 16:28:23 +0100
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	M'boumba Cedric Madianga <cedric.madianga@...il.com>
Cc:	Maxime Coquelin <mcoquelin.stm32@...il.com>, robh+dt@...nel.org,
	pawel.moll@....com, Mark Rutland <mark.rutland@....com>,
	ijc+devicetree@...lion.org.uk, Kumar Gala <galak@...eaurora.org>,
	linux@....linux.org.uk, Vinod Koul <vinod.koul@...el.com>,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org
Subject: Re: [PATCH v2 2/4] dmaengine: Add STM32 DMA driver

On 14/10/15 16:26, M'boumba Cedric Madianga wrote:
> 2015-10-14 16:24 GMT+02:00 Daniel Thompson <daniel.thompson@...aro.org>:
>>
>> Hmnnn...
>>
>> The dmaengine framework will WARN_ONCE() if an dmaengine is removed whilst
>> it is active and also works hard to ensure dmaengine modules are not removed
>> whilst there are active drivers using the framework.
>>
>> How do we get into this function whilst there is still an active DMA
>> channels?
>
> For example, when a user try "rmmod stm32-dma" in uart console.
> It will enter in stm32_dma_remove while there is potentially still active DMA.

Check dmaengine.c for yourself but I think in this case the dmaengine 
framework will hold references to the module and prevent the remove from 
taking place.


Daniel.
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