linux-kernel - Re: [PATCH V2] dma: tegra: avoid channel lock up after free

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Date:	Tue, 30 Oct 2012 12:05:27 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Dmitry Osipenko <digetx@...il.com>, ldewangan@...dia.com
CC:	vinod.koul@...el.com, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] dma: tegra: avoid channel lock up after free

On 10/29/2012 05:20 PM, Dmitry Osipenko wrote:
> Fixed channel "lock up" after free.
> 
> Lock scenario: Channel 1 was allocated and prepared as slave_sg, used and freed.
> Now preparation of cyclic dma on channel 1 will fail with err "DMA configuration
> conflict" because tdc->isr_handler still selected to handle_once_dma_done.
> 
> This happens because tegra_dma_abort_all() won't be called on channel freeing
> if pending list is empty or channel not busy. We need to clear isr_handler
> on channel freeing to avoid locking. Also I added small optimization to prepare
> functions, so current channel type checked before making allocations.

Reviewed-by: Stephen Warren <swarren@...dia.com>

I believe this looks OK. However, I would like Laxman to also ack/review
this since he wrote the driver.
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