linux-kernel - Re: [PATCH 2/2] dma/ep93xx_dma: prevent ep93xx_dma

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Date:	Thu, 24 Nov 2011 07:47:31 +0200
From:	Mika Westerberg <mika.westerberg@....fi>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	H Hartley Sweeten <hartleys@...ionengravers.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"rmallon@...il.com" <rmallon@...il.com>,
	Rafal Prylowski <prylowski@...asoft.pl>
Subject: Re: [PATCH 2/2] dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to
 access empty list

On Wed, Nov 23, 2011 at 04:30:34PM +0530, Vinod Koul wrote:
> 
> will you still hit the problem if you do a proper check in tasklet for 
> a) if list is empty
> b) if _get_active_desc() returns valid desc
> and the _get_active_desc() returns NULL on not finding active desc

No, with the above the problem goes away.

> The point is by adding a flag you are avoiding the condition hence it is
> working for you whereas on other approach you exit gracefully without
> crashing in all the cases (including potentially uncovered ones)

Ok I see.

I'll prepare a new version where ep93xx_dma_get_active() returns NULL in case
of empty active list, and handle it properly in callers.
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