lkml.org 
[lkml]   [2011]   [Nov]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRE: [PATCH 2/2] dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to access empty list
From
Date
On Tue, 2011-11-22 at 14:26 -0600, H Hartley Sweeten wrote:
> On Tuesday, November 22, 2011 12:46 PM, Mika Westerberg wrote:
> > From: Rafal Prylowski <prylowski@metasoft.pl>
> >
> > If dma_terminate_all() is called before the ep93xx_dma_tasklet()
> gets to run,
> > it tries to access an empty ->active list causing following OOPS:
>
> [snip]
>
> > As we expect that the ->active list is never empty when the
> ep93xx_dma_tasklet()
> > is called, we fix this by adding a new flag per channel
> EP93XX_DMA_IS_RUNNING
> > which determines whether the channel is running or not.
> >
> > We also add BUG_ON() to ep93xx_dma_get_active() to make sure that
> similar
> > problems will be caught early.
My $0.02

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

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)


--
~Vinod



\
 
 \ /
  Last update: 2011-11-23 12:07    [W:0.053 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site