Re: dmatest regression in 3.10-rc1

From: Will Deacon
Date: Mon May 20 2013 - 05:59:46 EST


Hi Andy,

On Mon, May 20, 2013 at 08:52:34AM +0100, Andy Shevchenko wrote:
> On Fri, 2013-05-17 at 15:18 +0100, Will Deacon wrote:
> > On Fri, May 17, 2013 at 01:34:23PM +0100, Vinod Koul wrote:
> > > On Thu, May 16, 2013 at 04:35:53PM +0100, Will Deacon wrote:
> > > > Right, so I think I understand what's causing this, but I'll leave it to
> > > > Andriy to suggest a fix.
>
> Thanks for the report.
>
> Unfortunately neither me nor other guys in the team could not reproduce
> mentioned issue on our hardware.
> Nevertheless I will try to allocate time and suggest possible fix if any
> comes to my mind. So, your testing and analysis is appreciated.

Sure. They way I trigger it is to unload the module whilst the DMA is
ongoing (I'm using a software model, so I can make the DMA nice and slow --
I guess you could try using some large buffers).

My script (I just run from busybox) is:

#!/bin/sh

mount proc -t proc /proc
mount sysfs -t sysfs /sys
mount debugfs -t debugfs /sys/kernel/debug

echo 9 > /proc/sysrq-trigger

modprobe dmatest
echo 8 > /sys/kernel/debug/dmatest/iterations
echo 8 > /sys/kernel/debug/dmatest/threads_per_chan
echo 131072 > /sys/kernel/debug/dmatest/test_buf_size
echo 1 > /sys/kernel/debug/dmatest/run
modprobe -r dmatest

Will
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