linux-kernel - Re: [PATCH] dmatest: abort transfers immediately when asked for

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Date:	Tue, 21 May 2013 20:24:15 +0300
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Will Deacon <will.deacon@....com>
Cc:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Vinod Koul <vinod.koul@...el.com>,
	"djbw @ fb . com" <djbw@...com>,
	"linux-kernel @ vger . kernel . org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel @ lists . infradead . org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>
Subject: Re: [PATCH] dmatest: abort transfers immediately when asked for

On Tue, May 21, 2013 at 6:11 PM, Will Deacon <will.deacon@....com> wrote:
> Hi Andy,
>
> On Tue, May 21, 2013 at 01:33:17PM +0100, Andy Shevchenko wrote:
>> When thread is going to be stopped we have to unconditionally terminate all
>> ongoing transfers. Otherwise it would be possible that callback function will
>> be called on the next interrupt and will try to access to already freed
>> structures.
>>
>> The patch introduces specific error message for this, though it doesn't
>> increase the counter of the failed tests.
>>
>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
>> Reported-by: Will Deacon <will.deacon@....com>
>
> Thanks for persevering with this! Although this patch definitely fixes the
> panic I was seeing, I now observe buffer verification failures in subsequent
> test runs after an aborted run:

I think the description to the commit adfa543e "dmatest: don't use
set_freezable_with_signal()" may shed light on this.

The background (if  I got it correctly) is in race with done flag. So,
we got a callback call from the DMA engine, but we don't know which
transfer triggers it.
I might be wrong. This is just an assumption.

Have you ever see such behaviour on pre v3.10-rc1 kernels? (I mean
with old dmatest module)

--
With Best Regards,
Andy Shevchenko
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