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

From: Andy Shevchenko
Date: Wed May 22 2013 - 09:26:26 EST

On Wed, May 22, 2013 at 3:41 PM, Will Deacon <will.deacon@xxxxxxx> wrote:
> On Tue, May 21, 2013 at 06:24:15PM +0100, Andy Shevchenko wrote:
>> On Tue, May 21, 2013 at 6:11 PM, Will Deacon <will.deacon@xxxxxxx> wrote:
>> > 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.
> I've not managed to work out exactly what's going on, but it's certainly
> something like that. In fact, I just managed to trigger a case where all but
> one of the transfers is aborted, whilst the remaining one fails. Looking at
> the code, I can't see how that situation comes about, since the threads are
> protected with the info mutex and kthread_stop is synchronous.

>> Have you ever see such behaviour on pre v3.10-rc1 kernels? (I mean
>> with old dmatest module)
> No, dmatest from 3.9 is completely reliable in my experience.

Yeah, I supposed that was a rhetorical question.

So, have I understood correctly that if you revert the 77101ce5
("cancel thread ...")
everything is working fine / as before?

With Best Regards,
Andy Shevchenko
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