linux-kernel - Re: [RFC: PATCH 2/2] iio: adc: exynos_adc: Handle timeout and race conditions

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Message-ID: <515EFE0C.2030401@metafoo.de>
Date:	Fri, 05 Apr 2013 18:38:36 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Doug Anderson <dianders@...omium.org>
CC:	Naveen Krishna Chatradhi <ch.naveen@...sung.com>,
	linux-iio <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-samsung-soc@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Naveen Krishna <naveenkrishna.ch@...il.com>
Subject: Re: [RFC: PATCH 2/2] iio: adc: exynos_adc: Handle timeout and race
 conditions

On 04/05/2013 04:56 PM, Doug Anderson wrote:
> Lars,
> 
> On Fri, Apr 5, 2013 at 1:53 AM, Lars-Peter Clausen <lars@...afoo.de> wrote:
>> Since we sleep inside the protected section we need to use a mutex.
> 
> Ah, good point.
> 
>> It's not the timeout case I'm worried about, but the case where the transfer
>> is interrupted by the user. Even though it is rather unlikely for the
>> problem to occur we should still try to avoid it, this is one of these
>> annoying heisenbugs that happen once in a while and nobody is able to
>> reproduce them.
> 
> Yes, of course.  Then we can also get extra confidence that the reset
> logic works well by stressing out this case...  :)
> 
> This makes me think, though.  Given how fast we expect the ADC
> transaction to finish, would there be any benefit to making the wait
> non-interruptible and then shortening the timeout a whole lot.  If we
> shortened to 1ms then we're really not "non-interruptible" for very
> long and there's less chance of subtle bugs in the way that reset
> works.

Yes, that could also work.

- Lars
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