linux-kernel - Re: [1/4] gpio: gpio-f7188x: Use mutex for access serialisation.

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Date:	Thu, 10 Sep 2015 00:01:40 +0200
From:	Simon Guinot <simon.guinot@...uanux.org>
To:	Vincent Pelletier <plr.vincent@...il.com>
Cc:	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
	Vincent Donnefort <vdonnefort@...il.com>,
	Yoann Sculo <yoann@...lo.fr>
Subject: Re: [1/4] gpio: gpio-f7188x: Use mutex for access serialisation.

On Thu, Sep 03, 2015 at 08:05:40PM +0200, Vincent Pelletier wrote:
> Hi,
> 
> On Fri, 21 Aug 2015 22:48:24 +0200, Vincent Pelletier
> <plr.vincent@...il.com> wrote:
> > On Fri, 21 Aug 2015 19:52:16 +0200, Simon Guinot
> > <simon.guinot@...uanux.org> wrote:
> > > Please, could you describe a setup (as simple as possible) allowing to
> > > reproduce the issue ? I'll try it on my side.
> > [...]
> > > Please try to make the module list needed to reproduce the issue as
> > > short as possible. Ideally only gpio_f7188x would be needed.
> > 
> > The simplest I could find so far needs gpio-input-polled with 20ms
> > polling period (I didn't try to change polling period), and a shell loop
> > writing to gpioXX/value.
> 
> Have you had a chance to reproduce this issue ?
> Can I do something to help ?

Hi Vincent,

Vincent (Donnefort) finally succeeds to reproduce the issue. The setup
is quite simple. You only have to flood the gpio-f7188x driver via the
sysfs GPIO interface. Nothing more is needed.

After some debugging we discovered that the problem comes from the
__request_region function which don't handle very well concurrent
requests on a muxed region.

I will send a patch as a reply to this email. Please, can you test it ?

Thanks,

Simon

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