Re: [PATCH 4/9] gpiolib: use gpio_chips list in sysfs ops

From: Grant Likely
Date: Sat Feb 09 2013 - 05:11:39 EST

On Tue, 5 Feb 2013 18:15:54 +0100, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> On Sat, Feb 2, 2013 at 5:29 PM, Alexandre Courbot <acourbot@xxxxxxxxxx> wrote:
> > This makes the code both simpler and faster compared to parsing the GPIO
> > number space.
> >
> > Signed-off-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
> Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Applied, thanks.

However, this code is incorrect (it was incorrect before you touched it,
so not your fault). Moving it to a list makes it a lot worse though
because it introduces the possibility of dereferencing an invalid
pointer. The hooks need to grab the spinlock before parsing the list.

I've got a patch which I'll post. I'd appreciate it if you can test

In actual fact, I'd like to replace the spinlock with a mutex, but that
requires some auditing to make sure there aren't any users from an
atomic context.


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