linux-kernel - Re: [PATCH 4/9] gpiolib: use gpio

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Message-ID: <CAAVeFuLW5pP=Kk7wh63eNAuycvEcXV1op6GkXyZwK85Gqz+DJQ@mail.gmail.com>
Date:	Sat, 9 Feb 2013 22:53:22 +0900
From:	Alexandre Courbot <acourbot@...dia.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arch <linux-arch@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/9] gpiolib: use gpio_chips list in sysfs ops

On Sat, Feb 9, 2013 at 6:37 PM, Grant Likely <grant.likely@...retlab.ca> wrote:
> 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
> also.
>
> 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.

I thought about doing that as well actually, but left it for later. It
looks safe at first sight, but as you mention we cannot exclude a few
users will break as a consequence of such a switch.

In any case, I plan to give it a try once that big chunk is merged.

Alex.
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