linux-kernel - Re: [PATCH] gpiolib: Fix locking on gpio debugfs files

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Message-ID: <51187376.2060106@nvidia.com>
Date:	Mon, 11 Feb 2013 13:28:38 +0900
From:	Alex Courbot <acourbot@...dia.com>
To:	Grant Likely <grant.likely@...retlab.ca>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH] gpiolib: Fix locking on gpio debugfs files

On 02/09/2013 07:34 PM, Grant Likely wrote:
> The debugfs files really need to hold the gpiolib spinlock before
> accessing the list. Otherwise chip addition/removal will cause an oops.
>
> Cc: Alexandre Courbot <acourbot@...dia.com>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: Grant Likely <grant.likely@...retlab.ca>

Tested-by: Alexandre Courbot <acourbot@...dia.com>

Just wondering: if we manage to change this spinlock into a mutex in the 
future, wouldn't it be better to acquire it only once in 
gpiolib_seq_start() and release it in gpiolib_seq_stop()?

Even though the protection introduced by this patch definitely improves 
the situation, it seems to me that chips could still be removed while 
being displayed by gpiolib_seq_show().

Thanks,
Alex.
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