linux-kernel - Re: [PATCH v4 1/8] [media] soc_camera: Do not decrement endpoint node refcount in the loop

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Message-ID: <1411983923.3050.1.camel@pengutronix.de>
Date:	Mon, 29 Sep 2014 11:45:23 +0200
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Dan Carpenter <dan.carpenter@...cle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>
Cc:	Grant Likely <grant.likely@...aro.org>, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	kernel@...gutronix.de, Russell King <rmk+kernel@....linux.org.uk>,
	linux-media@...r.kernel.org,
	Guennadi Liakhovetski <g.liakhovetski@....de>
Subject: Re: [PATCH v4 1/8] [media] soc_camera: Do not decrement endpoint
 node refcount in the loop

Am Montag, den 29.09.2014, 12:13 +0300 schrieb Dan Carpenter:
> On Mon, Sep 29, 2014 at 10:15:44AM +0200, Philipp Zabel wrote:
> > In preparation for a following patch, stop decrementing the endpoint node
> > refcount in the loop. This temporarily leaks a reference to the endpoint node,
> > which will be fixed by having of_graph_get_next_endpoint decrement the refcount
> > of its prev argument instead.
> 
> Don't do this...
> 
> My understanding (and I haven't invested much time into trying to
> understand this beyond glancing at the change) is that patch 1 and 2,
> introduce small bugs that are fixed in patch 3?
>
> Just fold all three patches into one patch.  We need an Ack from Mauro
> and Greg and then send the patch through Grant's tree.

Yes. Patches 1 and 2 leak a reference on of_nodes touched by the loop.
As far as I am aware, all users of this code don't use the reference
counting (CONFIG_OF_DYNAMIC is disabled), so this bug should be
theoretical.

I'd be happy do as you suggest if Mauro and Greg agree.

regards
Philipp

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