linux-kernel - Re: [PATCH] clocksource: Do not drop unheld reference on device node

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Message-ID: <20131122161607.GA5088@ulmo.nvidia.com>
Date:	Fri, 22 Nov 2013 17:16:09 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Rob Herring <rob.herring@...xeda.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clocksource: Do not drop unheld reference on device node

On Sat, Oct 19, 2013 at 12:49:48AM +0200, Thierry Reding wrote:
> When booting a recent kernel on ARM with OF_DYNAMIC enabled, the kernel
> warns about the following:
> 
> 	[    0.000000] ERROR: Bad of_node_put() on /timer@...04600
> 	[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.0-rc5-next-20131017-00077-gedfd827-dirty #406
> 	[    0.000000] [<c0015b68>] (unwind_backtrace+0x0/0xf4) from [<c00117e4>] (show_stack+0x10/0x14)
> 	[    0.000000] [<c00117e4>] (show_stack+0x10/0x14) from [<c055f734>] (dump_stack+0x9c/0xc8)
> 	[    0.000000] [<c055f734>] (dump_stack+0x9c/0xc8) from [<c03b47d4>] (of_node_release+0x90/0x9c)
> 	[    0.000000] [<c03b47d4>] (of_node_release+0x90/0x9c) from [<c03b5084>] (of_find_matching_node_and_match+0x78/0xb4)
> 	[    0.000000] [<c03b5084>] (of_find_matching_node_and_match+0x78/0xb4) from [<c07887c8>] (clocksource_of_init+0x60/0x70)
> 	[    0.000000] [<c07887c8>] (clocksource_of_init+0x60/0x70) from [<c076e99c>] (start_kernel+0x1f4/0x33c)
> 	[    0.000000] [<c076e99c>] (start_kernel+0x1f4/0x33c) from [<80008074>] (0x80008074)
> 
> This is caused by clocksource_of_init() dropping a reference on the
> device node that it never took. The reference taken by the loop is
> implicitly dropped on subsequent iterations. See the implementation of
> and the comment on top of the of_find_matching_node_and_match()
> function for reference (no pun intended).
> 
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  drivers/clocksource/clksrc-of.c | 1 -
>  1 file changed, 1 deletion(-)

Can someone look at this?

Thierry

> diff --git a/drivers/clocksource/clksrc-of.c b/drivers/clocksource/clksrc-of.c
> index 35639cf4..b9ddd9e 100644
> --- a/drivers/clocksource/clksrc-of.c
> +++ b/drivers/clocksource/clksrc-of.c
> @@ -35,6 +35,5 @@ void __init clocksource_of_init(void)
>  
>  		init_func = match->data;
>  		init_func(np);
> -		of_node_put(np);
>  	}
>  }
> -- 
> 1.8.4
> 

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