Re: [PATCH] thermal: tegra: delete unneeded of_node_put

Jon Hunter
2017-07-17T13:47:14Z

On 15/07/17 09:42, Julia Lawall wrote:
> Device node iterators perform an of_node_put on each iteration, so putting
> an of_node_put before a continue results in a double put.
>
> The semantic match that finds this problem is as follows
> (http://coccinelle.lip6.fr):
>
> // <smpl>
> @@
> expression e1;
> local idexpression child;
> iterator name for_each_child_of_node;
> @@
>
> for_each_child_of_node(e1,child) {
> ... when != of_node_get(child)
> * of_node_put(child);
> ...
> * continue;
> }
> // </smpl>
>
> Furthermore, the call to thermal_of_cooling_device_register immediately
> calls __thermal_cooling_device_register with the same arguments. The
> latter function stores the device node argument, which is the second
> argument of for_each_child_of_node, in the returned thermal_cooling_device
> structure. This returned structure is then stored in the cdev field of
> stc. Thus it seems that the second argument of for_each_child_of_node
> escapes the scope of the for_each_child_of_node, so an explicit of_node_get
> on success of thermal_of_cooling_device_register is also needed.
>
> Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
>
> ---
> drivers/thermal/tegra/soctherm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/thermal/tegra/soctherm.c b/drivers/thermal/tegra/soctherm.c
> index 7d2db23..10f4fdd 100644
> --- a/drivers/thermal/tegra/soctherm.c
> +++ b/drivers/thermal/tegra/soctherm.c
> @@ -1014,7 +1014,6 @@ static void soctherm_init_hw_throt_cdev(struct platform_device *pdev)
> tcd = thermal_of_cooling_device_register(np_stcc,
> (char *)name, ts,
> &throt_cooling_ops);
> - of_node_put(np_stcc);
> if (IS_ERR_OR_NULL(tcd)) {
> dev_err(dev,
> "throttle-cfg: %s: failed to register cooling device\n",
> @@ -1022,6 +1021,7 @@ static void soctherm_init_hw_throt_cdev(struct platform_device *pdev)
> continue;
> }
>
> + of_node_get(np_stcc);
> stc->cdev = tcd;
> stc->init = true;
> }

Thanks for fixing this. However, I am wondering if it is better for the
'of_node_get' to be placed within the
thermal_of_cooling_device_register() function as it seems a bit odd if
the caller needs to know that this is being stored for later use.

Also, taking a quick look, I see a couple other drivers calling
thermal_of_cooling_device_register() and they are also not calling
of_node_get on success. So it maybe easier to fix placing it in the
thermal_of_cooling_device_register() function.

Cheers
Jon

--
nvpublic