Re: [RFC/PATCH] of: of_find_node_by_name - stop dropping reference to 'from' node

From: Frank Rowand
Date: Thu Apr 21 2016 - 18:35:23 EST


On 4/19/2016 10:05 AM, Dmitry Torokhov wrote:
> Majority of the callers of of_find_node_by_name() do not expect that it
> will drop reference to the 'from' node if it was passed in, causing
> potential refcount underflows, etc, so let's stop doing this.
>
> Most of the callers that were handling dropping of reference done by
> of_find_node_by_name() actually wanted for_each_node_by_name() instead.
>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> ---
>
> If this is acceptable I can make changes to other of_find_node_*()
> methods...

No. It is correct for of_find_by_name() to call of_node_put() for
the from argument. The callers should be fixed.

-Frank

>
> arch/arm/mach-omap2/omap_hwmod_3xxx_data.c | 2 ++
> arch/powerpc/platforms/83xx/mpc832x_mds.c | 2 +-
> arch/powerpc/platforms/83xx/mpc832x_rdb.c | 2 +-
> arch/powerpc/platforms/83xx/mpc836x_mds.c | 2 +-
> arch/powerpc/platforms/cell/interrupt.c | 3 +--
> arch/powerpc/platforms/cell/setup.c | 3 +--
> arch/powerpc/platforms/cell/spider-pic.c | 3 +--
> arch/powerpc/platforms/powermac/feature.c | 2 +-
> arch/powerpc/platforms/powermac/pic.c | 2 --
> drivers/input/misc/twl4030-vibra.c | 8 +-------
> drivers/of/base.c | 3 +--
> drivers/pci/hotplug/rpadlpar_core.c | 4 ++--
> drivers/video/backlight/tps65217_bl.c | 4 ++--
> include/linux/of.h | 12 +++++++++---
> 14 files changed, 24 insertions(+), 28 deletions(-)

< snip >

> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index b299de2..45fc458 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -826,7 +826,7 @@ EXPORT_SYMBOL(of_find_node_opts_by_path);
> * @from: The node to start searching from or NULL, the node
> * you pass will not be searched, only the next one
> * will; typically, you pass what the previous call
> - * returned. of_node_put() will be called on it
> + * returned.
> * @name: The name string to match against
> *
> * Returns a node pointer with refcount incremented, use
> @@ -843,7 +843,6 @@ struct device_node *of_find_node_by_name(struct device_node *from,
> if (np->name && (of_node_cmp(np->name, name) == 0)
> && of_node_get(np))
> break;
> - of_node_put(from);
> raw_spin_unlock_irqrestore(&devtree_lock, flags);
> return np;
> }

< snip >