Re: [PATCH v2 3/7] dt/powerpc/powernv: Use of_get_child_by_name to get a named child.

On Fri, 2012-09-14 at 09:19 +0100, Srinivas KANDAGATLA wrote:

You've introduced a refcounting bug here.

The return value of of_get_child_by_name() has its refcount elevated
(via of_node_get()), so you have to drop that reference with
of_node_put().

The old code was safe because it only used np inside the loop, and the
loop logic deals with dropping the refcount for you.

And yes of_platform_device_create() takes a reference for itself.

cheers

On 17/09/12 03:07, Michael Ellerman wrote:

On Fri, 2012-09-14 at 09:19 +0100, Srinivas KANDAGATLA wrote:

quoted

From: Srinivas Kandagatla <redacted>

As follow-up to "dt: introduce of_get_child_by_name to get child node by
name." patch, This patch removes some of the code duplication in the
driver by replacing it with of_get_child_by_name instead.

Signed-off-by: Srinivas Kandagatla <redacted>
---
 arch/powerpc/platforms/powernv/opal.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index aaa0dba..6dfb8af 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c

@@ -294,11 +294,9 @@ static int __init opal_init(void)
 		consoles = of_node_get(opal_node);
 
 	/* Register serial ports */
-	for_each_child_of_node(consoles, np) {
-		if (strcmp(np->name, "serial"))
-			continue;
+	np = of_get_child_by_name(consoles, "serial");
+	if (np)
 		of_platform_device_create(np, NULL, NULL);
-	}
 	of_node_put(consoles);

You've introduced a refcounting bug here.

The return value of of_get_child_by_name() has its refcount elevated
(via of_node_get()), so you have to drop that reference with
of_node_put().

I agree..
Will take care of it in v3 patch-series.

The old code was safe because it only used np inside the loop, and the
loop logic deals with dropping the refcount for you.

And yes of_platform_device_create() takes a reference for itself.

cheers