On 10/20/21 4:39 AM, Nathan Lynch wrote:

Wan Jiabing [off-list ref] writes:

quoted

Fix following coccicheck warning:
./drivers/pci/hotplug/pnv_php.c:161:2-13: ERROR: probable double put.

Device node iterators put the previous value of the index variable, so
an explicit put causes a double put.

I suppose Coccinelle doesn't take into account that this code is
detaching and freeing the nodes.

quoted

diff --git a/drivers/pci/hotplug/pnv_php.c b/drivers/pci/hotplug/pnv_php.c
index f4c2e6e01be0..f3da4f95d73f 100644
--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c

@@ -158,7 +158,6 @@ static void pnv_php_detach_device_nodes(struct device_node *parent)
 	for_each_child_of_node(parent, dn) {
 		pnv_php_detach_device_nodes(dn);
 
-		of_node_put(dn);
 		of_detach_node(dn);
 	}

The code might be improved by comments explaining how the bare
of_node_put() corresponds to a "get" somewhere else in the driver, and
how it doesn't render the ongoing traversal unsafe. It looks suspicious
on first review, but I believe it's intentional and probably correct as
written.

This is a common usage pattern which if we put a comment about the pattern here
we need to do it every where. I suppose a better solution is to wrap this put in
a more descriptive function name like of_node_long_put() or something of the
sort the makes it obvious we are dropping a long held global scope reference.

-Tyrel