A refcount issue can appeared in __fwnode_link_del() due to the
pr_debug() call:
WARNING: CPU: 0 PID: 901 at lib/refcount.c:25 refcount_warn_saturate+0xe5/0x110
Call Trace:
<TASK>
...
of_node_get+0x1e/0x30
of_fwnode_get+0x28/0x40
fwnode_full_name_string+0x34/0x90
fwnode_string+0xdb/0x140
...
vsnprintf+0x17b/0x630
...
__fwnode_link_del+0x25/0xa0
fwnode_links_purge+0x39/0xb0
of_node_release+0xd9/0x180
...
Indeed, an fwnode (of_node) is being destroyed and so, of_node_release()
is called because the of_node refcount reached 0.
>From of_node_release() several function calls are done and lead to
a pr_debug() calls with %pfwf to print the fwnode full name.
The issue is not present if we change %pfwf to %pfwP.
To print the full name, %pfwf iterates over the current node and its
parents and obtain/drop a reference to all nodes involved.
In order to allow to print the full name (%pfwf) of a node while it is
being destroyed, do not obtain/drop a reference to this current node.
Fixes: a92eb7621b9f ("lib/vsprintf: Make use of fwnode API to obtain node names and separators")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Herve Codina <herve.codina@xxxxxxxxxxx>
Reviewed-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
Changes v2 -> v3
- Fix typo in comment ("ie parents node" -> "i.e. parent nodes")
- Add 'Reviewed-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>'
- Add 'Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>'
Changes v1 -> v2
- Avoid handling current node out of the loop. Instead obtain/drop references
in the loop based on the depth value.
- Remove some of the backtrace lines in the commit log.
lib/vsprintf.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index afb88b24fa74..2aa408441cd3 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2110,15 +2110,20 @@ char *fwnode_full_name_string(struct fwnode_handle *fwnode, char *buf,
/* Loop starting from the root node to the current node. */
for (depth = fwnode_count_parents(fwnode); depth >= 0; depth--) {
- struct fwnode_handle *__fwnode =
- fwnode_get_nth_parent(fwnode, depth);
+ /*
+ * Only get a reference for other nodes (i.e. parent nodes).
+ * fwnode refcount may be 0 here.
+ */
+ struct fwnode_handle *__fwnode = depth ?
+ fwnode_get_nth_parent(fwnode, depth) : fwnode;
buf = string(buf, end, fwnode_get_name_prefix(__fwnode),
default_str_spec);
buf = string(buf, end, fwnode_get_name(__fwnode),
default_str_spec);
- fwnode_handle_put(__fwnode);
+ if (depth)
+ fwnode_handle_put(__fwnode);
}
return buf;
--
2.41.0
