ieee1394: nodemgr: fix rwsem recursion

nodemgr_update_pdrv grabbed an rw semaphore (as reader) which was
already taken by its caller's caller, nodemgr_probe_ne (as reader too).
Reported by Miles Lane, call path pointed out by Arjan van de Ven.

FIXME:
Shouldn't we rather use class->sem there, not class->subsys.rwsem?

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 5 insertions, 4 deletions

diff --git a/drivers/ieee1394/nodemgr.c b/drivers/ieee1394/nodemgr.c
index eabc51b23c0b..f087f7e2b691 100644
--- a/drivers/ieee1394/nodemgr.c
+++ b/drivers/ieee1394/nodemgr.c
@@ -1316,6 +1316,7 @@ static void nodemgr_node_scan(struct host_info *hi, int generation)
 }
 
 
+/* Caller needs to hold nodemgr_ud_class.subsys.rwsem as reader. */
 static void nodemgr_suspend_ne(struct node_entry *ne)
 {
         struct class_device *cdev;
@@ -1368,15 +1369,14 @@ static void nodemgr_resume_ne(struct node_entry *ne)
 }
 
 
+/* Caller needs to hold nodemgr_ud_class.subsys.rwsem as reader. */
 static void nodemgr_update_pdrv(struct node_entry *ne)
 {
         struct unit_directory *ud;
         struct hpsb_protocol_driver *pdrv;
-        struct class *class = &nodemgr_ud_class;
         struct class_device *cdev;
 
-        down_read(&class->subsys.rwsem);
-        list_for_each_entry(cdev, &class->children, node) {
+        list_for_each_entry(cdev, &nodemgr_ud_class.children, node) {
                 ud = container_of(cdev, struct unit_directory, class_dev);
                 if (ud->ne != ne || !ud->device.driver)
                         continue;
@@ -1389,7 +1389,6 @@ static void nodemgr_update_pdrv(struct node_entry *ne)
                         up_write(&ud->device.bus->subsys.rwsem);
                 }
         }
-        up_read(&class->subsys.rwsem);
 }
 
 
@@ -1420,6 +1419,8 @@ static void nodemgr_irm_write_bc(struct node_entry *ne, int generation)
 }
 
 
+/* Caller needs to hold nodemgr_ud_class.subsys.rwsem as reader because the
+ * calls to nodemgr_update_pdrv() and nodemgr_suspend_ne() here require it. */
 static void nodemgr_probe_ne(struct host_info *hi, struct node_entry *ne, int generation)
 {
         struct device *dev;