HID: eliminate a double lock in debug code
The path around the loop ends with the lock held, so the call to mutex_lock
is moved before the beginning of the loop.
A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)
// <smpl>
@locked@
expression E1;
position p;
@@
read_lock(E1@p,...);
@r exists@
expression x <= locked.E1;
expression locked.E1;
expression E2;
identifier lock;
position locked.p,p1,p2;
@@
*lock@p1 (E1@p,...);
... when != E1
when != \(x = E2\|&x\)
*lock@p2 (E1,...);
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index c940267..850d02a 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -949,8 +949,8 @@
int ret = 0, len;
DECLARE_WAITQUEUE(wait, current);
+ mutex_lock(&list->read_mutex);
while (ret == 0) {
- mutex_lock(&list->read_mutex);
if (list->head == list->tail) {
add_wait_queue(&list->hdev->debug_wait, &wait);
set_current_state(TASK_INTERRUPTIBLE);