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authorJulia Lawall <julia@diku.dk>2010-06-20 13:24:35 +0200
committerJiri Kosina <jkosina@suse.cz>2010-06-21 13:41:54 +0200
commitca9fe1588427f246ad4c389b0170b29a432804b6 (patch)
tree79a8faa2a25efe789fb06be64bff5034c8659f65 /drivers/hid/hid-debug.c
parent6e32819e12ffbd507eced11a1871700a387d5407 (diff)
downloadblackbird-op-linux-ca9fe1588427f246ad4c389b0170b29a432804b6.tar.gz
blackbird-op-linux-ca9fe1588427f246ad4c389b0170b29a432804b6.zip
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>
Diffstat (limited to 'drivers/hid/hid-debug.c')
-rw-r--r--drivers/hid/hid-debug.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index c94026768570..850d02a7a925 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -949,8 +949,8 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
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);
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