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| author | Julia Lawall <julia@diku.dk> | 2010-06-20 13:24:35 +0200 |
|---|---|---|
| committer | Jiri Kosina <jkosina@suse.cz> | 2010-06-21 13:41:54 +0200 |
| commit | ca9fe1588427f246ad4c389b0170b29a432804b6 (patch) | |
| tree | 79a8faa2a25efe789fb06be64bff5034c8659f65 /drivers/hid/hid-debug.c | |
| parent | 6e32819e12ffbd507eced11a1871700a387d5407 (diff) | |
| download | lwn-ca9fe1588427f246ad4c389b0170b29a432804b6.tar.gz lwn-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.c | 2 |
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); |