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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>
This commit is contained in:
Julia Lawall 2010-06-20 13:24:35 +02:00 committed by Jiri Kosina
parent 6e32819e12
commit ca9fe15884
1 changed files with 1 additions and 1 deletions
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2
drivers/hid/hid-debug.c
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@ -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);