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SubjectRe: [PATCH 1/2] drivers/hid: Eliminate a double lock
On Sun, 20 Jun 2010, Julia Lawall wrote:

> From: Julia Lawall <julia@diku.dk>
>
> 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/)
[ ... ]
> 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 @@ 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);

Applied, thanks Julia.

--
Jiri Kosina
SUSE Labs, Novell Inc.


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