diff options
| -rw-r--r-- | drivers/usb/core/urb.c | 50 |
1 files changed, 21 insertions, 29 deletions
diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c index 7c0555548ac..419e6b34e2f 100644 --- a/drivers/usb/core/urb.c +++ b/drivers/usb/core/urb.c @@ -137,6 +137,16 @@ void usb_anchor_urb(struct urb *urb, struct usb_anchor *anchor) } EXPORT_SYMBOL_GPL(usb_anchor_urb); +/* Callers must hold anchor->lock */ +static void __usb_unanchor_urb(struct urb *urb, struct usb_anchor *anchor) +{ + urb->anchor = NULL; + list_del(&urb->anchor_list); + usb_put_urb(urb); + if (list_empty(&anchor->urb_list)) + wake_up(&anchor->wait); +} + /** * usb_unanchor_urb - unanchors an URB * @urb: pointer to the urb to anchor @@ -156,17 +166,14 @@ void usb_unanchor_urb(struct urb *urb) return; spin_lock_irqsave(&anchor->lock, flags); - if (unlikely(anchor != urb->anchor)) { - /* we've lost the race to another thread */ - spin_unlock_irqrestore(&anchor->lock, flags); - return; - } - urb->anchor = NULL; - list_del(&urb->anchor_list); + /* + * At this point, we could be competing with another thread which + * has the same intention. To protect the urb from being unanchored + * twice, only the winner of the race gets the job. + */ + if (likely(anchor == urb->anchor)) + __usb_unanchor_urb(urb, anchor); spin_unlock_irqrestore(&anchor->lock, flags); - usb_put_urb(urb); - if (list_empty(&anchor->urb_list)) - wake_up(&anchor->wait); } EXPORT_SYMBOL_GPL(usb_unanchor_urb); @@ -749,20 +756,11 @@ EXPORT_SYMBOL_GPL(usb_unpoison_anchored_urbs); void usb_unlink_anchored_urbs(struct usb_anchor *anchor) { struct urb *victim; - unsigned long flags; - spin_lock_irqsave(&anchor->lock, flags); - while (!list_empty(&anchor->urb_list)) { - victim = list_entry(anchor->urb_list.prev, struct urb, - anchor_list); - usb_get_urb(victim); - spin_unlock_irqrestore(&anchor->lock, flags); - /* this will unanchor the URB */ + while ((victim = usb_get_from_anchor(anchor)) != NULL) { usb_unlink_urb(victim); usb_put_urb(victim); - spin_lock_irqsave(&anchor->lock, flags); } - spin_unlock_irqrestore(&anchor->lock, flags); } EXPORT_SYMBOL_GPL(usb_unlink_anchored_urbs); @@ -799,12 +797,11 @@ struct urb *usb_get_from_anchor(struct usb_anchor *anchor) victim = list_entry(anchor->urb_list.next, struct urb, anchor_list); usb_get_urb(victim); - spin_unlock_irqrestore(&anchor->lock, flags); - usb_unanchor_urb(victim); + __usb_unanchor_urb(victim, anchor); } else { - spin_unlock_irqrestore(&anchor->lock, flags); victim = NULL; } + spin_unlock_irqrestore(&anchor->lock, flags); return victim; } @@ -826,12 +823,7 @@ void usb_scuttle_anchored_urbs(struct usb_anchor *anchor) while (!list_empty(&anchor->urb_list)) { victim = list_entry(anchor->urb_list.prev, struct urb, anchor_list); - usb_get_urb(victim); - spin_unlock_irqrestore(&anchor->lock, flags); - /* this may free the URB */ - usb_unanchor_urb(victim); - usb_put_urb(victim); - spin_lock_irqsave(&anchor->lock, flags); + __usb_unanchor_urb(victim, anchor); } spin_unlock_irqrestore(&anchor->lock, flags); } |