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hci_usb: replace mb with smp_mb

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smp_mb is enough for ordering memory operations among processors,and mb is
more expensive than smp_mb for UP machine, so replace it with smp_mb().

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ming Lei 2008-09-22 19:21:51 -07:00 committed by David S. Miller
parent d48abfecea
commit ca330c5a91
1 changed files with 5 additions and 5 deletions
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10
drivers/bluetooth/hci_usb.h
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@ -70,8 +70,8 @@ static inline void _urb_queue_head(struct _urb_queue *q, struct _urb *_urb)
{
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
/* _urb_unlink needs to know which spinlock to use, thus mb(). */
_urb->queue = q; mb(); list_add(&_urb->list, &q->head);
/* _urb_unlink needs to know which spinlock to use, thus smp_mb(). */
_urb->queue = q; smp_mb(); list_add(&_urb->list, &q->head);
spin_unlock_irqrestore(&q->lock, flags);
}
@ -79,8 +79,8 @@ static inline void _urb_queue_tail(struct _urb_queue *q, struct _urb *_urb)
{
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
/* _urb_unlink needs to know which spinlock to use, thus mb(). */
_urb->queue = q; mb(); list_add_tail(&_urb->list, &q->head);
/* _urb_unlink needs to know which spinlock to use, thus smp_mb(). */
_urb->queue = q; smp_mb(); list_add_tail(&_urb->list, &q->head);
spin_unlock_irqrestore(&q->lock, flags);
}
@ -89,7 +89,7 @@ static inline void _urb_unlink(struct _urb *_urb)
struct _urb_queue *q;
unsigned long flags;
mb();
smp_mb();
q = _urb->queue;
/* If q is NULL, it will die at easy-to-debug NULL pointer dereference.
No need to BUG(). */