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USB: UHCI: Use ACCESS_ONCE rather than using a full compiler barrier

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This patch (as1462) updates the special accessor functions defined in
uhci-hcd.h.  Rather than using a full compiler barrier, all we really
need is the ACCESS_ONCE() mechanism, because the idea is to force the
compiler to store a fixed copy of a possibly changing value.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern 2011-05-18 10:44:50 +02:00 committed by Greg Kroah-Hartman
parent 8452c6745e
commit bab1ff1bda
1 changed files with 2 additions and 12 deletions
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14
drivers/usb/host/uhci-hcd.h
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@ -168,12 +168,7 @@ struct uhci_qh {
* We need a special accessor for the element pointer because it is
* subject to asynchronous updates by the controller.
*/
static inline __le32 qh_element(struct uhci_qh *qh) {
__le32 element = qh->element;
barrier();
return element;
}
#define qh_element(qh) ACCESS_ONCE((qh)->element)
#define LINK_TO_QH(qh) (UHCI_PTR_QH | cpu_to_le32((qh)->dma_handle))
@ -263,12 +258,7 @@ struct uhci_td {
* We need a special accessor for the control/status word because it is
* subject to asynchronous updates by the controller.
*/
static inline u32 td_status(struct uhci_td *td) {
__le32 status = td->status;
barrier();
return le32_to_cpu(status);
}
#define td_status(td) le32_to_cpu(ACCESS_ONCE((td)->status))
#define LINK_TO_TD(td) (cpu_to_le32((td)->dma_handle))