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Commit bab1ff1b authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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USB: UHCI: Use ACCESS_ONCE rather than using a full compiler barrier 



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: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 8452c674

drivers/usb/host/uhci-hcd.h

+2 −12
Original line number Diff line number Diff line
@@ -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))