Re: [patch 4/4] UHCI: add missing memory barriers

[Greg KH <gregkh@suse.de>]

On Mon, Dec 12, 2005 at 07:27:45PM -0500, Jeff Garzik wrote:
> Greg Kroah-Hartman wrote:
> >From: Alan Stern <stern@rowland.harvard.edu>
> >
> >This patch (as617) adds a couple of memory barriers that Ben H. forgot in
> >his recent suspend/resume fix.
> >
> >Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
> >Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
> >
> >---
> > drivers/usb/host/uhci-hcd.c |    2 ++
> > 1 file changed, 2 insertions(+)
> >
> >--- greg-2.6.orig/drivers/usb/host/uhci-hcd.c
> >+++ greg-2.6/drivers/usb/host/uhci-hcd.c
> >@@ -717,6 +717,7 @@ static int uhci_suspend(struct usb_hcd *
> > 	 * at the source, so we must turn off PIRQ.
> > 	 */
> > 	pci_write_config_word(to_pci_dev(uhci_dev(uhci)), USBLEGSUP, 0);
> >+	mb();
> > 	clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
> > 	uhci->hc_inaccessible = 1;
> > 	hcd->poll_rh = 0;
> >@@ -738,6 +739,7 @@ static int uhci_resume(struct usb_hcd *h
> > 	 * really don't want to keep a stale HCD_FLAG_HW_ACCESSIBLE=0
> > 	 */
> > 	set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
> >+	mb();
> 
> Are these just guesses, or what?
> 
> Why not smp_mb__before_clear_bit() or smp_mb__after_clear_bit() ?

I don't know, Alan?