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

From: Jeff Garzik
Date: Mon Dec 12 2005 - 19:27:09 EST


Greg Kroah-Hartman wrote:
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
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() ?

Jeff



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