[PATCH] xen: Use wmb instead of rmb in xen_evtchn_do_upcall().

[Jeremy Fitzhardinge]

From: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>

This patch is ported one from 534:77db69c38249 of linux-2.6.18-xen.hg.
Use wmb instead of rmb to enforce ordering between
evtchn_upcall_pending and evtchn_pending_sel stores
in xen_evtchn_do_upcall().

Cc: Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>
Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
---
drivers/xen/events.c |    3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

===================================================================
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -529,7 +529,7 @@ void xen_evtchn_do_upcall(struct pt_regs *regs)

#ifndef CONFIG_X86 /* No need for a barrier -- XCHG is a barrier on x86. */
		/* Clear master flag /before/ clearing selector flag. */
-		rmb();
+		wmb();
#endif
		pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
		while (pending_words != 0) {
--
1.5.3



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