From: Isaku Yamahata <yamahata@valinux.co.jp>
Date: Mon, 16 Jun 2008 21:58:13 +0000 (-0700)
Subject: xen: Use wmb instead of rmb in xen_evtchn_do_upcall().
X-Git-Tag: v2.6.26-rc8~12^2~2
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=46539383791a0e59a4af7412056dfbfc5240af0a;p=~shefty%2Frdma-dev.git

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

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@eu.citrix.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: the arch/x86 maintainers <x86@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 4f0f22b020e..76e5b7386af 100644
--- 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) {