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List:       xen-cvs
Subject:    [Xen-changelog] [xen-unstable] evtchn_do_upcall() has a micro
From:       Xen patchbot-unstable <patchbot-unstable () lists ! xensource ! com>
Date:       2006-06-30 15:40:45
Message-ID: E1FwL6s-0007ND-L9 () xenbits ! xensource ! com
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# HG changeset patch
# User kaf24@firebug.cl.cam.ac.uk
# Node ID c9696012fe05347ad6a0d503bc55b53b76783af3
# Parent  5db7bbccf4d2d759265415085fa81094893f60a9
evtchn_do_upcall() has a micro optimization which is depends on that xchg is a barrier.
However xchg of IA64 has acquire semantics so that event
channel notification is lost sometimes. This patch fixes it.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
---
 linux-2.6-xen-sparse/drivers/xen/core/evtchn.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletion(-)

diff -r 5db7bbccf4d2 -r c9696012fe05 linux-2.6-xen-sparse/drivers/xen/core/evtchn.c
--- a/linux-2.6-xen-sparse/drivers/xen/core/evtchn.c	Fri Jun 30 10:04:22 2006 +0100
+++ b/linux-2.6-xen-sparse/drivers/xen/core/evtchn.c	Fri Jun 30 10:07:38 2006 +0100
@@ -219,7 +219,10 @@ asmlinkage void evtchn_do_upcall(struct 
 
 	vcpu_info->evtchn_upcall_pending = 0;
 
-	/* NB. No need for a barrier here -- XCHG is a barrier on x86. */
+#ifndef CONFIG_X86 /* No need for a barrier -- XCHG is a barrier on x86. */
+	/* Clear master pending flag /before/ clearing selector flag. */
+	rmb();
+#endif
 	l1 = xchg(&vcpu_info->evtchn_pending_sel, 0);
 	while (l1 != 0) {
 		l1i = __ffs(l1);

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