From mboxrd@z Thu Jan  1 00:00:00 1970
From: Samuel Thibault <samuel.thibault@eu.citrix.com>
Subject: Re: evtchn_do_upcall() barrier between upcall_pending and
	pending_sel
Date: Thu, 8 May 2008 11:34:30 +0100
Message-ID: <20080508103430.GF4365@implementation.uk.xensource.com>
References: <20080508101829.GC4365@implementation.uk.xensource.com>
	<C44893C7.2067B%keir.fraser@eu.citrix.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
Return-path: <xen-devel-bounces@lists.xensource.com>
Content-Disposition: inline
In-Reply-To: <C44893C7.2067B%keir.fraser@eu.citrix.com>
List-Unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xensource.com>
List-Help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-Subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
Sender: xen-devel-bounces@lists.xensource.com
Errors-To: xen-devel-bounces@lists.xensource.com
To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: xen-devel@lists.xensource.com
List-Id: xen-devel@lists.xenproject.org

Keir Fraser, le Thu 08 May 2008 11:25:59 +0100, a écrit :
> Makes sense, yes.

Here are fixes then.



evtchn: Use wmb instead of rmb to enforce ordering between
evtchn_upcall_pending and evtchn_pending_sel stores.
 
Signed-off-by: Samuel Thibault <samuel.thibault@eu.citrix.com>

diff -r e39cf97647af drivers/xen/core/evtchn.c
--- a/drivers/xen/core/evtchn.c	Mon May 05 10:17:41 2008 +0100
+++ b/drivers/xen/core/evtchn.c	Thu May 08 11:33:59 2008 +0100
@@ -246,7 +246,7 @@ asmlinkage void evtchn_do_upcall(struct 
 
 #ifndef CONFIG_X86 /* No need for a barrier -- XCHG is a barrier on x86. */
 		/* Clear master flag /before/ clearing selector flag. */
-		rmb();
+		wmb();
 #endif
 		l1 = xchg(&vcpu_info->evtchn_pending_sel, 0);
 


minios: in non-x86 case, use wmb to enforce ordering between
evtchn_upcall_pending and evtchn_pending_sel stores.

Signed-off-by: Samuel Thibault <samuel.thibault@eu.citrix.com>

diff -r 4965e711fee8 extras/mini-os/hypervisor.c
--- a/extras/mini-os/hypervisor.c	Wed May 07 15:36:32 2008 +0100
+++ b/extras/mini-os/hypervisor.c	Thu May 08 11:31:35 2008 +0100
@@ -46,7 +46,11 @@ void do_hypervisor_callback(struct pt_re
     in_callback = 1;
    
     vcpu_info->evtchn_upcall_pending = 0;
-    /* NB. No need for a barrier here -- XCHG is a barrier on x86. */
+    /* NB x86. No need for a barrier here -- XCHG is a barrier on x86. */
+#if !defined(__i386__) && !defined(__x86_64__)
+    /* clear master flag /before/ clearing selector flag. */
+    wmb();
+#endif
     l1 = xchg(&vcpu_info->evtchn_pending_sel, 0);
     while ( l1 != 0 )
     {