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[Xen-devel] [PATCH] make SMP boot again with gcc 4

To: xen-devel@xxxxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH] make SMP boot again with gcc 4
From: Rik van Riel <riel@xxxxxxxxxx>
Date: Mon, 28 Mar 2005 15:34:42 -0500 (EST)
Delivery-date: Tue, 29 Mar 2005 06:59:27 +0000
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For unknown reasons, this bug doesn't show up when Xen is compiled
with gcc-3.4, so I was off on a wild goose chase for a few days.
With this barrier added, the system boots fine again.

Note that we should probably move barrier into cpu_relax, but that's
a story for another patch.

Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>

--- xen-unstable/xen/arch/x86/smpboot.c.barrier 2005-03-28 15:17:11.000000000 
+++ xen-unstable/xen/arch/x86/smpboot.c 2005-03-28 15:32:30.000000000 -0500
@@ -413,8 +413,10 @@ void __init start_secondary(void)
-    while (!atomic_read(&smp_commenced))
-        rep_nop();
+    while (!atomic_read(&smp_commenced)) {
+        cpu_relax();
+        barrier();
+    }
 #ifdef __i386__

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