On x86, x2apic mode accesses for sending IPI's don't have serializing
semantics. If the IPI receiver refers(in lock-free fashion) to some memory setup
by the sender, the need for smp_mb() before sending the IPI becomes critical in
x2apic mode.

Add the smp_mb() in native_flush_tlb_others() before sending the IPI.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
---

Index: linux-2.6.git/arch/x86/kernel/tlb_32.c
===================================================================
--- linux-2.6.git.orig/arch/x86/kernel/tlb_32.c	2008-10-13 10:04:12.000000000 -0700
+++ linux-2.6.git/arch/x86/kernel/tlb_32.c	2008-11-04 10:01:16.000000000 -0800
@@ -154,6 +154,12 @@
 	flush_mm = mm;
 	flush_va = va;
 	cpus_or(flush_cpumask, cpumask, flush_cpumask);
+
+	/*
+	 * Make the above memory operations globally visible before
+	 * sending the IPI.
+	 */
+	smp_mb();
 	/*
 	 * We have to send the IPI only to
 	 * CPUs affected.
Index: linux-2.6.git/arch/x86/kernel/tlb_64.c
===================================================================
--- linux-2.6.git.orig/arch/x86/kernel/tlb_64.c	2008-10-31 11:15:11.000000000 -0700
+++ linux-2.6.git/arch/x86/kernel/tlb_64.c	2008-11-04 10:01:31.000000000 -0800
@@ -183,6 +183,11 @@
 	cpus_or(f->flush_cpumask, cpumask, f->flush_cpumask);
 
 	/*
+	 * Make the above memory operations globally visible before
+	 * sending the IPI.
+	 */
+	smp_mb();
+	/*
 	 * We have to send the IPI only to
 	 * CPUs affected.
 	 */

-- 

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