x86: add smp_mb() before sending INVALIDATE_TLB_VECTOR

Impact: fix rare x2apic hang

On x86, x2apic mode accesses for sending IPI's don't have serializing
semantics. If the IPI receivner 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>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 0 deletions

diff --git a/arch/x86/kernel/tlb_32.c b/arch/x86/kernel/tlb_32.c
index e00534b33534..f4049f3513b6 100644
--- a/arch/x86/kernel/tlb_32.c
+++ b/arch/x86/kernel/tlb_32.c
@@ -154,6 +154,12 @@ void native_flush_tlb_others(const cpumask_t *cpumaskp, struct mm_struct *mm,
         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.