[Xen-changelog] Add a read barrier to the time-values-uptodate xenlinux time checking function.

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID e3d7c21838661f1dd83c0ce49c3852a0c706f2cd
# Parent  f4cef1aa25218c37c1ed94d00acaa2741abd0d1c
Add a read barrier to the time-values-uptodate xenlinux time checking function.
Also fix monotonic clock to use just a compile barrier instead of smp_rmb.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r f4cef1aa2521 -r e3d7c2183866 
linux-2.6-xen-sparse/arch/i386/kernel/time-xen.c
--- a/linux-2.6-xen-sparse/arch/i386/kernel/time-xen.c  Tue Mar 14 15:09:34 2006
+++ b/linux-2.6-xen-sparse/arch/i386/kernel/time-xen.c  Tue Mar 14 16:35:38 2006
@@ -332,6 +332,7 @@
        src = &HYPERVISOR_shared_info->vcpu_info[cpu].time;
        dst = &per_cpu(shadow_time, cpu);
 
+       rmb();
        return (dst->version == src->version);
 }
 
@@ -558,11 +559,11 @@
 
        do {
                local_time_version = shadow->version;
-               smp_rmb();
+               barrier();
                time = shadow->system_timestamp + get_nsec_offset(shadow);
                if (!time_values_up_to_date(cpu))
                        get_time_values_from_xen();
-               smp_rmb();
+               barrier();
        } while (local_time_version != shadow->version);
 
        put_cpu();

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