[PATCH] x86-64: Fix bad assumption that dualcore cpus have synced TSCs

This should resolve the issue seen in bugme bug #5105, where it is assumed
that dualcore x86_64 systems have synced TSCs.  This is not the case, and
alternate timesources should be used instead.

For more details, see:
http://bugzilla.kernel.org/show_bug.cgi?id=5105

Andi's earlier concerns that the TSCs should be synced on dualcore systems
have been resolved by confirmation from AMD folks that they can be
unsynced.

Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 2373cb8b86250744018a1ecdd48fc7b6da21248a..703acde2a1a58647978e48cc3b4a5cf216eabc0c 100644 (file)
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -959,9 +959,6 @@ static __init int unsynchronized_tsc(void)
           are handled in the OEM check above. */
        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
                return 0;
-       /* All in a single socket - should be synchronized */
-       if (cpus_weight(cpu_core_map[0]) == num_online_cpus())
-               return 0;
 #endif
        /* Assume multi socket systems are not synchronized */
        return num_online_cpus() > 1;