[IA64] Turn on CONFIG_HAVE_UNSTABLE_CLOCK

sched_clock() on ia64 is based on ar.itc, so is never
completely synchronized between cpus. On some platforms
(e.g. certain models of SGI Altix) it may be running at
radically different frequencies.

Based on a patch from Dimitri Sivanich which set this
just for SN2 && GENERIC kernels ... it is needed for
all ia64 machines.

Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 3d31636cbafb..6183aeccecf1 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -17,6 +17,7 @@ config IA64
         select ACPI if (!IA64_HP_SIM)
         select PM if (!IA64_HP_SIM)
         select ARCH_SUPPORTS_MSI
+        select HAVE_UNSTABLE_SCHED_CLOCK
         select HAVE_IDE
         select HAVE_OPROFILE
         select HAVE_KPROBES