[IA64] implement ticket locks for Itanium

Back in January 2008 Nick Piggin implemented "ticket" spinlocks
for X86 (See commit 314cdbefd1fd0a7acf3780e9628465b77ea6a836).

IA64 implementation has a couple of differences because of the
available atomic operations ... e.g. we have no fetchadd2 instruction
that operates on a 16-bit quantity so we make ticket locks use
a 32-bit word for each of the current ticket and now-serving values.

Performance on uncontended locks is about 8% worse than the previous
implementation, but this seems a good trade for determinism in the
contended case. Performance impact on macro-level benchmarks is in
the noise.

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

1 files changed, 1 insertions, 3 deletions

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 6851e52ed5a2..1ee596cd942f 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -60,9 +60,7 @@ config IOMMU_HELPER
        bool
 
 config GENERIC_LOCKBREAK
-        bool
-        default y
-        depends on SMP && PREEMPT
+        def_bool n
 
 config RWSEM_XCHGADD_ALGORITHM
         bool