s390: enable ARCH_USE_CMPXCHG_LOCKREF

Enable ARCH_USE_CMPXCHG_LOCKREF since it shows performance improvements
with Linus' simple stat() test case of up to 50% on a 30 cpu system.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 701fe8c59e1f..83e5d216105e 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -44,6 +44,11 @@ extern void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags);
 extern int arch_spin_trylock_retry(arch_spinlock_t *);
 extern void arch_spin_relax(arch_spinlock_t *lock);
 
+static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
+{
+        return lock.owner_cpu == 0;
+}
+
 static inline void arch_spin_lock(arch_spinlock_t *lp)
 {
         int old;