locking/mutexes: Use MUTEX_SPIN_ON_OWNER when appropriate

4badad35 ("locking/mutex: Disable optimistic spinning on some
architectures") added a ARCH_SUPPORTS_ATOMIC_RMW flag to
disable the mutex optimistic feature on specific archs.

Because CONFIG_MUTEX_SPIN_ON_OWNER only depended on DEBUG and
SMP, it was ok to have the ->owner field conditional a bit
flexible. However by adding a new variable to the matter,
we can waste space with the unused field, ie: CONFIG_SMP &&
(!CONFIG_MUTEX_SPIN_ON_OWNER && !CONFIG_DEBUG_MUTEX).

Signed-off-by: Davidlohr Bueso <[email protected]>
Acked-by: Jason Low <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: [email protected]
Cc: Davidlohr Bueso <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Jason Low <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Tim Chen <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 8d5535c58cc28578714c99eb6a4c16bbdd5726a9..e4c29418f4072c101adcc0bc5928d5798d5b0fcd 100644 (file)
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -52,7 +52,7 @@ struct mutex {
        atomic_t                count;
        spinlock_t              wait_lock;
        struct list_head        wait_list;
-#if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
+#if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_MUTEX_SPIN_ON_OWNER)
        struct task_struct      *owner;
 #endif
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER

diff --git a/kernel/locking/mutex.h b/kernel/locking/mutex.h
index 4115fbf83b12ed11e2b05bc7cccfb5933cb3311d..5cda397607f25011eedcc4cbcab7aeef9d211321 100644 (file)
--- a/kernel/locking/mutex.h
+++ b/kernel/locking/mutex.h
@@ -16,7 +16,7 @@
 #define mutex_remove_waiter(lock, waiter, ti) \
                __list_del((waiter)->list.prev, (waiter)->list.next)
 
-#ifdef CONFIG_SMP
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
 static inline void mutex_set_owner(struct mutex *lock)
 {
        lock->owner = current;