[PATCH -tip/master 5/7] locking/mutex: Use MUTEX_SPIN_ON_OWNER when appropriate

From: Davidlohr Bueso
Date: Mon Jul 28 2014 - 01:20:06 EST

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 &&

Signed-off-by: Davidlohr Bueso <davidlohr@xxxxxx>
include/linux/mutex.h | 2 +-
kernel/locking/mutex.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 8d5535c..e4c2941 100644
--- 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)
struct task_struct *owner;
diff --git a/kernel/locking/mutex.h b/kernel/locking/mutex.h
index 4115fbf..5cda397 100644
--- 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
static inline void mutex_set_owner(struct mutex *lock)
lock->owner = current;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/