Commit 7608a43d authored Jul 30, 2014 by Davidlohr Bueso Committed by Ingo Molnar Aug 13, 2014

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 <davidlohr@hp.com>
Acked-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: aswin@hp.com
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/1406752916-3341-5-git-send-email-davidlohr@hp.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 76916515

include/linux/mutex.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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

kernel/locking/mutex.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;

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