From 66cdc93b8c030db70a50563ac26f02301dde30ff Mon Sep 17 00:00:00 2001 From: Gunnar Beutner Date: Tue, 18 Oct 2011 02:54:35 +0200 Subject: [PATCH] Remove the spinlocks for mutex_enter()/mutex_exit() The m_owner variable is protected by the mutex itself. Reading the variable is guaranteed to be atomic (due to it being a word-sized reference) and ACCESS_ONCE() takes care of read cache effects. Signed-off-by: Brian Behlendorf --- include/sys/mutex.h | 28 +--------------------------- 1 file changed, 1 insertion(+), 27 deletions(-) diff --git a/include/sys/mutex.h b/include/sys/mutex.h index c55104a417..21f161cfbe 100644 --- a/include/sys/mutex.h +++ b/include/sys/mutex.h @@ -103,45 +103,19 @@ extern int spl_mutex_spin_max(void); #define MUTEX(mp) ((struct mutex *)(mp)) -static inline kthread_t * -spl_mutex_get_owner(kmutex_t *mp) -{ - return mp->m_owner; -} - static inline void spl_mutex_set_owner(kmutex_t *mp) { - unsigned long flags; - - spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags); mp->m_owner = current; - spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags); } static inline void spl_mutex_clear_owner(kmutex_t *mp) { - unsigned long flags; - - spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags); mp->m_owner = NULL; - spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags); -} - -static inline kthread_t * -mutex_owner(kmutex_t *mp) -{ - unsigned long flags; - kthread_t *owner; - - spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags); - owner = spl_mutex_get_owner(mp); - spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags); - - return owner; } +#define mutex_owner(mp) (ACCESS_ONCE((mp)->m_owner)) #define mutex_owned(mp) (mutex_owner(mp) == current) #define MUTEX_HELD(mp) mutex_owned(mp) #define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))