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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 <behlendorf1@llnl.gov>
This commit is contained in:
Gunnar Beutner 2011-10-18 02:54:35 +02:00 committed by Brian Behlendorf
parent 3160d4f56b
commit 66cdc93b8c
1 changed files with 1 additions and 27 deletions
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28
include/sys/mutex.h
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@ -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))