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Avoid some unnecessary seq_cst memory ordering

master
Chris Robinson 2016-11-22 03:40:15 -08:00
parent c618971758
commit 8492c2845d
1 changed files with 8 additions and 6 deletions
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14
common/rwlock.c
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@ -11,10 +11,10 @@
/* A simple spinlock. Yield the thread while the given integer is set by
* another. Could probably be improved... */
#define LOCK(l) do { \
while(ATOMIC_EXCHANGE(int, &(l), true) == true) \
while(ATOMIC_EXCHANGE(int, &(l), true, almemory_order_acq_rel) == true) \
althrd_yield(); \
} while(0)
#define UNLOCK(l) ATOMIC_STORE(&(l), false)
#define UNLOCK(l) ATOMIC_STORE(&(l), false, almemory_order_release)
void RWLockInit(RWLock *lock)
@ -30,7 +30,8 @@ void ReadLock(RWLock *lock)
{
LOCK(lock->read_entry_lock);
LOCK(lock->read_lock);
if(IncrementRef(&lock->read_count) == 1)
/* NOTE: ATOMIC_ADD returns the *old* value! */
if(ATOMIC_ADD(&lock->read_count, 1, almemory_order_acq_rel) == 0)
LOCK(lock->write_lock);
UNLOCK(lock->read_lock);
UNLOCK(lock->read_entry_lock);
@ -38,13 +39,14 @@ void ReadLock(RWLock *lock)
void ReadUnlock(RWLock *lock)
{
if(DecrementRef(&lock->read_count) == 0)
/* NOTE: ATOMIC_SUB returns the *old* value! */
if(ATOMIC_SUB(&lock->read_count, 1, almemory_order_acq_rel) == 1)
UNLOCK(lock->write_lock);
}
void WriteLock(RWLock *lock)
{
if(IncrementRef(&lock->write_count) == 1)
if(ATOMIC_ADD(&lock->write_count, 1, almemory_order_acq_rel) == 0)
LOCK(lock->read_lock);
LOCK(lock->write_lock);
}
@ -52,6 +54,6 @@ void WriteLock(RWLock *lock)
void WriteUnlock(RWLock *lock)
{
UNLOCK(lock->write_lock);
if(DecrementRef(&lock->write_count) == 0)
if(ATOMIC_SUB(&lock->write_count, 1, almemory_order_acq_rel) == 1)
UNLOCK(lock->read_lock);
}