On Thu, Jan 30, 2014 at 10:50:41AM -0500, Waiman Long wrote:
> One more thing, I often see line like
>
> #define queue_write_unlock queue_write_unlock
>
> So exactly what effect does this macro have?
Makes sure the below doesn't emit another version.
#ifndef queue_write_unlock
/**
* queue_write_unlock - release write lock of a queue rwlock
* @lock : Pointer to queue rwlock structure
*/
static inline void queue_write_unlock(struct qrwlock *lock)
{
/*
* If the writer field is atomic, it can be cleared directly.
* Otherwise, an atomic subtraction will be used to clear it.
*/
smp_mb__before_atomic_dec();
atomic_sub(_QW_LOCKED, &lock->cnts);
}
#endif
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