/**
* wait_queue_t of Linux (version < 2.6.34) is a FIFO list for exclusively
* waiting threads, which is not always desirable because all threads will
* be waken up again and again, even user only needs a few of them to be
* active most time. This is not good for performance because cache can
* be polluted by different threads.
*
* LIFO list can resolve this problem because we always wakeup the most
* recent active thread by default.
*
* NB: please don't call non-exclusive & exclusive wait on the same
* waitq if add_wait_queue_exclusive_head is used.
*/
void
add_wait_queue_exclusive_head(wait_queue_head_t *waitq, wait_queue_t *link)
{
unsigned long flags;
spin_lock_irqsave(&LINUX_WAITQ_HEAD(waitq)->lock, flags);
__add_wait_queue_exclusive(LINUX_WAITQ_HEAD(waitq), LINUX_WAITQ(link));
spin_unlock_irqrestore(&LINUX_WAITQ_HEAD(waitq)->lock, flags);
}
void
init_waitqueue_entry_current(wait_queue_t *link)
{
init_waitqueue_entry(LINUX_WAITQ(link), current);
}
void
cfs_waitlink_init(cfs_waitlink_t *link)
{
init_waitqueue_entry(LINUX_WAITQ(link), current);
}
void
cfs_waitq_add_exclusive(cfs_waitq_t *waitq,
cfs_waitlink_t *link)
{
add_wait_queue_exclusive(LINUX_WAITQ_HEAD(waitq), LINUX_WAITQ(link));
}
void
cfs_waitq_del(cfs_waitq_t *waitq, cfs_waitlink_t *link)
{
remove_wait_queue(LINUX_WAITQ_HEAD(waitq), LINUX_WAITQ(link));
}
