On 8/23/18 7:08 AM, Jianchao Wang wrote:
> @@ -491,31 +525,27 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
> __acquires(lock)
> {
> struct rq_wait *rqw = get_rq_wait(rwb, wb_acct);
> - DECLARE_WAITQUEUE(wait, current);
> - bool has_sleeper;
> -
> - has_sleeper = wq_has_sleeper(&rqw->wait);
> - if (!has_sleeper && rq_wait_inc_below(rqw, get_limit(rwb, rw)))
> + struct wait_queue_entry wait;
> + struct wbt_wait_data data = {
> + .curr = current,
> + .rwb = rwb,
> + .rqw = rqw,
> + .rw = rw,
> + };
> +
> + if (!wq_has_sleeper(&rqw->wait) &&
> + rq_wait_inc_below(rqw, get_limit(rwb, rw)))
> return;
>
> - add_wait_queue_exclusive(&rqw->wait, &wait);
> - do {
> - set_current_state(TASK_UNINTERRUPTIBLE);
> -
> - if (!has_sleeper && rq_wait_inc_below(rqw, get_limit(rwb, rw)))
> - break;
> -
> - if (lock) {
> - spin_unlock_irq(lock);
> - io_schedule();
> - spin_lock_irq(lock);
> - } else
> - io_schedule();
> - has_sleeper = false;
> - } while (1);
> -
> - __set_current_state(TASK_RUNNING);
> - remove_wait_queue(&rqw->wait, &wait);
> + wbt_init_wait(&wait, &data);
> + prepare_to_wait_exclusive(&rqw->wait, &wait,
> + TASK_UNINTERRUPTIBLE);
> + if (lock) {
> + spin_unlock_irq(lock);
> + io_schedule();
> + spin_lock_irq(lock);
> + } else
> + io_schedule();
Aren't we still missing a get-token attempt after adding to the
waitqueue? For the case where someone frees the token after your initial
check, but before you add yourself to the waitqueue.
--
Jens Axboe
