On 6/25/18 9:12 AM, Josef Bacik wrote:
> +static void __blkcg_iolatency_throttle(struct rq_qos *rqos,
> + struct iolatency_grp *iolat,
> + spinlock_t *lock, bool issue_as_root,
> + bool use_memdelay)
> + __releases(lock)
> + __acquires(lock)
> +{
> + struct rq_wait *rqw = &iolat->rq_wait;
> + unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay);
> + DEFINE_WAIT(wait);
> + bool first_block = true;
> +
> + if (use_delay)
> + blkcg_schedule_throttle(rqos->q, use_memdelay);
> +
> + /*
> + * To avoid priority inversions we want to just take a slot if we are
> + * issuing as root. If we're being killed off there's no point in
> + * delaying things, we may have been killed by OOM so throttling may
> + * make recovery take even longer, so just let the IO's through so the
> + * task can go away.
> + */
> + if (issue_as_root || fatal_signal_pending(current)) {
> + atomic_inc(&rqw->inflight);
> + return;
> + }
> +
> + if (iolatency_may_queue(iolat, &wait, first_block))
> + return;
> +
> + do {
> + prepare_to_wait_exclusive(&rqw->wait, &wait,
> + TASK_UNINTERRUPTIBLE);
> +
> + iolatency_may_queue(iolat, &wait, first_block);
> + first_block = false;
> +
> + if (lock) {
> + spin_unlock_irq(lock);
> + io_schedule();
> + spin_lock_irq(lock);
> + } else {
> + io_schedule();
> + }
> + } while (1);
So how does this wait loop ever exit?
--
Jens Axboe
