[PATCH v5 04/21] gpu: host1x: Remove cancelled waiters immediately

[Dmitry Osipenko]

11.01.2021 16:00, Mikko Perttunen пишет:
> -void host1x_intr_put_ref(struct host1x *host, unsigned int id, void *ref)
> +void host1x_intr_put_ref(struct host1x *host, unsigned int id, void *ref,
> +			 bool flush)
>  {
>  	struct host1x_waitlist *waiter = ref;
>  	struct host1x_syncpt *syncpt;
>  
> -	while (atomic_cmpxchg(&waiter->state, WLS_PENDING, WLS_CANCELLED) ==
> -	       WLS_REMOVED)
> -		schedule();
> +	atomic_cmpxchg(&waiter->state, WLS_PENDING, WLS_CANCELLED);
>  
>  	syncpt = host->syncpt + id;
> -	(void)process_wait_list(host, syncpt,
> -				host1x_syncpt_load(host->syncpt + id));
> +
> +	spin_lock(&syncpt->intr.lock);
> +	if (atomic_cmpxchg(&waiter->state, WLS_CANCELLED, WLS_HANDLED) ==
> +	    WLS_CANCELLED) {
> +		list_del(&waiter->list);
> +		kref_put(&waiter->refcount, waiter_release);
> +	}
> +	spin_unlock(&syncpt->intr.lock);
> +
> +	if (flush) {
> +		/* Wait until any concurrently executing handler has finished. */
> +		while (atomic_read(&waiter->state) != WLS_HANDLED)
> +			cpu_relax();
> +	}

A busy-loop shouldn't be used in kernel unless there is a very good
reason. The wait_event() should be used instead.

But please don't hurry to update this patch, we may need or want to
retire the host1x-waiter and then these all waiter-related patches won't
be needed.