Re: [PATCH] io stalls (was: -rc7 Re: Linux 2.4.21-rc6)

[Andrea Arcangeli]

On Mon, Jun 09, 2003 at 05:39:23PM -0400, Chris Mason wrote:
> +	if (!waitqueue_active(&q->wait_for_requests[rw]))
> +		clear_queue_full(q, rw);

you've an smp race above, the smp safe implementation is this:

	if (!waitqueue_active(&q->wait_for_requests[rw])) {
		clear_queue_full(q, rw);
		mb();
		if (unlikely(waitqueue_active(&q->wait_for_requests[rw])))
			wake_up(&q->wait_for_requests[rw]);
	}

I'm also unsure what the "waited" logic does, it doesn't seem necessary.

Andrea