linux-kernel - Re: [RFC/PATCH 3/5] rt: plist_head

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Date:	Tue, 23 Oct 2007 11:10:20 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
cc:	linux-kernel@...r.kernel.org, Daniel Walker <dwalker@...sta.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Gregory Haskins <ghaskins@...ell.com>,
	Oleg Nesterov <oleg@...sign.ru>
Subject: Re: [RFC/PATCH 3/5] rt: plist_head_splice


--
On Tue, 23 Oct 2007, Peter Zijlstra wrote:
> +
> +void plist_head_splice(struct plist_head *src, struct plist_head *dst)
> +{
> +	struct plist_node *src_iter_first, *src_iter_last, *dst_iter;
> +	struct plist_node *tail = container_of(dst, struct plist_node, plist);
> +
> +	dst_iter = next_prio(tail);
> +
> +	while (!plist_head_empty(src) && dst_iter != tail) {
> +		src_iter_first = plist_first(src);
> +
> +		src_iter_last = next_prio(src_iter_first);
> +		src_iter_last = prev_node(src_iter_last);
> +
> +		WARN_ON(src_iter_first->prio != src_iter_last->prio);
> +		WARN_ON(list_empty(&src_iter_first->plist.prio_list));
> +
> +		while (src_iter_first->prio > dst_iter->prio) {
> +			dst_iter = next_prio(dst_iter);
> +			if (dst_iter == tail)
> +				goto tail;
> +		}
> +
> +		list_del_init(&src_iter_first->plist.prio_list);
> +
> +		if (src_iter_first->prio < dst_iter->prio) {

I may be confused here, but shouldn't we be linking the
src_iter_first->prio_list somewhere here? Doesn't all different prios need
to be in its separate prio_list? Otherwise two splices in a row can cause
the above WARN_ON (prio != prio).

-- Steve


> +			list_add_tail(&src_iter_first->plist.node_list,
> +					&dst_iter->plist.node_list);
> +		} else if (src_iter_first->prio == dst_iter->prio) {
> +			dst_iter = next_prio(dst_iter);
> +		} else BUG();
> +
> +		list_splice2_tail(&src_iter_first->plist.node_list,
> +			       	  &src_iter_last->plist.node_list,
> +				  &dst_iter->plist.node_list);
> +	}
> +
> +tail:
> +	list_splice_tail_init(&src->prio_list, &dst->prio_list);
> +	list_splice_tail_init(&src->node_list, &dst->node_list);
> +}
>
> --
>
>
>
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