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Subject: Re: [RFC/PATCH 3/5] rt: plist_head_splice
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Daniel Walker <dwalker@mvista.com>,
       Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
       Gregory Haskins <ghaskins@novell.com>, Oleg Nesterov <oleg@tv-sign.ru>
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On Tue, 2007-10-23 at 11:10 -0400, Steven Rostedt wrote:
> --
> 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 =3D container_of(dst, struct plist_node, plis=
t);
> > +
> > +	dst_iter =3D next_prio(tail);
> > +
> > +	while (!plist_head_empty(src) && dst_iter !=3D tail) {
> > +		src_iter_first =3D plist_first(src);
> > +
> > +		src_iter_last =3D next_prio(src_iter_first);
> > +		src_iter_last =3D prev_node(src_iter_last);
> > +
> > +		WARN_ON(src_iter_first->prio !=3D src_iter_last->prio);
> > +		WARN_ON(list_empty(&src_iter_first->plist.prio_list));
> > +
> > +		while (src_iter_first->prio > dst_iter->prio) {
> > +			dst_iter =3D next_prio(dst_iter);
> > +			if (dst_iter =3D=3D tail)
> > +				goto tail;
> > +		}
> > +
> > +		list_del_init(&src_iter_first->plist.prio_list);
> > +
> > +		if (src_iter_first->prio < dst_iter->prio) {
>=20
> I may be confused here, but shouldn't we be linking the
> src_iter_first->prio_list somewhere here? Doesn't all different prios nee=
d
> to be in its separate prio_list? Otherwise two splices in a row can cause
> the above WARN_ON (prio !=3D prio).
>=20

> > +			list_add_tail(&src_iter_first->plist.node_list,
> > +					&dst_iter->plist.node_list);

Uhm, yeah, that was supposed the be prio_list indeed.

Thanks!

> > +		} else if (src_iter_first->prio =3D=3D dst_iter->prio) {
> > +			dst_iter =3D 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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