From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: Re: [PATCH]: Schedule correct qdisc in watchdog. Date: Mon, 18 Aug 2008 10:35:59 +0000 Message-ID: <20080818103559.GA6548@ff.dom.local> References: <20080818091011.GC5434@ff.dom.local> <20080818.023105.01989851.davem@davemloft.net> <20080818094727.GA6388@ff.dom.local> <20080818.031003.115715822.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org To: David Miller Return-path: Received: from ug-out-1314.google.com ([66.249.92.170]:27321 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752062AbYHRKgJ (ORCPT ); Mon, 18 Aug 2008 06:36:09 -0400 Received: by ug-out-1314.google.com with SMTP id c2so169143ugf.37 for ; Mon, 18 Aug 2008 03:36:05 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20080818.031003.115715822.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Aug 18, 2008 at 03:10:03AM -0700, David Miller wrote: > From: Jarek Poplawski > Date: Mon, 18 Aug 2008 09:47:27 +0000 > > > Maybe I wrote this wrong. wd->qdisc stores qdisc from the > > qdisc_watchdog_init() time, and this could be &noop_qdisc. > > So qdisc_root() would schedule wrong qdisc later. BTW, my > > version would probably do the same for root qdisc, but in > > these tests there was a problem with leafs. > > qdisc_watchdog_init() is only invoked by: > > net/sched/sch_cbq.c: qdisc_watchdog_init(&q->watchdog, sch); > net/sched/sch_hfsc.c: qdisc_watchdog_init(&q->watchdog, sch); > net/sched/sch_htb.c: qdisc_watchdog_init(&q->watchdog, sch); > net/sched/sch_netem.c: qdisc_watchdog_init(&q->watchdog, sch); > net/sched/sch_tbf.c: qdisc_watchdog_init(&q->watchdog, sch); > > These "q" things are the scheduler private structs, and 'sch' of the > qdisc type indicated by the source file the code in question resides > :-) > > This watchdog is different from the TX timeout watchdog which is > implemented in net/sch/sch_generic.c, which you may be confusing this > qdisc_watchdog_init() one with. I don't think I wrote anything which could suggest I confused these watchdogs. > > The watchdog we are discussing here is purely for qdiscs where time > based events modify qdisc state (such as making new quotas available > for a flow, thus making certain packets eligible for scheduling that > were not beforehand) > > So really, it cannot be &noop_qdisc as far as I can see. > :-) Sure, ->sch is never &noop_qdisc, but your qdisc_root(sch) most probably is at the moment of qdisc_watchdog_init(). My version can do the same if eg. htb is root qdisc because at the moment of qdisc_create() qdisc_sleeping could be &noop_qdisc as well. But, in case we have a qdisc_sleeping already, it should work. So these patches will stop break things, but these qdisc_watchdog() calls would be sometimes/always useless. Jarek P.