From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Valente Subject: [PATCH] sched: fix virtual-start-time update in QFQ Date: Sat, 15 Sep 2012 12:41:35 +0200 Message-ID: <20120915104134.GA29862@paolo-ThinkPad-W520> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: fchecconi@gmail.com, rizzo@iet.unipi.it, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, paolo.valente@unimore.it To: davem@davemloft.net, shemminger@vyatta.com, jhs@mojatatu.com Return-path: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org If the old timestamps of a class, say cl, are stale when the class becomes active, then QFQ may assign to cl a much higher start time than the maximum value allowed. This may happen when QFQ assigns to the start time of cl the finish time of a group whose classes are characterized by a higher value of the ratio max_class_pkt/weight_of_the_class with respect to that of cl. Inserting a class with a too high start time into the bucket list corrupts the data structure and may eventually lead to crashes. This patch limits the maximum start time assigned to a class. Signed-off-by: Paolo Valente --- net/sched/sch_qfq.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c index e4723d3..211a212 100644 --- a/net/sched/sch_qfq.c +++ b/net/sched/sch_qfq.c @@ -865,7 +865,10 @@ static void qfq_update_start(struct qfq_sched *q, struct qfq_class *cl) if (mask) { struct qfq_group *next = qfq_ffs(q, mask); if (qfq_gt(roundedF, next->F)) { - cl->S = next->F; + if (qfq_gt(limit, next->F)) + cl->S = next->F; + else /* preserve timestamp correctness */ + cl->S = limit; return; } } -- 1.7.9.5