Commit 71261956 authored Sep 15, 2012 by Paolo Valente Committed by David S. Miller Sep 19, 2012

pkt_sched: fix virtual-start-time update in QFQ



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 <paolo.valente@unimore.it>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 15c04175

net/sched/sch_qfq.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -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)) {
		if (qfq_gt(limit, next->F))
		cl->S = next->F;
		else /* preserve timestamp correctness */
		cl->S = limit;
		return;
		}
		}

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