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Commit 2540e051 authored by Jarek Poplawski's avatar Jarek Poplawski Committed by David S. Miller
Browse files

pkt_sched: Fix qdisc_watchdog() vs. dev_deactivate() race 



dev_deactivate() can skip rescheduling of a qdisc by qdisc_watchdog()
or other timer calling netif_schedule() after dev_queue_deactivate().
We prevent this checking aliveness before scheduling the timer. Since
during deactivation the root qdisc is available only as qdisc_sleeping
additional accessor qdisc_root_sleeping() is created.

With feedback from Herbert Xu <herbert@gondor.apana.org.au>

Signed-off-by: default avatarJarek Poplawski <jarkao2@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5e739d17

include/net/sch_generic.h

+5 −0
Original line number Diff line number Diff line
@@ -193,6 +193,11 @@ static inline struct Qdisc *qdisc_root(struct Qdisc *qdisc) 
	return qdisc->dev_queue->qdisc;

}



static inline struct Qdisc *qdisc_root_sleeping(struct Qdisc *qdisc)

{

	return qdisc->dev_queue->qdisc_sleeping;

}



/* The qdisc root lock is a mechanism by which to top level

 * of a qdisc tree can be locked from any qdisc node in the

 * forest.  This allows changing the configuration of some

net/sched/sch_api.c

+4 −0
Original line number Diff line number Diff line
@@ -444,6 +444,10 @@ void qdisc_watchdog_schedule(struct qdisc_watchdog *wd, psched_time_t expires) 
{

	ktime_t time;



	if (test_bit(__QDISC_STATE_DEACTIVATED,

		     &qdisc_root_sleeping(wd->qdisc)->state))

		return;



	wd->qdisc->flags |= TCQ_F_THROTTLED;

	time = ktime_set(0, 0);

	time = ktime_add_ns(time, PSCHED_US2NS(expires));

net/sched/sch_cbq.c

+4 −0
Original line number Diff line number Diff line
@@ -521,6 +521,10 @@ static void cbq_ovl_delay(struct cbq_class *cl) 
	struct cbq_sched_data *q = qdisc_priv(cl->qdisc);

	psched_tdiff_t delay = cl->undertime - q->now;



	if (test_bit(__QDISC_STATE_DEACTIVATED,

		     &qdisc_root_sleeping(cl->qdisc)->state))

		return;



	if (!cl->delayed) {

		psched_time_t sched = q->now;

		ktime_t expires;