> ---------------->
>
> pkt_sched: Destroy qdiscs under rtnl_lock again.
>
> We don't need to trigger __qdisc_destroy() as an RCU callback because
> the use of qdisc isn't controlled by RCU alone: after querying RCU
> with synchronize_rcu() in dev_deactivate() we additionaly wait in a
> loop checking some flags. After the loop is done there could be no
> outstanding use of the qdisc, so call_rcu() doesn't make any sense.
>
> On the other hand, current calling Qdisc's ->destroy() from a softirq
> context without locking (rtnl) can break various things like:
> qdisc_put_rtab(), tcf_destroy_chain() (e.g. u32_destroy()), and
> probably more.
>
>
> Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
>
> ---
>
> net/sched/sch_generic.c | 8 ++------
> 1 files changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index 4685746..e7379d2 100644
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -518,12 +518,8 @@ void qdisc_reset(struct Qdisc *qdisc)
> }
> EXPORT_SYMBOL(qdisc_reset);
>
> -/* this is the rcu callback function to clean up a qdisc when there
> - * are no further references to it */
> -
> -static void __qdisc_destroy(struct rcu_head *head)
> +static void __qdisc_destroy(struct Qdisc *qdisc)
> {
> - struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
> const struct Qdisc_ops *ops = qdisc->ops;
>
> #ifdef CONFIG_NET_SCHED
> @@ -554,7 +550,7 @@ void qdisc_destroy(struct Qdisc *qdisc)
> if (qdisc->parent)
> list_del(&qdisc->list);
>
> - call_rcu(&qdisc->q_rcu, __qdisc_destroy);
> + __qdisc_destroy(qdisc);
> }
> EXPORT_SYMBOL(qdisc_destroy);
>
> --
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