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net_sched: fix a missing rcu barrier in mini_qdisc_pair_swap() 

The rcu_barrier_bh() in mini_qdisc_pair_swap() is to wait for
flying RCU callback installed by a previous mini_qdisc_pair_swap(),
however we miss it on the tp_head==NULL path, which leads to that
the RCU callback still uses miniq_old->rcu after it is freed together
with qdisc in qdisc_graft(). So just add it on that path too.

Fixes: 46209401f8 ("net: core: introduce mini_Qdisc and eliminate usage of tp->q for clsact fastpath ")
Reported-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Tested-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: Jiri Pirko <jiri@mellanox.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Cong Wang 2017-12-20 23:26:24 -08:00 committed by David S. Miller
parent c1a8d0a3ac
commit b2fb01f426
1 changed files with 3 additions and 1 deletions
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4
net/sched/sch_generic.c
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@ -1040,6 +1040,8 @@ void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,
if (!tp_head) {
RCU_INIT_POINTER(*miniqp->p_miniq, NULL);
/* Wait for flying RCU callback before it is freed. */
rcu_barrier_bh();
return;
}
@ -1055,7 +1057,7 @@ void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,
rcu_assign_pointer(*miniqp->p_miniq, miniq);
if (miniq_old)
/* This is counterpart of the rcu barrier above. We need to
/* This is counterpart of the rcu barriers above. We need to
* block potential new user of miniq_old until all readers
* are not seeing it.
*/