Re: [Patch net-next] net_sched: call qdisc_reset() with qdisc lock

From: Cong Wang <redacted>
Date: Thu, 21 Dec 2017 16:03:29 -0800

qdisc_reset() should always be called with qdisc spinlock
and with BH disabled, otherwise qdisc ->reset() could race
with TX BH.

Fixes: 7bbde83b1860 ("net: sched: drop qdisc_reset from dev_graft_qdisc")
Reported-by: Jakub Kicinski <redacted>
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Cong Wang <redacted>

There doesn't seem to be agreement over whether qdisc_reset() really
needs to run with the lock held.  In fact, the general consensus is
that this really shouldn't run until a grace period had occurred and
therefore parallel TX paths cannot be running any longer.

In any event, this was supposed to work towards a bug fix which
ultimately was fixed instead with the ptr_ring change from John.

So this seems unnecessary now.

If you disagree, please repost with an updated commit message which
explains things further.

Thank you.