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Commit 52fbb290 authored Jun 09, 2016 by Eric Dumazet Committed by David S. Miller Jun 09, 2016

net: sched: fix qdisc->running lockdep annotations



1) qdisc_run_begin() is really using the equivalent of a trylock.
  Instead of using write_seqcount_begin(), use a combination of
  raw_write_seqcount_begin() and correct lockdep annotation.

2) sch_direct_xmit() should use regular spin_lock(root_lock)

Fixes: f9eb8aea ("net_sched: transform qdisc running bit into a seqcount")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 5362855a

include/net/sch_generic.h

+5 −1

Original line number	Diff line number	Diff line
		@@ -97,7 +97,11 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc)
		{
		if (qdisc_is_running(qdisc))
		return false;
		write_seqcount_begin(&qdisc->running);
		/* Variant of write_seqcount_begin() telling lockdep a trylock
		* was attempted.
		*/
		raw_write_seqcount_begin(&qdisc->running);
		seqcount_acquire(&qdisc->running.dep_map, 0, 1, _RET_IP_);
		return true;
		}

net/sched/sch_generic.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -137,10 +137,10 @@ int sch_direct_xmit(struct sk_buff skb, struct Qdisc q,

		HARD_TX_UNLOCK(dev, txq);
		} else {
		spin_lock_nested(root_lock, SINGLE_DEPTH_NESTING);
		spin_lock(root_lock);
		return qdisc_qlen(q);
		}
		spin_lock_nested(root_lock, SINGLE_DEPTH_NESTING);
		spin_lock(root_lock);

		if (dev_xmit_complete(ret)) {
		/* Driver sent out skb successfully or skb was consumed */