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: f9eb8aea2a1e ("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>

1 files changed, 5 insertions, 1 deletions

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 49534e28824b..a4c0f1649e2b 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -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;
 }