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>

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 49534e2..a4c0f16 100644 (file)
--- 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;
 }
 

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index cebea73..cad810b 100644 (file)
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -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 */