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 <[email protected]>
Reported-by: David Ahern <[email protected]>
---
include/net/sch_generic.h | 6 +++++-
net/sched/sch_generic.c | 4 ++--
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index c4f5749342ec..d53ecfc1d60e 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -104,7 +104,11 @@ 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 cebea73e70ac..cad810b45e31 100644
--- 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 */
--
2.8.0.rc3.226.g39d4020
