From d806b5437b1d0c9f3252997f36ee5aa80e40ed4b Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Tue, 15 May 2018 16:24:36 +0200 Subject: [PATCH] sched: replace __QDISC_STATE_RUNNING bit with a spin lock So that we can use lockdep on it. The newly introduced sequence lock has the same scope of busylock, so it shares the same lockdep annotation, but it's only used for NOLOCK qdiscs. With this changeset we acquire such lock in the control path around flushing operation (qdisc reset), to allow more NOLOCK qdisc perf improvement in the next patch. Signed-off-by: Paolo Abeni Signed-off-by: David S. Miller --- include/net/sch_generic.h | 10 +++++----- net/sched/sch_generic.c | 11 +++++++++++ 2 files changed, 16 insertions(+), 5 deletions(-) diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 4d2b37226e75c..98c10a28cd01c 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -30,7 +30,6 @@ struct qdisc_rate_table { enum qdisc_state_t { __QDISC_STATE_SCHED, __QDISC_STATE_DEACTIVATED, - __QDISC_STATE_RUNNING, }; struct qdisc_size_table { @@ -102,6 +101,7 @@ struct Qdisc { refcount_t refcnt; spinlock_t busylock ____cacheline_aligned_in_smp; + spinlock_t seqlock; }; static inline void qdisc_refcount_inc(struct Qdisc *qdisc) @@ -111,17 +111,17 @@ static inline void qdisc_refcount_inc(struct Qdisc *qdisc) refcount_inc(&qdisc->refcnt); } -static inline bool qdisc_is_running(const struct Qdisc *qdisc) +static inline bool qdisc_is_running(struct Qdisc *qdisc) { if (qdisc->flags & TCQ_F_NOLOCK) - return test_bit(__QDISC_STATE_RUNNING, &qdisc->state); + return spin_is_locked(&qdisc->seqlock); return (raw_read_seqcount(&qdisc->running) & 1) ? true : false; } static inline bool qdisc_run_begin(struct Qdisc *qdisc) { if (qdisc->flags & TCQ_F_NOLOCK) { - if (test_and_set_bit(__QDISC_STATE_RUNNING, &qdisc->state)) + if (!spin_trylock(&qdisc->seqlock)) return false; } else if (qdisc_is_running(qdisc)) { return false; @@ -138,7 +138,7 @@ static inline void qdisc_run_end(struct Qdisc *qdisc) { write_seqcount_end(&qdisc->running); if (qdisc->flags & TCQ_F_NOLOCK) - clear_bit(__QDISC_STATE_RUNNING, &qdisc->state); + spin_unlock(&qdisc->seqlock); } static inline bool qdisc_may_bulk(const struct Qdisc *qdisc) diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index ff3ce71aec937..a126f16bc30b9 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -858,6 +858,11 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, lockdep_set_class(&sch->busylock, dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); + /* seqlock has the same scope of busylock, for NOLOCK qdisc */ + spin_lock_init(&sch->seqlock); + lockdep_set_class(&sch->busylock, + dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); + seqcount_init(&sch->running); lockdep_set_class(&sch->running, dev->qdisc_running_key ?: &qdisc_running_key); @@ -1097,6 +1102,10 @@ static void dev_deactivate_queue(struct net_device *dev, qdisc = rtnl_dereference(dev_queue->qdisc); if (qdisc) { + bool nolock = qdisc->flags & TCQ_F_NOLOCK; + + if (nolock) + spin_lock_bh(&qdisc->seqlock); spin_lock_bh(qdisc_lock(qdisc)); if (!(qdisc->flags & TCQ_F_BUILTIN)) @@ -1106,6 +1115,8 @@ static void dev_deactivate_queue(struct net_device *dev, qdisc_reset(qdisc); spin_unlock_bh(qdisc_lock(qdisc)); + if (nolock) + spin_unlock_bh(&qdisc->seqlock); } } -- 2.39.5