[PATCH net-next 3/3] net: sched: remove qdisc->empty for lockless qdisc

Yunsheng Lin
2021-05-28T02:50:13Z

As MISSED and DRAINING state are used to indicate a non-empty
qdisc, qdisc->empty is not longer needed, so remove it.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
---
include/net/sch_generic.h | 13 +++----------
net/sched/sch_generic.c | 3 ---
2 files changed, 3 insertions(+), 13 deletions(-)

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 177f240..c99ffe9 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -117,8 +117,6 @@ struct Qdisc {
spinlock_t busylock ____cacheline_aligned_in_smp;
spinlock_t seqlock;

- /* for NOLOCK qdisc, true if there are no enqueued skbs */
- bool empty;
struct rcu_head rcu;

/* private data */
@@ -165,7 +163,7 @@ static inline bool qdisc_is_percpu_stats(const struct Qdisc *q)
static inline bool qdisc_is_empty(const struct Qdisc *qdisc)
{
if (qdisc_is_percpu_stats(qdisc))
- return READ_ONCE(qdisc->empty);
+ return nolock_qdisc_is_empty(qdisc);
return !READ_ONCE(qdisc->q.qlen);
}

@@ -173,7 +171,7 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc)
{
if (qdisc->flags & TCQ_F_NOLOCK) {
if (spin_trylock(&qdisc->seqlock))
- goto nolock_empty;
+ return true;

/* If the MISSED flag is set, it means other thread has
* set the MISSED flag before second spin_trylock(), so
@@ -195,12 +193,7 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc)
/* Retry again in case other CPU may not see the new flag
* after it releases the lock at the end of qdisc_run_end().
*/
- if (!spin_trylock(&qdisc->seqlock))
- return false;
-
-nolock_empty:
- WRITE_ONCE(qdisc->empty, false);
- return true;
+ return spin_trylock(&qdisc->seqlock);
} else if (qdisc_is_running(qdisc)) {
return false;
}
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 83d7f5f..1abd9c7 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -707,8 +707,6 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
need_retry = false;

goto retry;
- } else {
- WRITE_ONCE(qdisc->empty, true);
}

return skb;
@@ -909,7 +907,6 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
sch->enqueue = ops->enqueue;
sch->dequeue = ops->dequeue;
sch->dev_queue = dev_queue;
- sch->empty = true;
dev_hold(dev);
refcount_set(&sch->refcnt, 1);

--
2.7.4