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From:   Yunsheng Lin <linyunsheng@huawei.com>
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Subject: [PATCH net-next v2 3/3] net: sched: remove qdisc->empty for lockless qdisc
Date:   Thu, 3 Jun 2021 09:48:00 +0800
Message-ID: <1622684880-39895-4-git-send-email-linyunsheng@huawei.com>
In-Reply-To: <1622684880-39895-1-git-send-email-linyunsheng@huawei.com>
References: <1622684880-39895-1-git-send-email-linyunsheng@huawei.com>
MIME-Version: 1.0
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Precedence: bulk

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