netdev - [PATCH RFC net-next 3/5] Revert "net/sched: Fix mirred deadlock on device recursion"

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Message-ID: <20251006193103.2684156-4-edumazet@google.com>
Date: Mon,  6 Oct 2025 19:31:01 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Jamal Hadi Salim <jhs@...atatu.com>, 
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH RFC net-next 3/5] Revert "net/sched: Fix mirred deadlock on
 device recursion"

This reverts commits 0f022d32c3eca477fbf79a205243a6123ed0fe11
and 44180feaccf266d9b0b28cc4ceaac019817deb5c.

Prior patch in this series implemented loop detection
in act_mirred, we can remove q->owner to save some cycles
in the fast path.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/sch_generic.h | 1 -
 net/core/dev.c            | 6 ------
 net/sched/sch_generic.c   | 2 --
 3 files changed, 9 deletions(-)

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 738cd5b13c62fb8501619625880b87991f3dc17c..32e9961570b467b6066f1bb2c00ff1a270e342bc 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -117,7 +117,6 @@ struct Qdisc {
 	struct qdisc_skb_head	q;
 	struct gnet_stats_basic_sync bstats;
 	struct gnet_stats_queue	qstats;
-	int                     owner;
 	unsigned long		state;
 	unsigned long		state2; /* must be written under qdisc spinlock */
 	struct Qdisc            *next_sched;
diff --git a/net/core/dev.c b/net/core/dev.c
index a64cef2c537e98ee87776e6f8d3ca3d98f0711b3..0ff178399b2d28ca2754b3f06d69a97f5d6dcf71 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4167,10 +4167,6 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
 		return rc;
 	}
 
-	if (unlikely(READ_ONCE(q->owner) == smp_processor_id())) {
-		kfree_skb_reason(skb, SKB_DROP_REASON_TC_RECLASSIFY_LOOP);
-		return NET_XMIT_DROP;
-	}
 	/*
 	 * Heuristic to force contended enqueues to serialize on a
 	 * separate lock before trying to get qdisc main lock.
@@ -4210,9 +4206,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
 		qdisc_run_end(q);
 		rc = NET_XMIT_SUCCESS;
 	} else {
-		WRITE_ONCE(q->owner, smp_processor_id());
 		rc = dev_qdisc_enqueue(skb, q, &to_free, txq);
-		WRITE_ONCE(q->owner, -1);
 		if (qdisc_run_begin(q)) {
 			if (unlikely(contended)) {
 				spin_unlock(&q->busylock);
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 1e008a228ebdf846d4ef7f83d655ac1142ec3596..dfa8e8e667d24a435b0c9cb3c1f05c8075f63e89 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -679,7 +679,6 @@ struct Qdisc noop_qdisc = {
 		.qlen = 0,
 		.lock = __SPIN_LOCK_UNLOCKED(noop_qdisc.skb_bad_txq.lock),
 	},
-	.owner = -1,
 };
 EXPORT_SYMBOL(noop_qdisc);
 
@@ -985,7 +984,6 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
 	sch->enqueue = ops->enqueue;
 	sch->dequeue = ops->dequeue;
 	sch->dev_queue = dev_queue;
-	sch->owner = -1;
 	netdev_hold(dev, &sch->dev_tracker, GFP_KERNEL);
 	refcount_set(&sch->refcnt, 1);
 
-- 
2.51.0.618.g983fd99d29-goog