linux-kernel - [PATCH 4.4 077/135] net: Revert "pkt_sched: fq: use proper locking in fq_dump

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Message-Id: <20200629155309.2495516-78-sashal@kernel.org>
Date:   Mon, 29 Jun 2020 11:52:11 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 4.4 077/135] net: Revert "pkt_sched: fq: use proper locking in fq_dump_stats()"

From: Toke Høiland-Jørgensen <toke@...hat.com>

This reverts commit 191cf872190de28a92e1bd2b56d8860e37e07443 which is
commit 695b4ec0f0a9cf29deabd3ac075911d58b31f42b upstream.

That commit should never have been backported since it relies on a change in
locking semantics that was introduced in v4.8 and not backported. Because of
this, the backported commit to sch_fq leads to lockups because of the double
locking.

Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sched/sch_fq.c | 32 ++++++++++++++------------------
 1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index f4aa2ab4713a2..eb814ffc09023 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -830,24 +830,20 @@ static int fq_dump(struct Qdisc *sch, struct sk_buff *skb)
 static int fq_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 {
 	struct fq_sched_data *q = qdisc_priv(sch);
-	struct tc_fq_qd_stats st;
-
-	sch_tree_lock(sch);
-
-	st.gc_flows		  = q->stat_gc_flows;
-	st.highprio_packets	  = q->stat_internal_packets;
-	st.tcp_retrans		  = q->stat_tcp_retrans;
-	st.throttled		  = q->stat_throttled;
-	st.flows_plimit		  = q->stat_flows_plimit;
-	st.pkts_too_long	  = q->stat_pkts_too_long;
-	st.allocation_errors	  = q->stat_allocation_errors;
-	st.time_next_delayed_flow = q->time_next_delayed_flow - ktime_get_ns();
-	st.flows		  = q->flows;
-	st.inactive_flows	  = q->inactive_flows;
-	st.throttled_flows	  = q->throttled_flows;
-	st.pad			  = 0;
-
-	sch_tree_unlock(sch);
+	u64 now = ktime_get_ns();
+	struct tc_fq_qd_stats st = {
+		.gc_flows		= q->stat_gc_flows,
+		.highprio_packets	= q->stat_internal_packets,
+		.tcp_retrans		= q->stat_tcp_retrans,
+		.throttled		= q->stat_throttled,
+		.flows_plimit		= q->stat_flows_plimit,
+		.pkts_too_long		= q->stat_pkts_too_long,
+		.allocation_errors	= q->stat_allocation_errors,
+		.flows			= q->flows,
+		.inactive_flows		= q->inactive_flows,
+		.throttled_flows	= q->throttled_flows,
+		.time_next_delayed_flow	= q->time_next_delayed_flow - now,
+	};
 
 	return gnet_stats_copy_app(d, &st, sizeof(st));
 }
-- 
2.25.1