linux-kernel - [PATCH rcu/dev 1/3] net: Use call_rcu_flush() for qdisc_free

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Message-Id: <20221117031551.1142289-1-joel@joelfernandes.org>
Date:   Thu, 17 Nov 2022 03:15:48 +0000
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Cong Wang <xiyou.wangcong@...il.com>,
        David Ahern <dsahern@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
        Paolo Abeni <pabeni@...hat.com>, rcu@...r.kernel.org,
        rostedt@...dmis.org, paulmck@...nel.org, fweisbec@...il.com
Subject: [PATCH rcu/dev 1/3] net: Use call_rcu_flush() for qdisc_free_cb

In a networking test on ChromeOS, we find that using the new CONFIG_RCU_LAZY
causes a networking test to fail in the teardown phase.

The failure happens during: ip netns del <name>

Using ftrace, I found the callbacks it was queuing which this series fixes. Use
call_rcu_flush() to revert to the old behavior. With that, the test passes.

Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 net/sched/sch_generic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index a9aadc4e6858..63fbf640d3b2 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1067,7 +1067,7 @@ static void qdisc_destroy(struct Qdisc *qdisc)
 
 	trace_qdisc_destroy(qdisc);
 
-	call_rcu(&qdisc->rcu, qdisc_free_cb);
+	call_rcu_flush(&qdisc->rcu, qdisc_free_cb);
 }
 
 void qdisc_put(struct Qdisc *qdisc)
-- 
2.38.1.584.g0f3c55d4c2-goog