linux-kernel - [PATCH v2 1/2] net: Use call_rcu_flush() for dst_destroy

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Message-Id: <20221118191909.1756624-1-joel@joelfernandes.org>
Date:   Fri, 18 Nov 2022 19:19:08 +0000
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        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>, netdev@...r.kernel.org,
        Paolo Abeni <pabeni@...hat.com>, rcu@...r.kernel.org,
        rostedt@...dmis.org, paulmck@...nel.org, fweisbec@...il.com
Subject: [PATCH v2 1/2] net: Use call_rcu_flush() for dst_destroy_rcu

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/core/dst.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dst.c b/net/core/dst.c
index bc9c9be4e080..15b16322703f 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -174,7 +174,7 @@ void dst_release(struct dst_entry *dst)
 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
 					     __func__, dst, newrefcnt);
 		if (!newrefcnt)
-			call_rcu(&dst->rcu_head, dst_destroy_rcu);
+			call_rcu_flush(&dst->rcu_head, dst_destroy_rcu);
 	}
 }
 EXPORT_SYMBOL(dst_release);
-- 
2.38.1.584.g0f3c55d4c2-goog