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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Cc: Eric Dumazet <edumazet@google.com>,
	Taehee Yoo <ap420073@gmail.com>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	David Ahern <dsahern@kernel.org>,
	"David S . Miller" <davem@davemloft.net>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.1 140/451] ipv6: mcast: remove one synchronize_net() barrier in ipv6_mc_down()
Date: Sun, 24 Mar 2024 19:06:56 -0400
Message-ID: <20240324231207.1351418-141-sashal@kernel.org>
In-Reply-To: <20240324231207.1351418-1-sashal@kernel.org>
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From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 17ef8efc00b34918b966388b2af0993811895a8c ]

As discussed in the past (commit 2d3916f31891 ("ipv6: fix skb drops
in igmp6_event_query() and igmp6_event_report()")) I think the
synchronize_net() call in ipv6_mc_down() is not needed.

Under load, synchronize_net() can last between 200 usec and 5 ms.

KASAN seems to agree as well.

Fixes: f185de28d9ae ("mld: add new workqueues for process mld events")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Taehee Yoo <ap420073@gmail.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv6/mcast.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 566f3b7b957e9..a777695389403 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -2722,7 +2722,6 @@ void ipv6_mc_down(struct inet6_dev *idev)
 	/* Should stop work after group drop. or we will
 	 * start work again in mld_ifc_event()
 	 */
-	synchronize_net();
 	mld_query_stop_work(idev);
 	mld_report_stop_work(idev);
 
-- 
2.43.0