netdev - [PATCH net-next 1/6] ipv6: mcast: remove one synchronize_net() barrier in ipv6_mc

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Message-ID: <20240209153101.3824155-2-edumazet@google.com>
Date: Fri,  9 Feb 2024 15:30:56 +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: David Ahern <dsahern@...nel.org>, Pablo Neira Ayuso <pablo@...filter.org>, 
	Florian Westphal <fw@...len.de>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>, Taehee Yoo <ap420073@...il.com>, 
	Cong Wang <xiyou.wangcong@...il.com>
Subject: [PATCH net-next 1/6] ipv6: mcast: remove one synchronize_net()
 barrier in ipv6_mc_down()

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@...gle.com>
Cc: Taehee Yoo <ap420073@...il.com>
Cc: Cong Wang <xiyou.wangcong@...il.com>
Cc: David Ahern <dsahern@...nel.org>
---
 net/ipv6/mcast.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index bc6e0a0bad3c12d641a1dc60a8c790a6e72b1b5f..76ee1615ff2a07e1dd496aada377a7feb4703e8c 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -2719,7 +2719,6 @@ 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);
 
-- 
2.43.0.687.g38aa6559b0-goog