netdev - [PATCH net-next 2/4] net: no longer hold RTNL while calling flush_all

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Message-ID: <20250107173838.1130187-3-edumazet@google.com>
Date: Tue,  7 Jan 2025 17:38:36 +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: netdev@...r.kernel.org, Simon Horman <horms@...nel.org>, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 2/4] net: no longer hold RTNL while calling flush_all_backlogs()

flush_all_backlogs() is called from unregister_netdevice_many_notify()
as part of netdevice dismantles.

This is currently called under RTNL, and can last up to 20ms on busy hosts.

There is no reason to block RTNL at this stage.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/dev.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 9e1eb272e4feaf40dc87defd54d691634e0902e5..ef6426aad84dc00740a1716c8fd4cfd48ee17cf3 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11526,8 +11526,10 @@ void unregister_netdevice_many_notify(struct list_head *head,
 		unlist_netdevice(dev);
 		WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERING);
 	}
-	flush_all_backlogs();
 
+	__rtnl_unlock();
+	flush_all_backlogs();
+	rtnl_lock();
 	synchronize_net();
 
 	list_for_each_entry(dev, head, unreg_list) {
-- 
2.47.1.613.gc27f4b7a9f-goog