From: Jakub Kicinski <kuba@kernel.org>
Date: Thu, 16 Jan 2025 03:17:07 +0000 (-0800)
Subject: Merge branch 'net-reduce-rtnl-pressure-in-unregister_netdevice'
X-Git-Tag: v6.14-rc1~162^2~48
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=707ec6279dd12b785677976c045e0b9896ca1f2e;p=thirdparty%2Flinux.git

Merge branch 'net-reduce-rtnl-pressure-in-unregister_netdevice'

Eric Dumazet says:

====================
net: reduce RTNL pressure in unregister_netdevice()

One major source of RTNL contention resides in unregister_netdevice()

Due to RCU protection of various network structures, and
unregister_netdevice() being a synchronous function,
it is calling potentially slow functions while holding RTNL.

I think we can release RTNL in two points, so that three
slow functions are called while RTNL can be used
by other threads.

v1: https://lore.kernel.org/netdev/20250107130906.098fc8d6@kernel.org/T/#m398c95f5778e1ff70938e079d3c4c43c050ad2a6
====================

Link: https://patch.msgid.link/20250114205531.967841-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

707ec6279dd12b785677976c045e0b9896ca1f2e
diff --cc net/core/dev.c
index b6722ed9767a9,3c87cb1cb8771..782ae3ff3f8d8
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@@ -11724,13 -11623,13 +11772,15 @@@ void unregister_netdevice_many_notify(s
  	list_for_each_entry(dev, head, unreg_list) {
  		/* And unlink it from device chain. */
  		unlist_netdevice(dev);
 +		netdev_lock(dev);
  		WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERING);
 +		netdev_unlock(dev);
  	}
- 	flush_all_backlogs();
  
+ 	rtnl_drop_if_cleanup_net();
+ 	flush_all_backlogs();
  	synchronize_net();
+ 	rtnl_acquire_if_cleanup_net();
  
  	list_for_each_entry(dev, head, unreg_list) {
  		struct sk_buff *skb = NULL;