Commit 4c2bd791 authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

net: let lockdep compare instance locks 



AFAIU always returning -1 from lockdep's compare function
basically disables checking of dependencies between given
locks. Try to be a little more precise about what guarantees
that instance locks won't deadlock.

Right now we only nest them under protection of rtnl_lock.
Mostly in unregister_netdevice_many() and dev_close_many().

Acked-by: default avatarStanislav Fomichev <sdf@fomichev.me>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250517200810.466531-1-kuba@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 6a7e8b5d

include/net/netdev_lock.h

+7 −8
Original line number Diff line number Diff line
@@ -99,16 +99,15 @@ static inline void netdev_unlock_ops_compat(struct net_device *dev) 
static inline int netdev_lock_cmp_fn(const struct lockdep_map *a,

				     const struct lockdep_map *b)

{

	/* Only lower devices currently grab the instance lock, so no

	 * real ordering issues can occur. In the near future, only

	 * hardware devices will grab instance lock which also does not

	 * involve any ordering. Suppress lockdep ordering warnings

	 * until (if) we start grabbing instance lock on pure SW

	 * devices (bond/team/veth/etc).

	 */

	if (a == b)

		return 0;

	return -1;



	/* Allow locking multiple devices only under rtnl_lock,

	 * the exact order doesn't matter.

	 * Note that upper devices don't lock their ops, so nesting

	 * mostly happens in batched device removal for now.

	 */

	return lockdep_rtnl_is_held() ? -1 : 1;

}



#define netdev_lockdep_set_classes(dev)				\