Since blamed commit, unregister_netdevice_many_notify() takes the netdev mutex if the device needs it. This isn't a problem in itself, the problem is that the list can be very long, so it may lock a LOT of mutexes, but lockdep engine can only deal with MAX_LOCK_DEPTH held locks: unshare -n bash -c 'for i in $(seq 1 100);do ip link add foo$i type dummy;done' BUG: MAX_LOCK_DEPTH too low! turning off the locking correctness validator. depth: 48 max: 48! 48 locks held by kworker/u16:1/69: #0: ffff8880010b7148 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x7ed/0x1350 #1: ffffc900004a7d40 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0xcf3/0x1350 #2: ffffffff8bc6fbd0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xab/0x7f0 #3: ffffffff8bc8daa8 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch+0x7e/0x2e0 #4: ffff88800b5e9cb0 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: unregister_netdevice_many_notify+0x1056/0x1b00 [..] Work around this limitation by chopping the list into smaller chunks and process them individually for LOCKDEP enabled kernels. Fixes: 7e4d784f5810 ("net: hold netdev instance lock during rtnetlink operations") Signed-off-by: Florian Westphal --- net/core/dev.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index 9a09b48c9371..7e35aa4ebc74 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -12208,6 +12208,38 @@ static void unregister_netdevice_close_many(struct list_head *head) } } +static void unregister_netdevice_close_many_lockdep(struct list_head *head) +{ +#ifdef CONFIG_LOCKDEP + unsigned int lock_depth = lockdep_depth(current); + unsigned int lock_count = lock_depth; + struct net_device *dev, *tmp; + LIST_HEAD(done_head); + + list_for_each_entry_safe(dev, tmp, head, unreg_list) { + if (netdev_need_ops_lock(dev)) + lock_count++; + + /* we'll run out of lockdep keys, reduce size. */ + if (lock_count >= MAX_LOCK_DEPTH - 1) { + LIST_HEAD(tmp_head); + + list_cut_before(&tmp_head, head, &dev->unreg_list); + unregister_netdevice_close_many(&tmp_head); + lock_count = lock_depth; + list_splice_tail(&tmp_head, &done_head); + } + } + + unregister_netdevice_close_many(head); + + list_for_each_entry_safe_reverse(dev, tmp, &done_head, unreg_list) + list_move(&dev->unreg_list, head); +#else + unregister_netdevice_close_many(head); +#endif +} + void unregister_netdevice_many_notify(struct list_head *head, u32 portid, const struct nlmsghdr *nlh) { @@ -12237,7 +12269,7 @@ void unregister_netdevice_many_notify(struct list_head *head, BUG_ON(dev->reg_state != NETREG_REGISTERED); } - unregister_netdevice_close_many(head); + unregister_netdevice_close_many_lockdep(head); flush_all_backlogs(); -- 2.49.1