Re: [PATCH] nbd: fix false lockdep deadlock warning

[Yu Kuai]

Hi,

在 2025/06/27 19:04, Ming Lei 写道:
> I guess the patch in the following link may be simper, both two take
> similar approach:
>
> https://lore.kernel.org/linux-block/aFjbavzLAFO0Q7n1@fedora/

I this the above approach has concurrent problems if nbd_start_device
concurrent with nbd_start_device:

t1:
nbd_start_device
lock
num_connections = 1
unlock
	t2:
	nbd_add_socket
	lock
	config->num_connections++
	unlock
		t3:
		nbd_start_device
		lock
		num_connections = 2
		unlock
		blk_mq_update_nr_hw_queues

blk_mq_update_nr_hw_queues
//nr_hw_queues updated to 1 before failure
return -EINVAL

Thanks,
Kuai