On (12/12/18 12:42), Sergey Senozhatsky wrote:
[..]
> > >> [ 87.255156] CPU0 CPU1
> > >> [ 87.255813] ---- ----
> > >> [ 87.256460] lock(&port_lock_key);
> > >> [ 87.256973] lock(console_owner);
> > >> [ 87.257829] lock(&port_lock_key);
> > >> [ 87.258680] lock(&obj_hash[i].lock);
>
> So it's like
>
> CPU0 CPU1
>
> uart_shutdown() db->lock
> uart_port->lock debug_print_object()
> free_page() printk
> debug_check_no_obj_freed uart_port->lock
> db->lock
>
>
> In this particular case we probably can just move free_page()
> out of uart_port lock scope. Note that free_page()->MM can printk()
> on its own.
>
[..]
>
> [1]
> https://lore.kernel.org/lkml/1542653726-5655-8-git-send-email-long...@redhat.com/T/#u
That said, I'd first try Waiman's patch. The one I suggested is
more of a defense move - there are too many things happening under
uart_port->lock. This is not the first time we see lockdep complaining
about the way uart and the rest of the kernel interact.
-ss
