From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Dmitry Safonov <dima@arista.com>
Cc: Jiri Slaby <jslaby@suse.cz>,
kernel test robot <rong.a.chen@intel.com>,
lkp@01.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Mikulas Patocka <mpatocka@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-serial@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Petr Mladek <pmladek@suse.com>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Waiman Long <longman@redhat.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [LKP] [tty] c96cf923a9: WARNING:possible_circular_locking_dependency_detected
Date: Wed, 12 Dec 2018 14:04:32 +0900 [thread overview]
Message-ID: <20181212050432.GE431@jagdpanzerIV> (raw)
In-Reply-To: <20181212034252.GD431@jagdpanzerIV>
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-longman@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
next prev parent reply other threads:[~2018-12-12 5:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-11 9:11 [LKP] [tty] c96cf923a9: WARNING:possible_circular_locking_dependency_detected kernel test robot
2018-12-11 13:49 ` Jiri Slaby
2018-12-11 20:59 ` Dmitry Safonov
2018-12-12 3:42 ` Sergey Senozhatsky
2018-12-12 5:04 ` Sergey Senozhatsky [this message]
2018-12-12 15:12 ` Waiman Long
2018-12-12 9:07 ` Peter Zijlstra
2018-12-13 5:38 ` Sergey Senozhatsky
2018-12-12 14:54 ` Dmitry Safonov
2018-12-13 2:19 ` Sergey Senozhatsky
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