From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linux Kernel list <linux-kernel@vger.kernel.org>
Subject: lockdep spew from tty
Date: Tue, 21 May 2013 11:22:00 +1000 [thread overview]
Message-ID: <1369099320.6387.33.camel@pasglop> (raw)
Hi Greg !
Caught that on a console today running some 3.10-almost-rc2
(based on ec50f2a97a4a7098a81b40030e0bfe28bdc43740). Right now I don't
have the bandwidth to investigate but I though you might be
interested :-)
I'll take another peek if it happens again.
======================================================
[ INFO: possible circular locking dependency detected ]
3.10.0-rc1-test #19 Not tainted
-------------------------------------------------------
kworker/24:1/1089 is trying to acquire lock:
(&ldata->output_lock){+.+...}, at: [<c00000000037aa0c>] .process_echoes+0x34/0x2ec
but task is already holding lock:
((&buf->work)){+.+...}, at: [<c0000000000778b4>] .process_one_work+0x1f8/0x43c
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 ((&buf->work)){+.+...}:
[<c00000000007714c>] .flush_work+0x38/0x258
[<c0000000000781e4>] .__cancel_work_timer+0xe0/0x140
[<c0000000003820c4>] .tty_port_destroy+0x14/0x2c
[<c000000000390d88>] .vc_deallocate+0xfc/0x128
[<c000000000385d8c>] .vt_ioctl+0xae4/0x13a4
[<c00000000037a218>] .tty_ioctl+0xd1c/0xe68
[<c0000000001403b0>] .vfs_ioctl+0x44/0x6c
[<c000000000140e54>] .do_vfs_ioctl+0x614/0x6ac
[<c000000000140f30>] .SyS_ioctl+0x44/0x70
[<c000000000009ca4>] syscall_exit+0x0/0x98
-> #1 (console_lock){+.+.+.}:
[<c00000000005aeec>] .console_lock+0x80/0x98
[<c00000000039180c>] .do_con_write.part.16+0x3c/0x1fb0
[<c0000000003937ec>] .con_write+0x28/0x40
[<c00000000037b344>] .n_tty_write+0x28c/0x424
[<c000000000377c84>] .tty_write+0x184/0x238
[<c00000000012f0ec>] .vfs_write+0xd4/0x1cc
[<c00000000012f5d0>] .SyS_write+0x48/0x7c
[<c000000000009ca4>] syscall_exit+0x0/0x98
-> #0 (&ldata->output_lock){+.+...}:
[<c0000000000a4dc4>] .lock_acquire+0x54/0x70
[<c000000000705780>] .mutex_lock_nested+0x9c/0x4d4
[<c00000000037aa0c>] .process_echoes+0x34/0x2ec
[<c00000000037cc04>] .n_tty_receive_buf+0xc64/0xf90
[<c000000000380d3c>] .flush_to_ldisc+0x110/0x1ac
[<c00000000007793c>] .process_one_work+0x280/0x43c
[<c000000000077d10>] .worker_thread+0x1e0/0x324
[<c00000000007e360>] .kthread+0xc8/0xd4
[<c000000000009fac>] .ret_from_kernel_thread+0x5c/0xb0
other info that might help us debug this:
Chain exists of:
&ldata->output_lock --> console_lock --> (&buf->work)
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock((&buf->work));
lock(console_lock);
lock((&buf->work));
lock(&ldata->output_lock);
*** DEADLOCK ***
2 locks held by kworker/24:1/1089:
#0: (events){.+.+.+}, at: [<c0000000000778b4>] .process_one_work+0x1f8/0x43c
#1: ((&buf->work)){+.+...}, at: [<c0000000000778b4>] .process_one_work+0x1f8/0x43c
stack backtrace:
CPU: 24 PID: 1089 Comm: kworker/24:1 Not tainted 3.10.0-rc1-test #19
Workqueue: events .flush_to_ldisc
Call Trace:
[c000003ed7c37350] [c000000000011b18] .show_stack+0x50/0x14c (unreliable)
[c000003ed7c37420] [c00000000070eb90] .dump_stack+0x28/0x3c
[c000003ed7c37490] [c00000000070b16c] .print_circular_bug+0x364/0x374
[c000003ed7c37540] [c0000000000a4088] .__lock_acquire+0x14d8/0x1d08
[c000003ed7c37690] [c0000000000a4dc4] .lock_acquire+0x54/0x70
[c000003ed7c37720] [c000000000705780] .mutex_lock_nested+0x9c/0x4d4
[c000003ed7c37830] [c00000000037aa0c] .process_echoes+0x34/0x2ec
[c000003ed7c378f0] [c00000000037cc04] .n_tty_receive_buf+0xc64/0xf90
[c000003ed7c37aa0] [c000000000380d3c] .flush_to_ldisc+0x110/0x1ac
[c000003ed7c37b60] [c00000000007793c] .process_one_work+0x280/0x43c
[c000003ed7c37c20] [c000000000077d10] .worker_thread+0x1e0/0x324
[c000003ed7c37cd0] [c00000000007e360] .kthread+0xc8/0xd4
Cheers,
Ben.
next reply other threads:[~2013-05-21 1:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-21 1:22 Benjamin Herrenschmidt [this message]
2013-05-21 7:31 ` lockdep spew from tty Benjamin Herrenschmidt
2013-05-21 21:03 ` Greg Kroah-Hartman
2013-05-21 21:46 ` Peter Hurley
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1369099320.6387.33.camel@pasglop \
--to=benh@kernel.crashing.org \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.