Re: 3.8-rc2 lockdep complains about console_lock vs. fb_notifier_list.rwsem

From: Sedat Dilek
Date: Wed Jan 16 2013 - 04:21:37 EST

On Tue, Jan 15, 2013 at 3:25 PM, Takashi Iwai <tiwai@xxxxxxx> wrote:
> At Sat, 5 Jan 2013 13:13:27 +0100,
> Sedat Dilek wrote:
>>
>> Hi Jiri,
>>
>> ...known issue (see thread in [1]), please feel free to test patches
>> from Alan and Andrew (see [1], [2] and [3]) and report.
>>
>> Regards,
>> - Sedat -
>>
>> [1] http://marc.info/?t=135309396400003&r=1&w=2
>> [2] http://ozlabs.org/~akpm/mmots/broken-out/fb-rework-locking-to-fix-lock-ordering-on-takeover.patch
>> [3] http://ozlabs.org/~akpm/mmots/broken-out/fb-rework-locking-to-fix-lock-ordering-on-takeover-fix.patch
>> [4] http://ozlabs.org/~akpm/mmots/broken-out/fb-rework-locking-to-fix-lock-ordering-on-takeover-fix-2.patch
>
> I've hit this bug and tried the patch [2] ([3] and [4] are gone).
> Unfortunately the deadlock is still reported, as seen below.
>
> A similar fix for fbcon_unbind(), splitting an unlocked version of
> unbind_con_driver() and call it?
>
> (BTW, the patch [2] contains strange characters in the comments, and
> has a few coding issues easily detected by checkpatch.pl.)
>

[ CCing Rafael as he asked in another thread if I had sent a patch ]

I noticed also some these "strange" chars in the patch from Andrew and
a patch of mine was sent as
"fb-Rework-locking-to-fix-lock-ordering-on-takeover-fix-comments.patch"
to the lists.

It is strange to me that Andrew or other maintainers himself did not
check with "checkpatch.pl".
This should be a common testcase!
Hey, noone is perfect :-).
( /me has also not checked with that script - I just saw it. )

Just as a note to the issue in general:
Andrew took over the patch from Alan which is very honest - he is not
the active TTY maintainer!
Didn't Greg takeover maintenance from Alan (after a dispute and blaming Alan)?
If this is true, why the hell is Greg not CCed?

Thanks for the real patch in the followup of this thread!
Who will take care of it :-)?

- Sedat

>
> thanks,
>
> Takashi
>
> ===
>
> [ 3.228454] [drm] Initialized drm 1.1.0 20060810
> [ 3.317144] [drm] radeon defaulting to kernel modesetting.
> [ 3.330546] [drm] radeon kernel modesetting enabled.
> [ 3.343942] checking generic (c0000000 1000000) vs hw (c0000000 10000000)
> [ 3.343946] fb: conflicting fb hw usage radeondrmfb vs VESA VGA - removing generic driver
> [ 3.357376]
> [ 3.357377] ======================================================
> [ 3.357378] [ INFO: possible circular locking dependency detected ]
> [ 3.357380] 3.8.0-rc3-test+ #82 Not tainted
> [ 3.357381] -------------------------------------------------------
> [ 3.357383] udevd/137 is trying to acquire lock:
> [ 3.357394] (console_lock){+.+.+.}, at: [<ffffffff8140385f>] unbind_con_driver+0x3f/0x200
> [ 3.357395]
> [ 3.357395] but task is already holding lock:
> [ 3.357402] ((fb_notifier_list).rwsem){.+.+.+}, at: [<ffffffff810799b1>] __blocking_notifier_call_chain+0x51/0xc0
> [ 3.357403]
> [ 3.357403] which lock already depends on the new lock.
> [ 3.357403]
> [ 3.357404]
> [ 3.357404] the existing dependency chain (in reverse order) is:
> [ 3.357407]
> [ 3.357407] -> #1 ((fb_notifier_list).rwsem){.+.+.+}:
> [ 3.357411] [<ffffffff810b605a>] lock_acquire+0xaa/0x210
> [ 3.357417] [<ffffffff81643dc2>] down_read+0x42/0x57
> [ 3.357419] [<ffffffff810799b1>] __blocking_notifier_call_chain+0x51/0xc0
> [ 3.357422] [<ffffffff81079a31>] blocking_notifier_call_chain+0x11/0x20
> [ 3.357426] [<ffffffff8138cbe6>] fb_notifier_call_chain+0x16/0x20
> [ 3.357428] [<ffffffff8138e302>] register_framebuffer+0x1c2/0x2f0
> [ 3.357433] [<ffffffff81d1748e>] vesafb_probe+0x6e0/0x760
> [ 3.357437] [<ffffffff8142afbe>] platform_drv_probe+0x3e/0x70
> [ 3.357440] [<ffffffff81428d26>] driver_probe_device+0x86/0x390
> [ 3.357442] [<ffffffff814290d3>] __driver_attach+0xa3/0xb0
> [ 3.357445] [<ffffffff81426dbd>] bus_for_each_dev+0x4d/0x90
> [ 3.357447] [<ffffffff814286a9>] driver_attach+0x19/0x20
> [ 3.357450] [<ffffffff81428308>] bus_add_driver+0x1a8/0x290
> [ 3.357452] [<ffffffff81429792>] driver_register+0x72/0x170
> [ 3.357455] [<ffffffff8142a7e1>] platform_driver_register+0x41/0x50
> [ 3.357458] [<ffffffff8142a806>] platform_driver_probe+0x16/0xa0
> [ 3.357460] [<ffffffff81d16d6b>] vesafb_init+0x215/0x258
> [ 3.357464] [<ffffffff810002e2>] do_one_initcall+0x122/0x180
> [ 3.357468] [<ffffffff816258ec>] kernel_init+0x1fc/0x370
> [ 3.357471] [<ffffffff8164e1fc>] ret_from_fork+0x7c/0xb0
> [ 3.357474]
> [ 3.357474] -> #0 (console_lock){+.+.+.}:
> [ 3.357476] [<ffffffff810b5055>] __lock_acquire+0x1385/0x1cc0
> [ 3.357478] [<ffffffff810b605a>] lock_acquire+0xaa/0x210
> [ 3.357482] [<ffffffff81048fbf>] console_lock+0x6f/0x80
> [ 3.357485] [<ffffffff8140385f>] unbind_con_driver+0x3f/0x200
> [ 3.357489] [<ffffffff8139aeb7>] fbcon_event_notify+0x447/0x8b0
> [ 3.357492] [<ffffffff8164a225>] notifier_call_chain+0x55/0x110
> [ 3.357495] [<ffffffff810799c7>] __blocking_notifier_call_chain+0x67/0xc0
> [ 3.357497] [<ffffffff81079a31>] blocking_notifier_call_chain+0x11/0x20
> [ 3.357500] [<ffffffff8138cbe6>] fb_notifier_call_chain+0x16/0x20
> [ 3.357502] [<ffffffff8138debb>] do_unregister_framebuffer+0x5b/0x110
> [ 3.357505] [<ffffffff8138e108>] do_remove_conflicting_framebuffers+0x158/0x190
> [ 3.357507] [<ffffffff8138e46a>] remove_conflicting_framebuffers+0x3a/0x60
> [ 3.357532] [<ffffffffa00df16b>] radeon_pci_probe+0x8b/0xd0 [radeon]
> [ 3.357536] [<ffffffff8136d5a6>] local_pci_probe+0x46/0x80
> [ 3.357539] [<ffffffff8136d7f1>] pci_device_probe+0x101/0x110
> [ 3.357542] [<ffffffff81428d26>] driver_probe_device+0x86/0x390
> [ 3.357544] [<ffffffff814290d3>] __driver_attach+0xa3/0xb0
> [ 3.357547] [<ffffffff81426dbd>] bus_for_each_dev+0x4d/0x90
> [ 3.357549] [<ffffffff814286a9>] driver_attach+0x19/0x20
> [ 3.357552] [<ffffffff81428308>] bus_add_driver+0x1a8/0x290
> [ 3.357554] [<ffffffff81429792>] driver_register+0x72/0x170
> [ 3.357557] [<ffffffff8136c60f>] __pci_register_driver+0x5f/0x70
> [ 3.357577] [<ffffffffa006ec3a>] drm_pci_init+0x11a/0x130 [drm]
> [ 3.357594] [<ffffffffa01c20ec>] radeon_init+0xec/0x1000 [radeon]
> [ 3.357597] [<ffffffff810002e2>] do_one_initcall+0x122/0x180
> [ 3.357600] [<ffffffff810c4b53>] load_module+0x1043/0x1510
> [ 3.357603] [<ffffffff810c50f7>] sys_init_module+0xd7/0x120
> [ 3.357605] [<ffffffff8164e2ad>] system_call_fastpath+0x1a/0x1f
> [ 3.357606]
> [ 3.357606] other info that might help us debug this:
> [ 3.357606]
> [ 3.357607] Possible unsafe locking scenario:
> [ 3.357607]
> [ 3.357608] CPU0 CPU1
> [ 3.357609] ---- ----
> [ 3.357611] lock((fb_notifier_list).rwsem);
> [ 3.357613] lock(console_lock);
> [ 3.357615] lock((fb_notifier_list).rwsem);
> [ 3.357616] lock(console_lock);
> [ 3.357617]
> [ 3.357617] *** DEADLOCK ***
> [ 3.357617]
> [ 3.357619] 5 locks held by udevd/137:
> [ 3.357624] #0: (&__lockdep_no_validate__){......}, at: [<ffffffff81429083>] __driver_attach+0x53/0xb0
> [ 3.357628] #1: (&__lockdep_no_validate__){......}, at: [<ffffffff81429091>] __driver_attach+0x61/0xb0
> [ 3.357633] #2: (registration_lock){+.+.+.}, at: [<ffffffff8138e45b>] remove_conflicting_framebuffers+0x2b/0x60
> [ 3.357637] #3: (&fb_info->lock){+.+.+.}, at: [<ffffffff8138d0c1>] lock_fb_info+0x21/0x60
> [ 3.357642] #4: ((fb_notifier_list).rwsem){.+.+.+}, at: [<ffffffff810799b1>] __blocking_notifier_call_chain+0x51/0xc0
> [ 3.357643]
> [ 3.357643] stack backtrace:
> [ 3.357645] Pid: 137, comm: udevd Not tainted 3.8.0-rc3-test+ #82
> [ 3.357646] Call Trace:
> [ 3.357652] [<ffffffff8163b136>] print_circular_bug+0x1fb/0x20c
> [ 3.357655] [<ffffffff810b5055>] __lock_acquire+0x1385/0x1cc0
> [ 3.357658] [<ffffffff810b605a>] lock_acquire+0xaa/0x210
> [ 3.357661] [<ffffffff8140385f>] ? unbind_con_driver+0x3f/0x200
> [ 3.357664] [<ffffffff810b2b0d>] ? trace_hardirqs_on+0xd/0x10
> [ 3.357667] [<ffffffff81048fbf>] console_lock+0x6f/0x80
> [ 3.357670] [<ffffffff8140385f>] ? unbind_con_driver+0x3f/0x200
> [ 3.357673] [<ffffffff8140385f>] unbind_con_driver+0x3f/0x200
> [ 3.357676] [<ffffffff8134c01e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> [ 3.357680] [<ffffffff8139aeb7>] fbcon_event_notify+0x447/0x8b0
> [ 3.357683] [<ffffffff8164a225>] notifier_call_chain+0x55/0x110
> [ 3.357685] [<ffffffff810799c7>] __blocking_notifier_call_chain+0x67/0xc0
> [ 3.357688] [<ffffffff81079a31>] blocking_notifier_call_chain+0x11/0x20
> [ 3.357690] [<ffffffff8138cbe6>] fb_notifier_call_chain+0x16/0x20
> [ 3.357693] [<ffffffff8138debb>] do_unregister_framebuffer+0x5b/0x110
> [ 3.357696] [<ffffffff8138e108>] do_remove_conflicting_framebuffers+0x158/0x190
> [ 3.357698] [<ffffffff8138e46a>] remove_conflicting_framebuffers+0x3a/0x60
> [ 3.357717] [<ffffffffa00df16b>] radeon_pci_probe+0x8b/0xd0 [radeon]
> [ 3.357721] [<ffffffff8136d5a6>] local_pci_probe+0x46/0x80
> [ 3.357724] [<ffffffff8136d7f1>] pci_device_probe+0x101/0x110
> [ 3.357727] [<ffffffff81428d26>] driver_probe_device+0x86/0x390
> [ 3.357729] [<ffffffff814290d3>] __driver_attach+0xa3/0xb0
> [ 3.357732] [<ffffffff81429030>] ? driver_probe_device+0x390/0x390
> [ 3.357734] [<ffffffff81426dbd>] bus_for_each_dev+0x4d/0x90
> [ 3.357737] [<ffffffff814286a9>] driver_attach+0x19/0x20
> [ 3.357740] [<ffffffff81428308>] bus_add_driver+0x1a8/0x290
> [ 3.357744] [<ffffffffa01c2000>] ? 0xffffffffa01c1fff
> [ 3.357747] [<ffffffff81429792>] driver_register+0x72/0x170
> [ 3.357749] [<ffffffffa01c2000>] ? 0xffffffffa01c1fff
> [ 3.357752] [<ffffffff8136c60f>] __pci_register_driver+0x5f/0x70
> [ 3.357762] [<ffffffffa006ec3a>] drm_pci_init+0x11a/0x130 [drm]
> [ 3.357764] [<ffffffffa01c2000>] ? 0xffffffffa01c1fff
> [ 3.357767] [<ffffffffa01c2000>] ? 0xffffffffa01c1fff
> [ 3.357784] [<ffffffffa01c20ec>] radeon_init+0xec/0x1000 [radeon]
> [ 3.357786] [<ffffffff810002e2>] do_one_initcall+0x122/0x180
> [ 3.357789] [<ffffffff810c4b53>] load_module+0x1043/0x1510
> [ 3.357792] [<ffffffff8135d260>] ? ddebug_proc_open+0xb0/0xb0
> [ 3.357796] [<ffffffff810c50f7>] sys_init_module+0xd7/0x120
> [ 3.357798] [<ffffffff8164e2ad>] system_call_fastpath+0x1a/0x1f
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