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* [lockdep] drm/i915: possible circular locking dependency in i915 driver init
@ 2016-08-14 14:01 Masami Hiramatsu
  2016-08-15  6:39 ` Daniel Vetter
  0 siblings, 1 reply; 3+ messages in thread
From: Masami Hiramatsu @ 2016-08-14 14:01 UTC (permalink / raw)
  To: Daniel Vetter, Jani Nikula, David Airlie
  Cc: linux-kernel, intel-gfx, dri-devel

Hello,

I've found a suspicious circular locking dependency in i915 by lockdep.
It seems main driver initialization thread and sub fbdev configuration
thread take locks in different order implicitly. Please check it.

The lockdep report is here.

[    4.254984] ======================================================
[    4.254984] [ INFO: possible circular locking dependency detected ]
[    4.254985] 4.8.0-rc1+ #8 Not tainted
[    4.254985] -------------------------------------------------------
[    4.254986] kworker/u16:1/72 is trying to acquire lock:
[    4.255001]  (&dev->mode_config.mutex){+.+.+.}, at: [<ffffffffc02eafb0>] drm_modeset_lock_all+0x40/0x130 [drm]
[    4.255001] 
               but task is already holding lock:
[    4.255005]  ((fb_notifier_list).rwsem){++++.+}, at: [<ffffffff980b2ea5>] __blocking_notifier_call_chain+0x35/0x70
[    4.255005] 
               which lock already depends on the new lock.

[    4.255005] 
               the existing dependency chain (in reverse order) is:
[    4.255006] 
               -> #1 ((fb_notifier_list).rwsem){++++.+}:
[    4.255009]        [<ffffffff980e7a00>] lock_acquire+0x100/0x1f0
[    4.255011]        [<ffffffff988b29a9>] down_write+0x49/0x80
[    4.255013]        [<ffffffff980b3031>] blocking_notifier_chain_register+0x21/0xb0
[    4.255015]        [<ffffffff984c93c8>] fb_register_client+0x18/0x20
[    4.255016]        [<ffffffff984c8c1e>] backlight_device_register+0x12e/0x250
[    4.255046]        [<ffffffffc04e3842>] intel_backlight_device_register+0xa2/0x160 [i915]
[    4.255070]        [<ffffffffc04b173e>] intel_connector_register+0xe/0x10 [i915]
[    4.255093]        [<ffffffffc04cd5db>] intel_dp_connector_register+0x1b/0x80 [i915]
[    4.255102]        [<ffffffffc02d943a>] drm_connector_register+0x4a/0x80 [drm]
[    4.255110]        [<ffffffffc02ddbe6>] drm_modeset_register_all+0x1c6/0x260 [drm]
[    4.255116]        [<ffffffffc02d4ba2>] drm_dev_register+0xc2/0xd0 [drm]
[    4.255135]        [<ffffffffc04212f1>] i915_driver_load+0x771/0x1460 [i915]
[    4.255153]        [<ffffffffc042c63f>] i915_pci_probe+0x4f/0x70 [i915]
[    4.255155]        [<ffffffff98497905>] local_pci_probe+0x45/0xa0
[    4.255157]        [<ffffffff98498d11>] pci_device_probe+0xe1/0x130
[    4.255159]        [<ffffffff985ae5e4>] driver_probe_device+0x224/0x430
[    4.255160]        [<ffffffff985ae8d3>] __driver_attach+0xe3/0xf0
[    4.255160]        [<ffffffff985ac166>] bus_for_each_dev+0x66/0xa0
[    4.255161]        [<ffffffff985adcee>] driver_attach+0x1e/0x20
[    4.255162]        [<ffffffff985ad7d0>] bus_add_driver+0x200/0x270
[    4.255164]        [<ffffffff985af520>] driver_register+0x60/0xe0
[    4.255165]        [<ffffffff98497230>] __pci_register_driver+0x60/0x70
[    4.255182]        [<ffffffffc035f05b>] i915_init+0x5b/0x62 [i915]
[    4.255183]        [<ffffffff9800217d>] do_one_initcall+0x3d/0x160
[    4.255186]        [<ffffffff981c6d8d>] do_init_module+0x5f/0x1f8
[    4.255187]        [<ffffffff9812fbdc>] load_module+0x246c/0x2bd0
[    4.255188]        [<ffffffff9813057c>] SYSC_finit_module+0xbc/0xf0
[    4.255190]        [<ffffffff981305ce>] SyS_finit_module+0xe/0x10
[    4.255191]        [<ffffffff988b5680>] entry_SYSCALL_64_fastpath+0x23/0xc1
[    4.255192] 
               -> #0 (&dev->mode_config.mutex){+.+.+.}:
[    4.255194]        [<ffffffff980e732c>] __lock_acquire+0x125c/0x14b0
[    4.255195]        [<ffffffff980e7a00>] lock_acquire+0x100/0x1f0
[    4.255197]        [<ffffffff988b0889>] mutex_lock_nested+0x69/0x3b0
[    4.255206]        [<ffffffffc02eafb0>] drm_modeset_lock_all+0x40/0x130 [drm]
[    4.255212]        [<ffffffffc03f877b>] drm_fb_helper_restore_fbdev_mode_unlocked+0x2b/0x80 [drm_kms_helper]
[    4.255217]        [<ffffffffc03f87fd>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
[    4.255240]        [<ffffffffc04c21da>] intel_fbdev_set_par+0x1a/0x60 [i915]
[    4.255242]        [<ffffffff984c2f2f>] fbcon_init+0x57f/0x600
[    4.255244]        [<ffffffff98555026>] visual_init+0xd6/0x130
[    4.255245]        [<ffffffff98556831>] do_bind_con_driver+0x1c1/0x3a0
[    4.255246]        [<ffffffff98556d16>] do_take_over_console+0x116/0x180
[    4.255247]        [<ffffffff984beb67>] do_fbcon_takeover+0x57/0xb0
[    4.255249]        [<ffffffff984c39a8>] fbcon_event_notify+0x658/0x750
[    4.255250]        [<ffffffff980b2c1a>] notifier_call_chain+0x4a/0x70
[    4.255251]        [<ffffffff980b2ebd>] __blocking_notifier_call_chain+0x4d/0x70
[    4.255253]        [<ffffffff980b2ef6>] blocking_notifier_call_chain+0x16/0x20
[    4.255254]        [<ffffffff984c940b>] fb_notifier_call_chain+0x1b/0x20
[    4.255255]        [<ffffffff984cb6c1>] register_framebuffer+0x251/0x330
[    4.255259]        [<ffffffffc03f8a7f>] drm_fb_helper_initial_config+0x25f/0x3f0 [drm_kms_helper]
[    4.255282]        [<ffffffffc04c3498>] intel_fbdev_initial_config+0x18/0x30 [i915]
[    4.255283]        [<ffffffff980b4aa7>] async_run_entry_fn+0x37/0x150
[    4.255284]        [<ffffffff980aa9c8>] process_one_work+0x1e8/0x710
[    4.255285]        [<ffffffff980aaf3b>] worker_thread+0x4b/0x4f0
[    4.255286]        [<ffffffff980b193f>] kthread+0xef/0x110
[    4.255287]        [<ffffffff988b58cf>] ret_from_fork+0x1f/0x40
[    4.255287] 
               other info that might help us debug this:

[    4.255288]  Possible unsafe locking scenario:

[    4.255288]        CPU0                    CPU1
[    4.255288]        ----                    ----
[    4.255289]   lock((fb_notifier_list).rwsem);
[    4.255290]                                lock(&dev->mode_config.mutex);
[    4.255290]                                lock((fb_notifier_list).rwsem);
[    4.255291]   lock(&dev->mode_config.mutex);
[    4.255291] 
                *** DEADLOCK ***

And i915 related kconfigs are here:
----
CONFIG_DRM_I915=m
CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT=y
CONFIG_DRM_I915_USERPTR=y
CONFIG_DRM_I915_GVT=y
# CONFIG_DRM_I915_WERROR is not set
# CONFIG_DRM_I915_DEBUG is not set
----

I've hit this on my DELL XPS15 which has skylake CPU/GPU.

Thanks,


-- 
Masami Hiramatsu <mhiramat@kernel.org>

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [lockdep] drm/i915: possible circular locking dependency in i915 driver init
  2016-08-14 14:01 [lockdep] drm/i915: possible circular locking dependency in i915 driver init Masami Hiramatsu
@ 2016-08-15  6:39 ` Daniel Vetter
  2016-08-15 10:16   ` Masami Hiramatsu
  0 siblings, 1 reply; 3+ messages in thread
From: Daniel Vetter @ 2016-08-15  6:39 UTC (permalink / raw)
  To: Masami Hiramatsu
  Cc: Daniel Vetter, Jani Nikula, David Airlie, intel-gfx,
	linux-kernel, dri-devel

On Sun, Aug 14, 2016 at 11:01:35PM +0900, Masami Hiramatsu wrote:
> Hello,
> 
> I've found a suspicious circular locking dependency in i915 by lockdep.
> It seems main driver initialization thread and sub fbdev configuration
> thread take locks in different order implicitly. Please check it.
> 
> The lockdep report is here.

Should be fixed in 4.8-rc2, please confirm.
-Daniel

> 
> [    4.254984] ======================================================
> [    4.254984] [ INFO: possible circular locking dependency detected ]
> [    4.254985] 4.8.0-rc1+ #8 Not tainted
> [    4.254985] -------------------------------------------------------
> [    4.254986] kworker/u16:1/72 is trying to acquire lock:
> [    4.255001]  (&dev->mode_config.mutex){+.+.+.}, at: [<ffffffffc02eafb0>] drm_modeset_lock_all+0x40/0x130 [drm]
> [    4.255001] 
>                but task is already holding lock:
> [    4.255005]  ((fb_notifier_list).rwsem){++++.+}, at: [<ffffffff980b2ea5>] __blocking_notifier_call_chain+0x35/0x70
> [    4.255005] 
>                which lock already depends on the new lock.
> 
> [    4.255005] 
>                the existing dependency chain (in reverse order) is:
> [    4.255006] 
>                -> #1 ((fb_notifier_list).rwsem){++++.+}:
> [    4.255009]        [<ffffffff980e7a00>] lock_acquire+0x100/0x1f0
> [    4.255011]        [<ffffffff988b29a9>] down_write+0x49/0x80
> [    4.255013]        [<ffffffff980b3031>] blocking_notifier_chain_register+0x21/0xb0
> [    4.255015]        [<ffffffff984c93c8>] fb_register_client+0x18/0x20
> [    4.255016]        [<ffffffff984c8c1e>] backlight_device_register+0x12e/0x250
> [    4.255046]        [<ffffffffc04e3842>] intel_backlight_device_register+0xa2/0x160 [i915]
> [    4.255070]        [<ffffffffc04b173e>] intel_connector_register+0xe/0x10 [i915]
> [    4.255093]        [<ffffffffc04cd5db>] intel_dp_connector_register+0x1b/0x80 [i915]
> [    4.255102]        [<ffffffffc02d943a>] drm_connector_register+0x4a/0x80 [drm]
> [    4.255110]        [<ffffffffc02ddbe6>] drm_modeset_register_all+0x1c6/0x260 [drm]
> [    4.255116]        [<ffffffffc02d4ba2>] drm_dev_register+0xc2/0xd0 [drm]
> [    4.255135]        [<ffffffffc04212f1>] i915_driver_load+0x771/0x1460 [i915]
> [    4.255153]        [<ffffffffc042c63f>] i915_pci_probe+0x4f/0x70 [i915]
> [    4.255155]        [<ffffffff98497905>] local_pci_probe+0x45/0xa0
> [    4.255157]        [<ffffffff98498d11>] pci_device_probe+0xe1/0x130
> [    4.255159]        [<ffffffff985ae5e4>] driver_probe_device+0x224/0x430
> [    4.255160]        [<ffffffff985ae8d3>] __driver_attach+0xe3/0xf0
> [    4.255160]        [<ffffffff985ac166>] bus_for_each_dev+0x66/0xa0
> [    4.255161]        [<ffffffff985adcee>] driver_attach+0x1e/0x20
> [    4.255162]        [<ffffffff985ad7d0>] bus_add_driver+0x200/0x270
> [    4.255164]        [<ffffffff985af520>] driver_register+0x60/0xe0
> [    4.255165]        [<ffffffff98497230>] __pci_register_driver+0x60/0x70
> [    4.255182]        [<ffffffffc035f05b>] i915_init+0x5b/0x62 [i915]
> [    4.255183]        [<ffffffff9800217d>] do_one_initcall+0x3d/0x160
> [    4.255186]        [<ffffffff981c6d8d>] do_init_module+0x5f/0x1f8
> [    4.255187]        [<ffffffff9812fbdc>] load_module+0x246c/0x2bd0
> [    4.255188]        [<ffffffff9813057c>] SYSC_finit_module+0xbc/0xf0
> [    4.255190]        [<ffffffff981305ce>] SyS_finit_module+0xe/0x10
> [    4.255191]        [<ffffffff988b5680>] entry_SYSCALL_64_fastpath+0x23/0xc1
> [    4.255192] 
>                -> #0 (&dev->mode_config.mutex){+.+.+.}:
> [    4.255194]        [<ffffffff980e732c>] __lock_acquire+0x125c/0x14b0
> [    4.255195]        [<ffffffff980e7a00>] lock_acquire+0x100/0x1f0
> [    4.255197]        [<ffffffff988b0889>] mutex_lock_nested+0x69/0x3b0
> [    4.255206]        [<ffffffffc02eafb0>] drm_modeset_lock_all+0x40/0x130 [drm]
> [    4.255212]        [<ffffffffc03f877b>] drm_fb_helper_restore_fbdev_mode_unlocked+0x2b/0x80 [drm_kms_helper]
> [    4.255217]        [<ffffffffc03f87fd>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
> [    4.255240]        [<ffffffffc04c21da>] intel_fbdev_set_par+0x1a/0x60 [i915]
> [    4.255242]        [<ffffffff984c2f2f>] fbcon_init+0x57f/0x600
> [    4.255244]        [<ffffffff98555026>] visual_init+0xd6/0x130
> [    4.255245]        [<ffffffff98556831>] do_bind_con_driver+0x1c1/0x3a0
> [    4.255246]        [<ffffffff98556d16>] do_take_over_console+0x116/0x180
> [    4.255247]        [<ffffffff984beb67>] do_fbcon_takeover+0x57/0xb0
> [    4.255249]        [<ffffffff984c39a8>] fbcon_event_notify+0x658/0x750
> [    4.255250]        [<ffffffff980b2c1a>] notifier_call_chain+0x4a/0x70
> [    4.255251]        [<ffffffff980b2ebd>] __blocking_notifier_call_chain+0x4d/0x70
> [    4.255253]        [<ffffffff980b2ef6>] blocking_notifier_call_chain+0x16/0x20
> [    4.255254]        [<ffffffff984c940b>] fb_notifier_call_chain+0x1b/0x20
> [    4.255255]        [<ffffffff984cb6c1>] register_framebuffer+0x251/0x330
> [    4.255259]        [<ffffffffc03f8a7f>] drm_fb_helper_initial_config+0x25f/0x3f0 [drm_kms_helper]
> [    4.255282]        [<ffffffffc04c3498>] intel_fbdev_initial_config+0x18/0x30 [i915]
> [    4.255283]        [<ffffffff980b4aa7>] async_run_entry_fn+0x37/0x150
> [    4.255284]        [<ffffffff980aa9c8>] process_one_work+0x1e8/0x710
> [    4.255285]        [<ffffffff980aaf3b>] worker_thread+0x4b/0x4f0
> [    4.255286]        [<ffffffff980b193f>] kthread+0xef/0x110
> [    4.255287]        [<ffffffff988b58cf>] ret_from_fork+0x1f/0x40
> [    4.255287] 
>                other info that might help us debug this:
> 
> [    4.255288]  Possible unsafe locking scenario:
> 
> [    4.255288]        CPU0                    CPU1
> [    4.255288]        ----                    ----
> [    4.255289]   lock((fb_notifier_list).rwsem);
> [    4.255290]                                lock(&dev->mode_config.mutex);
> [    4.255290]                                lock((fb_notifier_list).rwsem);
> [    4.255291]   lock(&dev->mode_config.mutex);
> [    4.255291] 
>                 *** DEADLOCK ***
> 
> And i915 related kconfigs are here:
> ----
> CONFIG_DRM_I915=m
> CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT=y
> CONFIG_DRM_I915_USERPTR=y
> CONFIG_DRM_I915_GVT=y
> # CONFIG_DRM_I915_WERROR is not set
> # CONFIG_DRM_I915_DEBUG is not set
> ----
> 
> I've hit this on my DELL XPS15 which has skylake CPU/GPU.
> 
> Thanks,
> 
> 
> -- 
> Masami Hiramatsu <mhiramat@kernel.org>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [lockdep] drm/i915: possible circular locking dependency in i915 driver init
  2016-08-15  6:39 ` Daniel Vetter
@ 2016-08-15 10:16   ` Masami Hiramatsu
  0 siblings, 0 replies; 3+ messages in thread
From: Masami Hiramatsu @ 2016-08-15 10:16 UTC (permalink / raw)
  To: Daniel Vetter
  Cc: Daniel Vetter, Jani Nikula, David Airlie, intel-gfx,
	linux-kernel, dri-devel

On Mon, 15 Aug 2016 08:39:29 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Sun, Aug 14, 2016 at 11:01:35PM +0900, Masami Hiramatsu wrote:
> > Hello,
> > 
> > I've found a suspicious circular locking dependency in i915 by lockdep.
> > It seems main driver initialization thread and sub fbdev configuration
> > thread take locks in different order implicitly. Please check it.
> > 
> > The lockdep report is here.
> 
> Should be fixed in 4.8-rc2, please confirm.

Thanks! I've confirmed this has fixed on 4.8-rc2.

Regards,

> -Daniel
> 
> > 
> > [    4.254984] ======================================================
> > [    4.254984] [ INFO: possible circular locking dependency detected ]
> > [    4.254985] 4.8.0-rc1+ #8 Not tainted
> > [    4.254985] -------------------------------------------------------
> > [    4.254986] kworker/u16:1/72 is trying to acquire lock:
> > [    4.255001]  (&dev->mode_config.mutex){+.+.+.}, at: [<ffffffffc02eafb0>] drm_modeset_lock_all+0x40/0x130 [drm]
> > [    4.255001] 
> >                but task is already holding lock:
> > [    4.255005]  ((fb_notifier_list).rwsem){++++.+}, at: [<ffffffff980b2ea5>] __blocking_notifier_call_chain+0x35/0x70
> > [    4.255005] 
> >                which lock already depends on the new lock.
> > 
> > [    4.255005] 
> >                the existing dependency chain (in reverse order) is:
> > [    4.255006] 
> >                -> #1 ((fb_notifier_list).rwsem){++++.+}:
> > [    4.255009]        [<ffffffff980e7a00>] lock_acquire+0x100/0x1f0
> > [    4.255011]        [<ffffffff988b29a9>] down_write+0x49/0x80
> > [    4.255013]        [<ffffffff980b3031>] blocking_notifier_chain_register+0x21/0xb0
> > [    4.255015]        [<ffffffff984c93c8>] fb_register_client+0x18/0x20
> > [    4.255016]        [<ffffffff984c8c1e>] backlight_device_register+0x12e/0x250
> > [    4.255046]        [<ffffffffc04e3842>] intel_backlight_device_register+0xa2/0x160 [i915]
> > [    4.255070]        [<ffffffffc04b173e>] intel_connector_register+0xe/0x10 [i915]
> > [    4.255093]        [<ffffffffc04cd5db>] intel_dp_connector_register+0x1b/0x80 [i915]
> > [    4.255102]        [<ffffffffc02d943a>] drm_connector_register+0x4a/0x80 [drm]
> > [    4.255110]        [<ffffffffc02ddbe6>] drm_modeset_register_all+0x1c6/0x260 [drm]
> > [    4.255116]        [<ffffffffc02d4ba2>] drm_dev_register+0xc2/0xd0 [drm]
> > [    4.255135]        [<ffffffffc04212f1>] i915_driver_load+0x771/0x1460 [i915]
> > [    4.255153]        [<ffffffffc042c63f>] i915_pci_probe+0x4f/0x70 [i915]
> > [    4.255155]        [<ffffffff98497905>] local_pci_probe+0x45/0xa0
> > [    4.255157]        [<ffffffff98498d11>] pci_device_probe+0xe1/0x130
> > [    4.255159]        [<ffffffff985ae5e4>] driver_probe_device+0x224/0x430
> > [    4.255160]        [<ffffffff985ae8d3>] __driver_attach+0xe3/0xf0
> > [    4.255160]        [<ffffffff985ac166>] bus_for_each_dev+0x66/0xa0
> > [    4.255161]        [<ffffffff985adcee>] driver_attach+0x1e/0x20
> > [    4.255162]        [<ffffffff985ad7d0>] bus_add_driver+0x200/0x270
> > [    4.255164]        [<ffffffff985af520>] driver_register+0x60/0xe0
> > [    4.255165]        [<ffffffff98497230>] __pci_register_driver+0x60/0x70
> > [    4.255182]        [<ffffffffc035f05b>] i915_init+0x5b/0x62 [i915]
> > [    4.255183]        [<ffffffff9800217d>] do_one_initcall+0x3d/0x160
> > [    4.255186]        [<ffffffff981c6d8d>] do_init_module+0x5f/0x1f8
> > [    4.255187]        [<ffffffff9812fbdc>] load_module+0x246c/0x2bd0
> > [    4.255188]        [<ffffffff9813057c>] SYSC_finit_module+0xbc/0xf0
> > [    4.255190]        [<ffffffff981305ce>] SyS_finit_module+0xe/0x10
> > [    4.255191]        [<ffffffff988b5680>] entry_SYSCALL_64_fastpath+0x23/0xc1
> > [    4.255192] 
> >                -> #0 (&dev->mode_config.mutex){+.+.+.}:
> > [    4.255194]        [<ffffffff980e732c>] __lock_acquire+0x125c/0x14b0
> > [    4.255195]        [<ffffffff980e7a00>] lock_acquire+0x100/0x1f0
> > [    4.255197]        [<ffffffff988b0889>] mutex_lock_nested+0x69/0x3b0
> > [    4.255206]        [<ffffffffc02eafb0>] drm_modeset_lock_all+0x40/0x130 [drm]
> > [    4.255212]        [<ffffffffc03f877b>] drm_fb_helper_restore_fbdev_mode_unlocked+0x2b/0x80 [drm_kms_helper]
> > [    4.255217]        [<ffffffffc03f87fd>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
> > [    4.255240]        [<ffffffffc04c21da>] intel_fbdev_set_par+0x1a/0x60 [i915]
> > [    4.255242]        [<ffffffff984c2f2f>] fbcon_init+0x57f/0x600
> > [    4.255244]        [<ffffffff98555026>] visual_init+0xd6/0x130
> > [    4.255245]        [<ffffffff98556831>] do_bind_con_driver+0x1c1/0x3a0
> > [    4.255246]        [<ffffffff98556d16>] do_take_over_console+0x116/0x180
> > [    4.255247]        [<ffffffff984beb67>] do_fbcon_takeover+0x57/0xb0
> > [    4.255249]        [<ffffffff984c39a8>] fbcon_event_notify+0x658/0x750
> > [    4.255250]        [<ffffffff980b2c1a>] notifier_call_chain+0x4a/0x70
> > [    4.255251]        [<ffffffff980b2ebd>] __blocking_notifier_call_chain+0x4d/0x70
> > [    4.255253]        [<ffffffff980b2ef6>] blocking_notifier_call_chain+0x16/0x20
> > [    4.255254]        [<ffffffff984c940b>] fb_notifier_call_chain+0x1b/0x20
> > [    4.255255]        [<ffffffff984cb6c1>] register_framebuffer+0x251/0x330
> > [    4.255259]        [<ffffffffc03f8a7f>] drm_fb_helper_initial_config+0x25f/0x3f0 [drm_kms_helper]
> > [    4.255282]        [<ffffffffc04c3498>] intel_fbdev_initial_config+0x18/0x30 [i915]
> > [    4.255283]        [<ffffffff980b4aa7>] async_run_entry_fn+0x37/0x150
> > [    4.255284]        [<ffffffff980aa9c8>] process_one_work+0x1e8/0x710
> > [    4.255285]        [<ffffffff980aaf3b>] worker_thread+0x4b/0x4f0
> > [    4.255286]        [<ffffffff980b193f>] kthread+0xef/0x110
> > [    4.255287]        [<ffffffff988b58cf>] ret_from_fork+0x1f/0x40
> > [    4.255287] 
> >                other info that might help us debug this:
> > 
> > [    4.255288]  Possible unsafe locking scenario:
> > 
> > [    4.255288]        CPU0                    CPU1
> > [    4.255288]        ----                    ----
> > [    4.255289]   lock((fb_notifier_list).rwsem);
> > [    4.255290]                                lock(&dev->mode_config.mutex);
> > [    4.255290]                                lock((fb_notifier_list).rwsem);
> > [    4.255291]   lock(&dev->mode_config.mutex);
> > [    4.255291] 
> >                 *** DEADLOCK ***
> > 
> > And i915 related kconfigs are here:
> > ----
> > CONFIG_DRM_I915=m
> > CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT=y
> > CONFIG_DRM_I915_USERPTR=y
> > CONFIG_DRM_I915_GVT=y
> > # CONFIG_DRM_I915_WERROR is not set
> > # CONFIG_DRM_I915_DEBUG is not set
> > ----
> > 
> > I've hit this on my DELL XPS15 which has skylake CPU/GPU.
> > 
> > Thanks,
> > 
> > 
> > -- 
> > Masami Hiramatsu <mhiramat@kernel.org>
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch


-- 
Masami Hiramatsu <mhiramat@kernel.org>

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2016-08-15 10:16 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-08-14 14:01 [lockdep] drm/i915: possible circular locking dependency in i915 driver init Masami Hiramatsu
2016-08-15  6:39 ` Daniel Vetter
2016-08-15 10:16   ` Masami Hiramatsu

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