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| Started by | Masami Hiramatsu <mhiramat@kernel.org> |
|---|---|
| First post | 2016-08-14 16:10 +0200 |
| Last post | 2016-08-15 12:20 +0200 |
| Articles | 3 — 2 participants |
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[lockdep] drm/i915: possible circular locking dependency in i915 driver init Masami Hiramatsu <mhiramat@kernel.org> - 2016-08-14 16:10 +0200
Re: [lockdep] drm/i915: possible circular locking dependency in i915 driver init Daniel Vetter <daniel@ffwll.ch> - 2016-08-15 08:40 +0200
Re: [lockdep] drm/i915: possible circular locking dependency in i915 driver init Masami Hiramatsu <mhiramat@kernel.org> - 2016-08-15 12:20 +0200
| From | Masami Hiramatsu <mhiramat@kernel.org> |
|---|---|
| Date | 2016-08-14 16:10 +0200 |
| Subject | [lockdep] drm/i915: possible circular locking dependency in i915 driver init |
| Message-ID | <s64gV-FC-7@gated-at.bofh.it> |
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>
[toc] | [next] | [standalone]
| From | Daniel Vetter <daniel@ffwll.ch> |
|---|---|
| Date | 2016-08-15 08:40 +0200 |
| Message-ID | <s6jJ0-22l-11@gated-at.bofh.it> |
| In reply to | #1462130 |
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
[toc] | [prev] | [next] | [standalone]
| From | Masami Hiramatsu <mhiramat@kernel.org> |
|---|---|
| Date | 2016-08-15 12:20 +0200 |
| Subject | Re: [lockdep] drm/i915: possible circular locking dependency in i915 driver init |
| Message-ID | <s6n9T-4ig-3@gated-at.bofh.it> |
| In reply to | #1462567 |
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>
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