On to, 2016-06-30 at 12:30 +0100, Chris Wilson wrote: > Backlights controlled by i915.ko and only associated with its > connectors > and also only associated with the intel_drmfb fbcon, controlled by > i915.ko. In this situation, we already handle adjusting the backlight > when the fbcon is blanked/unblanked and do not require backlight > trying > to do the same. > > Attempting to register with the fbdev as a client causes lockdep to > warn > about a dependency cycle: > > [Â Â Â 18.983763] ====================================================== > [Â Â Â 18.983763] [ INFO: possible circular locking dependency detected > ] > [Â Â Â 18.983766] 4.7.0-rc5+ #524 Tainted: GÂ Â Â Â Â Â Â Â Â Â Â O > [Â Â Â 18.983767] ------------------------------------------------------ > - > [Â Â Â 18.983767] kworker/u8:0/6 is trying to acquire lock: > [Â Â Â 18.983777]Â Â (&dev->mode_config.mutex){+.+.+.}, at: > [<ffffffff815afde0>] drm_modeset_lock_all+0x40/0x120 > [Â Â Â 18.983777] > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â but task is already holding lock: > [Â Â Â 18.983782]Â Â ((fb_notifier_list).rwsem){++++.+}, at: > [<ffffffff810ac195>] __blocking_notifier_call_chain+0x35/0x70 > [Â Â Â 18.983783] > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â which lock already depends on the new lock. > > [Â Â Â 18.983783] > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â the existing dependency chain (in reverse > order) is: > [Â Â Â 18.983785] > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â -> #1 ((fb_notifier_list).rwsem){++++.+}: > [Â Â Â 18.983789]Â Â Â Â Â Â Â Â [<ffffffff810df611>] lock_acquire+0xb1/0x200 > [Â Â Â 18.983792]Â Â Â Â Â Â Â Â [<ffffffff819a55b4>] down_write+0x44/0x80 > [Â Â Â 18.983795]Â Â Â Â Â Â Â Â [<ffffffff810abf91>] > blocking_notifier_chain_register+0x21/0xb0 > [Â Â Â 18.983798]Â Â Â Â Â Â Â Â [<ffffffff814c7448>] > fb_register_client+0x18/0x20 > [Â Â Â 18.983800]Â Â Â Â Â Â Â Â [<ffffffff814c6c86>] > backlight_device_register+0x136/0x260 > [Â Â Â 18.983852]Â Â Â Â Â Â Â Â [<ffffffffa0127eb2>] > intel_backlight_device_register+0xa2/0x160 [i915] > [Â Â Â 18.983892]Â Â Â Â Â Â Â Â [<ffffffffa00f46be>] > intel_connector_register+0xe/0x10 [i915] > [Â Â Â 18.983932]Â Â Â Â Â Â Â Â [<ffffffffa0112bfb>] > intel_dp_connector_register+0x1b/0x80 [i915] > [Â Â Â 18.983936]Â Â Â Â Â Â Â Â [<ffffffff8159dfea>] > drm_connector_register+0x4a/0x80 > [Â Â Â 18.983938]Â Â Â Â Â Â Â Â [<ffffffff8159fe44>] > drm_connector_register_all+0x64/0xf0 > [Â Â Â 18.983940]Â Â Â Â Â Â Â Â [<ffffffff815a2a64>] > drm_modeset_register_all+0x174/0x1c0 > [Â Â Â 18.983942]Â Â Â Â Â Â Â Â [<ffffffff81599b72>] > drm_dev_register+0xc2/0xd0 > [Â Â Â 18.983976]Â Â Â Â Â Â Â Â [<ffffffffa00621d7>] > i915_driver_load+0x1547/0x2200 [i915] > [Â Â Â 18.984010]Â Â Â Â Â Â Â Â [<ffffffffa006d80f>] i915_pci_probe+0x4f/0x70 > [i915] > [Â Â Â 18.984014]Â Â Â Â Â Â Â Â [<ffffffff814a2135>] > local_pci_probe+0x45/0xa0 > [Â Â Â 18.984015]Â Â Â Â Â Â Â Â [<ffffffff814a349b>] > pci_device_probe+0xdb/0x130 > [Â Â Â 18.984018]Â Â Â Â Â Â Â Â [<ffffffff815c07e3>] > driver_probe_device+0x223/0x440 > [Â Â Â 18.984020]Â Â Â Â Â Â Â Â [<ffffffff815c0ad5>] > __driver_attach+0xd5/0x100 > [Â Â Â 18.984022]Â Â Â Â Â Â Â Â [<ffffffff815be386>] > bus_for_each_dev+0x66/0xa0 > [Â Â Â 18.984023]Â Â Â Â Â Â Â Â [<ffffffff815c002e>] driver_attach+0x1e/0x20 > [Â Â Â 18.984025]Â Â Â Â Â Â Â Â [<ffffffff815bf9be>] > bus_add_driver+0x1ee/0x280 > [Â Â Â 18.984028]Â Â Â Â Â Â Â Â [<ffffffff815c1810>] > driver_register+0x60/0xe0 > [Â Â Â 18.984030]Â Â Â Â Â Â Â Â [<ffffffff814a1a10>] > __pci_register_driver+0x60/0x70 > [Â Â Â 18.984063]Â Â Â Â Â Â Â Â [<ffffffffa01a905b>] i915_init+0x5b/0x62 > [i915] > [Â Â Â 18.984067]Â Â Â Â Â Â Â Â [<ffffffff8100042d>] > do_one_initcall+0x3d/0x150 > [Â Â Â 18.984070]Â Â Â Â Â Â Â Â [<ffffffff811a935b>] > do_init_module+0x5f/0x1d9 > [Â Â Â 18.984073]Â Â Â Â Â Â Â Â [<ffffffff81124416>] > load_module+0x20e6/0x27e0 > [Â Â Â 18.984075]Â Â Â Â Â Â Â Â [<ffffffff81124d63>] > SYSC_finit_module+0xc3/0xf0 > [Â Â Â 18.984076]Â Â Â Â Â Â Â Â [<ffffffff81124dae>] > SyS_finit_module+0xe/0x10 > [Â Â Â 18.984079]Â Â Â Â Â Â Â Â [<ffffffff819a83a9>] > entry_SYSCALL_64_fastpath+0x1c/0xac > [Â Â Â 18.984081] > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â -> #0 (&dev->mode_config.mutex){+.+.+.}: > [Â Â Â 18.984083]Â Â Â Â Â Â Â Â [<ffffffff810df0ac>] > __lock_acquire+0x10fc/0x1260 > [Â Â Â 18.984085]Â Â Â Â Â Â Â Â [<ffffffff810df611>] lock_acquire+0xb1/0x200 > [Â Â Â 18.984088]Â Â Â Â Â Â Â Â [<ffffffff819a3097>] > mutex_lock_nested+0x67/0x3c0 > [Â Â Â 18.984090]Â Â Â Â Â Â Â Â [<ffffffff815afde0>] > drm_modeset_lock_all+0x40/0x120 > [Â Â Â 18.984093]Â Â Â Â Â Â Â Â [<ffffffff8158f79b>] > drm_fb_helper_restore_fbdev_mode_unlocked+0x2b/0x80 > [Â Â Â 18.984095]Â Â Â Â Â Â Â Â [<ffffffff8158f81d>] > drm_fb_helper_set_par+0x2d/0x50 > [Â Â Â 18.984134]Â Â Â Â Â Â Â Â [<ffffffffa0105f7a>] > intel_fbdev_set_par+0x1a/0x60 [i915] > [Â Â Â 18.984136]Â Â Â Â Â Â Â Â [<ffffffff814c13c6>] fbcon_init+0x586/0x610 > [Â Â Â 18.984139]Â Â Â Â Â Â Â Â [<ffffffff8154d16a>] visual_init+0xca/0x130 > [Â Â Â 18.984141]Â Â Â Â Â Â Â Â [<ffffffff8154e611>] > do_bind_con_driver+0x1c1/0x3a0 > [Â Â Â 18.984143]Â Â Â Â Â Â Â Â [<ffffffff8154eaf6>] > do_take_over_console+0x116/0x180 > [Â Â Â 18.984145]Â Â Â Â Â Â Â Â [<ffffffff814bd3a7>] > do_fbcon_takeover+0x57/0xb0 > [Â Â Â 18.984147]Â Â Â Â Â Â Â Â [<ffffffff814c1e48>] > fbcon_event_notify+0x658/0x750 > [Â Â Â 18.984150]Â Â Â Â Â Â Â Â [<ffffffff810abcae>] > notifier_call_chain+0x3e/0xb0 > [Â Â Â 18.984152]Â Â Â Â Â Â Â Â [<ffffffff810ac1ad>] > __blocking_notifier_call_chain+0x4d/0x70 > [Â Â Â 18.984154]Â Â Â Â Â Â Â Â [<ffffffff810ac1e6>] > blocking_notifier_call_chain+0x16/0x20 > [Â Â Â 18.984156]Â Â Â Â Â Â Â Â [<ffffffff814c748b>] > fb_notifier_call_chain+0x1b/0x20 > [Â Â Â 18.984158]Â Â Â Â Â Â Â Â [<ffffffff814c86b1>] > register_framebuffer+0x251/0x330 > [Â Â Â 18.984160]Â Â Â Â Â Â Â Â [<ffffffff8158fa9f>] > drm_fb_helper_initial_config+0x25f/0x3f0 > [Â Â Â 18.984199]Â Â Â Â Â Â Â Â [<ffffffffa0106b48>] > intel_fbdev_initial_config+0x18/0x30 [i915] > [Â Â Â 18.984201]Â Â Â Â Â Â Â Â [<ffffffff810adfd8>] > async_run_entry_fn+0x48/0x150 > [Â Â Â 18.984203]Â Â Â Â Â Â Â Â [<ffffffff810a3947>] > process_one_work+0x1e7/0x750 > [Â Â Â 18.984205]Â Â Â Â Â Â Â Â [<ffffffff810a3efb>] worker_thread+0x4b/0x4f0 > [Â Â Â 18.984207]Â Â Â Â Â Â Â Â [<ffffffff810aad4f>] kthread+0xef/0x110 > [Â Â Â 18.984208]Â Â Â Â Â Â Â Â [<ffffffff819a85ef>] ret_from_fork+0x1f/0x40 > [Â Â Â 18.984209] > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â other info that might help us debug this: > > [Â Â Â 18.984210]Â Â Possible unsafe locking scenario: > > [Â Â Â 18.984210]Â Â Â Â Â Â Â Â CPU0Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â > CPU1 > [Â Â Â 18.984211]Â Â Â Â Â Â Â Â ----Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â > ---- > [Â Â Â 18.984212]Â Â Â lock((fb_notifier_list).rwsem); > [Â Â Â 18.984213]Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â > Â Â lock(&dev- > >mode_config.mutex); > [Â Â Â 18.984215]Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â > Â Â lock((fb_notifier_list) > .rwsem); > [Â Â Â 18.984216]Â Â Â lock(&dev->mode_config.mutex); > [Â Â Â 18.984216] > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â *** DEADLOCK *** > > [Â Â Â 18.984217] 6 locks held by kworker/u8:0/6: > [Â Â Â 18.984220]Â Â #0:Â Â ("events_unbound"){.+.+.+}, at: > [<ffffffff810a38c9>] process_one_work+0x169/0x750 > [Â Â Â 18.984223]Â Â #1:Â Â ((&entry->work)){+.+.+.}, at: > [<ffffffff810a38c9>] process_one_work+0x169/0x750 > [Â Â Â 18.984227]Â Â #2:Â Â (registration_lock){+.+.+.}, at: > [<ffffffff814c8487>] register_framebuffer+0x27/0x330 > [Â Â Â 18.984231]Â Â #3:Â Â (console_lock){+.+.+.}, at: [<ffffffff814c86ce>] > register_framebuffer+0x26e/0x330 > [Â Â Â 18.984234]Â Â #4:Â Â (&fb_info->lock){+.+.+.}, at: > [<ffffffff814c78dd>] lock_fb_info+0x1d/0x40 > [Â Â Â 18.984238]Â Â #5:Â Â ((fb_notifier_list).rwsem){++++.+}, at: > [<ffffffff810ac195>] __blocking_notifier_call_chain+0x35/0x70 > [Â Â Â 18.984238] > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â stack backtrace: > [Â Â Â 18.984241] CPU: 2 PID: 6 Comm: kworker/u8:0 Tainted: > GÂ Â Â Â Â Â Â Â Â Â Â OÂ Â Â Â 4.7.0-rc5+ #524 > [Â Â Â 18.984242] Hardware name: Intel Corp. Broxton P/NOTEBOOK, BIOS > APLKRVPA.X64.0138.B33.1606250842 06/25/2016 > [Â Â Â 18.984244] Workqueue: events_unbound async_run_entry_fn > [Â Â Â 18.984248]Â Â 0000000000000000 ffff8800758577f0 ffffffff814507a5 > ffffffff828b9900 > [Â Â Â 18.984250]Â Â ffffffff828b9900 ffff880075857830 ffffffff810dc6fa > ffff880075857880 > [Â Â Â 18.984252]Â Â ffff88007584d688 0000000000000005 0000000000000006 > ffff88007584d6b0 > [Â Â Â 18.984253] Call Trace: > [Â Â Â 18.984257]Â Â [<ffffffff814507a5>] dump_stack+0x67/0x92 > [Â Â Â 18.984259]Â Â [<ffffffff810dc6fa>] print_circular_bug+0x1aa/0x200 > [Â Â Â 18.984261]Â Â [<ffffffff810df0ac>] __lock_acquire+0x10fc/0x1260 > [Â Â Â 18.984264]Â Â [<ffffffff810df611>] lock_acquire+0xb1/0x200 > [Â Â Â 18.984266]Â Â [<ffffffff815afde0>] ? > drm_modeset_lock_all+0x40/0x120 > [Â Â Â 18.984267]Â Â [<ffffffff815afde0>] ? > drm_modeset_lock_all+0x40/0x120 > [Â Â Â 18.984269]Â Â [<ffffffff819a3097>] mutex_lock_nested+0x67/0x3c0 > [Â Â Â 18.984271]Â Â [<ffffffff815afde0>] ? > drm_modeset_lock_all+0x40/0x120 > [Â Â Â 18.984273]Â Â [<ffffffff810fa85f>] ? > rcu_read_lock_sched_held+0x7f/0x90 > [Â Â Â 18.984276]Â Â [<ffffffff81208218>] ? > kmem_cache_alloc_trace+0x248/0x2b0 > [Â Â Â 18.984277]Â Â [<ffffffff815afdc5>] ? > drm_modeset_lock_all+0x25/0x120 > [Â Â Â 18.984279]Â Â [<ffffffff815afde0>] drm_modeset_lock_all+0x40/0x120 > [Â Â Â 18.984281]Â Â [<ffffffff8158f79b>] > drm_fb_helper_restore_fbdev_mode_unlocked+0x2b/0x80 > [Â Â Â 18.984283]Â Â [<ffffffff8158f81d>] drm_fb_helper_set_par+0x2d/0x50 > [Â Â Â 18.984322]Â Â [<ffffffffa0105f7a>] intel_fbdev_set_par+0x1a/0x60 > [i915] > [Â Â Â 18.984324]Â Â [<ffffffff814c13c6>] fbcon_init+0x586/0x610 > [Â Â Â 18.984326]Â Â [<ffffffff8154d16a>] visual_init+0xca/0x130 > [Â Â Â 18.984328]Â Â [<ffffffff8154e611>] do_bind_con_driver+0x1c1/0x3a0 > [Â Â Â 18.984330]Â Â [<ffffffff8154eaf6>] do_take_over_console+0x116/0x180 > [Â Â Â 18.984332]Â Â [<ffffffff814bd3a7>] do_fbcon_takeover+0x57/0xb0 > [Â Â Â 18.984334]Â Â [<ffffffff814c1e48>] fbcon_event_notify+0x658/0x750 > [Â Â Â 18.984336]Â Â [<ffffffff810abcae>] notifier_call_chain+0x3e/0xb0 > [Â Â Â 18.984338]Â Â [<ffffffff810ac1ad>] > __blocking_notifier_call_chain+0x4d/0x70 > [Â Â Â 18.984340]Â Â [<ffffffff810ac1e6>] > blocking_notifier_call_chain+0x16/0x20 > [Â Â Â 18.984342]Â Â [<ffffffff814c748b>] fb_notifier_call_chain+0x1b/0x20 > [Â Â Â 18.984344]Â Â [<ffffffff814c86b1>] register_framebuffer+0x251/0x330 > [Â Â Â 18.984347]Â Â [<ffffffff815b7e8d>] ? > vga_switcheroo_client_fb_set+0x5d/0x70 > [Â Â Â 18.984349]Â Â [<ffffffff8158fa9f>] > drm_fb_helper_initial_config+0x25f/0x3f0 > [Â Â Â 18.984388]Â Â [<ffffffffa0106b48>] > intel_fbdev_initial_config+0x18/0x30 [i915] > [Â Â Â 18.984389]Â Â [<ffffffff810adfd8>] async_run_entry_fn+0x48/0x150 > [Â Â Â 18.984391]Â Â [<ffffffff810a3947>] process_one_work+0x1e7/0x750 > [Â Â Â 18.984392]Â Â [<ffffffff810a38c9>] ? process_one_work+0x169/0x750 > [Â Â Â 18.984394]Â Â [<ffffffff810a3efb>] worker_thread+0x4b/0x4f0 > [Â Â Â 18.984396]Â Â [<ffffffff810a3eb0>] ? process_one_work+0x750/0x750 > [Â Â Â 18.984398]Â Â [<ffffffff810aad4f>] kthread+0xef/0x110 > [Â Â Â 18.984401]Â Â [<ffffffff819a85ef>] ret_from_fork+0x1f/0x40 > [Â Â Â 18.984402]Â Â [<ffffffff810aac60>] ? kthread_stop+0x2e0/0x2e0 > > Reported-by: Imre Deak <imre.deak at intel.com>
Thanks, it gets rid of the problem: Tested-by: Imre Deak <imre.deak at intel.com> --Imre