Quoting Mika Kahola (2018-12-04 09:46:39) > Occasionally, we get the following error in our CI runs > > [853.132830] Workqueue: events i915_hotplug_work_func [i915] > [853.132844] RIP: 0010:drm_wait_one_vblank+0x19b/0x1b0 > [853.132852] Code: fe ff ff e8 b7 4e a6 ff 48 89 e6 4c 89 ff e8 6c 5f ab ff 45 85 ed 0f 85 > 15 ff ff ff 89 ee 48 c7 c7 e8 03 10 82 e8 b5 4b a6 ff <0f> 0b e9 00 ff ff ff 0f 1f 40 00 66 > 2e 0f 1f 84 00 00 00 00 00 8b > [853.132859] RSP: 0018:ffffc9000146bca0 EFLAGS: 00010286 > [853.132866] RAX: 0000000000000000 RBX: ffff88849ef00000 RCX: 0000000000000000 > [853.132873] RDX: 0000000000000007 RSI: ffffffff820c6f58 RDI: 00000000ffffffff > [853.132879] RBP: 0000000000000000 R08: 000000007ffc637a R09: 0000000000000000 > [853.132884] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > [853.132890] R13: 0000000000000000 R14: 000000000000d0c2 R15: ffff8884a491e680 > [853.132897] FS: 0000000000000000(0000) GS:ffff8884afe80000(0000) knlGS:0000000000000000 > [853.132904] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [853.132910] CR2: 00007f63bf0df000 CR3: 0000000005210006 CR4: 0000000000760ee0 > [853.132916] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [853.132922] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [853.132927] PKRU: 55555554 > [853.132932] Call Trace: > [853.132949] ? wait_woken+0xa0/0xa0 > [853.133068] intel_dp_retrain_link+0x130/0x190 [i915] > [853.133176] intel_ddi_hotplug+0x54/0x2e0 [i915] > [853.133298] i915_hotplug_work_func+0x1a9/0x240 [i915] > [853.133324] process_one_work+0x262/0x630 > [853.133349] worker_thread+0x37/0x380 > [853.133365] ? process_one_work+0x630/0x630 > [853.133373] kthread+0x119/0x130 > [853.133383] ? kthread_park+0x80/0x80 > [853.133400] ret_from_fork+0x3a/0x50 > [853.133433] irq event stamp: 1426928 > > I suspect that this is caused by a racy condition when retraining the > DisplayPort link. My proposal is to wait for one additional vblank > event before we send out a hotplug event to userspace for reprobing. Problem is just by waiting for the next vblank doesn't rule out hitting the same race with another/delayed retraining. If you want serialisation, please do add some -- and it may be sensible for the hotplug to wait for the vblank after any ongoing work has finished. -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
