On 01/09/2017 08:59 AM, Daniel Vetter wrote: > On Mon, Jan 9, 2017 at 5:50 PM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote: >> On 01/09/2017 08:41 AM, Daniel Vetter wrote: >>> On Mon, Jan 9, 2017 at 2:40 PM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote: >>>> Well, now I found where the -2 comes from. >>>> intel_dp_register_mst_connector() calls drm_connector_register(), which >>>> fails to add the kobject (warning below). But, it does zero error >>>> checking on the drm_connector_register() call and leaves the >>>> partially-constructed connector in place. >>>> >>>> The next time some poor, hapless code goes and tries to do anything with >>>> that kdev, they oops. I'm perplexed by this, though. The >>>> drm_dp_mst_topology_cbs->register_connector just returns void. It seems >>>> a bit goofy that it can't even _return_ failure. >>>> >>>> Is there some stable code to go back to here? Or, is there something >>>> about my configuration that's unique? I really wonder why nobody else >>>> is running into this. >>>> >>>> There's probably some other race going on here. This warning doesn't >>>> happen on every boot. >>> This smells more like the root-cause: Something goes wrong on boot >>> that prevents connectors from properly registering, then we fall over >>> later on. And the register callback is intentionally void, assuming >>> that any prep work has been done earlier and that therefore the >>> register step can't fail. Can you pls check whether the oops later on >>> only happens together with this warning at boot, or whether they're >>> not correlated? >> >> Looking through my logs, I can't find any instance of the oops without >> the warning at boot. So I do think the later oops is entirely caused by >> the issue warned about in early boot. > > Hm, I guess then we'd need to fix that boot-up warning. Can you try to > figure out why it's unhappy? On a hunch it could be that we call > drm_connector_register from the mst probe worker before the main > driver load thread has reached the drm_dev_register call. A few printk > to decide whether that's the case (plus a few boot-up tests to gather > the statistics, sorry about that) would be real great. I think your suspicion is correct. The WARNING is getting printed from CPU0 (the drm_dp_mst_link_probe_work() thread) and we can see the drm_connector_register()s happening in parallel on CPU1 while the WARNING is getting printed out. This seems to happen very consistently when i915 is built into the kernel. > [ 1.404237] drm_dev_register(00000000000002da)::209092608 cpu: 1 > [ 1.404284] drm_connector_register(ffff88040ed3e800)::379 connector->registered: 0 cpu: 0 > [ 1.404293] sysfs_create_dir_ns()::53 error: -2 > [ 1.404295] create_dir()::75 error: -2 cpu: 0 > [ 1.404298] ------------[ cut here ]------------ > [ 1.404304] WARNING: CPU: 0 PID: 3 at lib/kobject.c:249 kobject_add_internal+0x273/0x330 > [ 1.404308] kobject_add_internal failed for card0-DP-3 (error: -2 parent: card0) > [ 1.404311] Modules linked in: > [ 1.404316] CPU: 0 PID: 3 Comm: kworker/0:0 Not tainted 4.10.0-rc3-i915borked-dirty #66 > [ 1.404319] Hardware name: LENOVO 20F5S7V800/20F5S7V800, BIOS R02ET50W (1.23 ) 09/20/2016 > [ 1.404325] Workqueue: events_long drm_dp_mst_link_probe_work > [ 1.404328] Call Trace: > [ 1.404334] dump_stack+0x67/0x99 > [ 1.404338] __warn+0xd1/0xf0 > [ 1.404342] warn_slowpath_fmt+0x4f/0x60 > [ 1.404345] kobject_add_internal+0x273/0x330 > [ 1.404347] kobject_add+0x65/0xb0 > [ 1.404352] ? klist_init+0x31/0x40 > [ 1.404356] device_add+0x102/0x5d0 > [ 1.404360] ? kfree_const+0x22/0x30 > [ 1.404364] device_create_groups_vargs+0xd8/0x100 > [ 1.404367] device_create_with_groups+0x36/0x40 > [ 1.404370] drm_connector_register(ffff88040c779000)::379 connector->registered: 0 cpu: 1 > [ 1.404374] ? vprintk_default+0x29/0x50 > [ 1.404375] ? printk+0x4d/0x4f > [ 1.404378] drm_sysfs_connector_add+0x60/0xe0 > [ 1.404381] drm_connector_register+0x4e/0x100 > [ 1.404383] intel_dp_register_mst_connector+0x41/0x50 > [ 1.404385] drm_dp_add_port+0x350/0x450 > [ 1.404388] ? rcu_early_boot_tests+0x1/0x10 > [ 1.404390] ? schedule_timeout+0x1cd/0x390 > [ 1.404392] ? __might_sleep+0x4a/0x90 > [ 1.404394] ? mutex_lock+0x25/0x50 > [ 1.404395] ? drm_dp_mst_wait_tx_reply+0x118/0x1e0 > [ 1.404397] ? prepare_to_wait_event+0x120/0x120 > [ 1.404399] ? drm_dp_check_mstb_guid+0x3d/0x120 > [ 1.404401] drm_dp_send_link_address+0x185/0x1f0 > [ 1.404403] drm_dp_check_and_send_link_address+0xad/0xc0 > [ 1.404405] drm_dp_mst_link_probe_work+0x57/0xa0 > [ 1.404407] process_one_work+0x14b/0x430 > [ 1.404408] worker_thread+0x12b/0x4a0 > [ 1.404410] kthread+0x10c/0x140 > [ 1.404411] ? process_one_work+0x430/0x430 > [ 1.404413] ? kthread_create_on_node+0x40/0x40 > [ 1.404415] ret_from_fork+0x27/0x40 > [ 1.404418] ---[ end trace 952a97b7cba4984f ]--- > [ 1.404420] drm_sysfs_connector_add() connector: ffff88040ed3e800 kdev: fffffffffffffffe > [ 1.404422] [drm:drm_sysfs_connector_add] *ERROR* failed to register connector device: -2 > [ 1.404453] drm_sysfs_connector_add() connector: ffff88040c779000 kdev: ffff88040c771c00 > [ 1.404508] drm_connector_register(ffff88040c779000)::402 connector->registered: 1 cpu: 1 > [ 1.404512] drm_connector_register(ffff88040ed3b800)::379 connector->registered: 0 cpu: 1 > [ 1.404531] drm_sysfs_connector_add() connector: ffff88040ed3b800 kdev: ffff88040c772000 > [ 1.404559] drm_connector_register(ffff88040ed3b800)::402 connector->registered: 1 cpu: 1 > [ 1.404564] drm_connector_register(ffff88040ed3c000)::379 connector->registered: 0 cpu: 1 > [ 1.404583] drm_sysfs_connector_add() connector: ffff88040ed3c000 kdev: ffff88040c772400 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
