I'm triggering the following call splat on 5.2-rt.

[   63.099414] 006: BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:968
[   63.108423] 006: in_atomic(): 0, irqs_disabled(): 1, pid: 173, name: kworker/6:1
[   63.115779] 006: CPU: 6 PID: 173 Comm: kworker/6:1 Not tainted 5.2.9-test-rt3 #229
[   63.123329] 006: Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016
[   63.132667] 006: Workqueue: events_long i915_hangcheck_elapsed [i915]
[   63.139125] 006:
[   63.141041] 006: Call Trace:
[   63.143916] 006:  dump_stack+0x5c/0x80
[   63.147654] 006:  ___might_sleep.cold.92+0x8d/0x9a
[   63.152423] 006:  rt_spin_lock+0x31/0x40
[   63.156332] 006:  intel_engine_breadcrumbs_irq+0x56/0x320 [i915]
[   63.162350] 006:  intel_engine_signal_breadcrumbs+0x11/0x20 [i915]
[   63.168540] 006:  i915_hangcheck_elapsed+0x199/0x420 [i915]
[   63.174129] 006:  ? __switch_to_asm+0x40/0x70
[   63.178468] 006:  ? __switch_to_asm+0x34/0x70
[   63.182807] 006:  ? __switch_to_asm+0x40/0x70
[   63.187145] 006:  ? __switch_to_asm+0x34/0x70
[   63.191483] 006:  ? __switch_to_asm+0x40/0x70
[   63.195822] 006:  ? __switch_to_asm+0x34/0x70
[   63.200160] 006:  ? __switch_to_asm+0x40/0x70
[   63.204497] 006:  ? __switch_to_asm+0x34/0x70
[   63.208834] 006:  ? __switch_to_asm+0x40/0x70
[   63.213164] 006:  ? __switch_to_asm+0x34/0x70
[   63.217504] 006:  ? __switch_to_asm+0x40/0x70
[   63.221840] 006:  ? __switch_to_asm+0x34/0x70
[   63.226171] 006:  ? __switch_to_asm+0x40/0x70
[   63.230507] 006:  ? __switch_to_asm+0x34/0x70
[   63.234846] 006:  ? __switch_to_asm+0x40/0x70
[   63.239185] 006:  ? __switch_to_asm+0x34/0x70
[   63.243522] 006:  ? __switch_to_asm+0x40/0x70
[   63.247860] 006:  ? __switch_to_asm+0x34/0x70
[   63.252199] 006:  ? __switch_to_asm+0x40/0x70
[   63.256537] 006:  ? __switch_to_asm+0x34/0x70
[   63.260873] 006:  ? __switch_to_asm+0x40/0x70
[   63.265213] 006:  ? __switch_to_asm+0x34/0x70
[   63.269551] 006:  ? __switch_to_asm+0x40/0x70
[   63.273889] 006:  ? __switch_to_asm+0x34/0x70
[   63.278229] 006:  ? __switch_to_asm+0x40/0x70
[   63.282565] 006:  ? __switch_to_asm+0x34/0x70
[   63.286904] 006:  ? __switch_to_asm+0x40/0x70
[   63.291245] 006:  ? __switch_to_asm+0x34/0x70
[   63.295582] 006:  ? __switch_to_asm+0x40/0x70
[   63.299921] 006:  ? _raw_spin_unlock_irq+0xa/0x50
[   63.304605] 006:  ? finish_task_switch+0x104/0x2e0
[   63.309375] 006:  process_one_work+0x1e8/0x4c0
[   63.313800] 006:  worker_thread+0x39/0x3d0
[   63.317878] 006:  ? process_one_work+0x4c0/0x4c0
[   63.322476] 006:  kthread+0x11d/0x140
[   63.326124] 006:  ? kthread_create_on_node+0x60/0x60
[   63.331066] 006:  ret_from_fork+0x35/0x40

Attached is the config and the full dmesg.

Note that I have NO_HZ_FULL enabled and the following on the command
line:

  nohz_full=2,3 isolcpus=2,3 rcu_nocbs=2,3


-- Steve