Fedora rawhide with debug config as 
http://pkgs.fedoraproject.org/cgit/rpms/kernel.git/tree/kernel-x86_64-debug.config

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Baffin [Radeon RX 460] (rev cf)
1 DP 4k monitor

This is something that seems to've started appearing after the rcu changes in this merge window
....

[   12.958667] =============================
[   12.958678] WARNING: suspicious RCU usage
[   12.958691] 4.13.0-0.rc2.git1.1.fc27.x86_64 #1 Not tainted
[   12.958701] -----------------------------
[   12.958714] ./include/linux/rcupdate.h:297 Illegal context switch in RCU read-side critical section!
[   12.958724] 
               other info that might help us debug this:

[   12.958737] 
               rcu_scheduler_active = 2, debug_locks = 1
[   12.958749] 1 lock held by amdgpu_cs:0/1226:
[   12.958758]  #0:  (rcu_read_lock){......}, at: [<ffffffffc04ff9b5>] amdgpu_bo_list_get+0x5/0x130 [amdgpu]
[   12.958874] 
               stack backtrace:
[   12.958890] CPU: 3 PID: 1226 Comm: amdgpu_cs:0 Not tainted 4.13.0-0.rc2.git1.1.fc27.x86_64 #1
[   12.958901] Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./990FXA-UD3 R5, BIOS F2 04/01/2015
[   12.958911] Call Trace:
[   12.958931]  dump_stack+0x8e/0xd6
[   12.958953]  lockdep_rcu_suspicious+0xc5/0x100
[   12.959033]  ? amdgpu_bo_list_get+0x81/0x130 [amdgpu]
[   12.959051]  ___might_sleep+0x1ad/0x250
[   12.959073]  __might_sleep+0x4a/0x80
[   12.959095]  __mutex_lock+0x59/0xa00
[   12.959110]  ? trace_hardirqs_on+0xd/0x10
[   12.959141]  ? lock_acquire+0xa3/0x1f0
[   12.959217]  ? amdgpu_bo_list_get+0x5/0x130 [amdgpu]
[   12.959243]  mutex_lock_nested+0x1b/0x20
[   12.959253]  ? mutex_lock_nested+0x1b/0x20
[   12.959321]  amdgpu_bo_list_get+0x81/0x130 [amdgpu]
[   12.959389]  amdgpu_cs_ioctl+0xcb/0x1c50 [amdgpu]
[   12.959413]  ? debug_check_no_obj_freed+0x15f/0x24a
[   12.959562]  ? amdgpu_cs_find_mapping+0xa0/0xa0 [amdgpu]
[   12.959607]  drm_ioctl_kernel+0x5d/0xb0 [drm]
[   12.959657]  drm_ioctl+0x31b/0x3d0 [drm]
[   12.959726]  ? amdgpu_cs_find_mapping+0xa0/0xa0 [amdgpu]
[   12.959767]  ? trace_hardirqs_on_caller+0xf4/0x190
[   12.959787]  ? trace_hardirqs_on+0xd/0x10
[   12.959870]  amdgpu_drm_ioctl+0x4f/0x90 [amdgpu]
[   12.959895]  do_vfs_ioctl+0xa6/0x6c0
[   12.959940]  SyS_ioctl+0x79/0x90
[   12.959968]  entry_SYSCALL_64_fastpath+0x1f/0xbe
[   12.959981] RIP: 0033:0x7fc88df4a267
[   12.959991] RSP: 002b:00007fc86a0b98b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[   12.960008] RAX: ffffffffffffffda RBX: 00007fc85c000000 RCX: 00007fc88df4a267
[   12.960031] RDX: 00007fc86a0b9a10 RSI: 00000000c0186444 RDI: 000000000000000c
[   12.960040] RBP: 0000000000021000 R08: 00007fc86a0b9900 R09: 00007fc86a0b9950
[   12.960050] R10: 0000000000000002 R11: 0000000000000246 R12: 00007fc860000000
[   12.960061] R13: 0000000002ef5000 R14: 0000000000000000 R15: 0000000000000000
[   12.960287] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:747
[   12.960301] in_atomic(): 1, irqs_disabled(): 0, pid: 1226, name: amdgpu_cs:0
[   12.960313] 1 lock held by amdgpu_cs:0/1226:
[   12.960323]  #0:  (rcu_read_lock){......}, at: [<ffffffffc04ff9b5>] amdgpu_bo_list_get+0x5/0x130 [amdgpu]
[   12.960422] CPU: 3 PID: 1226 Comm: amdgpu_cs:0 Not tainted 4.13.0-0.rc2.git1.1.fc27.x86_64 #1
[   12.960431] Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./990FXA-UD3 R5, BIOS F2 04/01/2015
[   12.960439] Call Trace:
[   12.960453]  dump_stack+0x8e/0xd6
[   12.960470]  ___might_sleep+0x164/0x250
[   12.960492]  __might_sleep+0x4a/0x80
[   12.960515]  __mutex_lock+0x59/0xa00
[   12.960530]  ? trace_hardirqs_on+0xd/0x10
[   12.960561]  ? lock_acquire+0xa3/0x1f0
[   12.960638]  ? amdgpu_bo_list_get+0x5/0x130 [amdgpu]
[   12.960673]  mutex_lock_nested+0x1b/0x20
[   12.960686]  ? mutex_lock_nested+0x1b/0x20
[   12.960758]  amdgpu_bo_list_get+0x81/0x130 [amdgpu]
[   12.960832]  amdgpu_cs_ioctl+0xcb/0x1c50 [amdgpu]
[   12.960861]  ? debug_check_no_obj_freed+0x15f/0x24a
[   12.961043]  ? amdgpu_cs_find_mapping+0xa0/0xa0 [amdgpu]
[   12.961083]  drm_ioctl_kernel+0x5d/0xb0 [drm]
[   12.961134]  drm_ioctl+0x31b/0x3d0 [drm]
[   12.961204]  ? amdgpu_cs_find_mapping+0xa0/0xa0 [amdgpu]
[   12.961241]  ? trace_hardirqs_on_caller+0xf4/0x190
[   12.961262]  ? trace_hardirqs_on+0xd/0x10
[   12.961346]  amdgpu_drm_ioctl+0x4f/0x90 [amdgpu]
[   12.961371]  do_vfs_ioctl+0xa6/0x6c0
[   12.961415]  SyS_ioctl+0x79/0x90
[   12.961443]  entry_SYSCALL_64_fastpath+0x1f/0xbe
[   12.961455] RIP: 0033:0x7fc88df4a267
[   12.961466] RSP: 002b:00007fc86a0b98b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[   12.961481] RAX: ffffffffffffffda RBX: 00007fc85c000000 RCX: 00007fc88df4a267
[   12.961488] RDX: 00007fc86a0b9a10 RSI: 00000000c0186444 RDI: 000000000000000c
[   12.961496] RBP: 0000000000021000 R08: 00007fc86a0b9900 R09: 00007fc86a0b9950
[   12.961504] R10: 0000000000000002 R11: 0000000000000246 R12: 00007fc860000000
[   12.961511] R13: 0000000002ef5000 R14: 0000000000000000 R15: 0000000000000000