syzbot

------------[ cut here ]------------
WARNING: drivers/gpu/drm/drm_vblank.c:1320 at drm_crtc_wait_one_vblank+0x19c/0x21c drivers/gpu/drm/drm_vblank.c:1320, CPU#1: kworker/1:3/1684
faux_driver vkms: [drm] vblank wait timed out on crtc 0
Modules linked in:
Kernel panic - not syncing: kernel: panic_on_warn set ...
CPU: 1 UID: 0 PID: 1684 Comm: kworker/1:3 Not tainted syzkaller #0 PREEMPT 
Hardware name: ARM-Versatile Express
Workqueue: events drm_fb_helper_damage_work
Call trace: 
[<80201a14>] (dump_backtrace) from [<80201b08>] (show_stack+0x18/0x1c arch/arm/kernel/traps.c:257)
 r7:8281f940 r6:00000000 r5:822a7ed4 r4:00000001
[<80201af0>] (show_stack) from [<8021e444>] (__dump_stack lib/dump_stack.c:94 [inline])
[<80201af0>] (show_stack) from [<8021e444>] (dump_stack_lvl+0x5c/0x70 lib/dump_stack.c:120)
[<8021e3e8>] (dump_stack_lvl) from [<8021e470>] (dump_stack+0x18/0x1c lib/dump_stack.c:129)
 r7:8281f940 r6:00000000 r5:8478ec00 r4:82a80d14
[<8021e458>] (dump_stack) from [<8020260c>] (vpanic+0x114/0x320 kernel/panic.c:650)
[<802024f8>] (vpanic) from [<8020284c>] (trace_suspend_resume+0x0/0x104 kernel/panic.c:787)
 r7:80b3b424
[<80202818>] (panic) from [<80250a4c>] (check_panic_on_warn kernel/panic.c:524 [inline])
[<80202818>] (panic) from [<80250a4c>] (get_taint+0x0/0x1c kernel/panic.c:519)
 r3:8280c544 r2:00000001 r1:8228ec2c r0:822964f4
[<802509d4>] (check_panic_on_warn) from [<80250bc8>] (__warn+0x98/0x1ac kernel/panic.c:1062)
[<80250b30>] (__warn) from [<80250ec4>] (warn_slowpath_fmt+0x1e8/0x1f4 kernel/panic.c:1097)
 r8:00000009 r7:8232396c r6:ea9addfc r5:8478ec00 r4:00000000
[<80250ce0>] (warn_slowpath_fmt) from [<80b3b424>] (drm_crtc_wait_one_vblank+0x19c/0x21c drivers/gpu/drm/drm_vblank.c:1320)
 r10:840b8a44 r9:ffffff92 r8:00000000 r7:00003e16 r6:00000000 r5:00000000
 r4:84053000
[<80b3b288>] (drm_crtc_wait_one_vblank) from [<80b3f00c>] (drm_client_modeset_wait_for_vblank+0x60/0x74 drivers/gpu/drm/drm_client_modeset.c:1331)
 r10:8302ae05 r9:84053000 r8:840b5800 r7:ea9adec4 r6:84053000 r5:00000000
 r4:83f30040
[<80b3efac>] (drm_client_modeset_wait_for_vblank) from [<80b58554>] (drm_fb_helper_fb_dirty drivers/gpu/drm/drm_fb_helper.c:236 [inline])
[<80b3efac>] (drm_client_modeset_wait_for_vblank) from [<80b58554>] (drm_fb_helper_damage_work+0x80/0x1e0 drivers/gpu/drm/drm_fb_helper.c:274)
 r7:ea9adec4 r6:840b58b8 r5:00000000 r4:840b5898
[<80b584d4>] (drm_fb_helper_damage_work) from [<8027666c>] (process_one_work+0x1b8/0x58c kernel/workqueue.c:3275)
 r9:8478ec00 r8:01800000 r7:ddde4d80 r6:8302ae00 r5:840b5898 r4:842bb600
[<802764b4>] (process_one_work) from [<80277430>] (process_scheduled_works kernel/workqueue.c:3358 [inline])
[<802764b4>] (process_one_work) from [<80277430>] (worker_thread+0x16c/0x318 kernel/workqueue.c:3439)
 r10:00000000 r9:842bb62c r8:8478ec00 r7:82804d80 r6:ddde4da0 r5:ddde4d80
 r4:842bb600
[<802772c4>] (worker_thread) from [<802813f4>] (kthread+0x11c/0x154 kernel/kthread.c:436)
 r10:00000000 r9:df915e88 r8:842bb580 r7:842bb600 r6:802772c4 r5:8478ec00
 r4:842c0cc0
[<802812d8>] (kthread) from [<80200114>] (ret_from_fork+0x14/0x20 arch/arm/kernel/entry-common.S:137)
Exception stack(0xea9adfb0 to 0xea9adff8)
dfa0:                                     00000000 00000000 00000000 00000000
dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:802812d8 r4:842c0cc0
SMP: failed to stop secondary CPUs
Rebooting in 86400 seconds..