Re: [syzbot] [dri?] WARNING in vkms_get_vblank_timestamp

[Daniel Vetter]

On Thu, Apr 06, 2023 at 10:57:48AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    4b0f4525dc4f Add linux-next specific files for 20230331
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13ea0159c80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=85cc4b935a1f7194
> dashboard link: https://syzkaller.appspot.com/bug?extid=75cc0f9f7e6324dd2501
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15cb3659c80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/8d06bb015df3/disk-4b0f4525.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6a1c1ebf3724/vmlinux-4b0f4525.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/4bb2b8d6cd7d/bzImage-4b0f4525.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+75cc0f9f7e6324dd2501@xxxxxxxxxxxxxxxxxxxxxxxxx

Should be fixed with f2c7ca890182 ("drm/atomic-helper: Don't set deadline
for modesets"). And maybe also 6f1ccbf07453 ("drm/vblank: Fix for drivers
that do not drm_vblank_init()").

Would be great if you can confirm. The regression was introduced in
d39e48ca80c0 ("drm/atomic-helper: Set fence deadline for vblank") if my
guess is correct.
-Daniel

> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 6019 at drivers/gpu/drm/vkms/vkms_crtc.c:103 vkms_get_vblank_timestamp+0x1cf/0x240 drivers/gpu/drm/vkms/vkms_crtc.c:103
> Modules linked in:
> CPU: 1 PID: 6019 Comm: syz-executor.1 Not tainted 6.3.0-rc4-next-20230331-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
> RIP: 0010:vkms_get_vblank_timestamp+0x1cf/0x240 drivers/gpu/drm/vkms/vkms_crtc.c:103
> Code: ce 73 fc e8 53 e9 63 fc 4c 89 e1 48 ba 00 00 00 00 00 fc ff df 48 c1 e9 03 80 3c 11 00 75 65 49 89 04 24 eb c4 e8 b1 ce 73 fc <0f> 0b eb bb e8 d8 80 c6 fc e9 de fe ff ff e8 0e 81 c6 fc e9 78 fe
> RSP: 0018:ffffc9000b3873d8 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000004e19fc6e8a RCX: 0000000000000000
> RDX: ffff8880756257c0 RSI: ffffffff850f429f RDI: 0000000000000006
> RBP: ffff88801dc84000 R08: 0000000000000006 R09: 0000004e19fc6e8a
> R10: 0000004e19fc6e8a R11: 0000000000000000 R12: ffffc9000b387540
> R13: 0000004e19fc6e8a R14: 0000000000004e20 R15: ffffffff850f40d0
> FS:  00007f5372809700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000202fc000 CR3: 0000000027361000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  drm_crtc_get_last_vbltimestamp+0x102/0x1a0 drivers/gpu/drm/drm_vblank.c:877
>  drm_crtc_next_vblank_start+0x13f/0x2b0 drivers/gpu/drm/drm_vblank.c:1006
>  set_fence_deadline drivers/gpu/drm/drm_atomic_helper.c:1531 [inline]
>  drm_atomic_helper_wait_for_fences+0x1b4/0x780 drivers/gpu/drm/drm_atomic_helper.c:1578
>  drm_atomic_helper_commit drivers/gpu/drm/drm_atomic_helper.c:2007 [inline]
>  drm_atomic_helper_commit+0x1bd/0x370 drivers/gpu/drm/drm_atomic_helper.c:1979
>  drm_atomic_commit+0x20a/0x300 drivers/gpu/drm/drm_atomic.c:1503
>  drm_client_modeset_commit_atomic+0x69b/0x7e0 drivers/gpu/drm/drm_client_modeset.c:1045
>  drm_client_modeset_commit_locked+0x149/0x580 drivers/gpu/drm/drm_client_modeset.c:1148
>  pan_display_atomic drivers/gpu/drm/drm_fb_helper.c:1690 [inline]
>  drm_fb_helper_pan_display+0x28f/0x970 drivers/gpu/drm/drm_fb_helper.c:1750
>  fb_pan_display+0x2fb/0x6c0 drivers/video/fbdev/core/fbmem.c:924
>  bit_update_start+0x49/0x1f0 drivers/video/fbdev/core/bitblit.c:387
>  fbcon_switch+0xbcf/0x1380 drivers/video/fbdev/core/fbcon.c:2169
>  redraw_screen+0x2bd/0x740 drivers/tty/vt/vt.c:965
>  fbcon_modechanged+0x526/0x620 drivers/video/fbdev/core/fbcon.c:2704
>  fbcon_update_vcs+0x3e/0x50 drivers/video/fbdev/core/fbcon.c:2749
>  do_fb_ioctl+0x6d7/0x740 drivers/video/fbdev/core/fbmem.c:1125
>  fb_ioctl+0xeb/0x150 drivers/video/fbdev/core/fbmem.c:1202
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:870 [inline]
>  __se_sys_ioctl fs/ioctl.c:856 [inline]
>  __x64_sys_ioctl+0x197/0x210 fs/ioctl.c:856
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f5371a8c0f9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f5372809168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007f5371bac050 RCX: 00007f5371a8c0f9
> RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000005
> RBP: 00007f5371ae7b39 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffd0e5e571f R14: 00007f5372809300 R15: 0000000000022000
>  </TASK>
> 
> 
> ---
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> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
> 
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> syzbot can test patches for this issue, for details see:
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch