[Bug 1844053] Re: task blocked for more than X seconds - events drm_fb_helper_dirty_work

[Thomas Huth]

The QEMU project is currently considering to move its bug tracking to
another system. For this we need to know which bugs are still valid
and which could be closed already. Thus we are setting older bugs to
"Incomplete" now.

If you still think this bug report here is valid, then please switch
the state back to "New" within the next 60 days, otherwise this report
will be marked as "Expired". Or please mark it as "Fix Released" if
the problem has been solved with a newer version of QEMU already.

Thank you and sorry for the inconvenience.


** Changed in: qemu
       Status: New => Incomplete

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Title:
  task blocked for more than X seconds - events drm_fb_helper_dirty_work

Status in QEMU:
  Incomplete

Bug description:
  I've had bunches of these errors on 9 different boots, between
  2019-08-21 and now, with Arch host and guest, from linux 5.1.16 to
  5.2.14 on host and guest, with QEMU 4.0.0 and 4.1.0.  spice 0.14.2,
  spice-gtk 0.37, spice-protocol 0.14.0, virt-viewer 8.0.

  I've been fighting with some other issues related to a 5.2 btrfs
  regression, a QEMU qxl regression (see bug 1843151) which I ran into
  when trying to temporarily abandon virtio-vga, and I haven't paid
  enough attention to what impact specifically this virtio_gpu issue has
  on the system In journalctl, I can see I often rebooted minutes after
  they occurred, but sometimes much later.  That must mean whenever I
  saw it happen that I rebooted the VM, or potentially it impacted
  functionality of the system.

  Please let me know if and how I can get more information for you if
  needed.

  I've replicated this on both a system with integrated ASPEED video,
  and on an AMD Vega 64 running amdgpu.

  As an example, I have one boot which reported at 122 seconds, 245,
  368, 491, 614, 737, 860, 983, 1105, 1228, then I rebooted.

  I have another that reported 122/245/368/491/614/737, went away for 10
  minutes, then started reporting again 122/245/368/491, and went away.
  Then, I rebooted about 20 hours later.

  Host system has no graphical impact when this happens, and logs
  nothing in its journalctl.

  Guest is tty mode only, with kernel argument "video=1280x1024".  No x
  server.

  ==========

  INFO: task kworker/0:1:15 blocked for more than 122 seconds.
        Not tainted 5.2.14-1 #1
  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  kworker/0:1     D    0    15      2 0x800004000
  Workqueue: events drm_fb_helper_dirty_work [drm_kms_helper]
  Call Trace:
   ? __schedule+0x27f/0x6d0
   schedule+0x3d/0xc0
   virtio_gpu_queue_fenced_ctrl_buffer+0xa1/0x130 [virtio_gpu]
   ? wait_woken+0x80/0x80
   virtio_gpu_surface_dirty+0x2a5/0x300 [virtio_gpu]
   drm_fb_helper_dirty_work+0x156/0x160 [drm_kms_helper]
   process_one_work+0x19a/0x3b0
   worker_tread+0x50/0x3a0
   kthread+0xfd/0x130
   ? process_one_work+0x3b0/0x3b0
   ? kthread_park+0x80/0x80
   ret_from_fork+0x35/0x40

  ==========

  /usr/bin/qemu-system-x86_64 \
     -name vm,process=qemu:vm \
     -no-user-config \
     -nodefaults \
     -nographic \
     -uuid <uuid> \
     -pidfile <pidfile> \
     -machine q35,accel=kvm,vmport=off,dump-guest-core=off \
     -cpu SandyBridge-IBRS \
     -smp cpus=4,cores=2,threads=1,sockets=2 \
     -m 4G \
     -drive if=pflash,format=raw,readonly,file=/usr/share/ovmf/x64/OVMF_CODE.fd 
\
     -drive if=pflash,format=raw,file=/var/qemu/efivars/vm.fd \
     -monitor telnet:localhost:8000,server,nowait,nodelay \
     -spice unix,addr=/tmp/spice.vm.sock,disable-ticketing \
     -device ioh3420,id=pcie.1,bus=pcie.0,slot=0 \
     -device virtio-vga,bus=pcie.1,addr=0 \
     -usbdevice tablet \
     -netdev bridge,id=network0,br=br0 \
     -device 
virtio-net-pci,netdev=network0,mac=F4:F6:34:F6:34:2d,bus=pcie.0,addr=3 \
     -device virtio-scsi-pci,id=scsi1 \
     -drive 
driver=raw,node-name=hd0,file=/dev/lvm/vm,if=none,discard=unmap,cache=none,aio=threads

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