[Qemu-devel] [Bug 1793791] Re: Crash with nbd_reply_chunk_iter_receive: Assertion `chunk->flags & NBD_REPLY_FLAG_DONE' failed

[Matthew Schumacher]

Okay, this is probably a race condition bug.  If remove:

<iothreads>1</iothreads>
and
iothread='1' from the disk which causes the command to change from: 

-device virtio-blk-
pci,iothread=iothread1,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-
disk0,id=virtio-disk0,bootindex=2,write-cache=on

to

-device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-
disk0,id=virtio-disk0,bootindex=2,write-cache=on

I don't get crashes anymore.

So for sure it has something to do with iothreads.

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https://bugs.launchpad.net/bugs/1793791

Title:
  Crash with nbd_reply_chunk_iter_receive: Assertion `chunk->flags &
  NBD_REPLY_FLAG_DONE' failed

Status in QEMU:
  New

Bug description:
  Qemu version on both sides: 2.12.1
  Host A Linux: 4.9.76
  Host B Linux: 4.14.67

  While calling from Host A:
  virsh migrate virtualmachine qemu+ssh://hostB/system --live --undefinesource 
--persistent --verbose --copy-storage-all

  I get a qemu crash with:

  2018-09-21 16:12:23.073+0000: 14428: info : virObjectUnref:350 : 
OBJECT_UNREF: obj=0x7f922c03d990
  qemu-system-x86_64: block/nbd-client.c:606: nbd_reply_chunk_iter_receive: 
Assertion `chunk->flags & NBD_REPLY_FLAG_DONE' failed.
  2018-09-21 16:12:41.230+0000: shutting down, reason=crashed
  2018-09-21 16:12:52.900+0000: shutting down, reason=failed

  It doesn't do it every time, but most of the time.

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