[Bug 1836855] Re: virtio_scsi_ctx_check failed when detach virtio_scsi disk

[Launchpad Bug Tracker <1836855@bugs.launchpad.net>]

[Expired for QEMU because there has been no activity for 60 days.]

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

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Title:
  virtio_scsi_ctx_check failed when detach virtio_scsi disk

Status in QEMU:
  Expired

Bug description:
  I found a problem  that virtio_scsi_ctx_check  failed when detaching
  virtio_scsi disk.  The  bt is below:

  (gdb) bt
  #0  0x0000ffffb02e1bd0 in raise () from /lib64/libc.so.6
  #1  0x0000ffffb02e2f7c in abort () from /lib64/libc.so.6
  #2  0x0000ffffb02db124 in __assert_fail_base () from /lib64/libc.so.6
  #3  0x0000ffffb02db1a4 in __assert_fail () from /lib64/libc.so.6
  #4  0x00000000004eb9a8 in virtio_scsi_ctx_check (d=d@entry=0xc70d790, s=<optimized out>, s=<optimized out>)
      at /Images/lzg/code/710/qemu-2.8.1/hw/scsi/virtio-scsi.c:243
  #5  0x00000000004ec87c in virtio_scsi_handle_cmd_req_prepare (s=s@entry=0xd27a7a0, req=req@entry=0xafc4b90)
      at /Images/lzg/code/710/qemu-2.8.1/hw/scsi/virtio-scsi.c:553
  #6  0x00000000004ecc20 in virtio_scsi_handle_cmd_vq (s=0xd27a7a0, vq=0xd283410)
      at /Images/lzg/code/710/qemu-2.8.1/hw/scsi/virtio-scsi.c:588
  #7  0x00000000004eda20 in virtio_scsi_data_plane_handle_cmd (vdev=0x0, vq=0xffffae7a6f98)
      at /Images/lzg/code/710/qemu-2.8.1/hw/scsi/virtio-scsi-dataplane.c:57
  #8  0x0000000000877254 in aio_dispatch (ctx=0xac61010) at util/aio-posix.c:323
  #9  0x00000000008773ec in aio_poll (ctx=0xac61010, blocking=true) at util/aio-posix.c:472
  #10 0x00000000005cd7cc in iothread_run (opaque=0xac5e4b0) at iothread.c:49
  #11 0x000000000087a8b8 in qemu_thread_start (args=0xac61360) at util/qemu-thread-posix.c:495
  #12 0x00000000008a04e8 in thread_entry_for_hotfix (pthread_cb=0x0) at uvp/hotpatch/qemu_hotpatch_helper.c:579
  #13 0x0000ffffb041c8bc in start_thread () from /lib64/libpthread.so.0
  #14 0x0000ffffb0382f8c in thread_start () from /lib64/libc.so.6

  assert(blk_get_aio_context(d->conf.blk) == s->ctx)  failed.

  I think this patch
  (https://git.qemu.org/?p=qemu.git;a=commitdiff;h=a6f230c8d13a7ff3a0c7f1097412f44bfd9eff0b)
  introduce this problem.

  commit a6f230c8d13a7ff3a0c7f1097412f44bfd9eff0b  move blockbackend
  back to main AioContext on unplug. It set the AioContext of

  SCSIDevice  to the main AioContex, but s->ctx is still the iothread
  AioContext.  Is this a bug?

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