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Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handle
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler |
Date: |
Tue, 11 Sep 2018 13:32:13 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
On 10/09/2018 16:56, Fam Zheng wrote:
> We have this unwanted call stack:
>
> > ...
> > #13 0x00005586602b7793 in virtio_scsi_handle_cmd_vq
> > #14 0x00005586602b8d66 in virtio_scsi_data_plane_handle_cmd
> > #15 0x00005586602ddab7 in virtio_queue_notify_aio_vq
> > #16 0x00005586602dfc9f in virtio_queue_host_notifier_aio_poll
> > #17 0x00005586607885da in run_poll_handlers_once
> > #18 0x000055866078880e in try_poll_mode
> > #19 0x00005586607888eb in aio_poll
> > #20 0x0000558660784561 in aio_wait_bh_oneshot
> > #21 0x00005586602b9582 in virtio_scsi_dataplane_stop
> > #22 0x00005586605a7110 in virtio_bus_stop_ioeventfd
> > #23 0x00005586605a9426 in virtio_pci_stop_ioeventfd
> > #24 0x00005586605ab808 in virtio_pci_common_write
> > #25 0x0000558660242396 in memory_region_write_accessor
> > #26 0x00005586602425ab in access_with_adjusted_size
> > #27 0x0000558660245281 in memory_region_dispatch_write
> > #28 0x00005586601e008e in flatview_write_continue
> > #29 0x00005586601e01d8 in flatview_write
> > #30 0x00005586601e04de in address_space_write
> > #31 0x00005586601e052f in address_space_rw
> > #32 0x00005586602607f2 in kvm_cpu_exec
> > #33 0x0000558660227148 in qemu_kvm_cpu_thread_fn
> > #34 0x000055866078bde7 in qemu_thread_start
> > #35 0x00007f5784906594 in start_thread
> > #36 0x00007f5784639e6f in clone
>
> Avoid it with the aio_disable_external/aio_enable_external pair, so that
> no vq poll handlers can be called in aio_wait_bh_oneshot.
I don't understand. We are in the vCPU thread, so not in the
AioContext's home thread. Why is aio_wait_bh_oneshot polling rather
than going through the aio_wait_bh path?
Thanks,
Paolo
- [Qemu-devel] [PATCH 0/2] virtio-scsi: Fix QEMU hang with vIOMMU and ATS, Fam Zheng, 2018/09/10
- [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Fam Zheng, 2018/09/10
- Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Fam Zheng, 2018/09/11
- Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Paolo Bonzini, 2018/09/11
- Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Fam Zheng, 2018/09/11
- Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Paolo Bonzini, 2018/09/12
- Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Fam Zheng, 2018/09/12
- Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Paolo Bonzini, 2018/09/12
- Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Fam Zheng, 2018/09/13
- Re: [Qemu-devel] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Paolo Bonzini, 2018/09/13
- Re: [Qemu-devel] [Qemu-block] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Paolo Bonzini, 2018/09/13
- Re: [Qemu-devel] [Qemu-block] [PATCH 2/2] virtio-scsi/virtio-blk: Disable poll handlers when stopping vq handler, Alex Williamson, 2018/09/13