On 03/12/2018 08:05 PM, John Snow wrote:
>
>
> On 03/09/2018 08:19 AM, Stefan Hajnoczi wrote:
>> Commit 00d09fdbbae5f7864ce754913efc84c12fdf9f1a ("vl: pause vcpus before
>> stopping iothreads") and commit dce8921b2baaf95974af8176406881872067adfa
>> ("iothread: Stop threads before main() quits") tried to work around the
>> fact that emulation was still active during termination by stopping
>> iothreads. They suffer from race conditions:
>> 1. virtio_scsi_handle_cmd_vq() racing with iothread_stop_all() hits the
>> virtio_scsi_ctx_check() assertion failure because the BDS AioContext
>> has been modified by iothread_stop_all().
>> 2. Guest vq kick racing with main loop termination leaves a readable
>> ioeventfd that is handled by the next aio_poll() when external
>> clients are enabled again, resulting in unwanted emulation activity.
>>
>> This patch obsoletes those commits by fully disabling emulation activity
>> when vcpus are stopped.
>>
>> Use the new vm_shutdown() function instead of pause_all_vcpus() so that
>> vm change state handlers are invoked too. Virtio devices will now stop
>> their ioeventfds, preventing further emulation activity after vm_stop().
>>
>> Note that vm_stop(RUN_STATE_SHUTDOWN) cannot be used because it emits a
>> QMP STOP event that may affect existing clients.
>>
>> It is no longer necessary to call replay_disable_events() directly since
>> vm_shutdown() does so already.
>>
>> Drop iothread_stop_all() since it is no longer used.
>>
>> Cc: Fam Zheng <[email protected]>
>> Cc: Kevin Wolf <[email protected]>
>> Signed-off-by: Stefan Hajnoczi <[email protected]>
>> Reviewed-by: Fam Zheng <[email protected]>
>> Acked-by: Paolo Bonzini <[email protected]>
>> Message-id: [email protected]
>> Signed-off-by: Stefan Hajnoczi <[email protected]>
Stefan, I see the same iotest regression that was reported by John Snow also
on s390. I can confirm that it works with this patch reverted.
Christian
