Re: [PATCH] runstate: ignore finishmigrate -> prelaunch transition

[Laurent Vivier <lvivier@redhat.com>]

Ping?

Thanks,
Laurent

On 12/12/2019 20:40, Laurent Vivier wrote:
> On 06/12/2019 20:52, Dr. David Alan Gilbert wrote:
>> * Laurent Vivier (lvivier@redhat.com) wrote:
>>> Commit 1bd71dce4bf2 tries to prevent a finishmigrate -> prelaunch
>>> transition by exiting at the beginning of the main_loop_should_exit()
>>> function if the state is already finishmigrate.
>>>
>>> As the finishmigrate state is set in the migration thread it can
>>> happen concurrently to the function. The migration thread and the
>>> function are normally protected by the iothread mutex and thus the
>>> state should no evolve between the start of the function and its end.
>>>
>>> Unfortunately during the function life the lock is released by
>>> pause_all_vcpus() just before the point we need to be sure we are
>>> not in finishmigrate state and if the migration thread is waiting
>>> for the lock it will take the opportunity to change the state
>>> to finishmigrate.
>>
>> Ewww.
>> I hate those short wakeups for pause_all_vcpus; I'm sure there are loads
>> more corners that break.
>>
>> Still, I _think_ this is an improvement, so:
>>
>> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>
> 
> Who volunteers to take this in his queue?
> 
> Thanks,
> Laurent
> 
>