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

[Laurent Vivier]

On 06/12/2019 20:52, Dr. David Alan Gilbert wrote:
> * Laurent Vivier (address@hidden) 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 <address@hidden>
> 

Who volunteers to take this in his queue?

Thanks,
Laurent