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Re: [Qemu-devel] [PATCH f0r 2.11] runstate/migrate: Two more transitions


From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH f0r 2.11] runstate/migrate: Two more transitions
Date: Sat, 9 Sep 2017 15:57:41 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

On 06/09/2017 15:40, Dr. David Alan Gilbert wrote:
>> There's a race if someone does a 'stop' near the end of migrate;
>> the migration process goes through two runstates:
>>     'finish migrate'
>>     'postmigrate'
>>
>> If the user issues a 'stop' between the two we end up with invalid
>> state transitions.
>> Add the transitions as valid.
>>
>> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> Queued
> 
>> ---
>>  vl.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/vl.c b/vl.c
>> index 99fcfa0442..bacb03f49d 100644
>> --- a/vl.c
>> +++ b/vl.c
>> @@ -621,6 +621,7 @@ static const RunStateTransition 
>> runstate_transitions_def[] = {
>>  
>>      { RUN_STATE_PAUSED, RUN_STATE_RUNNING },
>>      { RUN_STATE_PAUSED, RUN_STATE_FINISH_MIGRATE },
>> +    { RUN_STATE_PAUSED, RUN_STATE_POSTMIGRATE },

There is:

    if (s->state == MIGRATION_STATUS_COMPLETED) {
        ...
        runstate_set(RUN_STATE_POSTMIGRATE);
    } else {
        ...
        if (old_vm_running && !entered_postcopy) {
            vm_start();
        } else {
            if (runstate_check(RUN_STATE_FINISH_MIGRATE)) {
                runstate_set(RUN_STATE_POSTMIGRATE);
            }
        }
    }

Maybe the runstate_check should be in the "then" branch too, instead
of adding this transition?

Paolo

>>      { RUN_STATE_PAUSED, RUN_STATE_PRELAUNCH },
>>      { RUN_STATE_PAUSED, RUN_STATE_COLO},
>>  
>> @@ -633,6 +634,7 @@ static const RunStateTransition 
>> runstate_transitions_def[] = {
>>      { RUN_STATE_PRELAUNCH, RUN_STATE_INMIGRATE },
>>  
>>      { RUN_STATE_FINISH_MIGRATE, RUN_STATE_RUNNING },
>> +    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_PAUSED },
>>      { RUN_STATE_FINISH_MIGRATE, RUN_STATE_POSTMIGRATE },
>>      { RUN_STATE_FINISH_MIGRATE, RUN_STATE_PRELAUNCH },
>>      { RUN_STATE_FINISH_MIGRATE, RUN_STATE_COLO},
>> -- 
>> 2.13.3
>>
>>




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