Re: [Qemu-block] [Qemu-devel] [RFC v4 10/21] blockjobs: add NULL state

[John Snow]

On 02/28/2018 10:42 AM, Kevin Wolf wrote:
> Am 24.02.2018 um 00:51 hat John Snow geschrieben:
>> Add a new state that specifically demarcates when we begin to permanently
>> demolish a job after it has performed all work. This makes the transition
>> explicit in the STM table and highlights conditions under which a job may
>> be demolished.
>>
>>
>> Transitions:
>> Created   -> Null: Early failure event before the job is started
>> Concluded -> Null: Standard transition.
>>
>> Verbs:
>> None. This should not ever be visible to the monitor.
>>
>>  +-+
>>  |UNDEFINED|
>>  +--+--+
>> |
>>  +--v+
>>  |CREATED+--+
>>  +--++  |
>> |   |
>>  +--v+ +--+ |
>>+-+RUNNING<->PAUSED| |
>>| +--+-+--+ +--+ |
>>|| | |
>>|| +--+  |
>>|||  |
>>| +--v--+   +---+ |  |
>>+-+READY<--->STANDBY| |  |
>>| +--+--+   +---+ |  |
>>|||  |
>> +--v-+   +--v--+ |  |
>> |ABORTING+--->CONCLUDED<-+  |
>> ++   +--+--+|
>> |   |
>>  +--v-+ |
>>  |NULL<-+
>>  ++
>>
>> Signed-off-by: John Snow 
> 
> The commit message does not match the code:
> 
>> @@ -423,6 +424,7 @@ static void block_job_completed_single(BlockJob *job)
>>  QLIST_REMOVE(job, txn_list);
>>  block_job_txn_unref(job->txn);
>>  block_job_event_concluded(job);
>> +block_job_state_transition(job, BLOCK_JOB_STATUS_NULL);
>>  block_job_unref(job);
>>  }
>>  
>> @@ -734,9 +736,6 @@ static void block_job_event_completed(BlockJob *job, 
>> const char *msg)
>>  
>>  static void block_job_event_concluded(BlockJob *job)
>>  {
>> -if (block_job_is_internal(job) || !job->manual) {
>> -return;
>> -}
>>  block_job_state_transition(job, BLOCK_JOB_STATUS_CONCLUDED);
>>  }
> 
> Any job that transition to NULL goes first through CONCLUDED. There is
> no way to reach NULL directly from CREATED.
> 

Ah, that's true... I was trying to think of the case in which we do an
early uninit, but actually we just dismantle the job without having it
go to "null" first. I guess I found that edge case and then never did
anything about it except acknowledge it in the graph.

Something to fix...

> The second hunk addresses my comment in the previous patch, so it should
> probably be squashed in there.
> 
> Kevin
> 

Re: [Qemu-block] [Qemu-devel] [RFC v4 10/21] blockjobs: add NULL state

[Eric Blake]

On 02/23/2018 05:51 PM, John Snow wrote:

Add a new state that specifically demarcates when we begin to permanently
demolish a job after it has performed all work. This makes the transition
explicit in the STM table and highlights conditions under which a job may
be demolished.



Reviewed-by: Eric Blake 

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.   +1-919-301-3266
Virtualization:  qemu.org | libvirt.org