blockjobs: add NULL state
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. Alongside this state, add a new helper command "block_job_decommission", which transitions to the NULL state and puts down our implicit reference. This separates instances in the code for "block_job_unref" which merely undo a matching "block_job_ref" with instances intended to initiate the full destruction of the object. This decommission action also sets a number of fields to make sure that block internals or external users that are holding a reference to a job to see when it "finishes" are convinced that the job object is "done." This is necessary, for instance, to do a block_job_cancel_sync on a created object which will not make any progress. Now, all jobs must go through block_job_decommission prior to being freed, giving us start-to-finish state machine coverage for jobs. 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: NJohn Snow <jsnow@redhat.com> Signed-off-by: NKevin Wolf <kwolf@redhat.com>
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