On 02/23/2018 05:51 PM, John Snow wrote:
The state transition table has mostly been implied. We're about to make
it a bit more complex, so let's make the STM explicit instead.
Perform state transitions with a function that for now just asserts the
transition is appropriate.
Transitions:
Undefined -> Created: During job initialization.
Unless we use Created as the default state 0 for g_new0().
Created -> Running: Once the job is started.
Jobs cannot transition from "Created" to "Paused"
directly, but will instead synchronously transition
to running to paused immediately.
Running -> Paused: Normal workflow for pauses.
Running -> Ready: Normal workflow for jobs reaching their sync point.
(e.g. mirror)
Ready -> Standby: Normal workflow for pausing ready jobs.
Paused -> Running: Normal resume.
Standby -> Ready: Resume of a Standby job.
+---------+
|UNDEFINED|
+--+------+
|
+--v----+
|CREATED|
+--+----+
|
+--v----+ +------+
|RUNNING<----->PAUSED|
+--+----+ +------+
|
+--v--+ +-------+
|READY<------->STANDBY|
+-----+ +-------+
Notably, there is no state presently defined as of this commit that
deals with a job after the "running" or "ready" states, so this table
will be adjusted alongside the commits that introduce those states.
The ascii-art tables help in this and other patches. Thanks for
producing them.
Signed-off-by: John Snow <js...@redhat.com>
---
block/trace-events | 3 +++
blockjob.c | 42 ++++++++++++++++++++++++++++++++++++------
2 files changed, 39 insertions(+), 6 deletions(-)
+static void block_job_state_transition(BlockJob *job, BlockJobStatus s1)
+{
+ BlockJobStatus s0 = job->status;
+ if (s0 == s1) {
+ return;
+ }
+ assert(s1 >= 0 && s1 <= BLOCK_JOB_STATUS__MAX);
Or, if you keep the zero state distinct from valid states, this could be
'assert(s1 > 0 && ...)'
@@ -320,7 +349,7 @@ void block_job_start(BlockJob *job)
job->pause_count--;
job->busy = true;
job->paused = false;
- job->status = BLOCK_JOB_STATUS_RUNNING;
+ block_job_state_transition(job, BLOCK_JOB_STATUS_RUNNING);
bdrv_coroutine_enter(blk_bs(job->blk), job->co);
}
@@ -704,6 +733,7 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
job->refcnt = 1;
job->manual = (flags & BLOCK_JOB_MANUAL);
job->status = BLOCK_JOB_STATUS_CREATED;
+ block_job_state_transition(job, BLOCK_JOB_STATUS_CREATED);
Oops, missing a deletion of the job->status assignment line.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
