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

[Juan Quintela <quintela@redhat.com>]

"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> 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 <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

To answer Peter question:

int vm_stop(RunState state)
{
    .... we don't care about this case ....

    return do_vm_stop(state);
}

static int do_vm_stop(RunState state)
{
    int ret = 0;

    if (runstate_is_running()) {
        cpu_disable_ticks();
        pause_all_vcpus();
        runstate_set(state);
        vm_state_notify(0, state);
        qapi_event_send_stop(&error_abort);
    }

    bdrv_drain_all();
    replay_disable_events();
    ret = bdrv_flush_all();

    return ret;
}


int runstate_is_running(void)
{
    return runstate_check(RUN_STATE_RUNNING);
}


So, "stop" only changes states when we are in RUNNING state.
The idea was that after migration, the only valid command (as in the
film "it should do something")is "run".

Later, Juan.