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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <20170804175011.21944-1-dgilbert@redhat.com> (David Alan
	Gilbert's message of "Fri, 4 Aug 2017 18:50:11 +0100")
References: <20170804175011.21944-1-dgilbert@redhat.com>
Reply-To: quintela@redhat.com
Date: Tue, 08 Aug 2017 09:02:54 +0200
Message-ID: <874ltiee3l.fsf@secure.mitica>
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Subject: Re: [Qemu-devel] [PATCH f0r 2.11] runstate/migrate: Two more
 transitions
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To: "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>
Cc: qemu-devel@nongnu.org, peterx@redhat.com, lvivier@redhat.com, pbonzini@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.