On Mon, Nov 06, 2017 at 05:46:43PM +0800, Peter Xu wrote:
> +    /*
> +     * Try a time-consuming command, following by a OOB command, make
> +     * sure we get OOB command before the time-consuming one (which is
> +     * run in the parser).
> +     *
> +     * When writting up this test script, the only command that
> +     * support OOB is migrate-incoming.  It's not the best command to
> +     * test OOB but we don't really have a choice here.  We will check
> +     * arriving order but not command errors, which does not really
> +     * matter to us.
> +     */
> +    qmp_async("{ 'execute': 'dump-guest-memory',"
> +              "  'arguments': { 'paging': true, "
> +              "                 'protocol': 'file:/dev/null' }, "
> +              "  'id': 'time-consuming-cmd'}");
> +    qmp_async("{ 'execute': 'migrate-incoming', "
> +              "  'control': { 'run-oob': true }, "
> +              "  'id': 'oob-cmd' }");
> +
> +    /* Ignore all events.  Wait for 2 acks */
> +    while (acks < 2) {
> +        resp = qmp_receive();
> +        if (qdict_haskey(resp, "event")) {
> +            /* Skip possible events */
> +            continue;
> +        }
> +        cmd_id = qdict_get_str(resp, "id");
> +        if (acks == 0) {
> +            /* Need to receive OOB response first */
> +            g_assert_cmpstr(cmd_id, ==, "oob-cmd");
> +        } else if (acks == 1) {
> +            g_assert_cmpstr(cmd_id, ==, "time-consuming-cmd");
> +        }
> +        acks++;
> +    }

This test is non-deterministic.  The dump-guest-memory command could
complete first on a fast machine.

On a slow machine this test might take a long time...

Please introduce a test command that is deterministic.  For example,
when 'x-oob-test' is invoked without 'run-oob': true it waits until
invoked again, this time with 'run-oob': true.

We have similar interfaces in the block layer for controlling the order
in which parallel I/O requests are processed.  This allows test cases to
deterministically take specific code paths.