Re: [Qemu-devel] [PATCH 16/32] tests/qmp-test: Demonstrate QMP errors jumping the queue

[Eric Blake]

On 07/02/2018 11:22 AM, Markus Armbruster wrote:
> When OOB is enabled, out-of-band commands are executed right away,
> everything else is queued.  This lets out-of-band commands "jump the
> queue".
>
> However, certain errors are always reported right away, and therefore
> can jump the queue even when the erroneous input does not request
> out-of-band execution.  These errors are pretty unlikely to occur in
> production, but it's wrong all the same.  Mark FIXME.

Ouch.

> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>   monitor.c        | 1 +
>   tests/qmp-test.c | 7 +++++++
>   2 files changed, 8 insertions(+)

> +++ b/tests/qmp-test.c
> @@ -239,6 +239,13 @@ static void test_qmp_oob(void)
>       unblock_blocked_cmd();
>       recv_cmd_id(qts, "ib-blocks-1");
>       recv_cmd_id(qts, "ib-quick-1");
> +
> +    /* FIXME certain in-band errors overtake slow in-band command */
> +    send_cmd_that_blocks(qts, "blocks-2");
> +    qtest_async_qmp(qts, "{ 'id': 'err-2' }");

Since this has neither 'execute' nor 'exec-oob', we can't state whether 
it is in-band or out-of-band; back-compatibility says it should be 
treated as in-band.

> +    recv_cmd_id(qts, NULL);
> +    unblock_blocked_cmd();
> +    recv_cmd_id(qts, "blocks-2");

Thus, it should have been queued until after blocks-2 completed.

Useful test.
Reviewed-by: Eric Blake <address@hidden>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org