Re: [Qemu-devel] [PATCH v4 6/7] monitor: remove "x-oob", turn oob on by default

[Markus Armbruster <armbru@redhat.com>]

Peter Xu <peterx@redhat.com> writes:

> There was a regression reported by Eric Auger before with OOB:
>
>   http://lists.gnu.org/archive/html/qemu-devel/2018-03/msg06231.html
>
> It is fixed in 951702f39c ("monitor: bind dispatch bh to iohandler
> context", 2018-04-10).
>
> For the bug, we turned Out-Of-Band feature of monitors off for 2.12
> release.  Now we turn that on again after the 2.12 release.

Relating what happened in the order it happened could be easier to
understand.  Perhaps:

  OOB commands were introduced in commit cf869d53172.  Unfortunately, we
  ran into a regression, and had to disable them by default for 2.12
  (commit be933ffc23).

  The regression has since been fixed (commit 951702f39c7 "monitor: bind
  dispatch bh to iohandler context").  Time to re-enable OOB.

> This patch partly reverts be933ffc23 (monitor: new parameter "x-oob"),
> meanwhile turn it on again by default for non-MUX QMPs.  Note that we

"by default"?

> can't enable Out-Of-Band for monitors with MUX-typed chardev backends,
> because not all the chardev frontends can run without main thread, or
> can run in multiple threads.
>
> Some trivial touch-up in the test code is required to make sure qmp-test
> won't broke.

"won't break"

>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  include/monitor/monitor.h |  1 -
>  monitor.c                 | 17 +----------------
>  tests/libqtest.c          |  2 +-
>  tests/qmp-test.c          |  2 +-
>  vl.c                      |  5 -----
>  5 files changed, 3 insertions(+), 24 deletions(-)
>
> diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h
> index d6ab70cae2..0cb0538a31 100644
> --- a/include/monitor/monitor.h
> +++ b/include/monitor/monitor.h
> @@ -13,7 +13,6 @@ extern Monitor *cur_mon;
>  #define MONITOR_USE_READLINE  0x02
>  #define MONITOR_USE_CONTROL   0x04
>  #define MONITOR_USE_PRETTY    0x08
> -#define MONITOR_USE_OOB       0x10
>  
>  bool monitor_cur_is_qmp(void);
>  
> diff --git a/monitor.c b/monitor.c
> index c9a02ee40c..7fbcf84b02 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -4587,19 +4587,7 @@ void monitor_init(Chardev *chr, int flags)
>  {
>      Monitor *mon = g_malloc(sizeof(*mon));
>      bool use_readline = flags & MONITOR_USE_READLINE;
> -    bool use_oob = flags & MONITOR_USE_OOB;
> -
> -    if (use_oob) {
> -        if (CHARDEV_IS_MUX(chr)) {
> -            error_report("Monitor Out-Of-Band is not supported with "
> -                         "MUX typed chardev backend");
> -            exit(1);
> -        }
> -        if (use_readline) {
> -            error_report("Monitor Out-Of-band is only supported by QMP");
> -            exit(1);
> -        }
> -    }
> +    bool use_oob = (flags & MONITOR_USE_CONTROL) && !CHARDEV_IS_MUX(chr);

A comment explaining (briefly!) why MUX prevents oob would be useful
here.  Fortunately, you can simply steal from your commit message.

>  
>      monitor_data_init(mon, false, use_oob);
>  
> @@ -4701,9 +4689,6 @@ QemuOptsList qemu_mon_opts = {
>          },{
>              .name = "pretty",
>              .type = QEMU_OPT_BOOL,
> -        },{
> -            .name = "x-oob",
> -            .type = QEMU_OPT_BOOL,
>          },
>          { /* end of list */ }
>      },
> diff --git a/tests/libqtest.c b/tests/libqtest.c
> index 098af6aec4..c5cb3f925c 100644
> --- a/tests/libqtest.c
> +++ b/tests/libqtest.c
> @@ -213,7 +213,7 @@ QTestState *qtest_init_without_qmp_handshake(bool use_oob,
>                                    "-display none "
>                                    "%s", qemu_binary, socket_path,
>                                    getenv("QTEST_LOG") ? "/dev/fd/2" : "/dev/null",
> -                                  qmp_socket_path, use_oob ? ",x-oob=on" : "",
> +                                  qmp_socket_path, "",
>                                    extra_args ?: "");
>          execlp("/bin/sh", "sh", "-c", command, NULL);
>          exit(1);
> diff --git a/tests/qmp-test.c b/tests/qmp-test.c
> index a49cbc6fde..3747bf7fbb 100644
> --- a/tests/qmp-test.c
> +++ b/tests/qmp-test.c
> @@ -89,7 +89,7 @@ static void test_qmp_protocol(void)
>      g_assert(q);
>      test_version(qdict_get(q, "version"));
>      capabilities = qdict_get_qlist(q, "capabilities");
> -    g_assert(capabilities && qlist_empty(capabilities));
> +    g_assert(capabilities);
>      qobject_unref(resp);
>  
>      /* Test valid command before handshake */
> diff --git a/vl.c b/vl.c
> index 6e34fb348d..26a0bb3f0f 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2307,11 +2307,6 @@ static int mon_init_func(void *opaque, QemuOpts *opts, Error **errp)
>      if (qemu_opt_get_bool(opts, "pretty", 0))
>          flags |= MONITOR_USE_PRETTY;
>  
> -    /* OOB is off by default */
> -    if (qemu_opt_get_bool(opts, "x-oob", 0)) {
> -        flags |= MONITOR_USE_OOB;
> -    }
> -
>      chardev = qemu_opt_get(opts, "chardev");
>      chr = qemu_chr_find(chardev);
>      if (chr == NULL) {

Preferrably with the commit message touched up, and a common on MUX:
Reviewed-by: Markus Armbruster <armbru@redhat.com>