Re: [PATCH v6 09/12] hmp: Add support for coroutine command handlers

[Markus Armbruster]

Kevin Wolf <kwolf@redhat.com> writes:

> Often, QMP command handlers are not only called to handle QMP commands,
> but also from a corresponding HMP command handler. In order to give them
> a consistent environment, optionally run HMP command handlers in a
> coroutine, too.
>
> The implementation is a lot simpler than in QMP because for HMP, we
> still block the VM while the coroutine is running.
>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  monitor/monitor-internal.h |  1 +
>  monitor/hmp.c              | 38 ++++++++++++++++++++++++++++++++------
>  2 files changed, 33 insertions(+), 6 deletions(-)
>
> diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h
> index b55d6df07f..ad2e64be13 100644
> --- a/monitor/monitor-internal.h
> +++ b/monitor/monitor-internal.h
> @@ -74,6 +74,7 @@ typedef struct HMPCommand {
>      const char *help;
>      const char *flags; /* p=preconfig */
>      void (*cmd)(Monitor *mon, const QDict *qdict);
> +    bool coroutine;
>      /*
>       * @sub_table is a list of 2nd level of commands. If it does not exist,
>       * cmd should be used. If it exists, sub_table[?].cmd should be
> diff --git a/monitor/hmp.c b/monitor/hmp.c
> index 3e73a4c3ce..ab0e3e279f 100644
> --- a/monitor/hmp.c
> +++ b/monitor/hmp.c
> @@ -1056,12 +1056,25 @@ fail:
>      return NULL;
>  }
>  
> +typedef struct HandleHmpCommandCo {
> +    Monitor *mon;
> +    const HMPCommand *cmd;
> +    QDict *qdict;
> +    bool done;
> +} HandleHmpCommandCo;
> +
> +static void handle_hmp_command_co(void *opaque)
> +{
> +    HandleHmpCommandCo *data = opaque;
> +    data->cmd->cmd(data->mon, data->qdict);
> +    data->done = true;
> +}
> +
>  void handle_hmp_command(MonitorHMP *mon, const char *cmdline)
>  {
>      QDict *qdict;
>      const HMPCommand *cmd;
>      const char *cmd_start = cmdline;
> -    Monitor *old_mon;
>  
>      trace_handle_hmp_command(mon, cmdline);
>  
> @@ -1080,11 +1093,24 @@ void handle_hmp_command(MonitorHMP *mon, const char 
> *cmdline)
>          return;
>      }
>  
> -    /* old_mon is non-NULL when called from qmp_human_monitor_command() */
> -    old_mon = monitor_cur();
> -    monitor_set_cur(qemu_coroutine_self(), &mon->common);
> -    cmd->cmd(&mon->common, qdict);
> -    monitor_set_cur(qemu_coroutine_self(), old_mon);
> +    if (!cmd->coroutine) {
> +        /* old_mon is non-NULL when called from qmp_human_monitor_command() 
> */
> +        Monitor *old_mon = monitor_cur();
> +        monitor_set_cur(qemu_coroutine_self(), &mon->common);
> +        cmd->cmd(&mon->common, qdict);
> +        monitor_set_cur(qemu_coroutine_self(), old_mon);
> +    } else {
> +        HandleHmpCommandCo data = {
> +            .mon = &mon->common,
> +            .cmd = cmd,
> +            .qdict = qdict,
> +            .done = false,
> +        };
> +        Coroutine *co = qemu_coroutine_create(handle_hmp_command_co, &data);
> +        monitor_set_cur(co, &mon->common);

Where is the matching monitor_set_cur(co, NULL)?

> +        aio_co_enter(qemu_get_aio_context(), co);
> +        AIO_WAIT_WHILE(qemu_get_aio_context(), !data.done);
> +    }
>  
>      qobject_unref(qdict);
>  }