Re: [Qemu-devel] [RFC v5 09/26] monitor: create monitor dedicate iothread

[Stefan Hajnoczi]

On Tue, Dec 05, 2017 at 01:51:43PM +0800, Peter Xu wrote:
> @@ -208,6 +209,12 @@ struct Monitor {
>      QTAILQ_ENTRY(Monitor) entry;
>  };
>  
> +struct MonitorGlobal {
> +    IOThread *mon_iothread;
> +};
> +
> +static struct MonitorGlobal mon_global;

structs can be anonymous.  That avoids the QEMU coding style violation
(structs must be typedefed):

  static struct {
      IOThread *mon_iothread;
  } mon_global;

In general global variables are usually top-level variables in QEMU.
I'm not sure why wrapping globals in a struct is useful.

> @@ -4117,6 +4136,16 @@ void monitor_cleanup(void)
>  {
>      Monitor *mon, *next;
>  
> +    /*
> +     * We need to explicitly stop the iothread (but not destroy it),
> +     * cleanup the monitor resources, then destroy the iothread.  See
> +     * again on the glib bug mentioned in 2b316774f6 for a reason.
> +     *
> +     * TODO: the bug is fixed in glib 2.28, so we can remove this hack
> +     * as long as we won't support glib versions older than it.
> +     */

I find this comment confusing.  There is no GSource .finalize() in
monitor.c so why does monitor_cleanup() need to work around the bug?

I see that monitor_data_destroy() is not thread-safe so the IOThread
must be stopped first.  That is unrelated to glib.

> +    iothread_stop(mon_global.mon_iothread);
> +
>      qemu_mutex_lock(&monitor_lock);
>      QTAILQ_FOREACH_SAFE(mon, &mon_list, entry, next) {
>          QTAILQ_REMOVE(&mon_list, mon, entry);
> @@ -4124,6 +4153,9 @@ void monitor_cleanup(void)
>          g_free(mon);
>      }
>      qemu_mutex_unlock(&monitor_lock);
> +
> +    iothread_destroy(mon_global.mon_iothread);
> +    mon_global.mon_iothread = NULL;
>  }
>  
>  QemuOptsList qemu_mon_opts = {
> -- 
> 2.14.3
>

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