Re: [Qemu-devel] [RFC v4 09/27] monitor: create monitor dedicate iothread

[Dr. David Alan Gilbert]

* Peter Xu (address@hidden) wrote:
> Create one IOThread for the monitors, prepared to handle all the
> input/output IOs using existing iothread framework.
> 
> Signed-off-by: Peter Xu <address@hidden>
> ---
>  monitor.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/monitor.c b/monitor.c
> index a70ab5606b..4ce9828fab 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -76,6 +76,7 @@
>  #include "qmp-introspect.h"
>  #include "sysemu/qtest.h"
>  #include "sysemu/cpus.h"
> +#include "sysemu/iothread.h"
>  #include "qemu/cutils.h"
>  #include "qapi/qmp/dispatch.h"
>  
> @@ -208,6 +209,12 @@ struct Monitor {
>      QTAILQ_ENTRY(Monitor) entry;
>  };
>  
> +struct MonitorGlobal {
> +    IOThread *mon_iothread;
> +};
> +
> +static struct MonitorGlobal mon_global;
> +
>  /* QMP checker flags */
>  #define QMP_ACCEPT_UNKNOWNS 1
>  
> @@ -4034,12 +4041,24 @@ static void sortcmdlist(void)
>      qsort((void *)info_cmds, array_num, elem_size, compare_mon_cmd);
>  }
>  
> +static GMainContext *monitor_io_context_get(void)
> +{
> +    return iothread_get_g_main_context(mon_global.mon_iothread);
> +}
> +
> +static void monitor_iothread_init(void)
> +{
> +    mon_global.mon_iothread = iothread_create("monitor_iothread",
> +                                              &error_abort);

That name is one character too long for pthread_setname_np that it
ends up being passed too (it's 16 char including the terminator);
that probably means the thread ends up unnamed.  I suggest
you make it "mon_iothread"

> +}
> +
>  void monitor_init_globals(void)
>  {
>      monitor_init_qmp_commands();
>      monitor_qapi_event_init();
>      sortcmdlist();
>      qemu_mutex_init(&monitor_lock);
> +    monitor_iothread_init();
>  }
>  
>  /* These functions just adapt the readline interface in a typesafe way.  We
> @@ -4117,6 +4136,13 @@ 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.

I wonder if that bug is still live?   2b316774f6 says that:
   'glib developers found and fixed the deadlock as part of implementing
child sources.'
   but doesn't say which glib version that was fixed in; we have
increased the minimum glib version we support since 2013, so maybe...

Dave

> +     */
> +    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 +4150,9 @@ 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 = {
> -- 
> 2.13.6
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK