Re: [Qemu-devel] [RFC v4 15/27] monitor: let monitor_{suspend|resume} thread safe

[Dr. David Alan Gilbert]

* Peter Xu (address@hidden) wrote:
> Monitor code now can be run in more than one thread.  Let the suspend
> and resume code be thread safe.
> 
> Reviewed-by: Fam Zheng <address@hidden>
> Signed-off-by: Peter Xu <address@hidden>
> ---
>  monitor.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/monitor.c b/monitor.c
> index ec03f1b232..30f9cd80de 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -4003,7 +4003,7 @@ int monitor_suspend(Monitor *mon)
>  {
>      if (!mon->rs)
>          return -ENOTTY;
> -    mon->suspend_cnt++;
> +    atomic_inc(&mon->suspend_cnt);
>      return 0;
>  }
>  
> @@ -4011,8 +4011,9 @@ void monitor_resume(Monitor *mon)
>  {
>      if (!mon->rs)
>          return;
> -    if (--mon->suspend_cnt == 0)
> +    if (atomic_dec_fetch(&mon->suspend_cnt) == 0) {
>          readline_show_prompt(mon->rs);
> +    }
>  }
>  
>  static QObject *get_qmp_greeting(void)

Do you also need to do an atomic_read() in monitor_can_read?
(I guess the code in monitor_event is ok because it's only the mux
path, but still it's probably better to use all atomic ops on
the suspend_cnt variable to be consistent).

Dave

> -- 
> 2.13.6
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK