[PATCH xserver] Xi: Hold the input lock when sending events

[Peter Hutterer]

On Wed, Feb 22, 2017 at 10:48:24AM +0100, Olivier Fourdan wrote:
> Otherwise the output buffer will be accessed from different threads and
> cause all sorts of nasty and painful memory corruptions.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99164
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99887
> Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
> ---
>  Xi/xiproperty.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Xi/xiproperty.c b/Xi/xiproperty.c
> index b7a1f59..a68b4b3 100644
> --- a/Xi/xiproperty.c
> +++ b/Xi/xiproperty.c
> @@ -203,10 +203,12 @@ send_property_event(DeviceIntPtr dev, Atom property, int what)
>          .what = what
>      };
>  
> +    input_lock();
>      SendEventToAllWindows(dev, DevicePropertyNotifyMask, (xEvent *) &event, 1);
>  
>      SendEventToAllWindows(dev, GetEventFilter(dev, (xEvent *) &xi2),
>                            (xEvent *) &xi2, 1);
> +    input_unlock();

I don't think that's correct. The input thread is for event *generation*,
not processing events which is still done in the event queue. It replaces
the old sigio handler. 

I don't think anything gets here from within the input thread, does it? If
so, that's the bug to fix.

Cheers,
   Peter

>  }
>  
>  static int
> -- 
> 2.9.3