[vlc-devel] [PATCH 5/7] win32/window: simplify using semaphore

[Steve Lhomme]

On 2020-02-03 22:13, Rémi Denis-Courmont wrote:
> ---
>   modules/video_output/win32/window.c | 22 ++++++----------------
>   1 file changed, 6 insertions(+), 16 deletions(-)
> 
> diff --git a/modules/video_output/win32/window.c b/modules/video_output/win32/window.c
> index 3dc9cf32d2..00965f61fa 100644
> --- a/modules/video_output/win32/window.c
> +++ b/modules/video_output/win32/window.c
> @@ -50,8 +50,7 @@ typedef struct vout_window_sys_t
>   {
>       vlc_thread_t thread;
>       vlc_mutex_t  lock;
> -    vlc_cond_t   wait;
> -    bool         b_ready;
> +    vlc_sem_t    ready;
>   
>       HWND hwnd;
>   
> @@ -486,8 +485,8 @@ static void Close(vout_window_t *wnd)
>           PostMessage( sys->hwnd, WM_CLOSE, 0, 0 );
>   
>       vlc_join(sys->thread, NULL);
> +    vlc_sem_destroy( &sys->ready );
>       vlc_mutex_destroy( &sys->lock );
> -    vlc_cond_destroy( &sys->wait );
>   
>       if (sys->hwnd)
>           DestroyWindow( sys->hwnd );
> @@ -637,10 +636,7 @@ static void *EventThread( void *p_this )
>                       hInstance,            /* handle of this program instance */
>                       wnd );                           /* send vd to WM_CREATE */
>   
> -    vlc_mutex_lock( &sys->lock );
> -    sys->b_ready = true;
> -    vlc_cond_signal( &sys->wait );
> -    vlc_mutex_unlock( &sys->lock );
> +    vlc_sem_post( &sys->ready );
>   
>       if (sys->hwnd == NULL)
>       {
> @@ -738,8 +734,7 @@ static int Open(vout_window_t *wnd)
>           return VLC_EGENERIC;
>       }
>       vlc_mutex_init( &sys->lock );
> -    vlc_cond_init( &sys->wait );
> -    sys->b_ready = false;
> +    vlc_sem_init( &sys->ready, 0 );
>   
>       wnd->sys = sys;
>       if( vlc_clone( &sys->thread, EventThread, wnd, VLC_THREAD_PRIORITY_LOW ) )
> @@ -748,18 +743,13 @@ static int Open(vout_window_t *wnd)
>           return VLC_EGENERIC;
>       }
>   
> -    vlc_mutex_lock( &sys->lock );
> -    while( !sys->b_ready )
> -    {
> -        vlc_cond_wait( &sys->wait, &sys->lock );
> -    }
> +    vlc_sem_wait( &sys->ready );

Is this cancelable as it used to be ? If not we may end up in a state in 
which we can never leave the Open code.

Isn't a semaphore heavier to handle than a condition variable ?

> +
>       if (sys->hwnd == NULL)
>       {
> -        vlc_mutex_unlock( &sys->lock );
>           Close(wnd);
>           return VLC_EGENERIC;
>       }
> -    vlc_mutex_unlock( &sys->lock );
>   
>       wnd->sys = sys;
>       wnd->type = VOUT_WINDOW_TYPE_HWND;
> -- 
> 2.25.0
> 
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