[vlc-commits] wayland/shm: wait for buffers to be released

[Rémi Denis-Courmont]

vlc | branch: master | Rémi Denis-Courmont <remi at remlab.net> | Tue Nov 13 19:51:03 2018 +0200| [adce9a9a1c85beb1f408e9db1df09e4e6c3b8654] | committer: Rémi Denis-Courmont

wayland/shm: wait for buffers to be released

...before destroying them. Otherwise we can no longer keep track of
which picture buffer the display server still references, leading to
potential corruption.

To force the server to release all buffers, we must first detach the
any outstanding buffer from the display surface.

> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=adce9a9a1c85beb1f408e9db1df09e4e6c3b8654
---

 modules/video_output/wayland/shm.c | 52 +++++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 18 deletions(-)

diff --git a/modules/video_output/wayland/shm.c b/modules/video_output/wayland/shm.c
index 590cf78151..c05b5f4be0 100644
--- a/modules/video_output/wayland/shm.c
+++ b/modules/video_output/wayland/shm.c
@@ -72,12 +72,8 @@ static void buffer_release_cb(void *data, struct wl_buffer *buffer)
 {
     picture_t *pic = data;
 
-#ifndef NDEBUG
     assert(pic != NULL);
     wl_buffer_set_user_data(buffer, NULL);
-#else
-    (void) buffer;
-#endif
     picture_Release(pic);
 }
 
@@ -86,19 +82,6 @@ static const struct wl_buffer_listener buffer_cbs =
     buffer_release_cb,
 };
 
-static void PictureDetach(void *data, picture_t *pic)
-{
-    struct wl_buffer *buf = (struct wl_buffer *)pic->p_sys;
-
-    /* Detach the buffer if it is attached */
-    pic = wl_buffer_get_user_data(buf);
-    if (pic != NULL)
-        buffer_release_cb(pic, buf);
-
-    wl_buffer_destroy(buf);
-    (void) data;
-}
-
 static picture_pool_t *Pool(vout_display_t *vd, unsigned req)
 {
     vout_display_sys_t *sys = vd->sys;
@@ -245,14 +228,47 @@ static void Display(vout_display_t *vd, picture_t *pic)
     (void) pic;
 }
 
+static void PictureCheckAttached(void *data, picture_t *pic)
+{
+    unsigned *countp = data;
+
+    (*countp) += wl_buffer_get_user_data(pic->p_sys) != NULL;
+}
+
+static unsigned CountActiveBuffers(picture_pool_t *pool)
+{
+    unsigned count = 0;
+
+    picture_pool_Enum(pool, PictureCheckAttached, &count);
+    return count;
+}
+
+static void PictureBufferDestroy(void *data, picture_t *pic)
+{
+    struct wl_buffer *buf = (struct wl_buffer *)pic->p_sys;
+
+    wl_buffer_destroy(buf);
+    (void) data;
+}
+
 static void ResetPictures(vout_display_t *vd)
 {
     vout_display_sys_t *sys = vd->sys;
+    struct wl_display *display = sys->embed->display.wl;
+    struct wl_surface *surface = sys->embed->handle.wl;
 
     if (sys->pool == NULL)
         return;
 
-    picture_pool_Enum(sys->pool, PictureDetach, NULL);
+    wl_surface_attach(surface, NULL, 0, 0);
+    wl_surface_commit(surface);
+
+    /* Wait until all picture buffers are released by the server */
+    while (CountActiveBuffers(sys->pool) > 0)
+        wl_display_roundtrip_queue(display, sys->eventq);
+
+    /* Destroy the buffers */
+    picture_pool_Enum(sys->pool, PictureBufferDestroy, NULL);
     picture_pool_Release(sys->pool);
     sys->pool = NULL;
 }