From af023d7c95c3246e02791de14bf31f33a30072eb Mon Sep 17 00:00:00 2001
From: Matthew Waters <matthew@centricular.com>
Date: Fri, 20 Feb 2015 18:42:23 +1100
Subject: [PATCH] glememory: only store and act on the map flags on first/last
 map/unmap

Anytime else, we have no idea how to match up map and unmaps.
We also don't know exactly how the calling code is using us.
Also fixes the case where we're trying to transfer while someone else
is accessing our data pointer or texture resulting in mismatched video
frames.

https://bugzilla.gnome.org/show_bug.cgi?id=744839
---
 gst-libs/gst/gl/gstglmemory.c | 12 ++++++++----
 gst-libs/gst/gl/gstglmemory.h |  1 +
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/gst-libs/gst/gl/gstglmemory.c b/gst-libs/gst/gl/gstglmemory.c
index a4dbb5c76e..e9e77915cd 100644
--- a/gst-libs/gst/gl/gstglmemory.c
+++ b/gst-libs/gst/gl/gstglmemory.c
@@ -859,7 +859,9 @@ _gl_mem_map (GstGLMemory * gl_mem, gsize maxsize, GstMapFlags flags)
     data = gl_mem->data;
   }
 
-  gl_mem->map_flags = flags;
+  /* only store the first map flags, subsequent maps must be a subset of this */
+  if (gl_mem->map_count++ == 0)
+    gl_mem->map_flags = flags;
 
   g_mutex_unlock (&gl_mem->lock);
 
@@ -882,13 +884,15 @@ _gl_mem_unmap (GstGLMemory * gl_mem)
 {
   g_mutex_lock (&gl_mem->lock);
 
-  if (gl_mem->map_flags & GST_MAP_WRITE) {
-    if (!(gl_mem->map_flags & GST_MAP_GL))
+  if (gl_mem->map_count <= 1 && gl_mem->map_flags & GST_MAP_WRITE) {
+    if (!(gl_mem->map_flags & GST_MAP_GL)) {
       gst_gl_context_thread_add (gl_mem->context,
           (GstGLContextThreadFunc) _transfer_upload, gl_mem);
+    }
   }
 
-  gl_mem->map_flags = 0;
+  if (--gl_mem->map_count <= 0)
+    gl_mem->map_flags = 0;
 
   g_mutex_unlock (&gl_mem->lock);
 }
diff --git a/gst-libs/gst/gl/gstglmemory.h b/gst-libs/gst/gl/gstglmemory.h
index 7dad0aa2a9..ec23577551 100644
--- a/gst-libs/gst/gl/gstglmemory.h
+++ b/gst-libs/gst/gl/gstglmemory.h
@@ -103,6 +103,7 @@ struct _GstGLMemory
   guint                 tex_width;
   guint                 transfer_pbo;
   GstMapFlags           map_flags;
+  guint                 map_count;
 
   GMutex                lock;
 };