EXA: Make Prepare/FinishAccess tracking resilient to repeated / nested calls.

Use reference counting and do nothing unless the reference count transitions
to/from 0.

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=22822 .

As a bonus, this avoids calling the driver Prepare/FinishAccess hooks more than
once per pixmap and operation.

Also update the Doxygen documentation for the PrepareAccess driver hook to
better match current reality.

1 files changed, 5 insertions, 2 deletions

diff --git a/exa/exa_priv.h b/exa/exa_priv.h
index b3df1a586..f67a9cbd8 100644
--- a/exa/exa_priv.h
+++ b/exa/exa_priv.h
@@ -176,8 +176,11 @@ typedef struct {
     CARD32			 lastDefragment;
     CARD32			 nextDefragment;
 
-    /* Store all accessed pixmaps, so we can check for duplicates. */
-    PixmapPtr prepare_access[6];
+    /* Reference counting for accessed pixmaps */
+    struct {
+	PixmapPtr pixmap;
+	int count;
+    } access[EXA_NUM_PREPARE_INDICES];
 
     /* Holds information on fallbacks that cannot be relayed otherwise. */
     unsigned int fallback_flags;