[PATCH glx] glx: avoid memory leak when using indirect rendering

[Guilherme Quentel Melo]

When multiple processes are using GL with indirect rendering a race
condition can make drawables refcount never drop to zero.

Signed-off-by: Guilherme Quentel Melo <gqmelo at gmail.com>
---
 glx/glxext.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/glx/glxext.c b/glx/glxext.c
index e41b881..16b8039 100644
--- a/glx/glxext.c
+++ b/glx/glxext.c
@@ -469,6 +469,24 @@ __glXForceCurrent(__GLXclientState * cl, GLXContextTag tag, int *error)
 
     /* Make this context the current one for the GL. */
     if (!cx->isDirect) {
+        /*
+         ** If we are forcing the context it means someone already called makeCurrent before. If
+         ** we just call makeCurrent again, the drawable of this context will be left with one
+         ** refcount more forever and will never be freed.
+         **
+         ** This situation happens when there are many X clients using GL:
+         **
+         ** 1 - client1: calls glXMakeCurrent
+         **
+         ** 2 - client2: calls glXMakeCurrent
+         **     This is the first context switch for this client. So old_context_tag=0
+         **
+         ** 3 - client1: calls glXRender
+         **     For the client, its context is already current.
+         **     For the server side lastGLContext points to client2's context. So the execution path
+         **     will get here.
+         */
+        (*cx->loseCurrent) (cx);
         lastGLContext = cx;
         if (!(*cx->makeCurrent) (cx)) {
             /* Bind failed, and set the error code.  Bummer */
-- 
2.5.0