Demos (master): sharedtex_mt: fix rendering thread hang

[Brian Paul]

Module: Demos
Branch: master
Commit: 2b304e765695d385fd3bf414e6e444020bedb0a8
URL:    http://cgit.freedesktop.org/mesa/demos/commit/?id=2b304e765695d385fd3bf414e6e444020bedb0a8

Author: Awais Belal <awais_belal at mentor.com>
Date:   Mon Oct 12 07:32:37 2015 -0600

sharedtex_mt: fix rendering thread hang

XNextEvent is a blocking call which locks up the display mutex.  This
causes the rendering threads to hang when they call glXSwapBuffers() as
that tries to take the same mutex in underlying calls through XCopyArea().
So we only call XNextEvent when it has at least one event so we don't lock
indefinitely.

Patch slightly fixed by Brian to keep var declarations as-is and clean up
the patch description.

Signed-off-by: Awais Belal <awais_belal at mentor.com>
Reviewed-by: Brian Paul <brianp at vmware.com>

---

 src/xdemos/sharedtex_mt.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/xdemos/sharedtex_mt.c b/src/xdemos/sharedtex_mt.c
index a90903a..2068d4b 100644
--- a/src/xdemos/sharedtex_mt.c
+++ b/src/xdemos/sharedtex_mt.c
@@ -423,6 +423,13 @@ EventLoop(void)
    while (1) {
       int i;
       XEvent event;
+
+      /* Do we have an event? */
+      if (XPending(gDpy) == 0) {
+         usleep(10000);
+         continue;
+      }
+
       XNextEvent(gDpy, &event);
       for (i = 0; i < NumWindows; i++) {
 	 struct window *h = &Windows[i];