The DRM fd isn't actually non-blocking; use poll to check for events

When going off to try to read the DRM fd for events, make sure there's
something present before actually reading.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

1 files changed, 11 insertions, 2 deletions

diff --git a/src/uxa/intel_display.c b/src/uxa/intel_display.c
index 5c75deb9..e1dc6a84 100644
--- a/src/uxa/intel_display.c
+++ b/src/uxa/intel_display.c
@@ -2096,13 +2096,22 @@ drm_wakeup_handler(pointer data, int err, pointer p)
 }
 
 /*
- * Just try to read drm_events; the fd is non-blocking, so we'll get
- * zero if there aren't any events to read
+ * If there are any available, read drm_events
  */
 int
 intel_mode_read_drm_events(struct intel_screen_private *intel)
 {
         struct intel_mode *mode = intel->modes;
+        struct pollfd p = { .fd = mode->fd, .events = POLLIN };
+        int r;
+
+        do {
+                r = poll(&p, 1, 0);
+        } while (r == -1 && (errno == EINTR || errno == EAGAIN));
+
+        if (r <= 0)
+                return 0;
+
         return drmHandleEvent(mode->fd, &mode->event_context);
 }