uxa: Drain the DRM event queue before server regeneration

Adam Jackson notes that what appeared to be my paranoid ramblings in SNA
actually served a purpose - it prevents a server crash following
server regen if an indirect client happened to be running at the time
(e.g. LIBGL_INDIRECT_ALWAYS=1 glxgears).

Reported-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/intel.h

@@ -366,6 +366,7 @@ extern Bool intel_mode_pre_init(ScrnInfoPtr pScrn, int fd, int cpp);
 extern void intel_mode_init(struct intel_screen_private *intel);
 extern void intel_mode_disable_unused_functions(ScrnInfoPtr scrn);
 extern void intel_mode_remove_fb(intel_screen_private *intel);
+extern void intel_mode_close(intel_screen_private *intel);
 extern void intel_mode_fini(intel_screen_private *intel);
 
 extern int intel_get_pipe_from_crtc_id(drm_intel_bufmgr *bufmgr, xf86CrtcPtr crtc);

src/intel_display.c

@@ -31,6 +31,7 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/poll.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
@@ -1830,6 +1831,26 @@ intel_mode_remove_fb(intel_screen_private *intel)
 	}
 }
 
+static Bool has_pending_events(int fd)
+{
+	struct pollfd pfd;
+	pfd.fd = fd;
+	pfd.events = POLLIN;
+	return poll(&pfd, 1, 0) == 1;
+}
+
+void
+intel_mode_close(intel_screen_private *intel)
+{
+	struct intel_mode *mode = intel->modes;
+
+	if (mode == NULL)
+		return;
+
+	while (has_pending_events(mode->fd))
+		drmHandleEvent(mode->fd, &mode->event_context);
+}
+
 void
 intel_mode_fini(intel_screen_private *intel)
 {

src/intel_driver.c

@@ -1139,6 +1139,8 @@ static Bool I830CloseScreen(CLOSE_SCREEN_ARGS_DECL)
 	I830UeventFini(scrn);
 #endif
 
+	intel_mode_close(intel);
+
 	DeleteCallback(&FlushCallback, intel_flush_callback, scrn);
 
 	intel_glamor_close_screen(screen);