sna: Do not rely on udev_monitor_receive_device() being non-blocking

The libudev documentation says that is it non-blocking by default, but
experience shows otherwise.

Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/src/sna/sna_display.c b/src/sna/sna_display.c
index 231fc68..5187515 100644 (file)
--- a/src/sna/sna_display.c
+++ b/src/sna/sna_display.c
@@ -189,14 +189,19 @@ static inline struct sna_crtc *to_sna_crtc(xf86CrtcPtr crtc)
        return crtc->driver_private;
 }
 
-static bool sna_mode_has_pending_events(struct sna *sna)
+static inline bool event_pending(int fd)
 {
        struct pollfd pfd;
-       pfd.fd = sna->kgem.fd;
+       pfd.fd = fd;
        pfd.events = POLLIN;
        return poll(&pfd, 1, 0) == 1;
 }
 
+static bool sna_mode_has_pending_events(struct sna *sna)
+{
+       return event_pending(sna->kgem.fd);
+}
+
 static bool sna_mode_wait_for_event(struct sna *sna)
 {
        struct pollfd pfd;
@@ -411,17 +416,19 @@ sna_backlight_uevent(int fd, void *closure)
        DBG(("%s()\n", __FUNCTION__));
 
        /* Drain the event queue */
-       do {
+       while (event_pending(fd)) {
                struct udev_device *dev;
 
+               DBG(("%s: waiting for uevent\n", __FUNCTION__));
                dev = udev_monitor_receive_device(sna->mode.backlight_monitor);
                if (dev == NULL)
                        break;
 
                udev_device_unref(dev);
-       } while (1);
+       }
 
        /* Query all backlights for any changes */
+       DBG(("%s: probing backlights for changes\n", __FUNCTION__));
        for (i = 0; i < sna->mode.num_real_output; i++) {
                xf86OutputPtr output = config->output[i];
                struct sna_output *sna_output = to_sna_output(output);