--- systemd-213.old/src/udev/udevd.c	2014-06-06 01:09:22.464595897 -0400
+++ systemd-213.new/src/udev/udevd.c	2014-06-06 01:18:04.499589005 -0400
@@ -297,13 +297,30 @@ static void worker_new(struct event *eve
                                         d = udev_device_get_parent(d);
 
                                 if (d) {
-                                        fd_lock = open(udev_device_get_devnode(d), O_RDONLY|O_CLOEXEC|O_NOFOLLOW|O_NONBLOCK);
-                                        if (fd_lock >= 0 && flock(fd_lock, LOCK_SH|LOCK_NB) < 0) {
-                                                log_debug("Unable to flock(%s), skipping event handling: %m", udev_device_get_devnode(d));
-                                                err = -EWOULDBLOCK;
-                                                fd_lock = safe_close(fd_lock);
-                                                goto skip;
+                                        /*
+                                         * to accommodate cases where other prcoesses may already hold an
+                                         * incompatible flock (LOCK_EX), allow up to approximately 8 seconds
+                                         * (in 250 ms increments) to acquire an flock
+                                         */
+                                        int fl_err, fl_tries = 32, fl_try_us = 250000;
+                                        if ((fd_lock=open(udev_device_get_devnode(d),
+                                             O_RDONLY|O_CLOEXEC|O_NOFOLLOW|O_NONBLOCK)) >= 0) {
+
+                                                while ((fl_err=flock(fd_lock, LOCK_SH|LOCK_NB)) && --fl_tries) {
+                                                        log_debug("Unable to flock(%s[%s]); %d tries remaining: %m",
+                                                                  udev_device_get_devnode(d), udev_device_get_devnode(dev),
+                                                                  fl_tries);
+                                                        usleep(fl_try_us);
+                                                }
+                                                if (fl_err) {
+                                                        log_error("Unable to flock(%s[%s]); skipping event handling: %m",
+                                                                  udev_device_get_devnode(d), udev_device_get_devnode(dev));
+                                                        err = -EWOULDBLOCK;
+                                                        safe_close(fd_lock);
+                                                        goto skip;
+                                                }
                                         }
+                                        /* handle open failures? */
                                 }
                         }
 
@@ -318,6 +335,14 @@ static void worker_new(struct event *eve
                                 udev_device_update_db(dev);
                         }
 
+                        /*
+                         * explicitly unlock in case there are other open file descriptors
+                         * on the device; closing will only unlock the file after all such
+                         * descriptors are closed
+                         */
+                        if (fd_lock >= 0)
+                                flock(fd_lock, LOCK_UN);
+
                         safe_close(fd_lock);
 
                         /* send processed event back to libudev listeners */