+static void check_overlap(struct io_u *io_u)
+{
+ int res;
+
+ /*
+ * Allow only one thread to check for overlap at a time to prevent two
+ * threads from thinking the coast is clear and then submitting IOs
+ * that overlap with each other.
+ *
+ * If an overlap is found, release the lock and re-acquire it before
+ * checking again to give other threads a chance to make progress.
+ *
+ * If no overlap is found, release the lock when the io_u's
+ * IO_U_F_FLIGHT flag is set so that this io_u can be checked by other
+ * threads as they assess overlap.
+ */
+ res = pthread_mutex_lock(&overlap_check);
+ assert(res == 0);
+
+retry:
+ for_each_td(td) {
+ if (td->runstate <= TD_SETTING_UP ||
+ td->runstate >= TD_FINISHING ||
+ !td->o.serialize_overlap ||
+ td->o.io_submit_mode != IO_MODE_OFFLOAD)
+ continue;
+
+ if (!in_flight_overlap(&td->io_u_all, io_u))
+ continue;
+
+ res = pthread_mutex_unlock(&overlap_check);
+ assert(res == 0);
+ res = pthread_mutex_lock(&overlap_check);
+ assert(res == 0);
+ goto retry;
+ } end_for_each();
+}
+