Fix abstime_from_now.

prrt/util/time.c

@@ -16,8 +16,11 @@ struct timespec abstime_from_now(uint32_t wait_time) {
     struct timespec deadline;
     uint32_t diff_s = wait_time / 1000000;
     uint32_t diff_ns = (wait_time % 1000000) * 1000;
-    deadline.tv_sec = diff_s + now.tv_sec;
-    deadline.tv_nsec = diff_ns + now.tv_nsec;
+    __syscall_slong_t sum = diff_ns + now.tv_nsec;
+    __syscall_slong_t carry = (sum) / 1000000000;
+    __syscall_slong_t rest = (sum) % 1000000000;
+    deadline.tv_sec = diff_s + now.tv_sec + carry;
+    deadline.tv_nsec = rest;
     return deadline;
 }