+inline void
+os_sem_wait(os_sem_t *sem, char *what)
+{
+ kern_return_t ret;
+ restart:
+ FSHOW((stderr, "%s: os_sem_wait(%p)\n", what, sem));
+ ret = semaphore_wait(*sem);
+ FSHOW((stderr, "%s: os_sem_wait(%p) => %s\n", what, sem,
+ KERN_SUCCESS==ret ? "ok" : strerror(errno)));
+ switch (ret) {
+ case KERN_SUCCESS:
+ return;
+ /* It is unclear just when we can get this, but a sufficiently
+ * long wait seems to do that, at least sometimes.
+ *
+ * However, a wait that long is definitely abnormal for the
+ * GC, so we complain before retrying.
+ */
+ case KERN_OPERATION_TIMED_OUT:
+ fprintf(stderr, "%s: os_sem_wait(%p): %s", what, sem, strerror(errno));
+ /* This is analogous to POSIX EINTR. */
+ case KERN_ABORTED:
+ goto restart;
+ default:
+ lose("%s: os_sem_wait(%p): %lu, %s", what, sem, ret, strerror(errno));
+ }
+}
+
+void
+os_sem_post(os_sem_t *sem, char *what)
+{
+ if (KERN_SUCCESS!=semaphore_signal(*sem))
+ lose("%s: os_sem_post(%p): %s", what, sem, strerror(errno));
+ FSHOW((stderr, "%s: os_sem_post(%p) ok\n", what, sem));
+}
+
+void
+os_sem_destroy(os_sem_t *sem)
+{
+ if (-1==semaphore_destroy(current_mach_task, *sem))
+ lose("os_sem_destroy(%p): %s", sem, strerror(errno));
+}
+
+#endif
+
+#if defined(LISP_FEATURE_SB_WTIMER)
+
+# error Completely untested. Go ahead! Remove this line, try your luck!
+
+/*
+ * Waitable timer implementation for the safepoint-based (SIGALRM-free)
+ * timer facility using kqueue.
+ *
+ * Unlike FreeBSD with its ms (!) timer resolution, Darwin supports ns
+ * timer resolution -- or at least it pretends to do so on the API
+ * level (?). To use it, we need the *64 versions of the functions and
+ * structures.
+ *
+ * Unfortunately, I don't run Darwin, and can't test this code, so it's
+ * just a hopeful translation from FreeBSD.
+ */
+
+int
+os_create_wtimer()
+{
+ int kq = kqueue();
+ if (kq == -1)
+ lose("os_create_wtimer: kqueue");
+ return kq;
+}
+
+int
+os_wait_for_wtimer(int kq)
+{
+ struct kevent64_s ev;
+ int n;
+ if ( (n = kevent64(kq, 0, 0, &ev, 1, 0, 0)) == -1) {
+ if (errno != EINTR)
+ lose("os_wtimer_listen failed");
+ n = 0;
+ }
+ return n != 1;
+}
+
+void
+os_close_wtimer(int kq)
+{
+ if (close(kq) == -1)
+ lose("os_close_wtimer failed");
+}
+
+void
+os_set_wtimer(int kq, int sec, int nsec)
+{
+ int64_t nsec = ((int64_t) sec) * 1000000000 + (int64_t) nsec;
+
+ struct kevent64_s ev;
+ EV_SET64(&ev, 1, EVFILT_TIMER, EV_ADD|EV_ENABLE|EV_ONESHOT, NOTE_NSECONDS,
+ nsec, 0, 0, 0);
+ if (kevent64(kq, &ev, 1, 0, 0, 0, 0) == -1)
+ perror("os_set_wtimer: kevent");
+}
+
+void
+os_cancel_wtimer(int kq)
+{
+ struct kevent64_s ev;
+ EV_SET64(&ev, 1, EVFILT_TIMER, EV_DISABLE, 0, 0, 0, 0, 0);
+ if (kevent64(kq, &ev, 1, 0, 0, 0, 0) == -1 && errno != ENOENT)
+ perror("os_cancel_wtimer: kevent");
+}
+#endif