--- a/src/runtime/linux-os.c
+++ b/src/runtime/linux-os.c
@@ -54,6 +54,10 @@
 #include "gencgc-internal.h"
 #else
 #include "cheneygc-internal.h"
+#endif
+#include <fcntl.h>
+#ifdef LISP_FEATURE_SB_WTIMER
+# include <sys/timerfd.h>
 #endif
 
 #ifdef LISP_FEATURE_X86
@@ -482,3 +486,61 @@
 
     return copied_string(path);
 }
+
+#ifdef LISP_FEATURE_SB_WTIMER
+/*
+ * Waitable timer implementation for the safepoint-based (SIGALRM-free)
+ * timer facility using timerfd_create().
+ */
+int
+os_create_wtimer()
+{
+    int fd = timerfd_create(CLOCK_MONOTONIC, 0);
+    if (fd == -1)
+        lose("os_create_wtimer: timerfd_create");
+
+    /* Cannot count on TFD_CLOEXEC availability, so do it manually: */
+    if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
+        lose("os_create_wtimer: fcntl");
+
+    return fd;
+}
+
+int
+os_wait_for_wtimer(int fd)
+{
+    unsigned char buf[8];
+    int n = read(fd, buf, sizeof(buf));
+    if (n == -1) {
+        if (errno == EINTR)
+            return -1;
+        lose("os_wtimer_listen failed");
+    }
+    if (n != sizeof(buf))
+        lose("os_wtimer_listen read too little");
+    return 0;
+}
+
+void
+os_close_wtimer(int fd)
+{
+    if (close(fd) == -1)
+        lose("os_close_wtimer failed");
+}
+
+void
+os_set_wtimer(int fd, int sec, int nsec)
+{
+    struct itimerspec spec = { {0,0}, {0,0} };
+    spec.it_value.tv_sec = sec;
+    spec.it_value.tv_nsec = nsec;
+    if (timerfd_settime(fd, 0, &spec, 0) == -1)
+        lose("timerfd_settime");
+}
+
+void
+os_cancel_wtimer(int fd)
+{
+    os_set_wtimer(fd, 0, 0);
+}
+#endif