diff --git a/io/io_waituntil.c b/io/io_waituntil.c
new file mode 100644
index 0000000..3f16e61
--- /dev/null
+++ b/io/io_waituntil.c
@@ -0,0 +1,15 @@
+#include <unistd.h>
+#include <sys/time.h>
+#include <poll.h>
+#include <errno.h>
+#include "io_internal.h"
+#include "safemult.h"
+
+void io_waituntil(tai6464 t) {
+  uint64 x,y;
+  tai6464 now;
+  taia_now(&now);
+  if (!umult64(now.sec.x,1000,&x) || (y=x+now.nano/10000000)<x)
+    y=-1;	/* overflow; wait indefinitely */
+  io_waituntil2(y);
+}
diff --git a/io/io_waituntil2.c b/io/io_waituntil2.c
new file mode 100644
index 0000000..006d286
--- /dev/null
+++ b/io/io_waituntil2.c
@@ -0,0 +1,39 @@
+#include <unistd.h>
+#include <sys/time.h>
+#include <poll.h>
+#include <errno.h>
+#include "io_internal.h"
+
+int64 io_waituntil2(int64 milliseconds) {
+  struct pollfd* p;
+  long i,r;
+  if (!io_wanted_fds) return 0;
+  for (i=r=0; i<array_length(&io_fds,sizeof(io_entry)); ++i) {
+    io_entry* e=array_get(&io_fds,sizeof(io_entry),i);
+    if (!e) return -1;
+    e->canread=e->canwrite=0;
+    if (e->wantread || e->wantwrite) {
+      struct pollfd* p;
+      if ((p=array_allocate(&io_pollfds,sizeof(struct pollfd),r))) {
+	p->fd=i;
+	p->events=(e->wantread?POLLIN:0) + (e->wantwrite?POLLOUT:0);
+	++r;
+      } else
+	return -1;
+    }
+  }
+  p=array_start(&io_pollfds);
+again:
+  while ((i=poll(array_start(&io_pollfds),r,milliseconds))==0);
+  if (i==-1) {
+    if (errno==EINTR) goto again;
+    return -1;
+  }
+  for (i=0; i<r; ++i) {
+    io_entry* e=array_get(&io_fds,sizeof(io_entry),p->fd);
+    if (p->revents&POLLIN) e->canread=1;
+    if (p->revents&POLLOUT) e->canwrite=1;
+    p++;
+  }
+  return i;
+}