diff --git a/misc/cgo/testsanitizers/test.bash b/misc/cgo/testsanitizers/test.bash
index 67925e52ee..556ef10820 100755
--- a/misc/cgo/testsanitizers/test.bash
+++ b/misc/cgo/testsanitizers/test.bash
@@ -190,17 +190,12 @@ if test "$tsan" = "yes"; then
     fi
 
     if test "$ok" = "true"; then
-	# This test requires rebuilding os/user with -fsanitize=thread.
+	# These tests require rebuilding os/user with -fsanitize=thread.
 	testtsan tsan5.go "CGO_CFLAGS=-fsanitize=thread CGO_LDFLAGS=-fsanitize=thread" "-installsuffix=tsan"
-
-	# This test requires rebuilding runtime/cgo with -fsanitize=thread.
 	testtsan tsan6.go "CGO_CFLAGS=-fsanitize=thread CGO_LDFLAGS=-fsanitize=thread" "-installsuffix=tsan"
-
-	# This test requires rebuilding runtime/cgo with -fsanitize=thread.
 	testtsan tsan7.go "CGO_CFLAGS=-fsanitize=thread CGO_LDFLAGS=-fsanitize=thread" "-installsuffix=tsan"
-
-	# This test requires rebuilding runtime/cgo with -fsanitize=thread.
 	testtsan tsan10.go "CGO_CFLAGS=-fsanitize=thread CGO_LDFLAGS=-fsanitize=thread" "-installsuffix=tsan"
+	testtsan tsan11.go "CGO_CFLAGS=-fsanitize=thread CGO_LDFLAGS=-fsanitize=thread" "-installsuffix=tsan"
     fi
 fi
 
diff --git a/misc/cgo/testsanitizers/tsan11.go b/misc/cgo/testsanitizers/tsan11.go
new file mode 100644
index 0000000000..70ac9c8ae2
--- /dev/null
+++ b/misc/cgo/testsanitizers/tsan11.go
@@ -0,0 +1,55 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+// This program hung when run under the C/C++ ThreadSanitizer. TSAN defers
+// asynchronous signals until the signaled thread calls into libc. The runtime's
+// sysmon goroutine idles itself using direct usleep syscalls, so it could
+// run for an arbitrarily long time without triggering the libc interceptors.
+// See https://golang.org/issue/18717.
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+/*
+#cgo CFLAGS: -g -fsanitize=thread
+#cgo LDFLAGS: -g -fsanitize=thread
+
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void raise_usr2(int signo) {
+	raise(SIGUSR2);
+}
+
+static void register_handler(int signo) {
+	struct sigaction sa;
+	memset(&sa, 0, sizeof(sa));
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = SA_ONSTACK;
+	sa.sa_handler = raise_usr2;
+
+	if (sigaction(SIGUSR1, &sa, NULL) != 0) {
+		perror("failed to register SIGUSR1 handler");
+		exit(EXIT_FAILURE);
+	}
+}
+*/
+import "C"
+
+func main() {
+	ch := make(chan os.Signal)
+	signal.Notify(ch, syscall.SIGUSR2)
+
+	C.register_handler(C.int(syscall.SIGUSR1))
+	syscall.Kill(syscall.Getpid(), syscall.SIGUSR1)
+
+	<-ch
+}
diff --git a/src/runtime/lock_futex.go b/src/runtime/lock_futex.go
index 341c74ff39..c3ed3be00b 100644
--- a/src/runtime/lock_futex.go
+++ b/src/runtime/lock_futex.go
@@ -185,8 +185,14 @@ func notetsleep_internal(n *note, ns int64) bool {
 
 	deadline := nanotime() + ns
 	for {
+		if _cgo_yield != nil && ns > 10e6 {
+			ns = 10e6
+		}
 		gp.m.blocked = true
 		futexsleep(key32(&n.key), 0, ns)
+		if _cgo_yield != nil {
+			asmcgocall(_cgo_yield, nil)
+		}
 		gp.m.blocked = false
 		if atomic.Load(key32(&n.key)) != 0 {
 			break
diff --git a/src/runtime/lock_sema.go b/src/runtime/lock_sema.go
index e00b99164f..4a8295ff47 100644
--- a/src/runtime/lock_sema.go
+++ b/src/runtime/lock_sema.go
@@ -198,10 +198,9 @@ func notetsleep_internal(n *note, ns int64, gp *g, deadline int64) bool {
 		if _cgo_yield == nil {
 			semasleep(-1)
 		} else {
-			// Sleep for an arbitrary-but-moderate interval to poll libc interceptors.
+			// Sleep in arbitrary-but-moderate intervals to poll libc interceptors.
 			const ns = 10e6
-			for atomic.Loaduintptr(&n.key) == 0 {
-				semasleep(ns)
+			for semasleep(ns) < 0 {
 				asmcgocall(_cgo_yield, nil)
 			}
 		}
@@ -213,12 +212,18 @@ func notetsleep_internal(n *note, ns int64, gp *g, deadline int64) bool {
 	for {
 		// Registered. Sleep.
 		gp.m.blocked = true
+		if _cgo_yield != nil && ns > 10e6 {
+			ns = 10e6
+		}
 		if semasleep(ns) >= 0 {
 			gp.m.blocked = false
 			// Acquired semaphore, semawakeup unregistered us.
 			// Done.
 			return true
 		}
+		if _cgo_yield != nil {
+			asmcgocall(_cgo_yield, nil)
+		}
 		gp.m.blocked = false
 		// Interrupted or timed out. Still registered. Semaphore not acquired.
 		ns = deadline - nanotime()
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 5b907502d6..caeb51205b 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -3755,6 +3755,10 @@ func sysmon() {
 			}
 			unlock(&sched.lock)
 		}
+		// trigger libc interceptors if needed
+		if _cgo_yield != nil {
+			asmcgocall(_cgo_yield, nil)
+		}
 		// poll network if not polled for more than 10ms
 		lastpoll := int64(atomic.Load64(&sched.lastpoll))
 		now := nanotime()