2 files changed, 19 insertions, 0 deletions
diff --git a/src/runtime/testdata/testprogcgo/threadpprof.go b/src/runtime/testdata/testprogcgo/threadpprof.go
index f057d591c3..81965831a7 100644
--- a/src/runtime/testdata/testprogcgo/threadpprof.go
+++ b/src/runtime/testdata/testprogcgo/threadpprof.go
@@ -53,6 +53,18 @@ void pprofCgoThreadTraceback(void* parg) {
 int getCPUHogThreadCount() {
 	return __sync_add_and_fetch(&cpuHogThreadCount, 0);
 }
+
+static void* cpuHogDriver(void* arg __attribute__ ((unused))) {
+	while (1) {
+		cpuHogThread();
+	}
+	return 0;
+}
+
+void runCPUHogThread() {
+	pthread_t tid;
+	pthread_create(&tid, 0, cpuHogDriver, 0);
+}
 */
 import "C"
 
@@ -84,6 +96,8 @@ func CgoPprofThread() {
 		os.Exit(2)
 	}
 
+	C.runCPUHogThread()
+
 	t0 := time.Now()
 	for C.getCPUHogThreadCount() < 2 && time.Since(t0) < time.Second {
 		time.Sleep(100 * time.Millisecond)
diff --git a/src/runtime/testdata/testprogcgo/threadprof.go b/src/runtime/testdata/testprogcgo/threadprof.go
index 516f8dce9e..2d4c1039fb 100644
--- a/src/runtime/testdata/testprogcgo/threadprof.go
+++ b/src/runtime/testdata/testprogcgo/threadprof.go
@@ -2,7 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// We only build this file with the tag "threadprof", since it starts
+// a thread running a busy loop at constructor time.
+
 // +build !plan9,!windows
+// +build threadprof
 
 package main
 
@@ -21,6 +25,7 @@ static void *thread1(void *p) {
 	spinlock = 0;
 	return NULL;
 }
+
 __attribute__((constructor)) void issue9456() {
 	pthread_t tid;
 	pthread_create(&tid, 0, thread1, NULL);