1 files changed, 61 insertions, 0 deletions
diff --git a/src/runtime/testdata/testprogcgo/bindm.go b/src/runtime/testdata/testprogcgo/bindm.go
new file mode 100644
index 0000000000..c2003c2093
--- /dev/null
+++ b/src/runtime/testdata/testprogcgo/bindm.go
@@ -0,0 +1,61 @@
+// Copyright 2023 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.
+
+//go:build !plan9 && !windows
+
+// Test that callbacks from C to Go in the same C-thread always get the same m.
+// Make sure the extra M bind to the C-thread.
+
+package main
+
+/*
+extern void CheckBindM();
+*/
+import "C"
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"sync"
+	"sync/atomic"
+)
+
+var (
+	mutex      = sync.Mutex{}
+	cThreadToM = map[uintptr]uintptr{}
+	started    = atomic.Uint32{}
+)
+
+// same as CTHREADS in C, make sure all the C threads are actually started.
+const cThreadNum = 2
+
+func init() {
+	register("EnsureBindM", EnsureBindM)
+}
+
+//export GoCheckBindM
+func GoCheckBindM(thread uintptr) {
+	// Wait all threads start
+	if started.Load() != cThreadNum {
+		// Only once for each thread, since it will wait all threads start.
+		started.Add(1)
+		for started.Load() < cThreadNum {
+			runtime.Gosched()
+		}
+	}
+	m := runtime_getm_for_test()
+	mutex.Lock()
+	defer mutex.Unlock()
+	if savedM, ok := cThreadToM[thread]; ok && savedM != m {
+		fmt.Printf("m == %x want %x\n", m, savedM)
+		os.Exit(1)
+	}
+	cThreadToM[thread] = m
+}
+
+func EnsureBindM() {
+	C.CheckBindM()
+	fmt.Println("OK")
+}