misc/cgo/test: add test that gccgo fails

Gccgo isn't locking the OS thread properly during calls.

Change-Id: Idb2475291405e390cbb83abb27a402fd0381d0c4
Reviewed-on: https://go-review.googlesource.com/18882
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

misc/cgo/test/basic.go

@@ -162,3 +162,6 @@ func testUnsignedInt(t *testing.T) {
 func sliceOperands(array [2000]int) {
 	_ = array[C.KILO:C.KILO:C.KILO] // no type error
 }
+
+// set in cgo_thread_lock.go init
+var testThreadLockFunc = func(*testing.T) {}

misc/cgo/test/cgo_test.go

@@ -72,5 +72,6 @@ func TestCallGoWithString(t *testing.T)      { testCallGoWithString(t) }
 func Test14838(t *testing.T)                 { test14838(t) }
 func Test8756(t *testing.T)                  { test8756(t) }
 func Test17065(t *testing.T)                 { test17065(t) }
+func TestThreadLock(t *testing.T)            { testThreadLockFunc(t) }
 
 func BenchmarkCgoCall(b *testing.B) { benchCgoCall(b) }

misc/cgo/test/cgo_thread_lock.go

+// Copyright 2016 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.
+
+// +build linux,freebsd,openbsd
+
+package cgotest
+
+/*
+#include <unistd.h>
+#include <sys/syscall.h>
+void Gosched(void);
+static int Ctid(void) { Gosched(); return syscall(SYS_gettid); }
+*/
+import "C"
+
+import (
+	"runtime"
+	"syscall"
+	"testing"
+	"time"
+)
+
+//export Gosched
+func Gosched() {
+	runtime.Gosched()
+}
+
+func init() {
+	testThreadLockFunc = testThreadLock
+}
+
+func testThreadLock(t *testing.T) {
+	stop := make(chan int)
+	go func() {
+		// We need the G continue running,
+		// so the M has a chance to run this G.
+		for {
+			select {
+			case <-stop:
+				return
+			case <-time.After(time.Millisecond * 100):
+			}
+		}
+	}()
+	defer close(stop)
+
+	for i := 0; i < 1000; i++ {
+		if C.int(syscall.Gettid()) != C.Ctid() {
+			t.Fatalf("cgo has not locked OS thread")
+		}
+	}
+}