runtime/cgo: add TSAN locks around mmap call

Change-Id: I806cc5523b7b5e3278d01074bc89900d78700e0c
Reviewed-on: https://go-review.googlesource.com/23736
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

misc/cgo/testsanitizers/test.bash

@@ -111,61 +111,35 @@ if test "$tsan" = "yes"; then
      rm -f ${TMPDIR}/testsanitizers$$*
 fi
 
-if test "$tsan" = "yes"; then
+# Run a TSAN test.
+# $1 test name
+# $2 environment variables
+# $3 go run args
+testtsan() {
     err=${TMPDIR}/tsanerr$$.out
-
+    if ! env $2 go run $3 $1 2>$err; then
-    if ! go run tsan.go 2>$err; then
 	cat $err
-	echo "FAIL: tsan"
+	echo "FAIL: $1"
 	status=1
     elif grep -i warning $err >/dev/null 2>&1; then
 	cat $err
-	echo "FAIL: tsan"
+	echo "FAIL: $1"
 	status=1
     fi
+    rm -f $err
+}
 
-    if ! go run tsan2.go 2>$err; then
+if test "$tsan" = "yes"; then
-	cat $err
+    testtsan tsan.go
-	echo "FAIL: tsan2"
+    testtsan tsan2.go
-	status=1
+    testtsan tsan3.go
-    elif grep -i warning $err >/dev/null 2>&1; then
+    testtsan tsan4.go
-	cat $err
-	echo "FAIL: tsan2"
-	status=1
-    fi
-
-    if ! go run tsan3.go 2>$err; then
-	cat $err
-	echo "FAIL: tsan3"
-	status=1
-    elif grep -i warning $err >/dev/null 2>&1; then
-	cat $err
-	echo "FAIL: tsan3"
-	status=1
-    fi
-
-    if ! go run tsan4.go 2>$err; then
-	cat $err
-	echo "FAIL: tsan4"
-	status=1
-    elif grep -i warning $err >/dev/null 2>&1; then
-	cat $err
-	echo "FAIL: tsan4"
-	status=1
-    fi
 
     # This test requires rebuilding os/user with -fsanitize=thread.
-    if ! CGO_CFLAGS="-fsanitize=thread" CGO_LDFLAGS="-fsanitize=thread" go run -installsuffix=tsan tsan5.go 2>$err; then
+    testtsan tsan5.go "CGO_CFLAGS=-fsanitize=thread CGO_LDFLAGS=-fsanitize=thread" "-installsuffix=tsan"
-	cat $err
-	echo "FAIL: tsan5"
-	status=1
-    elif grep -i warning $err >/dev/null 2>&1; then
-	cat $err
-	echo "FAIL: tsan5"
-	status=1
-    fi
 
-    rm -f $err
+    # This test requires rebuilding runtime/cgo with -fsanitize=thread.
+    testtsan tsan6.go "CGO_CFLAGS=-fsanitize=thread CGO_LDFLAGS=-fsanitize=thread" "-installsuffix=tsan"
 fi
 
 exit $status

misc/cgo/testsanitizers/tsan6.go

@@ -0,0 +1,49 @@
+// 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.
+
+package main
+
+// Check that writes to Go allocated memory, with Go synchronization,
+// do not look like a race.
+
+/*
+#cgo CFLAGS: -fsanitize=thread
+#cgo LDFLAGS: -fsanitize=thread
+
+void f(char *p) {
+	*p = 1;
+}
+*/
+import "C"
+
+import (
+	"runtime"
+	"sync"
+)
+
+func main() {
+	var wg sync.WaitGroup
+	var mu sync.Mutex
+	c := make(chan []C.char, 100)
+	for i := 0; i < 10; i++ {
+		wg.Add(2)
+		go func() {
+			defer wg.Done()
+			for i := 0; i < 100; i++ {
+				c <- make([]C.char, 4096)
+				runtime.Gosched()
+			}
+		}()
+		go func() {
+			defer wg.Done()
+			for i := 0; i < 100; i++ {
+				p := &(<-c)[0]
+				mu.Lock()
+				C.f(p)
+				mu.Unlock()
+			}
+		}()
+	}
+	wg.Wait()
+}

src/runtime/cgo/gcc_mmap.c

@@ -8,11 +8,15 @@
 #include <stdint.h>
 #include <sys/mman.h>
 
+#include "libcgo.h"
+
 void *
 x_cgo_mmap(void *addr, uintptr_t length, int32_t prot, int32_t flags, int32_t fd, uint32_t offset) {
 	void *p;
 
+	_cgo_tsan_acquire();
 	p = mmap(addr, length, prot, flags, fd, offset);
+	_cgo_tsan_release();
 	if (p == MAP_FAILED) {
 		/* This is what the Go code expects on failure.  */
 		p = (void *) (uintptr_t) errno;