libgo: update to Go 1.11

    
    Reviewed-on: https://go-review.googlesource.com/136435

gotools/:
	* Makefile.am (mostlyclean-local): Run chmod on check-go-dir to
	make sure it is writable.
	(check-go-tools): Likewise.
	(check-vet): Copy internal/objabi to check-vet-dir.
	* Makefile.in: Rebuild.

From-SVN: r264546

3 files changed, 47 insertions, 2 deletions

diff --git a/libgo/go/context/benchmark_test.go b/libgo/go/context/benchmark_test.go
index 3c526dd..5d56863 100644
--- a/libgo/go/context/benchmark_test.go
+++ b/libgo/go/context/benchmark_test.go
@@ -13,6 +13,30 @@ import (
 	"time"
 )
 
+func BenchmarkCommonParentCancel(b *testing.B) {
+	root := WithValue(Background(), "key", "value")
+	shared, sharedcancel := WithCancel(root)
+	defer sharedcancel()
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		x := 0
+		for pb.Next() {
+			ctx, cancel := WithCancel(shared)
+			if ctx.Value("key").(string) != "value" {
+				b.Fatal("should not be reached")
+			}
+			for i := 0; i < 100; i++ {
+				x /= x + 1
+			}
+			cancel()
+			for i := 0; i < 100; i++ {
+				x /= x + 1
+			}
+		}
+	})
+}
+
 func BenchmarkWithTimeout(b *testing.B) {
 	for concurrency := 40; concurrency <= 4e5; concurrency *= 100 {
 		name := fmt.Sprintf("concurrency=%d", concurrency)
@@ -96,3 +120,21 @@ func buildContextTree(root Context, depth int) {
 		root, _ = WithCancel(root)
 	}
 }
+
+func BenchmarkCheckCanceled(b *testing.B) {
+	ctx, cancel := WithCancel(Background())
+	cancel()
+	b.Run("Err", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			ctx.Err()
+		}
+	})
+	b.Run("Done", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			select {
+			case <-ctx.Done():
+			default:
+			}
+		}
+	})
+}
diff --git a/libgo/go/context/context.go b/libgo/go/context/context.go
index 06580e0..1b4fa41 100644
--- a/libgo/go/context/context.go
+++ b/libgo/go/context/context.go
@@ -334,8 +334,9 @@ func (c *cancelCtx) Done() <-chan struct{} {
 
 func (c *cancelCtx) Err() error {
 	c.mu.Lock()
-	defer c.mu.Unlock()
-	return c.err
+	err := c.err
+	c.mu.Unlock()
+	return err
 }
 
 func (c *cancelCtx) String() string {
diff --git a/libgo/go/context/example_test.go b/libgo/go/context/example_test.go
index b2c2aa9..2b28b57 100644
--- a/libgo/go/context/example_test.go
+++ b/libgo/go/context/example_test.go
@@ -93,6 +93,8 @@ func ExampleWithTimeout() {
 	// context deadline exceeded
 }
 
+// This example demonstrates how a value can be passed to the context
+// and also how to retrieve it if it exists.
 func ExampleWithValue() {
 	type favContextKey string