goid: new package

Allows retrieving the goroutine ID for concurrency testing when the race
detector is enabled.

Updates #1472

PiperOrigin-RevId: 289155308

1 files changed, 74 insertions, 0 deletions

diff --git a/pkg/goid/goid_test.go b/pkg/goid/goid_test.go
new file mode 100644
index 000000000..31970ce79
--- /dev/null
+++ b/pkg/goid/goid_test.go
@@ -0,0 +1,74 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build race
+
+package goid
+
+import (
+	"runtime"
+	"sync"
+	"testing"
+)
+
+func TestInitialGoID(t *testing.T) {
+	const max = 10000
+	if id := goid(); id < 0 || id > max {
+		t.Errorf("got goid = %d, want 0 < goid <= %d", id, max)
+	}
+}
+
+// TestGoIDSquence verifies that goid returns values which could plausibly be
+// goroutine IDs. If this test breaks or becomes flaky, the structs in
+// goid_unsafe.go may need to be updated.
+func TestGoIDSquence(t *testing.T) {
+	// Goroutine IDs are cached by each P.
+	runtime.GOMAXPROCS(1)
+
+	// Fill any holes in lower range.
+	for i := 0; i < 50; i++ {
+		var wg sync.WaitGroup
+		wg.Add(1)
+		go func() {
+			wg.Done()
+
+			// Leak the goroutine to prevent the ID from being
+			// reused.
+			select {}
+		}()
+		wg.Wait()
+	}
+
+	id := goid()
+	for i := 0; i < 100; i++ {
+		var (
+			newID int64
+			wg    sync.WaitGroup
+		)
+		wg.Add(1)
+		go func() {
+			newID = goid()
+			wg.Done()
+
+			// Leak the goroutine to prevent the ID from being
+			// reused.
+			select {}
+		}()
+		wg.Wait()
+		if max := id + 100; newID <= id || newID > max {
+			t.Errorf("unexpected goroutine ID pattern, got goid = %d, want %d < goid <= %d (previous = %d)", newID, id, max, id)
+		}
+		id = newID
+	}
+}