Use containerd grpc server

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/atomic/atomic_boolean.go

@@ -0,0 +1,54 @@
+/*
+Copyright 2018 The Containerd 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.
+*/
+
+package atomic
+
+import "sync/atomic"
+
+// Bool is an atomic Boolean,
+// Its methods are all atomic, thus safe to be called by
+// multiple goroutines simultaneously.
+type Bool interface {
+	Set()
+	Unset()
+	IsSet() bool
+}
+
+// NewBool creates an Bool with given default value
+func NewBool(ok bool) Bool {
+	ab := new(atomicBool)
+	if ok {
+		ab.Set()
+	}
+	return ab
+}
+
+type atomicBool int32
+
+// Set sets the Boolean to true
+func (ab *atomicBool) Set() {
+	atomic.StoreInt32((*int32)(ab), 1)
+}
+
+// Unset sets the Boolean to false
+func (ab *atomicBool) Unset() {
+	atomic.StoreInt32((*int32)(ab), 0)
+}
+
+// IsSet returns whether the Boolean is true
+func (ab *atomicBool) IsSet() bool {
+	return atomic.LoadInt32((*int32)(ab)) == 1
+}