Add a new KeyedLocker, StripedKeyedLocker. This new implementation simply stores a striped set of reentrant locks.

--
MOS_MIGRATED_REVID=102198213

2 files changed, 50 insertions, 5 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/concurrent/RefCountedMultisetKeyedLocker.java b/src/main/java/com/google/devtools/build/lib/concurrent/RefCountedMultisetKeyedLocker.java
index 52109ad543..64d530e617 100644
--- a/src/main/java/com/google/devtools/build/lib/concurrent/RefCountedMultisetKeyedLocker.java
+++ b/src/main/java/com/google/devtools/build/lib/concurrent/RefCountedMultisetKeyedLocker.java
@@ -60,11 +60,6 @@ public class RefCountedMultisetKeyedLocker<K> implements KeyedLocker<K> {
                                        + "AutoUnlocker instance", key);
         throw new IllegalUnlockException(msg);
       }
-      if (!lock.isHeldByCurrentThread()) {
-        String msg = String.format("For key %s, the calling thread to 'close' must be the one "
-            + "that acquired the AutoUnlocker", key);
-        throw new IllegalUnlockException(msg);
-      }
       try {
         Lock waitersLock = waitersLocks.get(key);
         try {
diff --git a/src/main/java/com/google/devtools/build/lib/concurrent/StripedKeyedLocker.java b/src/main/java/com/google/devtools/build/lib/concurrent/StripedKeyedLocker.java
new file mode 100644
index 0000000000..505ea6c195
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/concurrent/StripedKeyedLocker.java
@@ -0,0 +1,50 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// 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 com.google.devtools.build.lib.concurrent;
+
+import com.google.common.util.concurrent.Striped;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.locks.Lock;
+
+/**
+ * An implementation of {@link KeyedLocker} backed by a {@link Striped}.
+ */
+public class StripedKeyedLocker<K> implements KeyedLocker<K> {
+
+  private final Striped<Lock> locks;
+
+  public StripedKeyedLocker(int stripes) {
+    locks = Striped.lock(stripes);
+  }
+
+  @Override
+  public AutoUnlocker lock(final K key) {
+    final Lock lock = locks.get(key);
+    lock.lock();
+    return new AutoUnlocker() {
+      private final AtomicBoolean closeCalled = new AtomicBoolean(false);
+
+      @Override
+      public void close() {
+        if (closeCalled.getAndSet(true)) {
+          String msg = String.format("For key %s, 'close' can be called at most once per "
+              + "AutoUnlocker instance", key);
+          throw new IllegalUnlockException(msg);
+        }
+        lock.unlock();
+      }
+    };
+  }
+}