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diff --git a/absl/synchronization/internal/create_thread_identity.h b/absl/synchronization/internal/create_thread_identity.h
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+++ b/absl/synchronization/internal/create_thread_identity.h
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+/*
+ * Copyright 2017 The Abseil 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.
+ */
+
+// Interface for getting the current ThreadIdentity, creating one if necessary.
+// See thread_identity.h.
+//
+// This file is separate from thread_identity.h because creating a new
+// ThreadIdentity requires slightly higher level libraries (per_thread_sem
+// and low_level_alloc) than accessing an existing one.  This separation allows
+// us to have a smaller //absl/base:base.
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_CREATE_THREAD_IDENTITY_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_CREATE_THREAD_IDENTITY_H_
+
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/port.h"
+
+namespace absl {
+namespace synchronization_internal {
+
+// Allocates and attaches a ThreadIdentity object for the calling thread.
+// For private use only.
+base_internal::ThreadIdentity* CreateThreadIdentity();
+
+// Returns the ThreadIdentity object representing the calling thread; guaranteed
+// to be unique for its lifetime.  The returned object will remain valid for the
+// program's lifetime; although it may be re-assigned to a subsequent thread.
+// If one does not exist for the calling thread, allocate it now.
+inline base_internal::ThreadIdentity* GetOrCreateCurrentThreadIdentity() {
+  base_internal::ThreadIdentity* identity =
+      base_internal::CurrentThreadIdentityIfPresent();
+  if (ABSL_PREDICT_FALSE(identity == nullptr)) {
+    return CreateThreadIdentity();
+  }
+  return identity;
+}
+
+}  // namespace synchronization_internal
+}  // namespace absl
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_CREATE_THREAD_IDENTITY_H_