SF: Generalize thread safety guards
Replace the guards with a uniform syntax that can be reused with
annotations other than mStateLock and SF_MAIN_THREAD.
Bug: 182939859
Test: Build
Change-Id: I03e6fe5d465111a5882d2fc1c09fe1dc9660aa07
diff --git a/services/surfaceflinger/ThreadContext.h b/services/surfaceflinger/ThreadContext.h
new file mode 100644
index 0000000..85c379d
--- /dev/null
+++ b/services/surfaceflinger/ThreadContext.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#pragma once
+
+namespace android {
+
+// Enforces exclusive access by the main thread.
+constexpr class [[clang::capability("mutex")]] {
+} kMainThreadContext;
+
+} // namespace android