libcamera: base: Add thread safety annotation macros

Clang compiler is able to do a thread safety analysis with
annotations [1]. This introduces the thread safety annotation
macros and also enable the analysis by adding -Wthread-safety
if a clang compiler is used.

[1] https://clang.llvm.org/docs/ThreadSafetyAnalysis.html.

Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/base/meson.build

@@ -19,6 +19,7 @@ libcamera_base_headers = files([
     'signal.h',
     'span.h',
     'thread.h',
+    'thread_annotations.h',
     'timer.h',
     'utils.h',
 ])

include/libcamera/base/thread_annotations.h

@@ -0,0 +1,80 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Google Inc.
+ *
+ * thread_annotation.h - Macro of Clang thread safety analysis
+ */
+
+#pragma once
+
+/*
+ * Enable thread safety attributes only with clang.
+ * The attributes can be safely erased when compiling with other compilers.
+ */
+#if defined(__clang__) && !defined(SWIG)
+#define LIBCAMERA_TSA_ATTRIBUTE__(x) __attribute__((x))
+#else
+#define LIBCAMERA_TSA_ATTRIBUTE__(x) /* no-op */
+#endif
+
+/* See https://clang.llvm.org/docs/ThreadSafetyAnalysis.html for these usages. */
+
+#define LIBCAMERA_TSA_CAPABILITY(x)			\
+	LIBCAMERA_TSA_ATTRIBUTE__(capability(x))
+
+#define LIBCAMERA_TSA_SCOPED_CAPABILITY			\
+	LIBCAMERA_TSA_ATTRIBUTE__(scoped_lockable)
+
+#define LIBCAMERA_TSA_GUARDED_BY(x)			\
+	LIBCAMERA_TSA_ATTRIBUTE__(guarded_by(x))
+
+#define LIBCAMERA_TSA_PT_GUARDED_BY(x)			\
+	LIBCAMERA_TSA_ATTRIBUTE__(pt_guarded_by(x))
+
+#define LIBCAMERA_TSA_ACQUIRED_BEFORE(...)			\
+	LIBCAMERA_TSA_ATTRIBUTE__(acquired_before(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_ACQUIRED_AFTER(...)			\
+	LIBCAMERA_TSA_ATTRIBUTE__(acquired_after(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_REQUIRES(...)					\
+	LIBCAMERA_TSA_ATTRIBUTE__(requires_capability(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_REQUIRES_SHARED(...)				\
+	LIBCAMERA_TSA_ATTRIBUTE__(requires_shared_capability(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_ACQUIRE(...)					\
+	LIBCAMERA_TSA_ATTRIBUTE__(acquire_capability(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_ACQUIRE_SHARED(...)				\
+	LIBCAMERA_TSA_ATTRIBUTE__(acquire_shared_capability(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_RELEASE(...)					\
+	LIBCAMERA_TSA_ATTRIBUTE__(release_capability(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_RELEASE_SHARED(...)				\
+	LIBCAMERA_TSA_ATTRIBUTE__(release_shared_capability(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_RELEASE_GENERIC(...)				\
+	LIBCAMERA_TSA_ATTRIBUTE__(release_generic_capability(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_TRY_ACQUIRE(...)					\
+	LIBCAMERA_TSA_ATTRIBUTE__(try_acquire_capability(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_TRY_ACQUIRE_SHARED(...)				\
+	LIBCAMERA_TSA_ATTRIBUTE__(try_acquire_shared_capability(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_EXCLUDES(...)				\
+	LIBCAMERA_TSA_ATTRIBUTE__(locks_excluded(__VA_ARGS__))
+
+#define LIBCAMERA_TSA_ASSERT_CAPABILITY(x)		\
+	LIBCAMERA_TSA_ATTRIBUTE__(assert_capability(x))
+
+#define LIBCAMERA_TSA_ASSERT_SHARED_CAPABILITY(x)		\
+	LIBCAMERA_TSA_ATTRIBUTE__(assert_shared_capability(x))
+
+#define LIBCAMERA_TSA_RETURN_CAPABILITY(x)		\
+	LIBCAMERA_TSA_ATTRIBUTE__(lock_returned(x))
+
+#define LIBCAMERA_TSA_NO_THREAD_SAFETY_ANALYSIS			\
+	LIBCAMERA_TSA_ATTRIBUTE__(no_thread_safety_analysis)

meson.build

@@ -72,6 +72,7 @@ if cc.get_id() == 'clang'
 
     cpp_arguments += [
         '-Wextra-semi',
+        '-Wthread-safety',
     ]
 endif