3 files changed, 106 insertions, 21 deletions

diff --git a/libutils/include/utils/Mutex.h b/libutils/include/utils/Mutex.h
index d106185f0..af6076cf3 100644
--- a/libutils/include/utils/Mutex.h
+++ b/libutils/include/utils/Mutex.h
@@ -28,6 +28,53 @@
 #include <utils/Errors.h>
 #include <utils/Timers.h>
 
+// Enable thread safety attributes only with clang.
+// The attributes can be safely erased when compiling with other compilers.
+#if defined(__clang__) && (!defined(SWIG))
+#define THREAD_ANNOTATION_ATTRIBUTE__(x) __attribute__((x))
+#else
+#define THREAD_ANNOTATION_ATTRIBUTE__(x)  // no-op
+#endif
+
+#define CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE__(capability(x))
+
+#define SCOPED_CAPABILITY THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable)
+
+#define GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x))
+
+#define PT_GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x))
+
+#define ACQUIRED_BEFORE(...) THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(__VA_ARGS__))
+
+#define ACQUIRED_AFTER(...) THREAD_ANNOTATION_ATTRIBUTE__(acquired_after(__VA_ARGS__))
+
+#define REQUIRES(...) THREAD_ANNOTATION_ATTRIBUTE__(requires_capability(__VA_ARGS__))
+
+#define REQUIRES_SHARED(...) THREAD_ANNOTATION_ATTRIBUTE__(requires_shared_capability(__VA_ARGS__))
+
+#define ACQUIRE(...) THREAD_ANNOTATION_ATTRIBUTE__(acquire_capability(__VA_ARGS__))
+
+#define ACQUIRE_SHARED(...) THREAD_ANNOTATION_ATTRIBUTE__(acquire_shared_capability(__VA_ARGS__))
+
+#define RELEASE(...) THREAD_ANNOTATION_ATTRIBUTE__(release_capability(__VA_ARGS__))
+
+#define RELEASE_SHARED(...) THREAD_ANNOTATION_ATTRIBUTE__(release_shared_capability(__VA_ARGS__))
+
+#define TRY_ACQUIRE(...) THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_capability(__VA_ARGS__))
+
+#define TRY_ACQUIRE_SHARED(...) \
+    THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_shared_capability(__VA_ARGS__))
+
+#define EXCLUDES(...) THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(__VA_ARGS__))
+
+#define ASSERT_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE__(assert_capability(x))
+
+#define ASSERT_SHARED_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE__(assert_shared_capability(x))
+
+#define RETURN_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x))
+
+#define NO_THREAD_SAFETY_ANALYSIS THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis)
+
 // ---------------------------------------------------------------------------
 namespace android {
 // ---------------------------------------------------------------------------
@@ -44,24 +91,24 @@ class Condition;
  * The mutex must be unlocked by the thread that locked it.  They are not
  * recursive, i.e. the same thread can't lock it multiple times.
  */
-class Mutex {
-public:
+class CAPABILITY("mutex") Mutex {
+  public:
     enum {
         PRIVATE = 0,
         SHARED = 1
     };
 
-                Mutex();
-    explicit    Mutex(const char* name);
-    explicit    Mutex(int type, const char* name = NULL);
-                ~Mutex();
+    Mutex();
+    explicit Mutex(const char* name);
+    explicit Mutex(int type, const char* name = NULL);
+    ~Mutex();
 
     // lock or unlock the mutex
-    status_t    lock();
-    void        unlock();
+    status_t lock() ACQUIRE();
+    void unlock() RELEASE();
 
     // lock if possible; returns 0 on success, error otherwise
-    status_t    tryLock();
+    status_t tryLock() TRY_ACQUIRE(true);
 
 #if defined(__ANDROID__)
     // Lock the mutex, but don't wait longer than timeoutNs (relative time).
@@ -75,32 +122,36 @@ public:
     // which is subject to NTP adjustments, and includes time during suspend,
     // so a timeout may occur even though no processes could run.
     // Not holding a partial wakelock may lead to a system suspend.
-    status_t    timedLock(nsecs_t timeoutNs);
+    status_t timedLock(nsecs_t timeoutNs) TRY_ACQUIRE(true);
 #endif
 
     // Manages the mutex automatically. It'll be locked when Autolock is
     // constructed and released when Autolock goes out of scope.
-    class Autolock {
-    public:
-        inline explicit Autolock(Mutex& mutex) : mLock(mutex)  { mLock.lock(); }
-        inline explicit Autolock(Mutex* mutex) : mLock(*mutex) { mLock.lock(); }
-        inline ~Autolock() { mLock.unlock(); }
-    private:
+    class SCOPED_CAPABILITY Autolock {
+      public:
+        inline explicit Autolock(Mutex& mutex) ACQUIRE(mutex) : mLock(mutex) { mLock.lock(); }
+        inline explicit Autolock(Mutex* mutex) ACQUIRE(mutex) : mLock(*mutex) { mLock.lock(); }
+        inline ~Autolock() RELEASE() { mLock.unlock(); }
+
+      private:
         Mutex& mLock;
+        // Cannot be copied or moved - declarations only
+        Autolock(const Autolock&);
+        Autolock& operator=(const Autolock&);
     };
 
-private:
+  private:
     friend class Condition;
 
     // A mutex cannot be copied
-                Mutex(const Mutex&);
-    Mutex&      operator = (const Mutex&);
+    Mutex(const Mutex&);
+    Mutex& operator=(const Mutex&);
 
 #if !defined(_WIN32)
     pthread_mutex_t mMutex;
 #else
-    void    _init();
-    void*   mState;
+    void _init();
+    void* mState;
 #endif
 };
 
diff --git a/libutils/tests/Android.bp b/libutils/tests/Android.bp
index 7b62c2436..08691756a 100644
--- a/libutils/tests/Android.bp
+++ b/libutils/tests/Android.bp
@@ -23,6 +23,7 @@ cc_test {
     srcs: [
         "BitSet_test.cpp",
         "LruCache_test.cpp",
+        "Mutex_test.cpp",
         "Singleton_test.cpp",
         "String8_test.cpp",
         "StrongPointer_test.cpp",
@@ -71,6 +72,7 @@ cc_test {
         "-Wall",
         "-Wextra",
         "-Werror",
+        "-Wthread-safety",
     ],
 }
 
diff --git a/libutils/tests/Mutex_test.cpp b/libutils/tests/Mutex_test.cpp
new file mode 100644
index 000000000..8a1805f51
--- /dev/null
+++ b/libutils/tests/Mutex_test.cpp
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+#include <utils/Mutex.h>
+
+#include <gtest/gtest.h>
+
+static android::Mutex mLock;
+static int i GUARDED_BY(mLock);
+
+void modifyLockedVariable() REQUIRES(mLock) {
+    i = 1;
+}
+
+TEST(Mutex, compile) {
+    android::Mutex::Autolock _l(mLock);
+    i = 0;
+    modifyLockedVariable();
+}
\ No newline at end of file