benchmark  1.9.4
mutex.h
1 #ifndef BENCHMARK_MUTEX_H_
2 #define BENCHMARK_MUTEX_H_
3 
4 #include <condition_variable>
5 #include <mutex>
6 
7 #include "check.h"
8 
9 // Enable thread safety attributes only with clang.
10 // The attributes can be safely erased when compiling with other compilers.
11 #if defined(HAVE_THREAD_SAFETY_ATTRIBUTES)
12 #define THREAD_ANNOTATION_ATTRIBUTE_(x) __attribute__((x))
13 #else
14 #define THREAD_ANNOTATION_ATTRIBUTE_(x) // no-op
15 #endif
16 
17 #define CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE_(capability(x))
18 
19 #define SCOPED_CAPABILITY THREAD_ANNOTATION_ATTRIBUTE_(scoped_lockable)
20 
21 #define GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE_(guarded_by(x))
22 
23 #define PT_GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE_(pt_guarded_by(x))
24 
25 #define ACQUIRED_BEFORE(...) \
26  THREAD_ANNOTATION_ATTRIBUTE_(acquired_before(__VA_ARGS__))
27 
28 #define ACQUIRED_AFTER(...) \
29  THREAD_ANNOTATION_ATTRIBUTE_(acquired_after(__VA_ARGS__))
30 
31 #define REQUIRES(...) \
32  THREAD_ANNOTATION_ATTRIBUTE_(requires_capability(__VA_ARGS__))
33 
34 #define REQUIRES_SHARED(...) \
35  THREAD_ANNOTATION_ATTRIBUTE_(requires_shared_capability(__VA_ARGS__))
36 
37 #define ACQUIRE(...) \
38  THREAD_ANNOTATION_ATTRIBUTE_(acquire_capability(__VA_ARGS__))
39 
40 #define ACQUIRE_SHARED(...) \
41  THREAD_ANNOTATION_ATTRIBUTE_(acquire_shared_capability(__VA_ARGS__))
42 
43 #define RELEASE(...) \
44  THREAD_ANNOTATION_ATTRIBUTE_(release_capability(__VA_ARGS__))
45 
46 #define RELEASE_SHARED(...) \
47  THREAD_ANNOTATION_ATTRIBUTE_(release_shared_capability(__VA_ARGS__))
48 
49 #define TRY_ACQUIRE(...) \
50  THREAD_ANNOTATION_ATTRIBUTE_(try_acquire_capability(__VA_ARGS__))
51 
52 #define TRY_ACQUIRE_SHARED(...) \
53  THREAD_ANNOTATION_ATTRIBUTE_(try_acquire_shared_capability(__VA_ARGS__))
54 
55 #define EXCLUDES(...) THREAD_ANNOTATION_ATTRIBUTE_(locks_excluded(__VA_ARGS__))
56 
57 #define ASSERT_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE_(assert_capability(x))
58 
59 #define ASSERT_SHARED_CAPABILITY(x) \
60  THREAD_ANNOTATION_ATTRIBUTE_(assert_shared_capability(x))
61 
62 #define RETURN_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE_(lock_returned(x))
63 
64 #define NO_THREAD_SAFETY_ANALYSIS \
65  THREAD_ANNOTATION_ATTRIBUTE_(no_thread_safety_analysis)
66 
67 namespace benchmark {
68 
69 typedef std::condition_variable Condition;
70 
71 // NOTE: Wrappers for std::mutex and std::unique_lock are provided so that
72 // we can annotate them with thread safety attributes and use the
73 // -Wthread-safety warning with clang. The standard library types cannot be
74 // used directly because they do not provide the required annotations.
75 class CAPABILITY("mutex") Mutex {
76  public:
77  Mutex() {}
78 
79  void lock() ACQUIRE() { mut_.lock(); }
80  void unlock() RELEASE() { mut_.unlock(); }
81  std::mutex& native_handle() { return mut_; }
82 
83  private:
84  std::mutex mut_;
85 };
86 
87 class SCOPED_CAPABILITY MutexLock {
88  typedef std::unique_lock<std::mutex> MutexLockImp;
89 
90  public:
91  MutexLock(Mutex& m) ACQUIRE(m) : ml_(m.native_handle()) {}
92  ~MutexLock() RELEASE() {}
93  MutexLockImp& native_handle() { return ml_; }
94 
95  private:
96  MutexLockImp ml_;
97 };
98 
99 class Barrier {
100  public:
101  Barrier(int num_threads) : running_threads_(num_threads) {}
102 
103  // Called by each thread
104  bool wait() EXCLUDES(lock_) {
105  bool last_thread = false;
106  {
107  MutexLock ml(lock_);
108  last_thread = createBarrier(ml);
109  }
110  if (last_thread) phase_condition_.notify_all();
111  return last_thread;
112  }
113 
114  void removeThread() EXCLUDES(lock_) {
115  MutexLock ml(lock_);
116  --running_threads_;
117  if (entered_ != 0) phase_condition_.notify_all();
118  }
119 
120  private:
121  Mutex lock_;
122  Condition phase_condition_;
123  int running_threads_;
124 
125  // State for barrier management
126  int phase_number_ = 0;
127  int entered_ = 0; // Number of threads that have entered this barrier
128 
129  // Enter the barrier and wait until all other threads have also
130  // entered the barrier. Returns iff this is the last thread to
131  // enter the barrier.
132  bool createBarrier(MutexLock& ml) REQUIRES(lock_) {
133  BM_CHECK_LT(entered_, running_threads_);
134  entered_++;
135  if (entered_ < running_threads_) {
136  // Wait for all threads to enter
137  int phase_number_cp = phase_number_;
138  auto cb = [this, phase_number_cp]() {
139  return this->phase_number_ > phase_number_cp ||
140  entered_ == running_threads_; // A thread has aborted in error
141  };
142  phase_condition_.wait(ml.native_handle(), cb);
143  if (phase_number_ > phase_number_cp) return false;
144  // else (running_threads_ == entered_) and we are the last thread.
145  }
146  // Last thread has reached the barrier
147  phase_number_++;
148  entered_ = 0;
149  return true;
150  }
151 };
152 
153 } // end namespace benchmark
154 
155 #endif // BENCHMARK_MUTEX_H_
Definition: mutex.h:99
Definition: mutex.h:87