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#ifndef BENCHMARK_MUTEX_H_
#define BENCHMARK_MUTEX_H_
#include <condition_variable>
#include <mutex>
#include "check.h"
// Enable thread safety attributes only with clang.
// The attributes can be safely erased when compiling with other compilers.
#if defined(HAVE_THREAD_SAFETY_ATTRIBUTES)
#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 benchmark {
typedef std::condition_variable Condition;
// NOTE: Wrappers for std::mutex and std::unique_lock are provided so that
// we can annotate them with thread safety attributes and use the
// -Wthread-safety warning with clang. The standard library types cannot be
// used directly because they do not provide the required annotations.
class CAPABILITY("mutex") Mutex {
public:
Mutex() {}
void lock() ACQUIRE() { mut_.lock(); }
void unlock() RELEASE() { mut_.unlock(); }
std::mutex& native_handle() { return mut_; }
private:
std::mutex mut_;
};
class SCOPED_CAPABILITY MutexLock {
typedef std::unique_lock<std::mutex> MutexLockImp;
public:
MutexLock(Mutex& m) ACQUIRE(m) : ml_(m.native_handle()) {}
~MutexLock() RELEASE() {}
MutexLockImp& native_handle() { return ml_; }
private:
MutexLockImp ml_;
};
class Barrier {
public:
Barrier(int num_threads) : running_threads_(num_threads) {}
// Called by each thread
bool wait() EXCLUDES(lock_) {
bool last_thread = false;
{
MutexLock ml(lock_);
last_thread = createBarrier(ml);
}
if (last_thread) phase_condition_.notify_all();
return last_thread;
}
void removeThread() EXCLUDES(lock_) {
MutexLock ml(lock_);
--running_threads_;
if (entered_ != 0) phase_condition_.notify_all();
}
private:
Mutex lock_;
Condition phase_condition_;
int running_threads_;
// State for barrier management
int phase_number_ = 0;
int entered_ = 0; // Number of threads that have entered this barrier
// Enter the barrier and wait until all other threads have also
// entered the barrier. Returns iff this is the last thread to
// enter the barrier.
bool createBarrier(MutexLock& ml) REQUIRES(lock_) {
CHECK_LT(entered_, running_threads_);
entered_++;
if (entered_ < running_threads_) {
// Wait for all threads to enter
int phase_number_cp = phase_number_;
auto cb = [this, phase_number_cp]() {
return this->phase_number_ > phase_number_cp ||
entered_ == running_threads_; // A thread has aborted in error
};
phase_condition_.wait(ml.native_handle(), cb);
if (phase_number_ > phase_number_cp) return false;
// else (running_threads_ == entered_) and we are the last thread.
}
// Last thread has reached the barrier
phase_number_++;
entered_ = 0;
return true;
}
};
} // end namespace benchmark
#endif // BENCHMARK_MUTEX_H_
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