70 lines
2.1 KiB
C++
70 lines
2.1 KiB
C++
// This file is part of Eigen, a lightweight C++ template library
|
|
// for linear algebra.
|
|
//
|
|
// Copyright (C) 2018 Rasmus Munk Larsen <rmlarsen@google.com>
|
|
//
|
|
// This Source Code Form is subject to the terms of the Mozilla
|
|
// Public License v. 2.0. If a copy of the MPL was not distributed
|
|
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
|
|
|
|
// Barrier is an object that allows one or more threads to wait until
|
|
// Notify has been called a specified number of times.
|
|
|
|
#ifndef EIGEN_CXX11_THREADPOOL_BARRIER_H
|
|
#define EIGEN_CXX11_THREADPOOL_BARRIER_H
|
|
|
|
#include "./InternalHeaderCheck.h"
|
|
|
|
namespace Eigen {
|
|
|
|
class Barrier {
|
|
public:
|
|
Barrier(unsigned int count) : state_(count << 1), notified_(false) {
|
|
eigen_plain_assert(((count << 1) >> 1) == count);
|
|
}
|
|
~Barrier() { eigen_plain_assert((state_ >> 1) == 0); }
|
|
|
|
void Notify() {
|
|
unsigned int v = state_.fetch_sub(2, std::memory_order_acq_rel) - 2;
|
|
if (v != 1) {
|
|
// Clear the lowest bit (waiter flag) and check that the original state
|
|
// value was not zero. If it was zero, it means that notify was called
|
|
// more times than the original count.
|
|
eigen_plain_assert(((v + 2) & ~1) != 0);
|
|
return; // either count has not dropped to 0, or waiter is not waiting
|
|
}
|
|
EIGEN_MUTEX_LOCK l(mu_);
|
|
eigen_plain_assert(!notified_);
|
|
notified_ = true;
|
|
cv_.notify_all();
|
|
}
|
|
|
|
void Wait() {
|
|
unsigned int v = state_.fetch_or(1, std::memory_order_acq_rel);
|
|
if ((v >> 1) == 0) return;
|
|
EIGEN_MUTEX_LOCK l(mu_);
|
|
while (!notified_) {
|
|
cv_.wait(l);
|
|
}
|
|
}
|
|
|
|
private:
|
|
EIGEN_MUTEX mu_;
|
|
EIGEN_CONDVAR cv_;
|
|
std::atomic<unsigned int> state_; // low bit is waiter flag
|
|
bool notified_;
|
|
};
|
|
|
|
// Notification is an object that allows a user to to wait for another
|
|
// thread to signal a notification that an event has occurred.
|
|
//
|
|
// Multiple threads can wait on the same Notification object,
|
|
// but only one caller must call Notify() on the object.
|
|
struct Notification : Barrier {
|
|
Notification() : Barrier(1){};
|
|
};
|
|
|
|
} // namespace Eigen
|
|
|
|
#endif // EIGEN_CXX11_THREADPOOL_BARRIER_H
|