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ticket-based fair mutex implementation
#include <condition_variable>
#include <mutex>
#include <thread>
class fair_mutex {
std::mutex mtx_;
std::condition_variable cv_;
unsigned int next_, curr_;
public:
fair_mutex() : next_(0), curr_(0) {}
~fair_mutex() = default;
fair_mutex(const fair_mutex&) = delete;
fair_mutex& operator=(const fair_mutex&) = delete;
void lock()
{
std::unique_lock<decltype(mtx_)> lk(mtx_);
const unsigned int self = next_++;
cv_.wait(lk, [&]{ return (self == curr_); });
}
bool try_lock()
{
std::lock_guard<decltype(mtx_)> lk(mtx_);
if (next_ != curr_)
return false;
++next_;
return true;
}
void unlock()
{
std::lock_guard<decltype(mtx_)> lk(mtx_);
++curr_;
cv_.notify_all();
}
};
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yohhoy commented Jan 19, 2017

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