rpcs3/Utilities/Semaphore.cpp

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#include "stdafx.h"
#include "Utilities/Semaphore.h"
bool semaphore_t::try_wait()
{
// check m_value without interlocked op
if (m_var.load().value == 0)
{
return false;
}
// try to decrement m_value atomically
const auto old = m_var.atomic_op([](sync_var_t& var)
{
if (var.value)
{
var.value--;
}
});
// recheck atomic result
if (old.value == 0)
{
return false;
}
return true;
}
bool semaphore_t::try_post()
{
// check m_value without interlocked op
if (m_var.load().value >= max_value)
{
return false;
}
// try to increment m_value atomically
const auto old = m_var.atomic_op([&](sync_var_t& var)
{
if (var.value < max_value)
{
var.value++;
}
});
// recheck atomic result
if (old.value >= max_value)
{
return false;
}
if (old.waiters)
{
// notify waiting thread
std::lock_guard<std::mutex> lock(m_mutex);
m_cv.notify_one();
}
return true;
}
void semaphore_t::wait()
{
if (m_var.atomic_op([](sync_var_t& var) -> bool
{
if (var.value)
{
var.value--;
return true;
}
else
{
//var.waiters++;
return false;
}
}))
{
return;
}
std::unique_lock<std::mutex> lock(m_mutex);
m_var.atomic_op([](sync_var_t& var)
{
var.waiters++;
});
while (!m_var.atomic_op([](sync_var_t& var) -> bool
{
if (var.value)
{
var.value--;
var.waiters--;
return true;
}
else
{
return false;
}
}))
{
m_cv.wait(lock);
}
}
bool semaphore_t::post_and_wait()
{
// TODO: merge these functions? Probably has a race condition.
if (try_wait()) return false;
try_post();
wait();
return true;
}