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Core/TaskScheduler: Fix race conditions when calling AddTask while workers are not idle 

Update TaskScheduler.cpp
This commit is contained in:
SirLynix 2024-02-02 16:20:40 +01:00
parent 44e55adcd9
commit fa73e463a6
1 changed files with 41 additions and 33 deletions
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74
src/Nazara/Core/TaskScheduler.cpp
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@ -62,14 +62,13 @@ namespace Nz
void AddTask(TaskScheduler::Task* task)
{
m_tasks.push(task);
if (!m_notifier.test_and_set())
m_notifier.notify_one();
WakeUp();
}
void Run()
{
bool idle = true;
m_notifier.wait(false); // wait until task scheduler finishes initializing
// Wait until task scheduler started
m_notifier.wait(false);
StackArray<unsigned int> randomWorkerIndices = NazaraStackArrayNoInit(unsigned int, m_owner.GetWorkerCount() - 1);
{
@ -84,9 +83,23 @@ namespace Nz
std::shuffle(randomWorkerIndices.begin(), randomWorkerIndices.end(), gen);
}
bool idle = false;
do
{
auto ExecuteTask = [&](TaskScheduler::Task* task)
// Wait for tasks if we don't have any right now
// FIXME: We can't use pop() because push() and pop() are not thread-safe (and push is called on another thread), but steal() is
// is it an issue?
std::optional<TaskScheduler::Task*> task = m_tasks.steal();
if (!task)
{
for (unsigned int workerIndex : randomWorkerIndices)
{
if (task = m_owner.GetWorker(workerIndex).StealTask())
break;
}
}
if (task)
{
if (idle)
{
@ -94,39 +107,22 @@ namespace Nz
idle = false;
}
(*task)();
};
// Wait for tasks if we don't have any right now
std::optional<TaskScheduler::Task*> task = m_tasks.pop();
if (task)
ExecuteTask(*task);
NAZARA_ASSUME(*task != nullptr);
(**task)();
}
else
{
// Try to steal a task from another worker in a random order to avoid contention
for (unsigned int workerIndex : randomWorkerIndices)
if (!idle)
{
if (task = m_owner.GetWorker(workerIndex).StealTask())
{
ExecuteTask(*task);
break;
}
m_owner.NotifyWorkerIdle();
idle = true;
}
if (!task)
{
if (!idle)
{
m_owner.NotifyWorkerIdle();
idle = true;
}
m_notifier.wait(false);
m_notifier.clear();
}
m_notifier.wait(false);
m_notifier.clear();
}
}
while (m_running);
while (m_running.load(std::memory_order_relaxed));
}
std::optional<TaskScheduler::Task*> StealTask()
@ -134,6 +130,12 @@ namespace Nz
return m_tasks.steal();
}
void WakeUp()
{
if (!m_notifier.test_and_set())
m_notifier.notify_one();
}
Worker& operator=(const Worker& worker) = delete;
Worker& operator=(Worker&&)
@ -153,7 +155,7 @@ namespace Nz
NAZARA_WARNING_POP()
TaskScheduler::TaskScheduler(unsigned int workerCount) :
m_idle(true),
m_idle(false),
m_nextWorkerIndex(0),
m_tasks(256 * sizeof(Task)),
m_workerCount(workerCount)
@ -161,11 +163,17 @@ namespace Nz
if (m_workerCount == 0)
m_workerCount = std::max(Core::Instance()->GetHardwareInfo().GetCpuThreadCount(), 1u);
m_idleWorkerCount = m_workerCount;
m_idleWorkerCount = 0;
m_workers.reserve(m_workerCount);
for (unsigned int i = 0; i < m_workerCount; ++i)
m_workers.emplace_back(*this, i);
for (unsigned int i = 0; i < m_workerCount; ++i)
m_workers[i].WakeUp();
// Wait until all worked started
WaitForTasks();
}
TaskScheduler::~TaskScheduler()