Atmosphere/mesosphere/source/threading/KMutex.cpp
2019-06-03 17:41:00 -07:00

62 lines
2.1 KiB
C++

#include <mesosphere/threading/KMutex.hpp>
#include <mesosphere/threading/KThread.hpp>
#include <mesosphere/threading/KScheduler.hpp>
namespace mesosphere
{
void KMutex::lock_slow_path(KThread &owner, KThread &requester)
{
// Requester is currentThread most of (all ?) the time
KCriticalSection &critsec = KScheduler::GetCriticalSection();
std::lock_guard criticalSection{critsec};
if (KCoreContext::GetCurrentInstance().GetScheduler()->IsActive()) {
requester.SetWantedMutex((uiptr)this);
owner.AddMutexWaiter(requester);
// If the requester is/was running, pause it (sets status even if force-paused).
requester.RescheduleIfStatusEquals(KThread::SchedulingStatus::Running, KThread::SchedulingStatus::Paused);
// If the owner is force-paused, temporarily wake it.
if (owner.IsForcePaused()) {
owner.AdjustScheduling(owner.RevertForcePauseToField());
}
// Commit scheduler changes NOW.
critsec.unlock();
critsec.lock();
/*
At this point, mutex ownership has been transferred to requester or another thread (false wake).
Make sure the requester, now resumed, isn't in any mutex wait list.
*/
owner.RemoveMutexWaiter(requester);
}
}
void KMutex::unlock_slow_path(KThread &owner)
{
std::lock_guard criticalSection{KScheduler::GetCriticalSection()};
size_t count;
KThread *newOwner = owner.RelinquishMutex(&count, (uiptr)this);
native_handle_type newTag;
if (newOwner != nullptr) {
// Wake up new owner
newTag = (native_handle_type)newOwner | (count > 1 ? 1 : 0);
// Sets status even if force-paused.
newOwner->RescheduleIfStatusEquals(KThread::SchedulingStatus::Paused, KThread::SchedulingStatus::Running);
} else {
// Free the mutex.
newTag = 0;
}
// Allow previous owner to get back to forced-sleep, if no other thread wants the kmutexes it is holding.
if (!owner.IsDying() && owner.GetNumberOfKMutexWaiters() == 0) {
owner.AdjustScheduling(owner.CommitForcePauseToField());
}
tag = newTag;
}
}