Kernel/Mutex: Propagate thread priority changes to other threads inheriting the priority via mutexes

This commit is contained in:
Subv 2017-01-02 19:38:08 -05:00
parent b6a0355568
commit d3ff5b91e1
5 changed files with 60 additions and 42 deletions

View file

@ -13,38 +13,6 @@
namespace Kernel {
/**
* Boost's a thread's priority to the best priority among the thread's held mutexes.
* This prevents priority inversion via priority inheritance.
*/
static void UpdateThreadPriority(Thread* thread) {
s32 best_priority = THREADPRIO_LOWEST;
for (auto& mutex : thread->held_mutexes) {
if (mutex->priority < best_priority)
best_priority = mutex->priority;
}
best_priority = std::min(best_priority, thread->nominal_priority);
thread->SetPriority(best_priority);
}
/**
* Elevate the mutex priority to the best priority
* among the priorities of all its waiting threads.
*/
static void UpdateMutexPriority(Mutex* mutex) {
s32 best_priority = THREADPRIO_LOWEST;
for (auto& waiter : mutex->GetWaitingThreads()) {
if (waiter->current_priority < best_priority)
best_priority = waiter->current_priority;
}
if (best_priority != mutex->priority) {
mutex->priority = best_priority;
UpdateThreadPriority(mutex->holding_thread.get());
}
}
void ReleaseThreadMutexes(Thread* thread) {
for (auto& mtx : thread->held_mutexes) {
mtx->lock_count = 0;
@ -83,9 +51,7 @@ void Mutex::Acquire(Thread* thread) {
priority = thread->current_priority;
thread->held_mutexes.insert(this);
holding_thread = thread;
UpdateThreadPriority(thread);
thread->UpdatePriority();
Core::System::GetInstance().PrepareReschedule();
}
@ -100,7 +66,7 @@ void Mutex::Release() {
// Yield to the next thread only if we've fully released the mutex
if (lock_count == 0) {
holding_thread->held_mutexes.erase(this);
UpdateThreadPriority(holding_thread.get());
holding_thread->UpdatePriority();
holding_thread = nullptr;
WakeupAllWaitingThreads();
Core::System::GetInstance().PrepareReschedule();
@ -110,12 +76,30 @@ void Mutex::Release() {
void Mutex::AddWaitingThread(SharedPtr<Thread> thread) {
WaitObject::AddWaitingThread(thread);
UpdateMutexPriority(this);
thread->pending_mutexes.insert(this);
UpdatePriority();
}
void Mutex::RemoveWaitingThread(Thread* thread) {
WaitObject::RemoveWaitingThread(thread);
UpdateMutexPriority(this);
thread->pending_mutexes.erase(this);
UpdatePriority();
}
void Mutex::UpdatePriority() {
if (!holding_thread)
return;
s32 best_priority = THREADPRIO_LOWEST;
for (auto& waiter : GetWaitingThreads()) {
if (waiter->current_priority < best_priority)
best_priority = waiter->current_priority;
}
if (best_priority != priority) {
priority = best_priority;
holding_thread->UpdatePriority();
}
}
} // namespace

View file

@ -39,6 +39,12 @@ public:
std::string name; ///< Name of mutex (optional)
SharedPtr<Thread> holding_thread; ///< Thread that has acquired the mutex
/**
* Elevate the mutex priority to the best priority
* among the priorities of all its waiting threads.
*/
void UpdatePriority();
bool ShouldWait(Thread* thread) const override;
void Acquire(Thread* thread) override;

View file

@ -105,15 +105,15 @@ void Thread::Stop() {
WakeupAllWaitingThreads();
// Release all the mutexes that this thread holds
ReleaseThreadMutexes(this);
// Clean up any dangling references in objects that this thread was waiting for
for (auto& wait_object : wait_objects) {
wait_object->RemoveWaitingThread(this);
}
wait_objects.clear();
// Release all the mutexes that this thread holds
ReleaseThreadMutexes(this);
// Mark the TLS slot in the thread's page as free.
u32 tls_page = (tls_address - Memory::TLS_AREA_VADDR) / Memory::PAGE_SIZE;
u32 tls_slot =
@ -515,8 +515,21 @@ void Thread::SetPriority(s32 priority) {
nominal_priority = current_priority = priority;
}
void Thread::UpdatePriority() {
s32 best_priority = nominal_priority;
for (auto& mutex : held_mutexes) {
if (mutex->priority < best_priority)
best_priority = mutex->priority;
}
BoostPriority(best_priority);
}
void Thread::BoostPriority(s32 priority) {
// If thread was ready, adjust queues
if (status == THREADSTATUS_READY)
ready_queue.move(this, current_priority, priority);
else
ready_queue.prepare(priority);
current_priority = priority;
}

View file

@ -89,6 +89,12 @@ public:
*/
void SetPriority(s32 priority);
/**
* Boost's a thread's priority to the best priority among the thread's held mutexes.
* This prevents priority inversion via priority inheritance.
*/
void UpdatePriority();
/**
* Temporarily boosts the thread's priority until the next time it is scheduled
* @param priority The new priority
@ -178,6 +184,9 @@ public:
/// Mutexes currently held by this thread, which will be released when it exits.
boost::container::flat_set<SharedPtr<Mutex>> held_mutexes;
/// Mutexes that this thread is currently waiting for.
boost::container::flat_set<SharedPtr<Mutex>> pending_mutexes;
SharedPtr<Process> owner_process; ///< Process that owns this thread
/// Objects that the thread is waiting on.

View file

@ -611,6 +611,12 @@ static ResultCode SetThreadPriority(Kernel::Handle handle, s32 priority) {
return ERR_INVALID_HANDLE;
thread->SetPriority(priority);
thread->UpdatePriority();
// Update the mutexes that this thread is waiting for
for (auto& mutex : thread->pending_mutexes)
mutex->UpdatePriority();
Core::System::GetInstance().PrepareReschedule();
return RESULT_SUCCESS;
}