Merge pull request #370 from Subv/sync_primitives

Kernel: Reworked the new kernel synchronization primitives.

14 files changed, 238 insertions, 443 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index c1a645460..b3807c204 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -42,8 +42,6 @@ add_library(core STATIC
     hle/kernel/client_port.h
     hle/kernel/client_session.cpp
     hle/kernel/client_session.h
-    hle/kernel/condition_variable.cpp
-    hle/kernel/condition_variable.h
     hle/kernel/errors.h
     hle/kernel/event.cpp
     hle/kernel/event.h
diff --git a/src/core/hle/kernel/condition_variable.cpp b/src/core/hle/kernel/condition_variable.cpp
deleted file mode 100644
index a786d7f74..000000000
--- a/src/core/hle/kernel/condition_variable.cpp
+++ /dev/null
@@ -1,64 +0,0 @@
-// Copyright 2018 yuzu emulator team
-// Licensed under GPLv2 or any later version
-// Refer to the license.txt file included.
-
-#include "common/assert.h"
-#include "core/hle/kernel/condition_variable.h"
-#include "core/hle/kernel/errors.h"
-#include "core/hle/kernel/kernel.h"
-#include "core/hle/kernel/object_address_table.h"
-#include "core/hle/kernel/thread.h"
-
-namespace Kernel {
-
-ConditionVariable::ConditionVariable() {}
-ConditionVariable::~ConditionVariable() {}
-
-ResultVal<SharedPtr<ConditionVariable>> ConditionVariable::Create(VAddr guest_addr,
-                                                                  std::string name) {
-    SharedPtr<ConditionVariable> condition_variable(new ConditionVariable);
-
-    condition_variable->name = std::move(name);
-    condition_variable->guest_addr = guest_addr;
-    condition_variable->mutex_addr = 0;
-
-    // Condition variables are referenced by guest address, so track this in the kernel
-    g_object_address_table.Insert(guest_addr, condition_variable);
-
-    return MakeResult<SharedPtr<ConditionVariable>>(std::move(condition_variable));
-}
-
-bool ConditionVariable::ShouldWait(Thread* thread) const {
-    return GetAvailableCount() <= 0;
-}
-
-void ConditionVariable::Acquire(Thread* thread) {
-    if (GetAvailableCount() <= 0)
-        return;
-
-    SetAvailableCount(GetAvailableCount() - 1);
-}
-
-ResultCode ConditionVariable::Release(s32 target) {
-    if (target == -1) {
-        // When -1, wake up all waiting threads
-        SetAvailableCount(static_cast<s32>(GetWaitingThreads().size()));
-        WakeupAllWaitingThreads();
-    } else {
-        // Otherwise, wake up just a single thread
-        SetAvailableCount(target);
-        WakeupWaitingThread(GetHighestPriorityReadyThread());
-    }
-
-    return RESULT_SUCCESS;
-}
-
-s32 ConditionVariable::GetAvailableCount() const {
-    return Memory::Read32(guest_addr);
-}
-
-void ConditionVariable::SetAvailableCount(s32 value) const {
-    Memory::Write32(guest_addr, value);
-}
-
-} // namespace Kernel
diff --git a/src/core/hle/kernel/condition_variable.h b/src/core/hle/kernel/condition_variable.h
deleted file mode 100644
index 1c9f06769..000000000
--- a/src/core/hle/kernel/condition_variable.h
+++ /dev/null
@@ -1,63 +0,0 @@
-// Copyright 2018 yuzu emulator team
-// Licensed under GPLv2 or any later version
-// Refer to the license.txt file included.
-
-#pragma once
-
-#include <string>
-#include <queue>
-#include "common/common_types.h"
-#include "core/hle/kernel/kernel.h"
-#include "core/hle/kernel/wait_object.h"
-#include "core/hle/result.h"
-
-namespace Kernel {
-
-class ConditionVariable final : public WaitObject {
-public:
-    /**
-     * Creates a condition variable.
-     * @param guest_addr Address of the object tracking the condition variable in guest memory. If
-     * specified, this condition variable will update the guest object when its state changes.
-     * @param name Optional name of condition variable.
-     * @return The created condition variable.
-     */
-    static ResultVal<SharedPtr<ConditionVariable>> Create(VAddr guest_addr,
-                                                          std::string name = "Unknown");
-
-    std::string GetTypeName() const override {
-        return "ConditionVariable";
-    }
-    std::string GetName() const override {
-        return name;
-    }
-
-    static const HandleType HANDLE_TYPE = HandleType::ConditionVariable;
-    HandleType GetHandleType() const override {
-        return HANDLE_TYPE;
-    }
-
-    s32 GetAvailableCount() const;
-    void SetAvailableCount(s32 value) const;
-
-    std::string name; ///< Name of condition variable (optional)
-    VAddr guest_addr; ///< Address of the guest condition variable value
-    VAddr mutex_addr; ///< (optional) Address of guest mutex value associated with this condition
-                      ///< variable, used for implementing events
-
-    bool ShouldWait(Thread* thread) const override;
-    void Acquire(Thread* thread) override;
-
-    /**
-     * Releases a slot from a condition variable.
-     * @param target The number of threads to wakeup, -1 is all.
-     * @return ResultCode indicating if the operation succeeded.
-     */
-    ResultCode Release(s32 target);
-
-private:
-    ConditionVariable();
-    ~ConditionVariable() override;
-};
-
-} // namespace Kernel
diff --git a/src/core/hle/kernel/errors.h b/src/core/hle/kernel/errors.h
index 29d8dfdaa..5be20c878 100644
--- a/src/core/hle/kernel/errors.h
+++ b/src/core/hle/kernel/errors.h
@@ -20,6 +20,7 @@ enum {
     MaxConnectionsReached = 52,
 
     // Confirmed Switch OS error codes
+    MisalignedAddress = 102,
     InvalidHandle = 114,
     Timeout = 117,
     SynchronizationCanceled = 118,
diff --git a/src/core/hle/kernel/kernel.h b/src/core/hle/kernel/kernel.h
index 053bf4e17..402ae900f 100644
--- a/src/core/hle/kernel/kernel.h
+++ b/src/core/hle/kernel/kernel.h
@@ -18,12 +18,10 @@ using Handle = u32;
 enum class HandleType : u32 {
     Unknown,
     Event,
-    Mutex,
     SharedMemory,
     Thread,
     Process,
     AddressArbiter,
-    ConditionVariable,
     Timer,
     ResourceLimit,
     CodeSet,
@@ -63,9 +61,7 @@ public:
     bool IsWaitable() const {
         switch (GetHandleType()) {
         case HandleType::Event:
-        case HandleType::Mutex:
         case HandleType::Thread:
-        case HandleType::ConditionVariable:
         case HandleType::Timer:
         case HandleType::ServerPort:
         case HandleType::ServerSession:
diff --git a/src/core/hle/kernel/mutex.cpp b/src/core/hle/kernel/mutex.cpp
index 0b9dc700c..63733ad79 100644
--- a/src/core/hle/kernel/mutex.cpp
+++ b/src/core/hle/kernel/mutex.cpp
@@ -7,6 +7,7 @@
 #include <boost/range/algorithm_ext/erase.hpp>
 #include "common/assert.h"
 #include "core/core.h"
+#include "core/hle/kernel/errors.h"
 #include "core/hle/kernel/handle_table.h"
 #include "core/hle/kernel/kernel.h"
 #include "core/hle/kernel/mutex.h"
@@ -15,124 +16,120 @@
 
 namespace Kernel {
 
-void ReleaseThreadMutexes(Thread* thread) {
-    for (auto& mtx : thread->held_mutexes) {
-        mtx->SetHasWaiters(false);
-        mtx->SetHoldingThread(nullptr);
-        mtx->WakeupAllWaitingThreads();
-    }
-    thread->held_mutexes.clear();
-}
+/// Returns the number of threads that are waiting for a mutex, and the highest priority one among
+/// those.
+static std::pair<SharedPtr<Thread>, u32> GetHighestPriorityMutexWaitingThread(
+    SharedPtr<Thread> current_thread, VAddr mutex_addr) {
 
-Mutex::Mutex() {}
-Mutex::~Mutex() {}
+    SharedPtr<Thread> highest_priority_thread;
+    u32 num_waiters = 0;
 
-SharedPtr<Mutex> Mutex::Create(SharedPtr<Kernel::Thread> holding_thread, VAddr guest_addr,
-                               std::string name) {
-    SharedPtr<Mutex> mutex(new Mutex);
+    for (auto& thread : current_thread->wait_mutex_threads) {
+        if (thread->mutex_wait_address != mutex_addr)
+            continue;
 
-    mutex->guest_addr = guest_addr;
-    mutex->name = std::move(name);
+        ASSERT(thread->status == THREADSTATUS_WAIT_MUTEX);
 
-    // If mutex was initialized with a holding thread, acquire it by the holding thread
-    if (holding_thread) {
-        mutex->Acquire(holding_thread.get());
+        ++num_waiters;
+        if (highest_priority_thread == nullptr ||
+            thread->GetPriority() < highest_priority_thread->GetPriority()) {
+            highest_priority_thread = thread;
+        }
     }
 
-    // Mutexes are referenced by guest address, so track this in the kernel
-    g_object_address_table.Insert(guest_addr, mutex);
-
-    return mutex;
+    return {highest_priority_thread, num_waiters};
 }
 
-bool Mutex::ShouldWait(Thread* thread) const {
-    auto holding_thread = GetHoldingThread();
-    return holding_thread != nullptr && thread != holding_thread;
+/// Update the mutex owner field of all threads waiting on the mutex to point to the new owner.
+static void TransferMutexOwnership(VAddr mutex_addr, SharedPtr<Thread> current_thread,
+                                   SharedPtr<Thread> new_owner) {
+    auto threads = current_thread->wait_mutex_threads;
+    for (auto& thread : threads) {
+        if (thread->mutex_wait_address != mutex_addr)
+            continue;
+
+        ASSERT(thread->lock_owner == current_thread);
+        current_thread->RemoveMutexWaiter(thread);
+        if (new_owner != thread)
+            new_owner->AddMutexWaiter(thread);
+    }
 }
 
-void Mutex::Acquire(Thread* thread) {
-    ASSERT_MSG(!ShouldWait(thread), "object unavailable!");
+ResultCode Mutex::TryAcquire(VAddr address, Handle holding_thread_handle,
+                             Handle requesting_thread_handle) {
+    // The mutex address must be 4-byte aligned
+    if ((address % sizeof(u32)) != 0) {
+        return ResultCode(ErrorModule::Kernel, ErrCodes::MisalignedAddress);
+    }
 
-    priority = thread->current_priority;
-    thread->held_mutexes.insert(this);
-    SetHoldingThread(thread);
-    thread->UpdatePriority();
-    Core::System::GetInstance().PrepareReschedule();
-}
+    SharedPtr<Thread> holding_thread = g_handle_table.Get<Thread>(holding_thread_handle);
+    SharedPtr<Thread> requesting_thread = g_handle_table.Get<Thread>(requesting_thread_handle);
 
-ResultCode Mutex::Release(Thread* thread) {
-    auto holding_thread = GetHoldingThread();
-    ASSERT(holding_thread);
+    // TODO(Subv): It is currently unknown if it is possible to lock a mutex in behalf of another
+    // thread.
+    ASSERT(requesting_thread == GetCurrentThread());
 
-    // We can only release the mutex if it's held by the calling thread.
-    ASSERT(thread == holding_thread);
+    u32 addr_value = Memory::Read32(address);
+
+    // If the mutex isn't being held, just return success.
+    if (addr_value != (holding_thread_handle | Mutex::MutexHasWaitersFlag)) {
+        return RESULT_SUCCESS;
+    }
+
+    if (holding_thread == nullptr)
+        return ERR_INVALID_HANDLE;
+
+    // Wait until the mutex is released
+    GetCurrentThread()->mutex_wait_address = address;
+    GetCurrentThread()->wait_handle = requesting_thread_handle;
+
+    GetCurrentThread()->status = THREADSTATUS_WAIT_MUTEX;
+    GetCurrentThread()->wakeup_callback = nullptr;
+
+    // Update the lock holder thread's priority to prevent priority inversion.
+    holding_thread->AddMutexWaiter(GetCurrentThread());
 
-    holding_thread->held_mutexes.erase(this);
-    holding_thread->UpdatePriority();
-    SetHoldingThread(nullptr);
-    SetHasWaiters(!GetWaitingThreads().empty());
-    WakeupAllWaitingThreads();
     Core::System::GetInstance().PrepareReschedule();
 
     return RESULT_SUCCESS;
 }
 
-void Mutex::AddWaitingThread(SharedPtr<Thread> thread) {
-    WaitObject::AddWaitingThread(thread);
-    thread->pending_mutexes.insert(this);
-    SetHasWaiters(true);
-    UpdatePriority();
-}
-
-void Mutex::RemoveWaitingThread(Thread* thread) {
-    WaitObject::RemoveWaitingThread(thread);
-    thread->pending_mutexes.erase(this);
-    if (!GetHasWaiters())
-        SetHasWaiters(!GetWaitingThreads().empty());
-    UpdatePriority();
-}
+ResultCode Mutex::Release(VAddr address) {
+    // The mutex address must be 4-byte aligned
+    if ((address % sizeof(u32)) != 0) {
+        return ResultCode(ErrorModule::Kernel, ErrCodes::MisalignedAddress);
+    }
 
-void Mutex::UpdatePriority() {
-    if (!GetHoldingThread())
-        return;
+    auto [thread, num_waiters] = GetHighestPriorityMutexWaitingThread(GetCurrentThread(), address);
 
-    u32 best_priority = THREADPRIO_LOWEST;
-    for (auto& waiter : GetWaitingThreads()) {
-        if (waiter->current_priority < best_priority)
-            best_priority = waiter->current_priority;
+    // There are no more threads waiting for the mutex, release it completely.
+    if (thread == nullptr) {
+        ASSERT(GetCurrentThread()->wait_mutex_threads.empty());
+        Memory::Write32(address, 0);
+        return RESULT_SUCCESS;
     }
 
-    if (best_priority != priority) {
-        priority = best_priority;
-        GetHoldingThread()->UpdatePriority();
-    }
-}
+    // Transfer the ownership of the mutex from the previous owner to the new one.
+    TransferMutexOwnership(address, GetCurrentThread(), thread);
 
-Handle Mutex::GetOwnerHandle() const {
-    GuestState guest_state{Memory::Read32(guest_addr)};
-    return guest_state.holding_thread_handle;
-}
+    u32 mutex_value = thread->wait_handle;
 
-SharedPtr<Thread> Mutex::GetHoldingThread() const {
-    GuestState guest_state{Memory::Read32(guest_addr)};
-    return g_handle_table.Get<Thread>(guest_state.holding_thread_handle);
-}
+    if (num_waiters >= 2) {
+        // Notify the guest that there are still some threads waiting for the mutex
+        mutex_value |= Mutex::MutexHasWaitersFlag;
+    }
 
-void Mutex::SetHoldingThread(SharedPtr<Thread> thread) {
-    GuestState guest_state{Memory::Read32(guest_addr)};
-    guest_state.holding_thread_handle.Assign(thread ? thread->guest_handle : 0);
-    Memory::Write32(guest_addr, guest_state.raw);
-}
+    // Grant the mutex to the next waiting thread and resume it.
+    Memory::Write32(address, mutex_value);
 
-bool Mutex::GetHasWaiters() const {
-    GuestState guest_state{Memory::Read32(guest_addr)};
-    return guest_state.has_waiters != 0;
-}
+    ASSERT(thread->status == THREADSTATUS_WAIT_MUTEX);
+    thread->ResumeFromWait();
 
-void Mutex::SetHasWaiters(bool has_waiters) {
-    GuestState guest_state{Memory::Read32(guest_addr)};
-    guest_state.has_waiters.Assign(has_waiters ? 1 : 0);
-    Memory::Write32(guest_addr, guest_state.raw);
-}
+    thread->lock_owner = nullptr;
+    thread->condvar_wait_address = 0;
+    thread->mutex_wait_address = 0;
+    thread->wait_handle = 0;
 
+    return RESULT_SUCCESS;
+}
 } // namespace Kernel
diff --git a/src/core/hle/kernel/mutex.h b/src/core/hle/kernel/mutex.h
index 38db21005..3117e7c70 100644
--- a/src/core/hle/kernel/mutex.h
+++ b/src/core/hle/kernel/mutex.h
@@ -15,87 +15,23 @@ namespace Kernel {
 
 class Thread;
 
-class Mutex final : public WaitObject {
+class Mutex final {
 public:
-    /**
-     * Creates a mutex.
-     * @param holding_thread Specifies a thread already holding the mutex. If not nullptr, this
-     * thread will acquire the mutex.
-     * @param guest_addr Address of the object tracking the mutex in guest memory. If specified,
-     * this mutex will update the guest object when its state changes.
-     * @param name Optional name of mutex
-     * @return Pointer to new Mutex object
-     */
-    static SharedPtr<Mutex> Create(SharedPtr<Kernel::Thread> holding_thread, VAddr guest_addr = 0,
-                                   std::string name = "Unknown");
+    /// Flag that indicates that a mutex still has threads waiting for it.
+    static constexpr u32 MutexHasWaitersFlag = 0x40000000;
+    /// Mask of the bits in a mutex address value that contain the mutex owner.
+    static constexpr u32 MutexOwnerMask = 0xBFFFFFFF;
 
-    std::string GetTypeName() const override {
-        return "Mutex";
-    }
-    std::string GetName() const override {
-        return name;
-    }
+    /// Attempts to acquire a mutex at the specified address.
+    static ResultCode TryAcquire(VAddr address, Handle holding_thread_handle,
+                                 Handle requesting_thread_handle);
 
-    static const HandleType HANDLE_TYPE = HandleType::Mutex;
-    HandleType GetHandleType() const override {
-        return HANDLE_TYPE;
-    }
-
-    u32 priority;     ///< The priority of the mutex, used for priority inheritance.
-    std::string name; ///< Name of mutex (optional)
-    VAddr guest_addr; ///< Address of the guest mutex value
-
-    /**
-     * 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;
-
-    void AddWaitingThread(SharedPtr<Thread> thread) override;
-    void RemoveWaitingThread(Thread* thread) override;
-
-    /**
-     * Attempts to release the mutex from the specified thread.
-     * @param thread Thread that wants to release the mutex.
-     * @returns The result code of the operation.
-     */
-    ResultCode Release(Thread* thread);
-
-    /// Gets the handle to the holding process stored in the guest state.
-    Handle GetOwnerHandle() const;
-
-    /// Gets the Thread pointed to by the owner handle
-    SharedPtr<Thread> GetHoldingThread() const;
-    /// Sets the holding process handle in the guest state.
-    void SetHoldingThread(SharedPtr<Thread> thread);
-
-    /// Returns the has_waiters bit in the guest state.
-    bool GetHasWaiters() const;
-    /// Sets the has_waiters bit in the guest state.
-    void SetHasWaiters(bool has_waiters);
+    /// Releases the mutex at the specified address.
+    static ResultCode Release(VAddr address);
 
 private:
-    Mutex();
-    ~Mutex() override;
-
-    /// Object in guest memory used to track the mutex state
-    union GuestState {
-        u32_le raw;
-        /// Handle of the thread that currently holds the mutex, 0 if available
-        BitField<0, 30, u32_le> holding_thread_handle;
-        /// 1 when there are threads waiting for this mutex, otherwise 0
-        BitField<30, 1, u32_le> has_waiters;
-    };
-    static_assert(sizeof(GuestState) == 4, "GuestState size is incorrect");
+    Mutex() = default;
+    ~Mutex() = default;
 };
 
-/**
- * Releases all the mutexes held by the specified thread
- * @param thread Thread that is holding the mutexes
- */
-void ReleaseThreadMutexes(Thread* thread);
-
 } // namespace Kernel
diff --git a/src/core/hle/kernel/svc.cpp b/src/core/hle/kernel/svc.cpp
index 633740992..c22da6e47 100644
--- a/src/core/hle/kernel/svc.cpp
+++ b/src/core/hle/kernel/svc.cpp
@@ -13,7 +13,6 @@
 #include "core/core_timing.h"
 #include "core/hle/kernel/client_port.h"
 #include "core/hle/kernel/client_session.h"
-#include "core/hle/kernel/condition_variable.h"
 #include "core/hle/kernel/event.h"
 #include "core/hle/kernel/handle_table.h"
 #include "core/hle/kernel/mutex.h"
@@ -262,32 +261,14 @@ static ResultCode ArbitrateLock(Handle holding_thread_handle, VAddr mutex_addr,
               "requesting_current_thread_handle=0x%08X",
               holding_thread_handle, mutex_addr, requesting_thread_handle);
 
-    SharedPtr<Thread> holding_thread = g_handle_table.Get<Thread>(holding_thread_handle);
-    SharedPtr<Thread> requesting_thread = g_handle_table.Get<Thread>(requesting_thread_handle);
-
-    ASSERT(requesting_thread);
-    ASSERT(requesting_thread == GetCurrentThread());
-
-    SharedPtr<Mutex> mutex = g_object_address_table.Get<Mutex>(mutex_addr);
-    if (!mutex) {
-        // Create a new mutex for the specified address if one does not already exist
-        mutex = Mutex::Create(holding_thread, mutex_addr);
-        mutex->name = Common::StringFromFormat("mutex-%llx", mutex_addr);
-    }
-
-    ASSERT(holding_thread == mutex->GetHoldingThread());
-
-    return WaitSynchronization1(mutex, requesting_thread.get());
+    return Mutex::TryAcquire(mutex_addr, holding_thread_handle, requesting_thread_handle);
 }
 
 /// Unlock a mutex
 static ResultCode ArbitrateUnlock(VAddr mutex_addr) {
     LOG_TRACE(Kernel_SVC, "called mutex_addr=0x%llx", mutex_addr);
 
-    SharedPtr<Mutex> mutex = g_object_address_table.Get<Mutex>(mutex_addr);
-    ASSERT(mutex);
-
-    return mutex->Release(GetCurrentThread());
+    return Mutex::Release(mutex_addr);
 }
 
 /// Break program execution
@@ -412,11 +393,6 @@ static ResultCode SetThreadPriority(Handle handle, u32 priority) {
     }
 
     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;
@@ -634,103 +610,75 @@ static ResultCode WaitProcessWideKeyAtomic(VAddr mutex_addr, VAddr condition_var
     SharedPtr<Thread> thread = g_handle_table.Get<Thread>(thread_handle);
     ASSERT(thread);
 
-    SharedPtr<Mutex> mutex = g_object_address_table.Get<Mutex>(mutex_addr);
-    if (!mutex) {
-        // Create a new mutex for the specified address if one does not already exist
-        mutex = Mutex::Create(thread, mutex_addr);
-        mutex->name = Common::StringFromFormat("mutex-%llx", mutex_addr);
-    }
-
-    SharedPtr<ConditionVariable> condition_variable =
-        g_object_address_table.Get<ConditionVariable>(condition_variable_addr);
-    if (!condition_variable) {
-        // Create a new condition_variable for the specified address if one does not already exist
-        condition_variable = ConditionVariable::Create(condition_variable_addr).Unwrap();
-        condition_variable->name =
-            Common::StringFromFormat("condition-variable-%llx", condition_variable_addr);
-    }
-
-    if (condition_variable->mutex_addr) {
-        // Previously created the ConditionVariable using WaitProcessWideKeyAtomic, verify
-        // everything is correct
-        ASSERT(condition_variable->mutex_addr == mutex_addr);
-    } else {
-        // Previously created the ConditionVariable using SignalProcessWideKey, set the mutex
-        // associated with it
-        condition_variable->mutex_addr = mutex_addr;
-    }
+    CASCADE_CODE(Mutex::Release(mutex_addr));
 
-    if (mutex->GetOwnerHandle()) {
-        // Release the mutex if the current thread is holding it
-        mutex->Release(thread.get());
-    }
+    SharedPtr<Thread> current_thread = GetCurrentThread();
+    current_thread->condvar_wait_address = condition_variable_addr;
+    current_thread->mutex_wait_address = mutex_addr;
+    current_thread->wait_handle = thread_handle;
+    current_thread->status = THREADSTATUS_WAIT_MUTEX;
+    current_thread->wakeup_callback = nullptr;
 
-    auto wakeup_callback = [mutex, nano_seconds](ThreadWakeupReason reason,
-                                                 SharedPtr<Thread> thread,
-                                                 SharedPtr<WaitObject> object, size_t index) {
-        ASSERT(thread->status == THREADSTATUS_WAIT_SYNCH_ANY);
+    current_thread->WakeAfterDelay(nano_seconds);
 
-        if (reason == ThreadWakeupReason::Timeout) {
-            thread->SetWaitSynchronizationResult(RESULT_TIMEOUT);
-            return true;
-        }
+    // Note: Deliberately don't attempt to inherit the lock owner's priority.
 
-        ASSERT(reason == ThreadWakeupReason::Signal);
+    Core::System::GetInstance().PrepareReschedule();
+    return RESULT_SUCCESS;
+}
 
-        // Now try to acquire the mutex and don't resume if it's not available.
-        if (!mutex->ShouldWait(thread.get())) {
-            mutex->Acquire(thread.get());
-            thread->SetWaitSynchronizationResult(RESULT_SUCCESS);
-            return true;
-        }
+/// Signal process wide key
+static ResultCode SignalProcessWideKey(VAddr condition_variable_addr, s32 target) {
+    LOG_TRACE(Kernel_SVC, "called, condition_variable_addr=0x%llx, target=0x%08x",
+              condition_variable_addr, target);
 
-        if (nano_seconds == 0) {
-            thread->SetWaitSynchronizationResult(RESULT_TIMEOUT);
-            return true;
-        }
+    u32 processed = 0;
+    auto& thread_list = Core::System::GetInstance().Scheduler().GetThreadList();
 
-        thread->wait_objects = {mutex};
-        mutex->AddWaitingThread(thread);
-        thread->status = THREADSTATUS_WAIT_SYNCH_ANY;
+    for (auto& thread : thread_list) {
+        if (thread->condvar_wait_address != condition_variable_addr)
+            continue;
 
-        // Create an event to wake the thread up after the
-        // specified nanosecond delay has passed
-        thread->WakeAfterDelay(nano_seconds);
-        thread->wakeup_callback = DefaultThreadWakeupCallback;
+        // Only process up to 'target' threads, unless 'target' is -1, in which case process
+        // them all.
+        if (target != -1 && processed >= target)
+            break;
 
-        Core::System::GetInstance().PrepareReschedule();
+        // If the mutex is not yet acquired, acquire it.
+        u32 mutex_val = Memory::Read32(thread->mutex_wait_address);
 
-        return false;
-    };
-    CASCADE_CODE(
-        WaitSynchronization1(condition_variable, thread.get(), nano_seconds, wakeup_callback));
+        if (mutex_val == 0) {
+            // We were able to acquire the mutex, resume this thread.
+            Memory::Write32(thread->mutex_wait_address, thread->wait_handle);
+            ASSERT(thread->status == THREADSTATUS_WAIT_MUTEX);
+            thread->ResumeFromWait();
 
-    return RESULT_SUCCESS;
-}
+            auto lock_owner = thread->lock_owner;
+            if (lock_owner)
+                lock_owner->RemoveMutexWaiter(thread);
 
-/// Signal process wide key
-static ResultCode SignalProcessWideKey(VAddr condition_variable_addr, s32 target) {
-    LOG_TRACE(Kernel_SVC, "called, condition_variable_addr=0x%llx, target=0x%08x",
-              condition_variable_addr, target);
+            thread->lock_owner = nullptr;
+            thread->mutex_wait_address = 0;
+            thread->condvar_wait_address = 0;
+            thread->wait_handle = 0;
+        } else {
+            // Couldn't acquire the mutex, block the thread.
+            Handle owner_handle = static_cast<Handle>(mutex_val & Mutex::MutexOwnerMask);
+            auto owner = g_handle_table.Get<Thread>(owner_handle);
+            ASSERT(owner);
+            ASSERT(thread->status != THREADSTATUS_RUNNING);
+            thread->status = THREADSTATUS_WAIT_MUTEX;
+            thread->wakeup_callback = nullptr;
 
-    // Wakeup all or one thread - Any other value is unimplemented
-    ASSERT(target == -1 || target == 1);
+            // Signal that the mutex now has a waiting thread.
+            Memory::Write32(thread->mutex_wait_address, mutex_val | Mutex::MutexHasWaitersFlag);
 
-    SharedPtr<ConditionVariable> condition_variable =
-        g_object_address_table.Get<ConditionVariable>(condition_variable_addr);
-    if (!condition_variable) {
-        // Create a new condition_variable for the specified address if one does not already exist
-        condition_variable = ConditionVariable::Create(condition_variable_addr).Unwrap();
-        condition_variable->name =
-            Common::StringFromFormat("condition-variable-%llx", condition_variable_addr);
-    }
+            owner->AddMutexWaiter(thread);
 
-    CASCADE_CODE(condition_variable->Release(target));
+            Core::System::GetInstance().PrepareReschedule();
+        }
 
-    if (condition_variable->mutex_addr) {
-        // If a mutex was created for this condition_variable, wait the current thread on it
-        SharedPtr<Mutex> mutex = g_object_address_table.Get<Mutex>(condition_variable->mutex_addr);
-        return WaitSynchronization1(mutex, GetCurrentThread());
+        ++processed;
     }
 
     return RESULT_SUCCESS;
diff --git a/src/core/hle/kernel/thread.cpp b/src/core/hle/kernel/thread.cpp
index f3a8aa4aa..36222d45f 100644
--- a/src/core/hle/kernel/thread.cpp
+++ b/src/core/hle/kernel/thread.cpp
@@ -77,9 +77,6 @@ void Thread::Stop() {
     }
     wait_objects.clear();
 
-    // Release all the mutexes that this thread holds
-    ReleaseThreadMutexes(this);
-
     // Mark the TLS slot in the thread's page as free.
     u64 tls_page = (tls_address - Memory::TLS_AREA_VADDR) / Memory::PAGE_SIZE;
     u64 tls_slot =
@@ -126,6 +123,19 @@ static void ThreadWakeupCallback(u64 thread_handle, int cycles_late) {
             resume = thread->wakeup_callback(ThreadWakeupReason::Timeout, thread, nullptr, 0);
     }
 
+    if (thread->mutex_wait_address != 0 || thread->condvar_wait_address != 0 ||
+        thread->wait_handle) {
+        ASSERT(thread->status == THREADSTATUS_WAIT_MUTEX);
+        thread->mutex_wait_address = 0;
+        thread->condvar_wait_address = 0;
+        thread->wait_handle = 0;
+
+        auto lock_owner = thread->lock_owner;
+        // Threads waking up by timeout from WaitProcessWideKey do not perform priority inheritance
+        // and don't have a lock owner.
+        ASSERT(lock_owner == nullptr);
+    }
+
     if (resume)
         thread->ResumeFromWait();
 }
@@ -151,6 +161,7 @@ void Thread::ResumeFromWait() {
     case THREADSTATUS_WAIT_HLE_EVENT:
     case THREADSTATUS_WAIT_SLEEP:
     case THREADSTATUS_WAIT_IPC:
+    case THREADSTATUS_WAIT_MUTEX:
         break;
 
     case THREADSTATUS_READY:
@@ -256,7 +267,9 @@ ResultVal<SharedPtr<Thread>> Thread::Create(std::string name, VAddr entry_point,
     thread->last_running_ticks = CoreTiming::GetTicks();
     thread->processor_id = processor_id;
     thread->wait_objects.clear();
-    thread->wait_address = 0;
+    thread->mutex_wait_address = 0;
+    thread->condvar_wait_address = 0;
+    thread->wait_handle = 0;
     thread->name = std::move(name);
     thread->callback_handle = wakeup_callback_handle_table.Create(thread).Unwrap();
     thread->owner_process = owner_process;
@@ -317,17 +330,8 @@ ResultVal<SharedPtr<Thread>> Thread::Create(std::string name, VAddr entry_point,
 void Thread::SetPriority(u32 priority) {
     ASSERT_MSG(priority <= THREADPRIO_LOWEST && priority >= THREADPRIO_HIGHEST,
                "Invalid priority value.");
-    Core::System::GetInstance().Scheduler().SetThreadPriority(this, priority);
-    nominal_priority = current_priority = priority;
-}
-
-void Thread::UpdatePriority() {
-    u32 best_priority = nominal_priority;
-    for (auto& mutex : held_mutexes) {
-        if (mutex->priority < best_priority)
-            best_priority = mutex->priority;
-    }
-    BoostPriority(best_priority);
+    nominal_priority = priority;
+    UpdatePriority();
 }
 
 void Thread::BoostPriority(u32 priority) {
@@ -377,6 +381,38 @@ VAddr Thread::GetCommandBufferAddress() const {
     return GetTLSAddress() + CommandHeaderOffset;
 }
 
+void Thread::AddMutexWaiter(SharedPtr<Thread> thread) {
+    thread->lock_owner = this;
+    wait_mutex_threads.emplace_back(std::move(thread));
+    UpdatePriority();
+}
+
+void Thread::RemoveMutexWaiter(SharedPtr<Thread> thread) {
+    boost::remove_erase(wait_mutex_threads, thread);
+    thread->lock_owner = nullptr;
+    UpdatePriority();
+}
+
+void Thread::UpdatePriority() {
+    // Find the highest priority among all the threads that are waiting for this thread's lock
+    u32 new_priority = nominal_priority;
+    for (const auto& thread : wait_mutex_threads) {
+        if (thread->nominal_priority < new_priority)
+            new_priority = thread->nominal_priority;
+    }
+
+    if (new_priority == current_priority)
+        return;
+
+    Core::System::GetInstance().Scheduler().SetThreadPriority(this, new_priority);
+
+    current_priority = new_priority;
+
+    // Recursively update the priority of the thread that depends on the priority of this one.
+    if (lock_owner)
+        lock_owner->UpdatePriority();
+}
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
 /**
diff --git a/src/core/hle/kernel/thread.h b/src/core/hle/kernel/thread.h
index dbf47e269..e0a3c0934 100644
--- a/src/core/hle/kernel/thread.h
+++ b/src/core/hle/kernel/thread.h
@@ -18,7 +18,7 @@
 enum ThreadPriority : u32 {
     THREADPRIO_HIGHEST = 0,       ///< Highest thread priority
     THREADPRIO_USERLAND_MAX = 24, ///< Highest thread priority for userland apps
-    THREADPRIO_DEFAULT = 48,      ///< Default thread priority for userland apps
+    THREADPRIO_DEFAULT = 44,      ///< Default thread priority for userland apps
     THREADPRIO_LOWEST = 63,       ///< Lowest thread priority
 };
 
@@ -43,6 +43,7 @@ enum ThreadStatus {
     THREADSTATUS_WAIT_IPC,       ///< Waiting for the reply from an IPC request
     THREADSTATUS_WAIT_SYNCH_ANY, ///< Waiting due to WaitSynch1 or WaitSynchN with wait_all = false
     THREADSTATUS_WAIT_SYNCH_ALL, ///< Waiting due to WaitSynchronizationN with wait_all = true
+    THREADSTATUS_WAIT_MUTEX,     ///< Waiting due to an ArbitrateLock/WaitProcessWideKey svc
     THREADSTATUS_DORMANT,        ///< Created but not yet made ready
     THREADSTATUS_DEAD            ///< Run to completion, or forcefully terminated
 };
@@ -54,7 +55,6 @@ enum class ThreadWakeupReason {
 
 namespace Kernel {
 
-class Mutex;
 class Process;
 
 class Thread final : public WaitObject {
@@ -104,17 +104,20 @@ public:
     void SetPriority(u32 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
      */
     void BoostPriority(u32 priority);
 
+    /// Adds a thread to the list of threads that are waiting for a lock held by this thread.
+    void AddMutexWaiter(SharedPtr<Thread> thread);
+
+    /// Removes a thread from the list of threads that are waiting for a lock held by this thread.
+    void RemoveMutexWaiter(SharedPtr<Thread> thread);
+
+    /// Recalculates the current priority taking into account priority inheritance.
+    void UpdatePriority();
+
     /**
      * Gets the thread's thread ID
      * @return The thread's ID
@@ -205,19 +208,22 @@ public:
 
     VAddr tls_address; ///< Virtual address of the Thread Local Storage of the thread
 
-    /// 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, in the same order as they were
     // passed to WaitSynchronization1/N.
     std::vector<SharedPtr<WaitObject>> wait_objects;
 
-    VAddr wait_address; ///< If waiting on an AddressArbiter, this is the arbitration address
+    /// List of threads that are waiting for a mutex that is held by this thread.
+    std::vector<SharedPtr<Thread>> wait_mutex_threads;
+
+    /// Thread that owns the lock that this thread is waiting for.
+    SharedPtr<Thread> lock_owner;
+
+    // If waiting on a ConditionVariable, this is the ConditionVariable  address
+    VAddr condvar_wait_address;
+    VAddr mutex_wait_address; ///< If waiting on a Mutex, this is the mutex address
+    Handle wait_handle;       ///< The handle used to wait for the mutex.
 
     std::string name;
 
diff --git a/src/core/hle/service/nvflinger/buffer_queue.cpp b/src/core/hle/service/nvflinger/buffer_queue.cpp
index 03a4fed59..e4ff2e267 100644
--- a/src/core/hle/service/nvflinger/buffer_queue.cpp
+++ b/src/core/hle/service/nvflinger/buffer_queue.cpp
@@ -9,7 +9,8 @@
 #include "core/core_timing.h"
 #include "core/hle/service/nvflinger/buffer_queue.h"
 
-namespace Service::NVFlinger {
+namespace Service {
+namespace NVFlinger {
 
 BufferQueue::BufferQueue(u32 id, u64 layer_id) : id(id), layer_id(layer_id) {
     native_handle = Kernel::Event::Create(Kernel::ResetType::OneShot, "BufferQueue NativeHandle");
@@ -110,4 +111,5 @@ void BufferQueue::SetBufferWaitEvent(Kernel::SharedPtr<Kernel::Event>&& wait_eve
     buffer_wait_event = std::move(wait_event);
 }
 
-} // namespace Service::NVFlinger
+} // namespace NVFlinger
+} // namespace Service
diff --git a/src/core/hle/service/nvflinger/buffer_queue.h b/src/core/hle/service/nvflinger/buffer_queue.h
index 95adc4706..1de5767cb 100644
--- a/src/core/hle/service/nvflinger/buffer_queue.h
+++ b/src/core/hle/service/nvflinger/buffer_queue.h
@@ -13,7 +13,8 @@ namespace CoreTiming {
 struct EventType;
 }
 
-namespace Service::NVFlinger {
+namespace Service {
+namespace NVFlinger {
 
 struct IGBPBuffer {
     u32_le magic;
@@ -97,4 +98,5 @@ private:
     Kernel::SharedPtr<Kernel::Event> buffer_wait_event;
 };
 
-} // namespace Service::NVFlinger
+} // namespace NVFlinger
+} // namespace Service
diff --git a/src/core/loader/nro.cpp b/src/core/loader/nro.cpp
index b5133e4d6..3853cfa1a 100644
--- a/src/core/loader/nro.cpp
+++ b/src/core/loader/nro.cpp
@@ -137,7 +137,7 @@ ResultStatus AppLoader_NRO::Load(Kernel::SharedPtr<Kernel::Process>& process) {
     process->address_mappings = default_address_mappings;
     process->resource_limit =
         Kernel::ResourceLimit::GetForCategory(Kernel::ResourceLimitCategory::APPLICATION);
-    process->Run(base_addr, 48, Memory::DEFAULT_STACK_SIZE);
+    process->Run(base_addr, THREADPRIO_DEFAULT, Memory::DEFAULT_STACK_SIZE);
 
     is_loaded = true;
     return ResultStatus::Success;
diff --git a/src/core/loader/nso.cpp b/src/core/loader/nso.cpp
index 3bc10ed0d..962bed2ab 100644
--- a/src/core/loader/nso.cpp
+++ b/src/core/loader/nso.cpp
@@ -165,7 +165,7 @@ ResultStatus AppLoader_NSO::Load(Kernel::SharedPtr<Kernel::Process>& process) {
     process->address_mappings = default_address_mappings;
     process->resource_limit =
         Kernel::ResourceLimit::GetForCategory(Kernel::ResourceLimitCategory::APPLICATION);
-    process->Run(Memory::PROCESS_IMAGE_VADDR, 48, Memory::DEFAULT_STACK_SIZE);
+    process->Run(Memory::PROCESS_IMAGE_VADDR, THREADPRIO_DEFAULT, Memory::DEFAULT_STACK_SIZE);
 
     is_loaded = true;
     return ResultStatus::Success;