1 files changed, 94 insertions, 0 deletions

diff --git a/src/core/hle/kernel/mutex.cpp b/src/core/hle/kernel/mutex.cpp
index 0b9dc700c..50a9a0805 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"
@@ -15,6 +16,30 @@
 
 namespace Kernel {
 
+/// 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(VAddr mutex_addr) {
+    auto& thread_list = Core::System::GetInstance().Scheduler().GetThreadList();
+
+    SharedPtr<Thread> highest_priority_thread;
+    u32 num_waiters = 0;
+
+    for (auto& thread : thread_list) {
+        if (thread->mutex_wait_address != mutex_addr)
+            continue;
+
+        ASSERT(thread->status == THREADSTATUS_WAIT_MUTEX);
+
+        ++num_waiters;
+        if (highest_priority_thread == nullptr ||
+            thread->GetPriority() < highest_priority_thread->GetPriority()) {
+            highest_priority_thread = thread;
+        }
+    }
+
+    return {highest_priority_thread, num_waiters};
+}
+
 void ReleaseThreadMutexes(Thread* thread) {
     for (auto& mtx : thread->held_mutexes) {
         mtx->SetHasWaiters(false);
@@ -135,4 +160,73 @@ void Mutex::SetHasWaiters(bool has_waiters) {
     Memory::Write32(guest_addr, guest_state.raw);
 }
 
+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);
+    }
+
+    SharedPtr<Thread> holding_thread = g_handle_table.Get<Thread>(holding_thread_handle);
+    SharedPtr<Thread> requesting_thread = g_handle_table.Get<Thread>(requesting_thread_handle);
+
+    // TODO(Subv): It is currently unknown if it is possible to lock a mutex in behalf of another
+    // thread.
+    ASSERT(requesting_thread == GetCurrentThread());
+
+    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
+    requesting_thread->mutex_wait_address = address;
+    requesting_thread->wait_handle = requesting_thread_handle;
+
+    requesting_thread->status = THREADSTATUS_WAIT_MUTEX;
+    requesting_thread->wakeup_callback = nullptr;
+
+    Core::System::GetInstance().PrepareReschedule();
+
+    return RESULT_SUCCESS;
+}
+
+ResultCode Mutex::Release(VAddr address) {
+    // The mutex address must be 4-byte aligned
+    if ((address % sizeof(u32)) != 0) {
+        return ResultCode(ErrorModule::Kernel, ErrCodes::MisalignedAddress);
+    }
+
+    auto [thread, num_waiters] = GetHighestPriorityMutexWaitingThread(address);
+
+    // There are no more threads waiting for the mutex, release it completely.
+    if (thread == nullptr) {
+        Memory::Write32(address, 0);
+        return RESULT_SUCCESS;
+    }
+
+    u32 mutex_value = thread->wait_handle;
+
+    if (num_waiters >= 2) {
+        // Notify the guest that there are still some threads waiting for the mutex
+        mutex_value |= Mutex::MutexHasWaitersFlag;
+    }
+
+    // Grant the mutex to the next waiting thread and resume it.
+    Memory::Write32(address, mutex_value);
+
+    ASSERT(thread->status == THREADSTATUS_WAIT_MUTEX);
+    thread->ResumeFromWait();
+
+    thread->condvar_wait_address = 0;
+    thread->mutex_wait_address = 0;
+    thread->wait_handle = 0;
+
+    return RESULT_SUCCESS;
+}
 } // namespace Kernel