3 files changed, 134 insertions, 24 deletions

diff --git a/src/core/hle/kernel/mutex.cpp b/src/core/hle/kernel/mutex.cpp
index 30dade552..1b7cda740 100644
--- a/src/core/hle/kernel/mutex.cpp
+++ b/src/core/hle/kernel/mutex.cpp
@@ -7,8 +7,10 @@
 #include <boost/range/algorithm_ext/erase.hpp>
 #include "common/assert.h"
 #include "core/core.h"
+#include "core/hle/kernel/handle_table.h"
 #include "core/hle/kernel/kernel.h"
 #include "core/hle/kernel/mutex.h"
+#include "core/hle/kernel/object_address_table.h"
 #include "core/hle/kernel/thread.h"
 
 namespace Kernel {
@@ -25,17 +27,25 @@ void ReleaseThreadMutexes(Thread* thread) {
 Mutex::Mutex() {}
 Mutex::~Mutex() {}
 
-SharedPtr<Mutex> Mutex::Create(bool initial_locked, VAddr addr, std::string name) {
+SharedPtr<Mutex> Mutex::Create(SharedPtr<Kernel::Thread> holding_thread, VAddr guest_addr,
+                               std::string name) {
     SharedPtr<Mutex> mutex(new Mutex);
 
     mutex->lock_count = 0;
-    mutex->addr = addr;
+    mutex->guest_addr = guest_addr;
     mutex->name = std::move(name);
     mutex->holding_thread = nullptr;
 
-    // Acquire mutex with current thread if initialized as locked
-    if (initial_locked)
-        mutex->Acquire(GetCurrentThread());
+    // If mutex was initialized with a holding thread, acquire it by the holding thread
+    if (holding_thread) {
+        mutex->Acquire(holding_thread.get());
+    }
+
+    // Mutexes are referenced by guest address, so track this in the kernel
+    g_object_address_table.Insert(guest_addr, mutex);
+
+    // Verify that the created mutex matches the guest state for the mutex
+    mutex->VerifyGuestState();
 
     return mutex;
 }
@@ -53,38 +63,60 @@ void Mutex::Acquire(Thread* thread) {
         thread->held_mutexes.insert(this);
         holding_thread = thread;
         thread->UpdatePriority();
+        UpdateGuestState();
         Core::System::GetInstance().PrepareReschedule();
     }
 
     lock_count++;
 }
 
-void Mutex::Release() {
-    // Only release if the mutex is held
-    if (lock_count > 0) {
-        lock_count--;
-
-        // Yield to the next thread only if we've fully released the mutex
-        if (lock_count == 0) {
-            holding_thread->held_mutexes.erase(this);
-            holding_thread->UpdatePriority();
-            holding_thread = nullptr;
-            WakeupAllWaitingThreads();
-            Core::System::GetInstance().PrepareReschedule();
+ResultCode Mutex::Release(Thread* thread) {
+    // We can only release the mutex if it's held by the calling thread.
+    if (thread != holding_thread) {
+        if (holding_thread) {
+            LOG_ERROR(
+                Kernel,
+                "Tried to release a mutex (owned by thread id %u) from a different thread id %u",
+                holding_thread->thread_id, thread->thread_id);
         }
+        // TODO(bunnei): Use correct error code
+        return ResultCode(-1);
+    }
+
+    // Note: It should not be possible for the situation where the mutex has a holding thread with a
+    // zero lock count to occur. The real kernel still checks for this, so we do too.
+    if (lock_count <= 0) {
+        // TODO(bunnei): Use correct error code
+        return ResultCode(-1);
+    }
+
+    lock_count--;
+
+    // Yield to the next thread only if we've fully released the mutex
+    if (lock_count == 0) {
+        holding_thread->held_mutexes.erase(this);
+        holding_thread->UpdatePriority();
+        holding_thread = nullptr;
+        WakeupAllWaitingThreads();
+        UpdateGuestState();
+        Core::System::GetInstance().PrepareReschedule();
     }
+
+    return RESULT_SUCCESS;
 }
 
 void Mutex::AddWaitingThread(SharedPtr<Thread> thread) {
     WaitObject::AddWaitingThread(thread);
     thread->pending_mutexes.insert(this);
     UpdatePriority();
+    UpdateGuestState();
 }
 
 void Mutex::RemoveWaitingThread(Thread* thread) {
     WaitObject::RemoveWaitingThread(thread);
     thread->pending_mutexes.erase(this);
     UpdatePriority();
+    UpdateGuestState();
 }
 
 void Mutex::UpdatePriority() {
@@ -103,4 +135,17 @@ void Mutex::UpdatePriority() {
     }
 }
 
-} // namespace
+void Mutex::UpdateGuestState() {
+    GuestState guest_state{Memory::Read32(guest_addr)};
+    guest_state.has_waiters.Assign(!GetWaitingThreads().empty());
+    guest_state.holding_thread_handle.Assign(holding_thread ? holding_thread->guest_handle : 0);
+    Memory::Write32(guest_addr, guest_state.raw);
+}
+
+void Mutex::VerifyGuestState() {
+    GuestState guest_state{Memory::Read32(guest_addr)};
+    ASSERT(guest_state.has_waiters == !GetWaitingThreads().empty());
+    ASSERT(guest_state.holding_thread_handle == holding_thread->guest_handle);
+}
+
+} // namespace Kernel
diff --git a/src/core/hle/kernel/mutex.h b/src/core/hle/kernel/mutex.h
index 503d3ee75..87e3c15ee 100644
--- a/src/core/hle/kernel/mutex.h
+++ b/src/core/hle/kernel/mutex.h
@@ -6,8 +6,10 @@
 
 #include <string>
 #include "common/common_types.h"
+#include "common/swap.h"
 #include "core/hle/kernel/kernel.h"
 #include "core/hle/kernel/wait_object.h"
+#include "core/hle/result.h"
 
 namespace Kernel {
 
@@ -17,11 +19,15 @@ class Mutex final : public WaitObject {
 public:
     /**
      * Creates a mutex.
-     * @param initial_locked Specifies if the mutex should be locked initially
+     * @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(bool initial_locked, VAddr addr, std::string name = "Unknown");
+    static SharedPtr<Mutex> Create(SharedPtr<Kernel::Thread> holding_thread, VAddr guest_addr = 0,
+                                   std::string name = "Unknown");
 
     std::string GetTypeName() const override {
         return "Mutex";
@@ -39,7 +45,7 @@ public:
     u32 priority;                     ///< The priority of the mutex, used for priority inheritance.
     std::string name;                 ///< Name of mutex (optional)
     SharedPtr<Thread> holding_thread; ///< Thread that has acquired the mutex
-    VAddr addr;
+    VAddr guest_addr;                 ///< Address of the guest mutex value
 
     /**
      * Elevate the mutex priority to the best priority
@@ -53,11 +59,32 @@ public:
     void AddWaitingThread(SharedPtr<Thread> thread) override;
     void RemoveWaitingThread(Thread* thread) override;
 
-    void Release();
+    /**
+     * 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);
 
 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");
+
+    /// Updates the state of the object tracking this mutex in guest memory
+    void UpdateGuestState();
+
+    /// Verifies the state of the object tracking this mutex in guest memory
+    void VerifyGuestState();
 };
 
 /**
@@ -66,4 +93,4 @@ private:
  */
 void ReleaseThreadMutexes(Thread* thread);
 
-} // namespace
+} // namespace Kernel
diff --git a/src/core/hle/svc.cpp b/src/core/hle/svc.cpp
index 133b868f2..c0e3200d4 100644
--- a/src/core/hle/svc.cpp
+++ b/src/core/hle/svc.cpp
@@ -122,6 +122,44 @@ static ResultCode GetProcessId(u32* process_id, Kernel::Handle process_handle) {
     return RESULT_SUCCESS;
 }
 
+/// Attempts to locks a mutex, creating it if it does not already exist
+static ResultCode LockMutex(Handle holding_thread_handle, VAddr mutex_addr,
+                            Handle requesting_thread_handle) {
+    LOG_TRACE(Kernel_SVC,
+              "called holding_thread_handle=0x%08X, mutex_addr=0x%llx, "
+              "requesting_current_thread_handle=0x%08X",
+              holding_thread_handle, mutex_addr, requesting_thread_handle);
+
+    SharedPtr<Kernel::Thread> holding_thread =
+        Kernel::g_handle_table.Get<Kernel::Thread>(holding_thread_handle);
+    SharedPtr<Kernel::Thread> requesting_thread =
+        Kernel::g_handle_table.Get<Kernel::Thread>(requesting_thread_handle);
+
+    ASSERT(holding_thread);
+    ASSERT(requesting_thread);
+
+    SharedPtr<Kernel::Mutex> mutex = Kernel::g_object_address_table.Get<Kernel::Mutex>(mutex_addr);
+    if (!mutex) {
+        // Create a new mutex for the specified address if one does not already exist
+        mutex = Kernel::Mutex::Create(holding_thread, mutex_addr);
+        mutex->name = Common::StringFromFormat("mutex-%llx", mutex_addr);
+    }
+
+    if (mutex->ShouldWait(requesting_thread.get())) {
+        // If we cannot lock the mutex, then put the thread too sleep and trigger a reschedule
+        requesting_thread->wait_objects = {mutex};
+        mutex->AddWaitingThread(requesting_thread);
+        requesting_thread->status = THREADSTATUS_WAIT_SYNCH_ANY;
+
+        Core::System::GetInstance().PrepareReschedule();
+    } else {
+        // The mutex is available, lock it
+        mutex->Acquire(requesting_thread.get());
+    }
+
+    return RESULT_SUCCESS;
+}
+
 /// Break program execution
 static void Break(u64 unk_0, u64 unk_1, u64 unk_2) {
     LOG_CRITICAL(Debug_Emulated, "Emulated program broke execution!");
@@ -371,8 +409,8 @@ static const FunctionDef SVC_Table[] = {
     {0x17, nullptr, "svcResetSignal"},
     {0x18, nullptr, "svcWaitSynchronization"},
     {0x19, nullptr, "svcCancelSynchronization"},
-    {0x1A, nullptr, "svcLockMutex"},
     {0x1B, nullptr, "svcUnlockMutex"},
+    {0x1A, HLE::Wrap<LockMutex>, "svcLockMutex"},
     {0x1C, nullptr, "svcWaitProcessWideKeyAtomic"},
     {0x1D, HLE::Wrap<SignalProcessWideKey>, "svcSignalProcessWideKey"},
     {0x1E, nullptr, "svcGetSystemTick"},