3 files changed, 411 insertions, 0 deletions

diff --git a/src/core/hle/kernel/k_condition_variable.cpp b/src/core/hle/kernel/k_condition_variable.cpp
new file mode 100644
index 000000000..ef5c17409
--- /dev/null
+++ b/src/core/hle/kernel/k_condition_variable.cpp
@@ -0,0 +1,347 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <vector>
+
+#include "core/arm/exclusive_monitor.h"
+#include "core/core.h"
+#include "core/hle/kernel/k_condition_variable.h"
+#include "core/hle/kernel/k_scheduler.h"
+#include "core/hle/kernel/k_scoped_scheduler_lock_and_sleep.h"
+#include "core/hle/kernel/k_synchronization_object.h"
+#include "core/hle/kernel/kernel.h"
+#include "core/hle/kernel/process.h"
+#include "core/hle/kernel/svc_common.h"
+#include "core/hle/kernel/svc_results.h"
+#include "core/hle/kernel/thread.h"
+#include "core/memory.h"
+
+namespace Kernel {
+
+namespace {
+
+bool ReadFromUser(Core::System& system, u32* out, VAddr address) {
+    *out = system.Memory().Read32(address);
+    return true;
+}
+
+bool WriteToUser(Core::System& system, VAddr address, const u32* p) {
+    system.Memory().Write32(address, *p);
+    return true;
+}
+
+bool UpdateLockAtomic(Core::System& system, u32* out, VAddr address, u32 if_zero,
+                      u32 new_orr_mask) {
+    auto& monitor = system.Monitor();
+    const auto current_core = system.CurrentCoreIndex();
+
+    // Load the value from the address.
+    const auto expected = monitor.ExclusiveRead32(current_core, address);
+
+    // Orr in the new mask.
+    u32 value = expected | new_orr_mask;
+
+    // If the value is zero, use the if_zero value, otherwise use the newly orr'd value.
+    if (!expected) {
+        value = if_zero;
+    }
+
+    // Try to store.
+    if (!monitor.ExclusiveWrite32(current_core, address, value)) {
+        // If we failed to store, try again.
+        return UpdateLockAtomic(system, out, address, if_zero, new_orr_mask);
+    }
+
+    // We're done.
+    *out = expected;
+    return true;
+}
+
+} // namespace
+
+KConditionVariable::KConditionVariable(Core::System& system_)
+    : system{system_}, kernel{system.Kernel()} {}
+
+KConditionVariable::~KConditionVariable() = default;
+
+ResultCode KConditionVariable::SignalToAddress(VAddr addr) {
+    Thread* owner_thread = kernel.CurrentScheduler()->GetCurrentThread();
+
+    // Signal the address.
+    {
+        KScopedSchedulerLock sl(kernel);
+
+        // Remove waiter thread.
+        s32 num_waiters{};
+        Thread* next_owner_thread =
+            owner_thread->RemoveWaiterByKey(std::addressof(num_waiters), addr);
+
+        // Determine the next tag.
+        u32 next_value{};
+        if (next_owner_thread) {
+            next_value = next_owner_thread->GetAddressKeyValue();
+            if (num_waiters > 1) {
+                next_value |= Svc::HandleWaitMask;
+            }
+
+            next_owner_thread->SetSyncedObject(nullptr, RESULT_SUCCESS);
+            next_owner_thread->Wakeup();
+        }
+
+        // Write the value to userspace.
+        if (!WriteToUser(system, addr, std::addressof(next_value))) {
+            if (next_owner_thread) {
+                next_owner_thread->SetSyncedObject(nullptr, Svc::ResultInvalidCurrentMemory);
+            }
+
+            return Svc::ResultInvalidCurrentMemory;
+        }
+    }
+
+    return RESULT_SUCCESS;
+}
+
+ResultCode KConditionVariable::WaitForAddress(Handle handle, VAddr addr, u32 value) {
+    Thread* cur_thread = kernel.CurrentScheduler()->GetCurrentThread();
+
+    // Wait for the address.
+    {
+        std::shared_ptr<Thread> owner_thread;
+        ASSERT(!owner_thread);
+        {
+            KScopedSchedulerLock sl(kernel);
+            cur_thread->SetSyncedObject(nullptr, RESULT_SUCCESS);
+
+            // Check if the thread should terminate.
+            R_UNLESS(!cur_thread->IsTerminationRequested(), Svc::ResultTerminationRequested);
+
+            {
+                // Read the tag from userspace.
+                u32 test_tag{};
+                R_UNLESS(ReadFromUser(system, std::addressof(test_tag), addr),
+                         Svc::ResultInvalidCurrentMemory);
+
+                // If the tag isn't the handle (with wait mask), we're done.
+                R_UNLESS(test_tag == (handle | Svc::HandleWaitMask), RESULT_SUCCESS);
+
+                // Get the lock owner thread.
+                owner_thread = kernel.CurrentProcess()->GetHandleTable().Get<Thread>(handle);
+                R_UNLESS(owner_thread, Svc::ResultInvalidHandle);
+
+                // Update the lock.
+                cur_thread->SetAddressKey(addr, value);
+                owner_thread->AddWaiter(cur_thread);
+                cur_thread->SetState(ThreadState::Waiting);
+                cur_thread->SetMutexWaitAddressForDebugging(addr);
+            }
+        }
+        ASSERT(owner_thread);
+    }
+
+    // Remove the thread as a waiter from the lock owner.
+    {
+        KScopedSchedulerLock sl(kernel);
+        Thread* owner_thread = cur_thread->GetLockOwner();
+        if (owner_thread != nullptr) {
+            owner_thread->RemoveWaiter(cur_thread);
+        }
+    }
+
+    // Get the wait result.
+    KSynchronizationObject* dummy{};
+    return cur_thread->GetWaitResult(std::addressof(dummy));
+}
+
+Thread* KConditionVariable::SignalImpl(Thread* thread) {
+    // Check pre-conditions.
+    ASSERT(kernel.GlobalSchedulerContext().IsLocked());
+
+    // Update the tag.
+    VAddr address = thread->GetAddressKey();
+    u32 own_tag = thread->GetAddressKeyValue();
+
+    u32 prev_tag{};
+    bool can_access{};
+    {
+        // TODO(bunnei): We should disable interrupts here via KScopedInterruptDisable.
+        // TODO(bunnei): We should call CanAccessAtomic(..) here.
+        can_access = true;
+        if (can_access) {
+            UpdateLockAtomic(system, std::addressof(prev_tag), address, own_tag,
+                             Svc::HandleWaitMask);
+        }
+    }
+
+    Thread* thread_to_close = nullptr;
+    if (can_access) {
+        if (prev_tag == InvalidHandle) {
+            // If nobody held the lock previously, we're all good.
+            thread->SetSyncedObject(nullptr, RESULT_SUCCESS);
+            thread->Wakeup();
+        } else {
+            // Get the previous owner.
+            auto owner_thread = kernel.CurrentProcess()->GetHandleTable().Get<Thread>(
+                prev_tag & ~Svc::HandleWaitMask);
+
+            if (owner_thread) {
+                // Add the thread as a waiter on the owner.
+                owner_thread->AddWaiter(thread);
+                thread_to_close = owner_thread.get();
+            } else {
+                // The lock was tagged with a thread that doesn't exist.
+                thread->SetSyncedObject(nullptr, Svc::ResultInvalidState);
+                thread->Wakeup();
+            }
+        }
+    } else {
+        // If the address wasn't accessible, note so.
+        thread->SetSyncedObject(nullptr, Svc::ResultInvalidCurrentMemory);
+        thread->Wakeup();
+    }
+
+    return thread_to_close;
+}
+
+void KConditionVariable::Signal(u64 cv_key, s32 count) {
+    // Prepare for signaling.
+    constexpr int MaxThreads = 16;
+
+    // TODO(bunnei): This should just be Thread once we implement KAutoObject instead of using
+    // std::shared_ptr.
+    std::vector<std::shared_ptr<Thread>> thread_list;
+    std::array<Thread*, MaxThreads> thread_array;
+    s32 num_to_close{};
+
+    // Perform signaling.
+    s32 num_waiters{};
+    {
+        KScopedSchedulerLock sl(kernel);
+
+        auto it = thread_tree.nfind_light({cv_key, -1});
+        while ((it != thread_tree.end()) && (count <= 0 || num_waiters < count) &&
+               (it->GetConditionVariableKey() == cv_key)) {
+            Thread* target_thread = std::addressof(*it);
+
+            if (Thread* thread = SignalImpl(target_thread); thread != nullptr) {
+                if (num_to_close < MaxThreads) {
+                    thread_array[num_to_close++] = thread;
+                } else {
+                    thread_list.push_back(SharedFrom(thread));
+                }
+            }
+
+            it = thread_tree.erase(it);
+            target_thread->ClearConditionVariable();
+            ++num_waiters;
+        }
+
+        // If we have no waiters, clear the has waiter flag.
+        if (it == thread_tree.end() || it->GetConditionVariableKey() != cv_key) {
+            const u32 has_waiter_flag{};
+            WriteToUser(system, cv_key, std::addressof(has_waiter_flag));
+        }
+    }
+
+    // Close threads in the array.
+    for (auto i = 0; i < num_to_close; ++i) {
+        thread_array[i]->Close();
+    }
+
+    // Close threads in the list.
+    for (auto it = thread_list.begin(); it != thread_list.end(); it = thread_list.erase(it)) {
+        (*it)->Close();
+    }
+}
+
+ResultCode KConditionVariable::Wait(VAddr addr, u64 key, u32 value, s64 timeout) {
+    // Prepare to wait.
+    Thread* cur_thread = kernel.CurrentScheduler()->GetCurrentThread();
+    Handle timer = InvalidHandle;
+
+    {
+        KScopedSchedulerLockAndSleep slp(kernel, timer, cur_thread, timeout);
+
+        // Set the synced object.
+        cur_thread->SetSyncedObject(nullptr, Svc::ResultTimedOut);
+
+        // Check that the thread isn't terminating.
+        if (cur_thread->IsTerminationRequested()) {
+            slp.CancelSleep();
+            return Svc::ResultTerminationRequested;
+        }
+
+        // Update the value and process for the next owner.
+        {
+            // Remove waiter thread.
+            s32 num_waiters{};
+            Thread* next_owner_thread =
+                cur_thread->RemoveWaiterByKey(std::addressof(num_waiters), addr);
+
+            // Update for the next owner thread.
+            u32 next_value{};
+            if (next_owner_thread != nullptr) {
+                // Get the next tag value.
+                next_value = next_owner_thread->GetAddressKeyValue();
+                if (num_waiters > 1) {
+                    next_value |= Svc::HandleWaitMask;
+                }
+
+                // Wake up the next owner.
+                next_owner_thread->SetSyncedObject(nullptr, RESULT_SUCCESS);
+                next_owner_thread->Wakeup();
+            }
+
+            // Write to the cv key.
+            {
+                const u32 has_waiter_flag = 1;
+                WriteToUser(system, key, std::addressof(has_waiter_flag));
+                // TODO(bunnei): We should call DataMemoryBarrier(..) here.
+            }
+
+            // Write the value to userspace.
+            if (!WriteToUser(system, addr, std::addressof(next_value))) {
+                slp.CancelSleep();
+                return Svc::ResultInvalidCurrentMemory;
+            }
+        }
+
+        // Update condition variable tracking.
+        {
+            cur_thread->SetConditionVariable(std::addressof(thread_tree), addr, key, value);
+            thread_tree.insert(*cur_thread);
+        }
+
+        // If the timeout is non-zero, set the thread as waiting.
+        if (timeout != 0) {
+            cur_thread->SetState(ThreadState::Waiting);
+            cur_thread->SetMutexWaitAddressForDebugging(addr);
+        }
+    }
+
+    // Cancel the timer wait.
+    if (timer != InvalidHandle) {
+        auto& time_manager = kernel.TimeManager();
+        time_manager.UnscheduleTimeEvent(timer);
+    }
+
+    // Remove from the condition variable.
+    {
+        KScopedSchedulerLock sl(kernel);
+
+        if (Thread* owner = cur_thread->GetLockOwner(); owner != nullptr) {
+            owner->RemoveWaiter(cur_thread);
+        }
+
+        if (cur_thread->IsWaitingForConditionVariable()) {
+            thread_tree.erase(thread_tree.iterator_to(*cur_thread));
+            cur_thread->ClearConditionVariable();
+        }
+    }
+
+    // Get the result.
+    KSynchronizationObject* dummy{};
+    return cur_thread->GetWaitResult(std::addressof(dummy));
+}
+
+} // namespace Kernel
diff --git a/src/core/hle/kernel/k_condition_variable.h b/src/core/hle/kernel/k_condition_variable.h
new file mode 100644
index 000000000..98ed5b323
--- /dev/null
+++ b/src/core/hle/kernel/k_condition_variable.h
@@ -0,0 +1,59 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "common/assert.h"
+#include "common/common_types.h"
+
+#include "core/hle/kernel/k_scheduler.h"
+#include "core/hle/kernel/kernel.h"
+#include "core/hle/kernel/thread.h"
+#include "core/hle/result.h"
+
+namespace Core {
+class System;
+}
+
+namespace Kernel {
+
+class KConditionVariable {
+public:
+    using ThreadTree = typename Thread::ConditionVariableThreadTreeType;
+
+    explicit KConditionVariable(Core::System& system_);
+    ~KConditionVariable();
+
+    // Arbitration
+    [[nodiscard]] ResultCode SignalToAddress(VAddr addr);
+    [[nodiscard]] ResultCode WaitForAddress(Handle handle, VAddr addr, u32 value);
+
+    // Condition variable
+    void Signal(u64 cv_key, s32 count);
+    [[nodiscard]] ResultCode Wait(VAddr addr, u64 key, u32 value, s64 timeout);
+
+private:
+    [[nodiscard]] Thread* SignalImpl(Thread* thread);
+
+    ThreadTree thread_tree;
+
+    Core::System& system;
+    KernelCore& kernel;
+};
+
+inline void BeforeUpdatePriority(const KernelCore& kernel, KConditionVariable::ThreadTree* tree,
+                                 Thread* thread) {
+    ASSERT(kernel.GlobalSchedulerContext().IsLocked());
+
+    tree->erase(tree->iterator_to(*thread));
+}
+
+inline void AfterUpdatePriority(const KernelCore& kernel, KConditionVariable::ThreadTree* tree,
+                                Thread* thread) {
+    ASSERT(kernel.GlobalSchedulerContext().IsLocked());
+
+    tree->insert(*thread);
+}
+
+} // namespace Kernel
diff --git a/src/core/hle/kernel/object.h b/src/core/hle/kernel/object.h
index e3391e2af..27124ef67 100644
--- a/src/core/hle/kernel/object.h
+++ b/src/core/hle/kernel/object.h
@@ -50,6 +50,11 @@ public:
     }
     virtual HandleType GetHandleType() const = 0;
 
+    void Close() {
+        // TODO(bunnei): This is a placeholder to decrement the reference count, which we will use
+        // when we implement KAutoObject instead of using shared_ptr.
+    }
+
     /**
      * Check if a thread can wait on the object
      * @return True if a thread can wait on the object, otherwise false