Kernel/Threads: Implement an SleepClientThread function for HLERequestContext-based services to make performing async tasks on the host while in an HLE service function easier.

An HLE service function that wants to perform an async operation should put the caller guest thread to sleep using SleepClientThread, passing in a callback to execute when the thread is resumed.
SleepClientThread returns a Kernel::Event that should be signaled to resume the guest thread when the host async operation completes.

src/core/hle/kernel/hle_ipc.cpp

@@ -6,6 +6,7 @@
 #include <boost/range/algorithm_ext/erase.hpp>
 #include "common/assert.h"
 #include "common/common_types.h"
+#include "core/hle/kernel/event.h"
 #include "core/hle/kernel/handle_table.h"
 #include "core/hle/kernel/hle_ipc.h"
 #include "core/hle/kernel/kernel.h"
@@ -24,6 +25,40 @@ void SessionRequestHandler::ClientDisconnected(SharedPtr<ServerSession> server_s
     boost::range::remove_erase(connected_sessions, server_session);
 }
 
+SharedPtr<Event> HLERequestContext::SleepClientThread(SharedPtr<Thread> thread,
+                                                      const std::string& reason, u64 timeout,
+                                                      WakeupCallback&& callback) {
+    // Put the client thread to sleep until the wait event is signaled or the timeout expires.
+    thread->wakeup_callback = [context = *this, callback](ThreadWakeupReason reason,
+                                                          SharedPtr<Thread> thread,
+                                                          SharedPtr<WaitObject> object) mutable {
+        ASSERT(thread->status == THREADSTATUS_WAIT_HLE_EVENT);
+        callback(thread, context, reason);
+
+        auto& process = thread->owner_process;
+        // We must copy the entire command buffer *plus* the entire static buffers area, since
+        // the translation might need to read from it in order to retrieve the StaticBuffer
+        // target addresses.
+        std::array<u32, IPC::COMMAND_BUFFER_LENGTH + 2 * IPC::MAX_STATIC_BUFFERS> cmd_buff;
+        Memory::ReadBlock(*process, thread->GetCommandBufferAddress(), cmd_buff.data(),
+                          cmd_buff.size() * sizeof(u32));
+        context.WriteToOutgoingCommandBuffer(cmd_buff.data(), *process, Kernel::g_handle_table);
+        // Copy the translated command buffer back into the thread's command buffer area.
+        Memory::WriteBlock(*process, thread->GetCommandBufferAddress(), cmd_buff.data(),
+                           cmd_buff.size() * sizeof(u32));
+    };
+
+    auto event = Kernel::Event::Create(Kernel::ResetType::OneShot, "HLE Pause Event: " + reason);
+    thread->status = THREADSTATUS_WAIT_HLE_EVENT;
+    thread->wait_objects = {event};
+    event->AddWaitingThread(thread);
+
+    if (timeout > 0)
+        thread->WakeAfterDelay(timeout);
+
+    return event;
+}
+
 HLERequestContext::HLERequestContext(SharedPtr<ServerSession> session)
     : session(std::move(session)) {
     cmd_buf[0] = 0;

src/core/hle/kernel/hle_ipc.h

@@ -6,6 +6,7 @@
 
 #include <array>
 #include <memory>
+#include <string>
 #include <vector>
 #include <boost/container/small_vector.hpp>
 #include "common/common_types.h"
@@ -22,6 +23,8 @@ namespace Kernel {
 
 class HandleTable;
 class Process;
+class Thread;
+class Event;
 
 /**
  * Interface implemented by HLE Session handlers.
@@ -140,6 +143,24 @@ public:
         return session;
     }
 
+    using WakeupCallback = std::function<void(SharedPtr<Thread> thread, HLERequestContext& context,
+                                              ThreadWakeupReason reason)>;
+
+    /*
+     * Puts the specified guest thread to sleep until the returned event is signaled or until the
+     * specified timeout expires.
+     * @param thread Thread to be put to sleep.
+     * @param reason Reason for pausing the thread, to be used for debugging purposes.
+     * @param timeout Timeout in nanoseconds after which the thread will be awoken and the callback
+     * invoked with a Timeout reason.
+     * @param callback Callback to be invoked when the thread is resumed. This callback must write
+     * the entire command response once again, regardless of the state of it before this function
+     * was called.
+     * @returns Event that when signaled will resume the thread and call the callback function.
+     */
+    SharedPtr<Event> SleepClientThread(SharedPtr<Thread> thread, const std::string& reason,
+                                       u64 timeout, WakeupCallback&& callback);
+
     /**
      * Resolves a object id from the request command buffer into a pointer to an object. See the
      * "HLE handle protocol" section in the class documentation for more details.

src/core/hle/kernel/thread.cpp

@@ -196,7 +196,8 @@ static void ThreadWakeupCallback(u64 thread_handle, int cycles_late) {
     }
 
     if (thread->status == THREADSTATUS_WAIT_SYNCH_ANY ||
-        thread->status == THREADSTATUS_WAIT_SYNCH_ALL || thread->status == THREADSTATUS_WAIT_ARB) {
+        thread->status == THREADSTATUS_WAIT_SYNCH_ALL || thread->status == THREADSTATUS_WAIT_ARB ||
+        thread->status == THREADSTATUS_WAIT_HLE_EVENT) {
 
         // Invoke the wakeup callback before clearing the wait objects
         if (thread->wakeup_callback)

src/core/hle/service/service.cpp

@@ -181,8 +181,16 @@ void ServiceFrameworkBase::HandleSyncRequest(SharedPtr<ServerSession> server_ses
     LOG_TRACE(Service, "%s",
               MakeFunctionString(info->name, GetServiceName().c_str(), cmd_buf).c_str());
     handler_invoker(this, info->handler_callback, context);
+
+    auto thread = Kernel::GetCurrentThread();
+    ASSERT(thread->status == THREADSTATUS_RUNNING || thread->status == THREADSTATUS_WAIT_HLE_EVENT);
+    // Only write the response immediately if the thread is still running. If the HLE handler put
+    // the thread to sleep then the writing of the command buffer will be deferred to the wakeup
+    // callback.
+    if (thread->status == THREADSTATUS_RUNNING) {
         context.WriteToOutgoingCommandBuffer(cmd_buf, *Kernel::g_current_process,
                                              Kernel::g_handle_table);
+    }
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////