Refactor Logging Impl

Loop on stop_token and remove final_entry in Entry.
Move Backend thread out of Impl Constructor to its own function.
Add Start function for backend thread.
Use stop token in PopWait and check if entry filename is nullptr before logging.

src/citra/citra.cpp

@@ -178,6 +178,7 @@ static void OnStatusMessageReceived(const Network::StatusMessageEntry& msg) {
 int main(int argc, char** argv) {
     Common::Log::Initialize();
     Common::Log::SetColorConsoleBackendEnabled(true);
+    Common::Log::Start();
     Common::DetachedTasks detached_tasks;
     Config config;
     int option_index = 0;

src/citra_qt/main.cpp

@@ -264,6 +264,8 @@ GMainWindow::GMainWindow(Core::System& system_)
     }
 #endif
 
+    Common::Log::Start();
+
     QStringList args = QApplication::arguments();
     if (args.length() >= 2) {
         BootGame(args[1]);

src/common/logging/backend.cpp

@@ -4,7 +4,6 @@
 
 #include <chrono>
 #include <exception>
-#include <thread>
 #include <vector>
 
 #include <fmt/format.h>
@@ -31,6 +30,7 @@
 #include "common/logging/log.h"
 #include "common/logging/log_entry.h"
 #include "common/logging/text_formatter.h"
+#include "common/polyfill_thread.h"
 #include "common/settings.h"
 #include "common/string_util.h"
 #include "common/thread.h"
@@ -219,6 +219,10 @@ public:
         initialization_in_progress_suppress_logging = false;
     }
 
+    static void Start() {
+        instance->StartBackendThread();
+    }
+
     Impl(const Impl&) = delete;
     Impl& operator=(const Impl&) = delete;
 
@@ -244,26 +248,7 @@ public:
 
 private:
     Impl(const std::string& file_backend_filename, const Filter& filter_)
-        : filter{filter_}, file_backend{file_backend_filename}, backend_thread{std::thread([this] {
-              Common::SetCurrentThreadName("citra:Log");
-              Entry entry;
-              const auto write_logs = [this, &entry]() {
-                  ForEachBackend([&entry](Backend& backend) { backend.Write(entry); });
-              };
-              while (true) {
-                  entry = message_queue.PopWait();
-                  if (entry.final_entry) {
-                      break;
-                  }
-                  write_logs();
-              }
-              // Drain the logging queue. Only writes out up to MAX_LOGS_TO_WRITE to prevent a
-              // case where a system is repeatedly spamming logs even on close.
-              int max_logs_to_write = filter.IsDebug() ? INT_MAX : 100;
-              while (max_logs_to_write-- && message_queue.Pop(entry)) {
-                  write_logs();
-              }
-          })} {
+        : filter{filter_}, file_backend{file_backend_filename} {
 #ifdef CITRA_LINUX_GCC_BACKTRACE
         int waker_pipefd[2];
         int done_printing_pipefd[2];
@@ -297,7 +282,7 @@ private:
                 }
                 line.pop_back(); // Remove newline
                 const auto frame_entry =
-                    CreateEntry(Class::Log, Level::Critical, "?", 0, "?", line);
+                    CreateEntry(Class::Log, Level::Critical, "?", 0, "?", std::move(line));
                 ForEachBackend([&frame_entry](Backend& backend) { backend.Write(frame_entry); });
             }
             using namespace std::literals;
@@ -326,15 +311,35 @@ private:
         StopBackendThread();
     }
 
+    void StartBackendThread() {
+        backend_thread = std::thread([this] {
+            Common::SetCurrentThreadName("citra:Log");
+            Entry entry;
+            const auto write_logs = [this, &entry]() {
+                ForEachBackend([&entry](Backend& backend) { backend.Write(entry); });
+            };
+            while (!stop.stop_requested()) {
+                entry = message_queue.PopWait(stop.get_token());
+                if (entry.filename != nullptr) {
+                    write_logs();
+                }
+            }
+            // Drain the logging queue. Only writes out up to MAX_LOGS_TO_WRITE to prevent a
+            // case where a system is repeatedly spamming logs even on close.
+            int max_logs_to_write = filter.IsDebug() ? INT_MAX : 100;
+            while (max_logs_to_write-- && message_queue.Pop(entry)) {
+                write_logs();
+            }
+        });
+    }
+
     void StopBackendThread() {
-        Entry stop_entry{};
-        stop_entry.final_entry = true;
-        message_queue.Push(stop_entry);
+        stop.request_stop();
         backend_thread.join();
     }
 
     Entry CreateEntry(Class log_class, Level log_level, const char* filename, unsigned int line_nr,
-                      const char* function, std::string message) const {
+                      const char* function, std::string&& message) const {
         using std::chrono::duration_cast;
         using std::chrono::microseconds;
         using std::chrono::steady_clock;
@@ -347,7 +352,6 @@ private:
             .line_num = line_nr,
             .function = function,
             .message = std::move(message),
-            .final_entry = false,
         };
     }
 
@@ -398,8 +402,9 @@ private:
     ColorConsoleBackend color_console_backend{};
     FileBackend file_backend;
 
+    std::stop_source stop;
     std::thread backend_thread;
-    MPSCQueue<Entry> message_queue{};
+    MPSCQueue<Entry, true> message_queue{};
     std::chrono::steady_clock::time_point time_origin{std::chrono::steady_clock::now()};
 
 #ifdef CITRA_LINUX_GCC_BACKTRACE
@@ -415,6 +420,10 @@ void Initialize() {
     Impl::Initialize();
 }
 
+void Start() {
+    Impl::Start();
+}
+
 void DisableLoggingInTests() {
     initialization_in_progress_suppress_logging = true;
 }

src/common/logging/backend.h

@@ -14,6 +14,8 @@ class Filter;
 /// Initializes the logging system. This should be the first thing called in main.
 void Initialize();
 
+void Start();
+
 void DisableLoggingInTests();
 
 /**

src/common/logging/log_entry.h

@@ -22,7 +22,6 @@ struct Entry {
     unsigned int line_num = 0;
     std::string function;
     std::string message;
-    bool final_entry = false;
 };
 
 } // namespace Common::Log