From b45c006ab9bdfb92fa6be66dcfa00099adbb85a8 Mon Sep 17 00:00:00 2001 From: Patric Stout Date: Thu, 17 Jun 2021 20:10:40 +0200 Subject: [PATCH] Fix: on startup, NewGRF scan could case race-condition (#9382) Creating a thread was not thread-safe. The irony. The video-driver has a function GameLoopPause() which first checks if the thread is the game-thread or not. For this it needs access to this->game_thread. This variable is set in StartNewThread(). However, due to timing, it is well possible GameLoopPause() is called from the thread well before this->game_thread is assigned. And so we have a race-condition! Simply solve this by preventing a thread to start till we are done with our bookkeeping. --- src/thread.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/src/thread.h b/src/thread.h index bcd4690811..24f4f8e2aa 100644 --- a/src/thread.h +++ b/src/thread.h @@ -14,6 +14,7 @@ #include "crashlog.h" #include #include +#include /** * Sleep on the current thread for a defined time. @@ -46,7 +47,17 @@ inline bool StartNewThread(std::thread *thr, const char *name, TFn&& _Fx, TArgs& { #ifndef NO_THREADS try { + static std::mutex thread_startup_mutex; + std::lock_guard lock(thread_startup_mutex); + std::thread t([] (const char *name, TFn&& F, TArgs&&... A) { + /* Delay starting the thread till the main thread is finished + * with the administration. This prevent race-conditions on + * startup. */ + { + std::lock_guard lock(thread_startup_mutex); + } + SetCurrentThreadName(name); CrashLog::InitThread(); try {