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Code Issues 1 Projects Releases Wiki Activity

fix a deadlock scenario in the overlay

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a 2024-08-18 03:20:55 +03:00
parent 6c78d51240
commit 9ba2b1f04b
1 changed files with 16 additions and 2 deletions
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18
overlay_experimental/steam_overlay.cpp
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@ -85,7 +85,23 @@ void Steam_Overlay::overlay_run_callback(void* object)
{ {
// PRINT_DEBUG_ENTRY(); // PRINT_DEBUG_ENTRY();
Steam_Overlay* _this = reinterpret_cast<Steam_Overlay*>(object); Steam_Overlay* _this = reinterpret_cast<Steam_Overlay*>(object);
// bail immediately if we can't lock the overlay mutex, deadlock scenario:
// 1. ** the background thread locks the global mutex
// 2. -- the user opens the overlay
// 3. -- the overlay proc is triggered the next frame, locking the overlay mutex
// 4. ** the background thread locks the global mutex and runs this callback
// 5. ** this callback (already having the global mutex) attempts to lock the overlay mutex (already locked before)
// 6. ** this callback, and the background thread, are now blocked, note that the global mutex is still locked
// 7. -- in the same frame, some code in the overlay proc attempts to call a steam API which usually locks the global mutex
// sice the global mutex is still locked, the overlay proc is also blocked,
// and now both the background thread and the overlay proc and locked
// even worse, the global mutex is locked forever now
if (!_this->overlay_mutex.try_lock()) return;
_this->steam_run_callback(); _this->steam_run_callback();
_this->overlay_mutex.unlock();
} }
void Steam_Overlay::overlay_networking_callback(void* object, Common_Message* msg) void Steam_Overlay::overlay_networking_callback(void* object, Common_Message* msg)
@ -1655,8 +1671,6 @@ void Steam_Overlay::networking_msg_received(Common_Message *msg)
void Steam_Overlay::steam_run_callback() void Steam_Overlay::steam_run_callback()
{ {
std::lock_guard<std::recursive_mutex> lock(overlay_mutex);
if (!Ready()) return; if (!Ready()) return;
if (overlay_state_changed) { if (overlay_state_changed) {