core_timing: request the timer thread's stop before waking it

CoreTiming::Reset set pause_event and event, and only then requested the
stop. The woken timer thread could take the wake-up, still see no stop
request, and go back to waiting on pause_event for good; the join that
follows then hung the frontend while booting a game ("Not Responding",
main thread in CoreTiming::Reset -> std::thread::join). Request the stop
first, so the thread sees it whenever it wakes.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/core/core_timing.cpp b/src/core/core_timing.cpp
index d2ee6769cc..b85bd30a58 100644
--- a/src/core/core_timing.cpp
+++ b/src/core/core_timing.cpp
@@ -304,10 +304,15 @@ std::optional<s64> CoreTiming::Advance() {
 
 void CoreTiming::Reset() {
     paused = true;
+    // Request the stop before waking the thread: woken first, it could take the wake-up, see no
+    // stop request yet, and go back to waiting on pause_event for good (the join below then hung
+    // the frontend at boot).
+    if (timer_thread.joinable()) {
+        timer_thread.request_stop();
+    }
     pause_event.Set();
     event.Set();
     if (timer_thread.joinable()) {
-        timer_thread.request_stop();
         timer_thread.join();
     }
     has_started = false;