Track whether the RCP hang timer has started to prevent double setting (#689)

* Track whether the RCP hang timer has started to prevent double setting

* removed single letter struct field

* remove debug lines

---------

Co-authored-by: someone2639 <someone2639@gmail.com>

src/boot/main.c

@@ -303,13 +303,17 @@ void handle_dp_complete(void) {
     sCurrentDisplaySPTask = NULL;
 }
 
-OSTimer RCPHangTimer;
+OSTimerEx RCPHangTimer;
 void start_rcp_hang_timer(void) {
-    osSetTimer(&RCPHangTimer, OS_USEC_TO_CYCLES(3000000), (OSTime) 0, &gIntrMesgQueue, (OSMesg) MESG_RCP_HUNG);
+    if (RCPHangTimer.started == FALSE) {
+        osSetTimer(&RCPHangTimer.timer, OS_USEC_TO_CYCLES(3000000), (OSTime) 0, &gIntrMesgQueue, (OSMesg) MESG_RCP_HUNG);
+        RCPHangTimer.started = TRUE;
+    }
 }
 
 void stop_rcp_hang_timer(void) {
-    osStopTimer(&RCPHangTimer);
+    osStopTimer(&RCPHangTimer.timer);
+    RCPHangTimer.started = FALSE;
 }
 
 void alert_rcp_hung_up(void) {

src/game/main.h

@@ -97,6 +97,16 @@ extern s8 gDebugLevelSelect;
 extern s8 gShowDebugText;
 #endif
 
+// Special struct that keeps track of whether its timer has been set.
+//  Without this check, there is a bug at high CPU loads in which
+//  the RCP timer gets set twice and the game tries to
+//  insert __osBaseTimer into a ring buffer that only contains itself,
+//  causing a particularly messy crash.
+typedef struct {
+    u8 started;
+    OSTimer timer;
+} OSTimerEx;
+
 void set_vblank_handler(s32 index, struct VblankHandler *handler, OSMesgQueue *queue, OSMesg *msg);
 void dispatch_audio_sptask(struct SPTask *spTask);
 void exec_display_list(struct SPTask *spTask);