From 42cbaed6318edd7fb3ce1d178520f53874ebd8ce Mon Sep 17 00:00:00 2001
From: someone2639 <someone2639@users.noreply.github.com>
Date: Fri, 22 Sep 2023 09:35:17 -0400
Subject: [PATCH] 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 | 10 +++++++---
 src/game/main.h | 10 ++++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/boot/main.c b/src/boot/main.c
index 65c45572..985b8243 100644
--- a/src/boot/main.c
+++ b/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) {
diff --git a/src/game/main.h b/src/game/main.h
index 26f4679f..2ee80007 100644
--- a/src/game/main.h
+++ b/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);