From 6718f078da77304fd5a75297734e9d860116a292 Mon Sep 17 00:00:00 2001
From: Damien George <damien@micropython.org>
Date: Thu, 12 Oct 2023 03:56:42 +0200
Subject: [PATCH] esp32/gccollect: Make level arg volatile to force recursive
function.
Otherwise the compiler may inline the gc_collect_inner() function and/or
remove the recursion, which is necessary to spill all the windowed
registers to the C stack.
---
.../vendor/ports/esp32/gccollect.c | 24 ++++++++-----------
1 file changed, 10 insertions(+), 14 deletions(-)
diff --git a/components/micropython/vendor/ports/esp32/gccollect.c b/components/micropython/vendor/ports/esp32/gccollect.c
index e16e8028ad..afded5129b 100644
--- a/components/micropython/vendor/ports/esp32/gccollect.c
+++ b/components/micropython/vendor/ports/esp32/gccollect.c
@@ -39,30 +39,25 @@
#include "xtensa/hal.h"
-static void gc_collect_inner(int level) {
+// The level argument must be volatile to force the compiler to emit code that
+// will call this function recursively, to nest the C stack.
+static void gc_collect_inner(volatile unsigned int level) {
if (level < XCHAL_NUM_AREGS / 8) {
+ // Go deeper on the stack to spill more registers from the register window.
gc_collect_inner(level + 1);
- if (level != 0) {
- return;
- }
- }
-
- if (level == XCHAL_NUM_AREGS / 8) {
- // get the sp
+ } else {
+ // Deep enough so that all registers are on the C stack, now trace the stack.
volatile uint32_t sp = (uint32_t)esp_cpu_get_sp();
gc_collect_root((void **)sp, ((mp_uint_t)MP_STATE_THREAD(stack_top) - sp) / sizeof(uint32_t));
- return;
}
-
- // trace root pointers from any threads
- #if MICROPY_PY_THREAD
- mp_thread_gc_others();
- #endif
}
void gc_collect(void) {
gc_collect_start();
gc_collect_inner(0);
+ #if MICROPY_PY_THREAD
+ mp_thread_gc_others();
+ #endif
gc_collect_end();
}
@@ -90,3 +85,4 @@ size_t gc_get_max_new_split(void) {
}
#endif
+
--
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