From 98eef79faaa36adbdd0b074c712aad5df7ef37a0 Mon Sep 17 00:00:00 2001 From: Jeff Epler Date: Fri, 17 Jul 2020 14:55:46 -0500 Subject: background_callback_gc_collect: We must traverse the whole list --- supervisor/shared/background_callback.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) (limited to 'supervisor') diff --git a/supervisor/shared/background_callback.c b/supervisor/shared/background_callback.c index 1be3cae2b..d10579c4f 100644 --- a/supervisor/shared/background_callback.c +++ b/supervisor/shared/background_callback.c @@ -108,6 +108,23 @@ void background_callback_reset() { } void background_callback_gc_collect(void) { + // We don't enter the callback critical section here. We rely on + // gc_collect_ptr _NOT_ entering background callbacks, so it is not + // possible for the list to be cleared. + // + // However, it is possible for the list to be extended. We make the + // minor assumption that no newly added callback is for a + // collectable object. That is, we only plug the hole where an + // object becomes collectable AFTER it is added but before the + // callback is run, not the hole where an object was ALREADY + // collectable but adds a background task for itself. + // + // It's necessary to traverse the whole list here, as the callbacks + // themselves can be in non-gc memory, and some of the cb->data + // objects themselves might be in non-gc memory. background_callback_t *cb = (background_callback_t*)callback_head; - gc_collect_ptr(cb); + while(cb) { + gc_collect_ptr(cb->data); + cb = cb->next; + } } -- cgit v1.2.3