From 56ebc0e857435b3111130260cfef77ef991e1cf0 Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Fri, 11 Oct 2024 13:47:22 -0400
Subject: [PATCH] Implement rb_gc_impl_ractor_cache_free

---
 gc/mmtk.c          | 23 ++++++++++++++---------
 gc/mmtk.h          |  2 ++
 gc/mmtk/src/api.rs |  8 ++++++++
 3 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/gc/mmtk.c b/gc/mmtk.c
index 594db224a9107c..be40f80b3038c5 100644
--- a/gc/mmtk.c
+++ b/gc/mmtk.c
@@ -9,6 +9,7 @@
 #include "gc/gc_impl.h"
 #include "gc/mmtk.h"
 
+#include "ccan/list/list.h"
 #include "darray.h"
 
 struct objspace {
@@ -27,7 +28,7 @@ struct objspace {
     struct MMTk_final_job *finalizer_jobs;
     rb_postponed_job_handle_t finalizer_postponed_job;
 
-    struct MMTk_ractor_cache *ractor_caches;
+    struct ccan_list_head ractor_caches;
     unsigned long live_ractor_cache_count;
 
     pthread_mutex_t mutex;
@@ -40,7 +41,7 @@ struct objspace {
 };
 
 struct MMTk_ractor_cache {
-    struct MMTk_ractor_cache *next_ractor_cache;
+    struct ccan_list_node list_node;
 
     MMTk_Mutator *mutator;
     bool gc_mutator_p;
@@ -187,12 +188,11 @@ rb_mmtk_get_mutators(void (*visit_mutator)(MMTk_Mutator *mutator, void *data), v
 {
     struct objspace *objspace = rb_gc_get_objspace();
 
-    struct MMTk_ractor_cache *ractor_cache = objspace->ractor_caches;
+    struct MMTk_ractor_cache *ractor_cache;
     RUBY_ASSERT(ractor_cache != NULL);
 
-    while (ractor_cache != NULL) {
+    ccan_list_for_each(&objspace->ractor_caches, ractor_cache, list_node) {
         visit_mutator(ractor_cache->mutator, data);
-        ractor_cache = ractor_cache->next_ractor_cache;
     }
 }
 
@@ -429,6 +429,8 @@ rb_gc_impl_objspace_init(void *objspace_ptr)
     objspace->finalizer_table = st_init_numtable();
     objspace->finalizer_postponed_job = rb_postponed_job_preregister(0, gc_run_finalizers, objspace);
 
+    ccan_list_head_init(&objspace->ractor_caches);
+
     objspace->mutex = (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;
     objspace->cond_world_stopped = (pthread_cond_t)PTHREAD_COND_INITIALIZER;
     objspace->cond_world_started = (pthread_cond_t)PTHREAD_COND_INITIALIZER;
@@ -450,8 +452,7 @@ rb_gc_impl_ractor_cache_alloc(void *objspace_ptr, void *ractor)
     objspace->live_ractor_cache_count++;
 
     struct MMTk_ractor_cache *cache = malloc(sizeof(struct MMTk_ractor_cache));
-    cache->next_ractor_cache = objspace->ractor_caches;
-    objspace->ractor_caches = cache;
+    ccan_list_add(&objspace->ractor_caches, &cache->list_node);
 
     cache->mutator = mmtk_bind_mutator(cache);
 
@@ -459,13 +460,17 @@ rb_gc_impl_ractor_cache_alloc(void *objspace_ptr, void *ractor)
 }
 
 void
-rb_gc_impl_ractor_cache_free(void *objspace_ptr, void *cache)
+rb_gc_impl_ractor_cache_free(void *objspace_ptr, void *cache_ptr)
 {
-    // TODO: implement mmtk_destroy_mutator
     struct objspace *objspace = objspace_ptr;
+    struct MMTk_ractor_cache *cache = cache_ptr;
+
+    ccan_list_del(&cache->list_node);
 
     RUBY_ASSERT(objspace->live_ractor_cache_count > 1);
     objspace->live_ractor_cache_count--;
+
+    mmtk_destroy_mutator(cache->mutator);
 }
 
 void rb_gc_impl_set_params(void *objspace_ptr) { }
diff --git a/gc/mmtk.h b/gc/mmtk.h
index 93ebdf70478324..1f220d9643e9a7 100644
--- a/gc/mmtk.h
+++ b/gc/mmtk.h
@@ -102,6 +102,8 @@ void mmtk_initialize_collection(MMTk_VMThread tls);
 
 MMTk_Mutator *mmtk_bind_mutator(MMTk_VMMutatorThread tls);
 
+void mmtk_destroy_mutator(MMTk_Mutator *mutator);
+
 void mmtk_handle_user_collection_request(MMTk_VMMutatorThread tls);
 
 void mmtk_set_gc_enabled(bool enable);
diff --git a/gc/mmtk/src/api.rs b/gc/mmtk/src/api.rs
index 3c51ba60c24f10..5a8ef5db04bc58 100644
--- a/gc/mmtk/src/api.rs
+++ b/gc/mmtk/src/api.rs
@@ -81,6 +81,14 @@ pub extern "C" fn mmtk_bind_mutator(tls: VMMutatorThread) -> *mut RubyMutator {
     Box::into_raw(memory_manager::bind_mutator(mmtk(), tls))
 }
 
+#[no_mangle]
+pub extern "C" fn mmtk_destroy_mutator(mutator: *mut RubyMutator) {
+    // notify mmtk-core about destroyed mutator
+    memory_manager::destroy_mutator(unsafe { &mut *mutator });
+    // turn the ptr back to a box, and let Rust properly reclaim it
+    let _ = unsafe { Box::from_raw(mutator) };
+}
+
 // =============== GC ===============
 
 #[no_mangle]