[Bug #18014] Fix memory leak in GC when using Ractors

When a Ractor is removed, the freelist in the Ractor cache is not
returned to the GC, leaving the freelist permanently lost. This commit
recycles the freelist when the Ractor is destroyed, preventing a memory
leak from occurring.

1 files changed, 54 insertions, 62 deletions

diff --git a/gc.c b/gc.c
index c7e3034240..9af83de055 100644
--- a/gc.c
+++ b/gc.c
@@ -1817,45 +1817,34 @@ heap_page_add_freeobj(rb_objspace_t *objspace, struct heap_page *page, VALUE obj
     gc_report(3, objspace, "heap_page_add_freeobj: add %p to freelist\n", (void *)obj);
 }
 
-static inline bool
+static inline void
 heap_add_freepage(rb_heap_t *heap, struct heap_page *page)
 {
     asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
     GC_ASSERT(page->free_slots != 0);
+    GC_ASSERT(page->freelist != NULL);
 
-    if (page->freelist) {
-        page->free_next = heap->free_pages;
-        heap->free_pages = page;
+    page->free_next = heap->free_pages;
+    heap->free_pages = page;
 
-        RUBY_DEBUG_LOG("page:%p freelist:%p", page, page->freelist);
+    RUBY_DEBUG_LOG("page:%p freelist:%p", page, page->freelist);
 
-        asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
-        return true;
-    }
-    else {
-        asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
-        return false;
-    }
+    asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
 }
 
 #if GC_ENABLE_INCREMENTAL_MARK
-static inline int
+static inline void
 heap_add_poolpage(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *page)
 {
     asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
-    if (page->freelist) {
-	page->free_next = heap->pooled_pages;
-	heap->pooled_pages = page;
-	objspace->rincgc.pooled_slots += page->free_slots;
-        asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
+    GC_ASSERT(page->free_slots != 0);
+    GC_ASSERT(page->freelist != NULL);
 
-	return TRUE;
-    }
-    else {
-        asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
+    page->free_next = heap->pooled_pages;
+    heap->pooled_pages = page;
+    objspace->rincgc.pooled_slots += page->free_slots;
 
-	return FALSE;
-    }
+    asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
 }
 #endif
 
@@ -2317,7 +2306,7 @@ rvargc_find_contiguous_slots(int slots, RVALUE *freelist)
 }
 #endif
 
-static inline bool heap_add_freepage(rb_heap_t *heap, struct heap_page *page);
+static inline void heap_add_freepage(rb_heap_t *heap, struct heap_page *page);
 static struct heap_page * heap_next_freepage(rb_objspace_t *objspace, rb_heap_t *heap);
 static inline void ractor_set_cache(rb_ractor_t *cr, struct heap_page *page);
 
@@ -5563,32 +5552,7 @@ gc_sweep_start(rb_objspace_t *objspace)
 
     rb_ractor_t *r = NULL;
     list_for_each(&GET_VM()->ractor.set, r, vmlr_node) {
-        struct heap_page *page = r->newobj_cache.using_page;
-        RVALUE *freelist = r->newobj_cache.freelist;
-        RUBY_DEBUG_LOG("ractor using_page:%p freelist:%p", page, freelist);
-
-        if (page && freelist) {
-            asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
-            if (page->freelist) {
-                RVALUE *p = page->freelist;
-                asan_unpoison_object((VALUE)p, false);
-                while (p->as.free.next) {
-                    RVALUE *prev = p;
-                    p = p->as.free.next;
-                    asan_poison_object((VALUE)prev);
-                    asan_unpoison_object((VALUE)p, false);
-                }
-                p->as.free.next = freelist;
-                asan_poison_object((VALUE)p);
-            }
-            else {
-                page->freelist = freelist;
-            }
-            asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
-        }
-
-        r->newobj_cache.using_page = NULL;
-        r->newobj_cache.freelist = NULL;
+        rb_gc_ractor_newobj_cache_clear(&r->newobj_cache);
     }
 }
 
@@ -5651,22 +5615,19 @@ gc_sweep_step(rb_objspace_t *objspace, rb_heap_t *heap)
 	else if (free_slots > 0) {
 #if GC_ENABLE_INCREMENTAL_MARK
 	    if (need_pool) {
-		if (heap_add_poolpage(objspace, heap, sweep_page)) {
-		    need_pool = FALSE;
-		}
+                heap_add_poolpage(objspace, heap, sweep_page);
+                need_pool = FALSE;
 	    }
 	    else {
-                if (heap_add_freepage(heap, sweep_page)) {
-                    swept_slots += free_slots;
-                    if (swept_slots > 2048) {
-                        break;
-                    }
+                heap_add_freepage(heap, sweep_page);
+                swept_slots += free_slots;
+                if (swept_slots > 2048) {
+                    break;
                 }
 	    }
 #else
-            if (heap_add_freepage(heap, sweep_page)) {
-                break;
-            }
+            heap_add_freepage(heap, sweep_page);
+            break;
 #endif
 	}
 	else {
@@ -8643,6 +8604,37 @@ rb_obj_gc_flags(VALUE obj, ID* flags, size_t max)
 /* GC */
 
 void
+rb_gc_ractor_newobj_cache_clear(rb_ractor_newobj_cache_t *newobj_cache)
+{
+    struct heap_page *page = newobj_cache->using_page;
+    RVALUE *freelist = newobj_cache->freelist;
+    RUBY_DEBUG_LOG("ractor using_page:%p freelist:%p", page, freelist);
+
+    if (page && freelist) {
+        asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
+        if (page->freelist) {
+            RVALUE *p = page->freelist;
+            asan_unpoison_object((VALUE)p, false);
+            while (p->as.free.next) {
+                RVALUE *prev = p;
+                p = p->as.free.next;
+                asan_poison_object((VALUE)prev);
+                asan_unpoison_object((VALUE)p, false);
+            }
+            p->as.free.next = freelist;
+            asan_poison_object((VALUE)p);
+        }
+        else {
+            page->freelist = freelist;
+        }
+        asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
+    }
+
+    newobj_cache->using_page = NULL;
+    newobj_cache->freelist = NULL;
+}
+
+void
 rb_gc_force_recycle(VALUE obj)
 {
     rb_objspace_t *objspace = &rb_objspace;