[runtime] Avoid freeing IMT thunks, some threads might still be executing them. This creates a memory leak, but its bounded. Fixes #39832. (#3767)

3 files changed, 1 insertions, 148 deletions

diff --git a/mono/metadata/domain-internals.h b/mono/metadata/domain-internals.h
index a3989ab74aa..d4d20ab25a4 100644
--- a/mono/metadata/domain-internals.h
+++ b/mono/metadata/domain-internals.h
@@ -380,9 +380,6 @@ struct _MonoDomain {
 	GHashTable	   *method_rgctx_hash;
 
 	GHashTable	   *generic_virtual_cases;
-	MonoThunkFreeList **thunk_free_lists;
-
-	GHashTable     *generic_virtual_thunks;
 
 	/* Information maintained by the JIT engine */
 	gpointer runtime_info;
diff --git a/mono/metadata/domain.c b/mono/metadata/domain.c
index a3ba4a76e04..f18f9b0d0de 100644
--- a/mono/metadata/domain.c
+++ b/mono/metadata/domain.c
@@ -1239,10 +1239,6 @@ mono_domain_free (MonoDomain *domain, gboolean force)
 		g_hash_table_destroy (domain->generic_virtual_cases);
 		domain->generic_virtual_cases = NULL;
 	}
-	if (domain->generic_virtual_thunks) {
-		g_hash_table_destroy (domain->generic_virtual_thunks);
-		domain->generic_virtual_thunks = NULL;
-	}
 	if (domain->ftnptrs_hash) {
 		g_hash_table_destroy (domain->ftnptrs_hash);
 		domain->ftnptrs_hash = NULL;
diff --git a/mono/metadata/object.c b/mono/metadata/object.c
index f827cb16009..d5b8dd5db52 100644
--- a/mono/metadata/object.c
+++ b/mono/metadata/object.c
@@ -1549,49 +1549,8 @@ mono_vtable_build_imt_slot (MonoVTable* vtable, int imt_slot)
 	mono_loader_unlock ();
 }
 
-
-/*
- * The first two free list entries both belong to the wait list: The
- * first entry is the pointer to the head of the list and the second
- * entry points to the last element.  That way appending and removing
- * the first element are both O(1) operations.
- */
-#ifdef MONO_SMALL_CONFIG
-#define NUM_FREE_LISTS		6
-#else
-#define NUM_FREE_LISTS		12
-#endif
-#define FIRST_FREE_LIST_SIZE	64
-#define MAX_WAIT_LENGTH 	50
 #define THUNK_THRESHOLD		10
 
-/*
- * LOCKING: The domain lock must be held.
- */
-static void
-init_thunk_free_lists (MonoDomain *domain)
-{
-	MONO_REQ_GC_NEUTRAL_MODE;
-
-	if (domain->thunk_free_lists)
-		return;
-	domain->thunk_free_lists = (MonoThunkFreeList **)mono_domain_alloc0 (domain, sizeof (gpointer) * NUM_FREE_LISTS);
-}
-
-static int
-list_index_for_size (int item_size)
-{
-	int i = 2;
-	int size = FIRST_FREE_LIST_SIZE;
-
-	while (item_size > size && i < NUM_FREE_LISTS - 1) {
-		i++;
-		size <<= 1;
-	}
-
-	return i;
-}
-
 /**
  * mono_method_alloc_generic_virtual_thunk:
  * @domain: a domain
@@ -1611,36 +1570,6 @@ mono_method_alloc_generic_virtual_thunk (MonoDomain *domain, int size)
 	static gboolean inited = FALSE;
 	static int generic_virtual_thunks_size = 0;
 
-	guint32 *p;
-	int i;
-	MonoThunkFreeList **l;
-
-	init_thunk_free_lists (domain);
-
-	size += sizeof (guint32);
-	if (size < sizeof (MonoThunkFreeList))
-		size = sizeof (MonoThunkFreeList);
-
-	i = list_index_for_size (size);
-	for (l = &domain->thunk_free_lists [i]; *l; l = &(*l)->next) {
-		if ((*l)->size >= size) {
-			MonoThunkFreeList *item = *l;
-			*l = item->next;
-			return ((guint32*)item) + 1;
-		}
-	}
-
-	/* no suitable item found - search lists of larger sizes */
-	while (++i < NUM_FREE_LISTS) {
-		MonoThunkFreeList *item = domain->thunk_free_lists [i];
-		if (!item)
-			continue;
-		g_assert (item->size > size);
-		domain->thunk_free_lists [i] = item->next;
-		return ((guint32*)item) + 1;
-	}
-
-	/* still nothing found - allocate it */
 	if (!inited) {
 		mono_counters_register ("Generic virtual thunk bytes",
 				MONO_COUNTER_GENERICS | MONO_COUNTER_INT, &generic_virtual_thunks_size);
@@ -1648,68 +1577,7 @@ mono_method_alloc_generic_virtual_thunk (MonoDomain *domain, int size)
 	}
 	generic_virtual_thunks_size += size;
 
-	p = (guint32 *)mono_domain_code_reserve (domain, size);
-	*p = size;
-
-	mono_domain_lock (domain);
-	if (!domain->generic_virtual_thunks)
-		domain->generic_virtual_thunks = g_hash_table_new (NULL, NULL);
-	g_hash_table_insert (domain->generic_virtual_thunks, p, p);
-	mono_domain_unlock (domain);
-
-	return p + 1;
-}
-
-/*
- * LOCKING: The domain lock must be held.
- */
-static void
-invalidate_generic_virtual_thunk (MonoDomain *domain, gpointer code)
-{
-	MONO_REQ_GC_NEUTRAL_MODE;
-
-	guint32 *p = (guint32 *)code;
-	MonoThunkFreeList *l = (MonoThunkFreeList*)(p - 1);
-	gboolean found = FALSE;
-
-	mono_domain_lock (domain);
-	if (!domain->generic_virtual_thunks)
-		domain->generic_virtual_thunks = g_hash_table_new (NULL, NULL);
-	if (g_hash_table_lookup (domain->generic_virtual_thunks, l))
-		found = TRUE;
-	mono_domain_unlock (domain);
-
-	if (!found)
-		/* Not allocated by mono_method_alloc_generic_virtual_thunk (), i.e. AOT */
-		return;
-	init_thunk_free_lists (domain);
-
-	while (domain->thunk_free_lists [0] && domain->thunk_free_lists [0]->length >= MAX_WAIT_LENGTH) {
-		MonoThunkFreeList *item = domain->thunk_free_lists [0];
-		int length = item->length;
-		int i;
-
-		/* unlink the first item from the wait list */
-		domain->thunk_free_lists [0] = item->next;
-		domain->thunk_free_lists [0]->length = length - 1;
-
-		i = list_index_for_size (item->size);
-
-		/* put it in the free list */
-		item->next = domain->thunk_free_lists [i];
-		domain->thunk_free_lists [i] = item;
-	}
-
-	l->next = NULL;
-	if (domain->thunk_free_lists [1]) {
-		domain->thunk_free_lists [1] = domain->thunk_free_lists [1]->next = l;
-		domain->thunk_free_lists [0]->length++;
-	} else {
-		g_assert (!domain->thunk_free_lists [0]);
-
-		domain->thunk_free_lists [0] = domain->thunk_free_lists [1] = l;
-		domain->thunk_free_lists [0]->length = 1;
-	}
+	return mono_domain_code_reserve (domain, size);
 }
 
 typedef struct _GenericVirtualCase {
@@ -1821,7 +1689,6 @@ mono_method_add_generic_virtual_invocation (MonoDomain *domain, MonoVTable *vtab
 	}
 
 	if (++gvc->count == THUNK_THRESHOLD) {
-		gpointer *old_thunk = (void **)*vtable_slot;
 		gpointer vtable_trampoline = NULL;
 		gpointer imt_trampoline = NULL;
 
@@ -1852,13 +1719,6 @@ mono_method_add_generic_virtual_invocation (MonoDomain *domain, MonoVTable *vtab
 				g_free (g_ptr_array_index (sorted, i));
 			g_ptr_array_free (sorted, TRUE);
 		}
-
-#ifndef __native_client__
-		/* We don't re-use any thunks as there is a lot of overhead */
-		/* to deleting and re-using code in Native Client.          */
-		if (old_thunk != vtable_trampoline && old_thunk != imt_trampoline)
-			invalidate_generic_virtual_thunk (domain, old_thunk);
-#endif
 	}
 
 	mono_domain_unlock (domain);