enable GC sooner when loading precompiled modules

part of #20671

src/dump.c

@@ -2123,6 +2123,18 @@ static void jl_insert_methods(linkedlist_t *list)
     }
 }
 
+static void linkedlist_to_array(jl_array_t *a, linkedlist_t *list)
+{
+    while (list) {
+        size_t i;
+        for (i = 0; i < list->count; i++) {
+            jl_array_ptr_1d_push(a, (jl_value_t*)list->def[i].meth);
+            jl_array_ptr_1d_push(a, (jl_value_t*)list->def[i].simpletype);
+        }
+        list = list->next;
+    }
+}
+
 static void jl_insert_backedges(linkedlist_t *list)
 {
     while (list) {
@@ -3047,6 +3059,20 @@ static int trace_method(jl_typemap_entry_t *entry, void *closure)
     return 1;
 }
 
+void jl_gc_mark_deserializer_state(jl_ptls_t ptls)
+{
+    size_t i;
+    for (i=0; i < flagref_list.len; ) {
+        jl_value_t **loc = (jl_value_t**)flagref_list.items[i];
+        if (loc)
+            jl_gc_push_root(ptls, *loc);
+        i += 2;
+    }
+    for (i=0; i < backref_list.len; i++) {
+        jl_gc_push_root(ptls, (jl_value_t*)backref_list.items[i]);
+    }
+}
+
 static jl_value_t *_jl_restore_incremental(ios_t *f)
 {
     if (ios_eof(f) || !jl_read_verify_header(f)) {
@@ -3100,14 +3126,19 @@ static jl_value_t *_jl_restore_incremental(ios_t *f)
     // now all of the interconnects will be created
     jl_recache_types(); // make all of the types identities correct
     init_order = jl_finalize_deserializer(&s, tracee_list); // done with f and s (needs to be after recache types)
+
+    jl_array_t *extmeths = jl_alloc_vec_any(0);  // make array of references for GC
+    linkedlist_to_array(extmeths, &external_methods);
+
+    JL_GC_PUSH3(&init_order, &restored, &extmeths);
+    jl_gc_enable(en);
+
     jl_insert_methods(&external_methods); // hook up methods of external generic functions (needs to be after recache types)
     jl_recache_other(); // make all of the other objects identities correct (needs to be after insert methods)
     jl_insert_backedges(&external_methods); // restore external backedges (needs to be after recache other)
     free_linkedlist(external_methods.next);
     serializer_worklist = NULL;
 
-    JL_GC_PUSH2(&init_order, &restored);
-    jl_gc_enable(en);
     arraylist_free(&flagref_list);
     arraylist_free(&backref_list);
     ios_close(f);

src/gc.c

@@ -1321,6 +1321,11 @@ NOINLINE static int gc_mark_module(jl_ptls_t ptls, jl_module_t *m,
     return refyoung;
 }
 
+void jl_gc_push_root(jl_ptls_t ptls, jl_value_t *v)
+{
+    gc_push_root(ptls, v, 0);
+}
+
 // Handle the case where the stack is only partially copied.
 STATIC_INLINE uintptr_t gc_get_stack_addr(void *_addr, uintptr_t offset,
                                           uintptr_t lb, uintptr_t ub)
@@ -1674,6 +1679,9 @@ static void mark_roots(jl_ptls_t ptls)
     // constants
     gc_push_root(ptls, jl_typetype_type, 0);
     gc_push_root(ptls, jl_emptytuple_type, 0);
+
+    // deserializer state during module reload
+    jl_gc_mark_deserializer_state(ptls);
 }
 
 // find unmarked objects that need to be finalized from the finalizer list "list".

src/gc.h

@@ -281,6 +281,7 @@ void gc_mark_object_list(jl_ptls_t ptls, arraylist_t *list, size_t start);
 void visit_mark_stack(jl_ptls_t ptls);
 void gc_debug_init(void);
 void jl_mark_box_caches(jl_ptls_t ptls);
+void jl_gc_mark_deserializer_state(jl_ptls_t ptls);
 
 // GC pages
 

src/julia_internal.h

@@ -350,6 +350,7 @@ jl_tupletype_t *jl_argtype_with_function(jl_function_t *f, jl_tupletype_t *types
 JL_DLLEXPORT jl_value_t *jl_apply_2va(jl_value_t *f, jl_value_t **args, uint32_t nargs);
 
 void jl_gc_setmark(jl_ptls_t ptls, jl_value_t *v);
+void jl_gc_push_root(jl_ptls_t ptls, jl_value_t *v);
 void jl_gc_sync_total_bytes(void);
 void jl_gc_track_malloced_array(jl_ptls_t ptls, jl_array_t *a);
 void jl_gc_count_allocd(size_t sz);