merge revision(s) 537183cd2ac0163851277b46a2f21ea5914c11c0: [Backport #19577]

Fix write barrier order for `klass` to `cme` edge

	Previously, the following crashes with
	`CFLAGS=-DRGENGC_CHECK_MODE=2 -DRUBY_DEBUG=1 -fno-inline`:

	    $ ./miniruby -e 'GC.stress = true; Marshal.dump({})'

	It crashes with a write barrier (WB) miss assertion on an edge from the
	`Hash` class object to a newly allocated negative method entry.

	This is due to usages of vm_ccs_create() running the WB too early,
	before the method entry is inserted into the cc table, so before the
	reference edge is established. The insertion can trigger GC and promote
	the class object, so running the WB after the insertion is necessary.
	Move the insertion into vm_ccs_create() and run the WB after the
	insertion.

	Discovered on CI:
	http://ci.rvm.jp/results/trunk-asserts@ruby-sp2-docker/4391770
	---
	 vm_eval.c       |  3 +--
	 vm_insnhelper.c | 10 ++++++----
	 vm_method.c     |  3 +--
	 3 files changed, 8 insertions(+), 8 deletions(-)

version.h

@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 2
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 80
+#define RUBY_PATCHLEVEL 81
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"

vm_eval.c

@@ -396,8 +396,7 @@ cc_new(VALUE klass, ID mid, int argc, const rb_callable_method_entry_t *cme)
             ccs = (struct rb_class_cc_entries *)ccs_data;
         }
         else {
-            ccs = vm_ccs_create(klass, cme);
+            ccs = vm_ccs_create(klass, cc_tbl, mid, cme);
-            rb_id_table_insert(cc_tbl, mid, (VALUE)ccs);
         }
 
         for (int i=0; i<ccs->len; i++) {

vm_insnhelper.c

@@ -1892,7 +1892,7 @@ static VALUE vm_call_general(rb_execution_context_t *ec, rb_control_frame_t *reg
 static VALUE vm_mtbl_dump(VALUE klass, ID target_mid);
 
 static struct rb_class_cc_entries *
-vm_ccs_create(VALUE klass, const rb_callable_method_entry_t *cme)
+vm_ccs_create(VALUE klass, struct rb_id_table *cc_tbl, ID mid, const rb_callable_method_entry_t *cme)
 {
     struct rb_class_cc_entries *ccs = ALLOC(struct rb_class_cc_entries);
 #if VM_CHECK_MODE > 0
@@ -1900,9 +1900,12 @@ vm_ccs_create(VALUE klass, const rb_callable_method_entry_t *cme)
 #endif
     ccs->capa = 0;
     ccs->len = 0;
-    RB_OBJ_WRITE(klass, &ccs->cme, cme);
+    ccs->cme = cme;
     METHOD_ENTRY_CACHED_SET((rb_callable_method_entry_t *)cme);
     ccs->entries = NULL;
+
+    rb_id_table_insert(cc_tbl, mid, (VALUE)ccs);
+    RB_OBJ_WRITTEN(klass, Qundef, cme);
     return ccs;
 }
 
@@ -2053,8 +2056,7 @@ vm_search_cc(const VALUE klass, const struct rb_callinfo * const ci)
         }
         else {
             // TODO: required?
-            ccs = vm_ccs_create(klass, cme);
+            ccs = vm_ccs_create(klass, cc_tbl, mid, cme);
-            rb_id_table_insert(cc_tbl, mid, (VALUE)ccs);
         }
     }
 

vm_method.c

@@ -1330,8 +1330,7 @@ cache_callable_method_entry(VALUE klass, ID mid, const rb_callable_method_entry_
         VM_ASSERT(ccs->cme == cme);
     }
     else {
-        ccs = vm_ccs_create(klass, cme);
+        ccs = vm_ccs_create(klass, cc_tbl, mid, cme);
-        rb_id_table_insert(cc_tbl, mid, (VALUE)ccs);
     }
 }