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author卜部昌平 <shyouhei@ruby-lang.org>2019-10-03 12:26:41 +0900
committer卜部昌平 <shyouhei@ruby-lang.org>2019-10-03 12:45:24 +0900
commiteb92159d72fc711387f7e17ffbaca1678f23fd47 (patch)
tree13c5177b80fbd50c7113eee5aca5158652f24f1b /vm.c
parentef697388becedf36966a2edcdcf88baca342b9e2 (diff)
downloadruby-eb92159d72fc711387f7e17ffbaca1678f23fd47.tar.gz
Revert https://github.com/ruby/ruby/pull/2486
This reverts commits: 10d6a3aca7 8ba48c1b85 fba8627dc1 dd883de5ba 6c6a25feca 167e6b48f1 7cb96d41a5 3207979278 595b3c4fdd 1521f7cf89 c11c5e69ac cf33608203 3632a812c0 f56506be0d 86427a3219 . The reason for the revert is that we observe ABA problem around inline method cache. When a cache misshits, we search for a method entry. And if the entry is identical to what was cached before, we reuse the cache. But the commits we are reverting here introduced situations where a method entry is freed, then the identical memory region is used for another method entry. An inline method cache cannot detect that ABA. Here is a code that reproduce such situation: ```ruby require 'prime' class << Integer alias org_sqrt sqrt def sqrt(n) raise end GC.stress = true Prime.each(7*37){} rescue nil # <- Here we populate CC class << Object.new; end # These adjacent remove-then-alias maneuver # frees a method entry, then immediately # reuses it for another. remove_method :sqrt alias sqrt org_sqrt end Prime.each(7*37).to_a # <- SEGV ```
Diffstat (limited to 'vm.c')
-rw-r--r--vm.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/vm.c b/vm.c
index 16a15c2151..e104688d71 100644
--- a/vm.c
+++ b/vm.c
@@ -298,6 +298,17 @@ rb_vm_cref_new_toplevel(void)
return vm_cref_new_toplevel(GET_EC());
}
+static void
+vm_cref_dump(const char *mesg, const rb_cref_t *cref)
+{
+ fprintf(stderr, "vm_cref_dump: %s (%p)\n", mesg, (void *)cref);
+
+ while (cref) {
+ fprintf(stderr, "= cref| klass: %s\n", RSTRING_PTR(rb_class_path(CREF_CLASS(cref))));
+ cref = CREF_NEXT(cref);
+ }
+}
+
void
rb_vm_block_ep_update(VALUE obj, const struct rb_block *dst, const VALUE *ep)
{
@@ -1595,7 +1606,7 @@ static enum rb_id_table_iterator_result
check_redefined_method(ID mid, VALUE value, void *data)
{
VALUE klass = (VALUE)data;
- const rb_method_entry_t *me = (const rb_method_entry_t *)value;
+ const rb_method_entry_t *me = (rb_method_entry_t *)value;
const rb_method_entry_t *newme = rb_method_entry(klass, mid);
if (newme != me) rb_vm_check_redefinition_opt_method(me, me->owner);