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Use atomic for method reference count [Bug #20934]

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This changes reference_count on rb_method_definition_struct into an
atomic.

Ractors can create additional references as part of `bind_call` or
(presumably) similar. Because this can be done inside Ractors, we should
use a lock or atomics so that we don't race and avoid incrementing.

Co-authored-by: wanabe <s.wanabe@gmail.com>
This commit is contained in:
John Hawthorn 2025-03-18 15:02:44 -07:00
parent 62cc3464d9
commit bfe6068417
Notes: git 2025-03-20 20:09:57 +00:00 
Merged: https://github.com/ruby/ruby/pull/12951
3 changed files with 29 additions and 11 deletions
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13
bootstraptest/test_ractor.rb
View File

@ -1937,3 +1937,16 @@ assert_equal 'LoadError', %q{
end
r.take
}
# bind_call in Ractor [Bug #20934]
assert_equal 'ok', %q{
2.times.map do
Ractor.new do
1000.times do
Object.instance_method(:itself).bind_call(self)
end
end
end.each(&:take)
GC.start
:ok.itself
}

4
method.h
View File

@ -15,6 +15,7 @@
#include "internal/imemo.h"
#include "internal/compilers.h"
#include "internal/static_assert.h"
#include "ruby/atomic.h"
#ifndef END_OF_ENUMERATION
# if defined(__GNUC__) &&! defined(__STRICT_ANSI__)
@ -181,7 +182,8 @@ struct rb_method_definition_struct {
unsigned int iseq_overload: 1;
unsigned int no_redef_warning: 1;
unsigned int aliased : 1;
int reference_count : 28;
rb_atomic_t reference_count;
union {
rb_method_iseq_t iseq;

23
vm_method.c
View File

@ -511,14 +511,13 @@ static void
rb_method_definition_release(rb_method_definition_t *def)
{
if (def != NULL) {
const int reference_count = def->reference_count;
def->reference_count--;
const unsigned int reference_count_was = RUBY_ATOMIC_FETCH_SUB(def->reference_count, 1);
VM_ASSERT(reference_count >= 0);
RUBY_ASSERT_ALWAYS(reference_count_was != 0);
if (def->reference_count == 0) {
if (METHOD_DEBUG) fprintf(stderr, "-%p-%s:%d (remove)\n", (void *)def,
rb_id2name(def->original_id), def->reference_count);
if (reference_count_was == 1) {
if (METHOD_DEBUG) fprintf(stderr, "-%p-%s:1->0 (remove)\n", (void *)def,
rb_id2name(def->original_id));
if (def->type == VM_METHOD_TYPE_BMETHOD && def->body.bmethod.hooks) {
xfree(def->body.bmethod.hooks);
}
@ -526,7 +525,7 @@ rb_method_definition_release(rb_method_definition_t *def)
}
else {
if (METHOD_DEBUG) fprintf(stderr, "-%p-%s:%d->%d (dec)\n", (void *)def, rb_id2name(def->original_id),
reference_count, def->reference_count);
reference_count_was, reference_count_was - 1);
}
}
}
@ -614,9 +613,13 @@ setup_method_cfunc_struct(rb_method_cfunc_t *cfunc, VALUE (*func)(ANYARGS), int
static rb_method_definition_t *
method_definition_addref(rb_method_definition_t *def, bool complemented)
{
if (!complemented && def->reference_count > 0) def->aliased = true;
def->reference_count++;
if (METHOD_DEBUG) fprintf(stderr, "+%p-%s:%d\n", (void *)def, rb_id2name(def->original_id), def->reference_count);
unsigned int reference_count_was = RUBY_ATOMIC_FETCH_ADD(def->reference_count, 1);
if (!complemented && reference_count_was > 0) {
/* TODO: A Ractor can reach this via UnboundMethod#bind */
def->aliased = true;
}
if (METHOD_DEBUG) fprintf(stderr, "+%p-%s:%d->%d\n", (void *)def, rb_id2name(def->original_id), reference_count_was, reference_count_was+1);
return def;
}