Fix GC race condition in autoload.
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2022-05-25 21:18:01 +09:00
@ -529,6 +529,7 @@ p Foo::Bar
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t2 = Thread.new {Bar}
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t1.join
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GC.start # force GC.
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t2.join
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Object.send(:remove_const, :Foo)
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33
variable.c
33
variable.c
@ -2669,12 +2669,6 @@ autoload_try_load(VALUE _arguments)
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{
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struct autoload_load_arguments *arguments = (struct autoload_load_arguments*)_arguments;
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// We have tried to require the autoload feature, so we shouldn't bother trying again in any
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// other threads. More specifically, `arguments->result` starts of as nil, but then contains the
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// result of `require` which is either true or false. Provided it's not nil, it means some other
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// thread has got as far as evaluating the require statement completely.
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if (arguments->result != Qnil) return arguments->result;
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// Try to require the autoload feature:
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rb_ensure(autoload_feature_require, _arguments, autoload_feature_require_ensure, _arguments);
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@ -2722,7 +2716,15 @@ rb_autoload_load(VALUE module, ID name)
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arguments.flag = ce->flag & (CONST_DEPRECATED | CONST_VISIBILITY_MASK);
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// Only one thread will enter here at a time:
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return rb_mutex_synchronize(arguments.mutex, autoload_try_load, (VALUE)&arguments);
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VALUE result = rb_mutex_synchronize(arguments.mutex, autoload_try_load, (VALUE)&arguments);
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// If you don't guard this value, it's possible for the autoload constant to
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// be freed by another thread which loads multiple constants, one of which
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// resolves to the constant this thread is trying to load, so proteect this
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// so that it is not freed until we are done with it in `autoload_try_load`:
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RB_GC_GUARD(autoload_const_value);
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return result;
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}
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VALUE
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@ -3312,18 +3314,19 @@ rb_const_set(VALUE klass, ID id, VALUE val)
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}
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static struct autoload_data *
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autoload_data_for_named_constant(VALUE mod, ID id, struct autoload_const **acp)
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autoload_data_for_named_constant(VALUE module, ID name, struct autoload_const **autoload_const_pointer)
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{
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struct autoload_data *ele;
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VALUE load = autoload_data(mod, id);
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if (!load) return 0;
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ele = get_autoload_data(load, acp);
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if (!ele) return 0;
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VALUE autoload_data_value = autoload_data(module, name);
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if (!autoload_data_value) return 0;
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struct autoload_data *autoload_data = get_autoload_data(autoload_data_value, autoload_const_pointer);
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if (!autoload_data) return 0;
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/* for autoloading thread, keep the defined value to autoloading storage */
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if (autoload_by_current(ele)) {
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return ele;
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if (autoload_by_current(autoload_data)) {
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return autoload_data;
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}
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return 0;
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}
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