From 3a2ac8282aef674f798dcef1909f569c78ca1a4b Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Fri, 12 May 2017 20:19:41 +0000 Subject: [PATCH] autoload: always wait on loading thread We cannot assume autoload_provided/rb_feature_provided returning TRUE means it is safe to proceed without waiting. Another thread may call rb_provide_feature before setting the constant (via autoload_const_set). So we must wait until autoload is completed by another thread. Note: this patch was tested with an explicit rb_thread_schedule in rb_provide_feature to make the race condition more apparent as suggested by : > --- a/load.c > +++ b/load.c > @@ -563,6 +563,7 @@ rb_provide_feature(VALUE feature) > rb_str_freeze(feature); > > rb_ary_push(features, rb_fstring(feature)); > +rb_thread_schedule(); > features_index_add(feature, INT2FIX(RARRAY_LEN(features)-1)); > reset_loaded_features_snapshot(); > } * variable.c (check_autoload_required): do not assume a provided feature means autoload is complete, always wait if autoload is being performed by another thread. [ruby-core:81105] [Bug #11384] Thanks to --- variable.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/variable.c b/variable.c index 6e883c7041..63c5f2aeab 100644 --- a/variable.c +++ b/variable.c @@ -1987,6 +1987,17 @@ check_autoload_required(VALUE mod, ID id, const char **loadingpath) if (!RSTRING_LEN(file) || !*RSTRING_PTR(file)) { rb_raise(rb_eArgError, "empty file name"); } + + /* + * if somebody else is autoloading, we MUST wait for them, since + * rb_provide_feature can provide a feature before autoload_const_set + * completes. We must wait until autoload_const_set finishes in + * the other thread. + */ + if (ele->state && ele->state->thread != rb_thread_current()) { + return load; + } + loading = RSTRING_PTR(file); safe = rb_safe_level(); rb_set_safe_level_force(0); -- EW