We need stricter locking before we can unload

Specifically, the "loose upgrades" behaviour that allows us to obtain an
exclusive right to load things while other requests are in progress (but
waiting on the exclusive lock for themselves) prevents us from treating
load & unload interchangeably: new things appearing is fine, but they do
*not* expect previously-present constants to vanish.

We can still use loose upgrades for unloading -- once someone has
decided to unload, they don't really care if someone else gets there
first -- it just needs to be tracked separately.

1 files changed, 8 insertions, 1 deletions

diff --git a/activesupport/lib/active_support/dependencies.rb b/activesupport/lib/active_support/dependencies.rb
index fc6f822969..18555fbcba 100644
--- a/activesupport/lib/active_support/dependencies.rb
+++ b/activesupport/lib/active_support/dependencies.rb
@@ -37,6 +37,13 @@ module ActiveSupport #:nodoc:
       Dependencies.interlock.loading { yield }
     end
 
+    # Execute the supplied block while holding an exclusive lock,
+    # preventing any other thread from being inside a #run_interlock
+    # block at the same time
+    def self.unload_interlock
+      Dependencies.interlock.unloading { yield }
+    end
+
     # :nodoc:
 
     # Should we turn on Ruby warnings on the first load of dependent files?
@@ -348,7 +355,7 @@ module ActiveSupport #:nodoc:
 
     def clear
       log_call
-      Dependencies.load_interlock do
+      Dependencies.unload_interlock do
         loaded.clear
         loading.clear
         remove_unloadable_constants!