Replace some global Hash usages with the new thread safe cache.

Summary of the changes:
 * Add thread_safe gem.
 * Use thread safe cache for digestor caching.
 * Replace manual synchronization with ThreadSafe::Cache in Relation::Delegation.
 * Replace @attribute_method_matchers_cache Hash with ThreadSafe::Cache.
 * Use TS::Cache to avoid the synchronisation overhead on listener retrieval.
 * Replace synchronisation with TS::Cache usage.
 * Use a preallocated array for performance/memory reasons.
 * Update the controllers cache to the new AS::Dependencies::ClassCache API.
   The original @controllers cache no longer makes much sense after @tenderlove's
   changes in 7b6bfe84f3 and f345e2380c.
 * Use TS::Cache in the connection pool to avoid locking overhead.
 * Use TS::Cache in ConnectionHandler.

1 files changed, 4 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/inflector/inflections.rb b/activesupport/lib/active_support/inflector/inflections.rb
index 6f259a093b..9cf4b2b2ba 100644
--- a/activesupport/lib/active_support/inflector/inflections.rb
+++ b/activesupport/lib/active_support/inflector/inflections.rb
@@ -1,3 +1,4 @@
+require 'thread_safe'
 require 'active_support/core_ext/array/prepend_and_append'
 require 'active_support/i18n'
 
@@ -24,9 +25,10 @@ module ActiveSupport
     # singularization rules that is runs. This guarantees that your rules run
     # before any of the rules that may already have been loaded.
     class Inflections
+      @__instance__ = ThreadSafe::Cache.new
+
       def self.instance(locale = :en)
-        @__instance__ ||= Hash.new { |h, k| h[k] = new }
-        @__instance__[locale]
+        @__instance__[locale] ||= new
       end
 
       attr_reader :plurals, :singulars, :uncountables, :humans, :acronyms, :acronym_regex