Introduce FiberLocalVar and LockLocalVar for alignment with Mutex s…

…cope.

# Conflicts:
#	lib/concurrent-ruby/concurrent/atomic/reentrant_read_write_lock.rb
#	spec/concurrent/atomic/reentrant_read_write_lock_spec.rb

lib/concurrent-ruby/concurrent/atomic/abstract_thread_local_var.rb → lib/concurrent-ruby/concurrent/atomic/fiber_local_var.rb

@@ -1,13 +1,7 @@
 require 'concurrent/constants'
 
 module Concurrent
-
-  # @!macro thread_local_var
-  # @!macro internal_implementation_note
-  # @!visibility private
-  class AbstractThreadLocalVar
-
-    # @!macro thread_local_var_method_initialize
+  class FiberLocalVar
     def initialize(default = nil, &default_block)
       if default && block_given?
         raise ArgumentError, "Cannot use both value and block as default value"
@@ -21,17 +15,17 @@ def initialize(default = nil, &default_block)
         @default = default
       end
 
-      allocate_storage
+      @name = :"concurrent_variable_#{object_id}"
     end
 
     # @!macro thread_local_var_method_get
     def value
-      raise NotImplementedError
+      Thread.current.fetch(@name) {default}
     end
 
     # @!macro thread_local_var_method_set
     def value=(value)
-      raise NotImplementedError
+      Thread.current[@name] = value
     end
 
     # @!macro thread_local_var_method_bind
@@ -49,11 +43,6 @@ def bind(value, &block)
 
     protected
 
-    # @!visibility private
-    def allocate_storage
-      raise NotImplementedError
-    end
-
     # @!visibility private
     def default
       if @default_block

lib/concurrent-ruby/concurrent/atomic/lock_local_var.rb

@@ -0,0 +1,20 @@
+require_relative 'fiber_local_var'
+require_relative 'thread_local_var'
+
+module Concurrent
+  def self.mutex_owned_per_thread?
+    mutex = Mutex.new
+
+    # Lock the mutex:
+    mutex.synchronize do
+      # Check if the mutex is still owned in a child fiber:
+      Fiber.new{mutex.owned?}.resume
+    end
+  end
+
+  if mutex_owned_per_thread?
+    LockLocalVar = ThreadLocalVar
+  else
+    LockLocalVar = FiberLocalVar
+  end
+end

lib/concurrent-ruby/concurrent/atomic/reentrant_read_write_lock.rb

@@ -4,7 +4,7 @@
 require 'concurrent/errors'
 require 'concurrent/synchronization/object'
 require 'concurrent/synchronization/lock'
-require 'concurrent/atomic/thread_local_var'
+require 'concurrent/atomic/lock_local_var'
 
 module Concurrent
 
@@ -111,7 +111,7 @@ def initialize
       @Counter    = AtomicFixnum.new(0)       # single integer which represents lock state
       @ReadQueue  = Synchronization::Lock.new # used to queue waiting readers
       @WriteQueue = Synchronization::Lock.new # used to queue waiting writers
-      @HeldCount  = ThreadLocalVar.new(0)     # indicates # of R & W locks held by this thread
+      @HeldCount  = LockLocalVar.new(0)       # indicates # of R & W locks held by this thread
     end
 
     # Execute a block operation within a read lock.