Better ReadWriteLock exception handling; added pending specs.

Author: jdantonio

lib/concurrent/atomic/read_write_lock.rb

@@ -14,6 +14,8 @@ module Concurrent
   # Any additional readers that come when the writer is already waiting, will also
   # wait (so writers are not starved).
   #
+  # This implementation is based on `java.util.concurrent.ReentrantReadWriteLock`.
+  #
   # @example
   #   lock = Concurrent::ReadWriteLock.new
   #   lock.with_read_lock  { data.retrieve }
@@ -22,6 +24,8 @@ module Concurrent
   # @note Do **not** try to acquire the write lock while already holding a read lock
   #   **or** try to acquire the write lock while you already have it.
   #   This will lead to deadlock
+  #
+  # @see http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/locks/ReentrantReadWriteLock.html java.util.concurrent.ReentrantReadWriteLock
   class ReadWriteLock
 
     # @!visibility private
@@ -69,8 +73,12 @@ def with_read_lock
       raise ArgumentError.new('no block given') unless block_given?
       acquire_read_lock
       yield
-    ensure => ex
-      release_read_lock unless ex.is_a? Concurrent::ResourceLimitError
+    rescue => ex
+      raise ex
+    ensure
+      if block_given? && ! ex.is_a?(Concurrent::ResourceLimitError)
+        release_read_lock
+      end
     end
 
     # Execute a block operation within a write lock.
@@ -86,8 +94,12 @@ def with_write_lock
       raise ArgumentError.new('no block given') unless block_given?
       acquire_write_lock
       yield
-    ensure => ex
-      release_write_lock unless ex.is_a? Concurrent::ResourceLimitError
+    rescue => ex
+      raise ex
+    ensure
+      if block_given? && ! ex.is_a?(Concurrent::ResourceLimitError)
+        release_write_lock
+      end
     end
 
     # Acquire a read lock.

spec/concurrent/atomic/read_write_lock_spec.rb

@@ -3,27 +3,80 @@ module Concurrent
   describe ReadWriteLock do
 
     context '#with_read_lock' do
-      pending
+
+      it 'acquires the lock'
+
+      it 'returns the value of the block operation'
+
+      it 'releases the lock'
+
+      it 'raises an exception if no block is given'
+
+      it 'raises an exception if maximum lock limit is exceeded'
+
+      it 'does not release the lock when an exception is raised'
     end
 
     context '#with_write_lock' do
-      pending
+
+      it 'acquires the lock'
+
+      it 'returns the value of the block operation'
+
+      it 'releases the lock'
+
+      it 'raises an exception if no block is given'
+
+      it 'raises an exception if maximum lock limit is exceeded'
+
+      it 'does not release the lock when an exception is raised'
     end
 
     context '#acquire_read_lock' do
-      pending
+
+      it 'increments the lock count'
+
+      it 'waits for a running writer to finish'
+
+      it 'does not wait for any running readers'
+
+      it 'raises an exception if maximum lock limit is exceeded'
     end
 
     context '#release_read_lock' do
-      pending
+
+      it 'decrements the counter'
+
+      it 'unblocks running writers'
     end
 
     context '#acquire_write_lock' do
-      pending
+
+      it 'increments the lock count'
+
+      it 'waits for a running writer to finish'
+
+      it 'waits for a running reader to finish'
+
+      it 'raises an exception if maximum lock limit is exceeded'
     end
 
     context '#release_write_lock' do
-      pending
+
+      it 'decrements the counter'
+
+      it 'unblocks running readers'
+
+      it 'unblocks running writers'
+    end
+
+    context '#to_s' do
+
+      it 'includes the running reader count'
+
+      it 'includes the running writer count'
+
+      it 'includes the waiting writer count'
     end
   end
 end