make sure connections returned after close are marked as in_use

activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb

@@ -235,6 +235,8 @@ def checkin(conn)
           conn.run_callbacks :checkin do
             conn.expire
           end
+
+          release conn
         end
       end
 
@@ -246,10 +248,7 @@ def remove(conn)
 
           # FIXME: we might want to store the key on the connection so that removing
           # from the reserved hash will be a little easier.
-          thread_id = @reserved_connections.keys.find { |k|
-            @reserved_connections[k] == conn
-          }
-          @reserved_connections.delete thread_id if thread_id
+          release conn
         end
       end
 
@@ -267,6 +266,20 @@ def reap
 
       private
 
+      def release(conn)
+        thread_id = nil
+
+        if @reserved_connections[current_connection_id] == conn
+          thread_id = current_connection_id
+        else
+          thread_id = @reserved_connections.keys.find { |k|
+            @reserved_connections[k] == conn
+          }
+        end
+
+        @reserved_connections.delete thread_id if thread_id
+      end
+
       def new_connection
         ActiveRecord::Base.send(spec.adapter_method, spec.config)
       end

activerecord/test/cases/connection_pool_test.rb

@@ -31,6 +31,16 @@ def active_connections(pool)
         pool.connections.find_all(&:in_use?)
       end
 
+      def test_checkout_after_close
+        connection = pool.connection
+        assert connection.in_use?
+
+        connection.close
+        assert !connection.in_use?
+
+        assert pool.connection.in_use?
+      end
+
       def test_released_connection_moves_between_threads
         thread_conn = nil