Ensure fiber is blocking so that forked process starts in blocking context.

Author: ioquatix

lib/async/container/generic.rb

@@ -161,7 +161,7 @@ def spawn(name: nil, restart: false, key: nil, &block)
 
 				@statistics.spawn!
 
-				Fiber.new do
+				fiber do
 					while @running
 						child = self.start(name, &block)
 
@@ -270,6 +270,18 @@ def delete(key, child)
 
 				@state.delete(child)
 			end
+			
+			private
+			
+			if Fiber.respond_to?(:blocking)
+				def fiber(&block)
+					Fiber.new(blocking: true, &block)
+				end
+			else
+				def fiber(&block)
+					Fiber.new(&block)
+				end
+			end
 		end
 	end
 end