Use a more gentle shutdown for SmallHTTPServer

* By opening a socket and send a special close message.
* Socket#close is very difficult to get right, notably Socket#accept
  does multiple blocking system calls, and if close(2) is done in the
  middle it might result in EBADF or worse, doing the call on an unrelated IO.

Author: eregon

spec/ruby/library/net/http/http/fixtures/http_server.rb

@@ -11,29 +11,23 @@ def printf(*args) end
   class SmallHTTPServer
     def initialize(bind_address)
       @server = TCPServer.new(bind_address, 0)
-      @running = Mutex.new
       @thread = Thread.new {
         Thread.current.abort_on_exception = true
         listen
       }
     end
 
+    def ip
+      @server.addr[3]
+    end
+
     def port
       @server.addr[1]
     end
 
     def listen
-      loop do
-        begin
-          client = @server.accept
-        rescue IOError => e
-          if @running.locked? # close
-            break
-          else
-            raise e
-          end
-        end
-
+      until @server.closed?
+        client = @server.accept
         handle_client(client)
       end
     end
@@ -43,6 +37,10 @@ def handle_client(client)
         until client.closed?
           request = client.gets("\r\n\r\n")
           break unless request
+          if request == "CLOSE"
+            @server.close
+            break
+          end
           handle_request(client, request)
         end
       ensure
@@ -95,8 +93,9 @@ def reply(client, body, request_method)
     end
 
     def close
-      @running.lock
-      @server.close
+      TCPSocket.open(ip, port) do |socket|
+        socket.write "CLOSE"
+      end
       @thread.join
     end
   end