diff -r a32ced15b883 Lib/test/test_asyncio/test_events.py
--- a/Lib/test/test_asyncio/test_events.py	Fri Jun 06 01:27:34 2014 -0500
+++ b/Lib/test/test_asyncio/test_events.py	Fri Jun 06 14:17:27 2014 +0200
@@ -1364,6 +1364,18 @@ class EventLoopTestsMixin:
         with self.assertRaises(RuntimeError):
             loop.add_writer(w, callback)
 
+    def test_read_from_self(self):
+        # Issue #21595: _read_from_self() should read all pending bytes, not
+        # only a single byte
+        def noop():
+            pass
+        # Write 16 bytes into the socket
+        for i in range(16):
+            self.loop._write_to_self()
+        self.loop._read_from_self()
+        # Ensure that _read_from_self() read all pending bytes
+        self.assertRaises(BlockingIOError, self.loop._ssock.recv, 4096)
+
 
 class SubprocessTestsMixin:
 
@@ -1673,6 +1685,21 @@ if sys.platform == 'win32':
 
         def test_remove_fds_after_closing(self):
             raise unittest.SkipTest("IocpEventLoop does not have add_reader()")
+
+        def test_read_from_self(self):
+            # Issue #21595: _read_from_self() should read all pending bytes, not
+            # only a single byte
+            def noop():
+                pass
+            test_utils.run_once(self.loop)
+            # Write 16 bytes into the socket
+            for i in range(16):
+                self.loop._write_to_self()
+            self.loop.run_until_complete(self.loop._self_reading_future)
+            # Ensure that _read_from_self() read all pending bytes
+            self.assertRaises(BlockingIOError, self.loop._ssock.recv, 4096)
+
+
 else:
     from asyncio import selectors