tpool: yield after setup() and before killall()

Fixes surprising errors in artificial IO-dry scenarios (like tests).
Won't hurt in real environment.

eventlet/tpool.py

@@ -13,11 +13,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import atexit
 import imp
 import os
 import sys
 import traceback
 
+import eventlet
 from eventlet import event, greenio, greenthread, patcher, timeout
 from eventlet.support import six
 
@@ -39,7 +41,7 @@ if six.PY3:
 Empty = Queue_module.Empty
 Queue = Queue_module.Queue
 
-_bytetosend = ' '.encode()
+_bytetosend = b' '
 _coro = None
 _nthreads = int(os.environ.get('EVENTLET_THREADPOOL_SIZE', 20))
 _reqq = _rspq = None
@@ -54,6 +56,7 @@ def tpool_trampoline():
         try:
             _c = _rsock.recv(1)
             assert _c
+        # FIXME: this is probably redundant since using sockets instead of pipe now
         except ValueError:
             break  # will be raised when pipe is closed
         while not _rspq.empty():
@@ -250,7 +253,7 @@ class Proxy(object):
 
 
 def setup():
-    global _rsock, _wsock, _threads, _coro, _setup_already, _rspq, _reqq
+    global _rsock, _wsock, _coro, _setup_already, _rspq, _reqq
     if _setup_already:
         return
     else:
@@ -271,7 +274,9 @@ def setup():
     sock.listen(1)
     csock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     csock.connect(sock.getsockname())
+    csock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, True)
     _wsock, _addr = sock.accept()
+    _wsock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, True)
     sock.close()
     _rsock = greenio.GreenSocket(csock)
 
@@ -283,12 +288,20 @@ def setup():
         _threads.append(t)
 
     _coro = greenthread.spawn_n(tpool_trampoline)
+    # This yield fixes subtle error with GreenSocket.__del__
+    eventlet.sleep(0)
 
 
+# Avoid ResourceWarning unclosed socket on Python3.2+
+@atexit.register
 def killall():
     global _setup_already, _rspq, _rsock, _wsock
     if not _setup_already:
         return
+
+    # This yield fixes freeze in some scenarios
+    eventlet.sleep(0)
+
     for thr in _threads:
         _reqq.put(None)
     for thr in _threads:
@@ -296,7 +309,7 @@ def killall():
     del _threads[:]
 
     # return any remaining results
-    while not _rspq.empty():
+    while (_rspq is not None) and not _rspq.empty():
         try:
             (e, rv) = _rspq.get(block=False)
             e.send(rv)
@@ -306,9 +319,11 @@ def killall():
 
     if _coro is not None:
         greenthread.kill(_coro)
+    if _rsock is not None:
         _rsock.close()
-    _wsock.close()
         _rsock = None
+    if _wsock is not None:
+        _wsock.close()
         _wsock = None
     _rspq = None
     _setup_already = False