Adding import locks around the places where we mess with sys.modules in patcher, at schmir's suggestion.

AUTHORS

@@ -59,6 +59,6 @@ Thanks To
 * Marcin Bachry, nice repro of a bug and good diagnosis leading to the fix
 * David Ziegler, reporting issue #53
 * Favo Yang, twisted hub patch
-* Schmir, patch that fixes readline method with chunked encoding in wsgi.py
+* Schmir, patch that fixes readline method with chunked encoding in wsgi.py, advice on patcher
 * Slide, for open-sourcing gogreen
 * Holger Krekel, websocket example small fix

eventlet/patcher.py

@@ -1,5 +1,5 @@
 import sys
-
+import imp
 
 __all__ = ['inject', 'import_patched', 'monkey_patch', 'is_monkey_patched']
 
@@ -11,6 +11,7 @@ class SysModulesSaver(object):
     constructor."""
     def __init__(self, module_names=()):
         self._saved = {}
+        imp.acquire_lock()
         self.save(*module_names)
 
     def save(self, *module_names):
@@ -22,6 +23,7 @@ class SysModulesSaver(object):
         """Restores the modules that the saver knows about into
         sys.modules.
         """
+        try:
             for modname, mod in self._saved.iteritems():
                 if mod is not None:
                     sys.modules[modname] = mod
@@ -30,6 +32,8 @@ class SysModulesSaver(object):
                         del sys.modules[modname]
                     except KeyError:
                         pass
+        finally:
+            imp.release_lock()
                 
 
 def inject(module_name, new_globals, *additional_modules):
@@ -63,7 +67,7 @@ def inject(module_name, new_globals, *additional_modules):
             _green_time_modules())
     
     # after this we are gonna screw with sys.modules, so capture the
-    # state of all the modules we're going to mess with
+    # state of all the modules we're going to mess with, and lock
     saver = SysModulesSaver([name for name, m in additional_modules])
     saver.save(module_name)
 
@@ -244,6 +248,8 @@ def monkey_patch(**on):
             # tell us whether or not we succeeded
             pass
 
+    imp.acquire_lock()
+    try:
         for name, mod in modules_to_patch:
             orig_mod = sys.modules.get(name)
             if orig_mod is None:
@@ -256,7 +262,8 @@ def monkey_patch(**on):
         # hacks ahead; this is necessary to prevent a KeyError on program exit
         if patched_thread:
             _patch_main_thread(sys.modules['threading'])
-
+    finally:
+        imp.release_lock()
 
 def _patch_main_thread(mod):
     """This is some gnarly patching specific to the threading module;