Fixing hang when importing a module that makes a tpooled MySQLdb connection, thanks to mikepk for getting to the bottom of this. Still needs a unit test.

AUTHORS

@@ -62,4 +62,5 @@ Thanks To
 * Favo Yang, twisted hub patch
 * 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
+* Holger Krekel, websocket example small fix
+* mikepk, debugging MySQLdb/tpool issues

eventlet/tpool.py

@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import imp
 import os
 import sys
 
@@ -97,8 +98,10 @@ def execute(meth,*args, **kwargs):
     global _threads
     setup()
     # if already in tpool, don't recurse into the tpool
+    # also, call functions directly if we're inside an import lock, because
+    # if meth does any importing (sadly common), it will hang
     my_thread = threading.currentThread()
-    if my_thread in _threads:
+    if my_thread in _threads or imp.lock_held():
         return meth(*args, **kwargs)
 
     cur = greenthread.getcurrent()