loadSerial wasn't protected by a lock.

src/ZODB/FileStorage.py

@@ -184,7 +184,7 @@
 #   may have a back pointer to a version record or to a non-version
 #   record.
 #
-__version__='$Revision: 1.37 $'[11:-2]
+__version__='$Revision: 1.38 $'[11:-2]
 
 import struct, time, os, bpthread, string, base64, sys
 from struct import pack, unpack
@@ -585,6 +585,8 @@ class FileStorage(BaseStorage.BaseStorage):
         finally: self._lock_release()
 
     def loadSerial(self, oid, serial):
+        self._lock_acquire()
+        try:
             _index=self._index
             file=self._file
             seek=file.seek
@@ -611,6 +613,7 @@ class FileStorage(BaseStorage.BaseStorage):
             # We got a backpointer, probably from a commit.
             pnv=read(8)
             return _loadBack(file, oid, pnv)[0]
+        finally: self._lock_release()
                     
     def modifiedInVersion(self, oid):
         self._lock_acquire()