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
@@ -585,32 +585,35 @@ class FileStorage(BaseStorage.BaseStorage):
         finally: self._lock_release()
 
     def loadSerial(self, oid, serial):
-        _index=self._index
-        file=self._file
-        seek=file.seek
-        read=file.read
-        pos=_index[oid]
-        while 1:
-            seek(pos)
-            h=read(42)
-            doid,dserial,prev,tloc,vlen,plen = unpack(">8s8s8s8sH8s", h)
-            if doid != oid: raise CorruptedDataError, h
-            if dserial == serial: break # Yeee ha!
-            # Keep looking for serial
-            pos=u64(prev)
-            if not pos: raise KeyError, serial
-            continue
-            
-        if vlen:
-            pnv=read(8) # Read location of non-version data
-            read(8) # skip past version link
-            read(vlen) # skip version
+        self._lock_acquire()
+        try:
+            _index=self._index
+            file=self._file
+            seek=file.seek
+            read=file.read
+            pos=_index[oid]
+            while 1:
+                seek(pos)
+                h=read(42)
+                doid,dserial,prev,tloc,vlen,plen = unpack(">8s8s8s8sH8s", h)
+                if doid != oid: raise CorruptedDataError, h
+                if dserial == serial: break # Yeee ha!
+                # Keep looking for serial
+                pos=u64(prev)
+                if not pos: raise KeyError, serial
+                continue
+
+            if vlen:
+                pnv=read(8) # Read location of non-version data
+                read(8) # skip past version link
+                read(vlen) # skip version
 
-        if plen != z64: return read(u64(plen))
+            if plen != z64: return read(u64(plen))
 
-        # We got a backpointer, probably from a commit.
-        pnv=read(8)
-        return _loadBack(file, oid, pnv)[0]
+            # 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()