diff --git a/python/devsup/db.py b/python/devsup/db.py
index d644021..5d6893b 100644
--- a/python/devsup/db.py
+++ b/python/devsup/db.py
@@ -1,15 +1,21 @@
+
+import threading, sys, traceback
+
+from util import Worker
+
 try:
     import _dbapi
 except ImportError:
     import _nullapi as _dbapi
-from _dbapi import _Field, _Record
 
 _rec_cache = {}
 _no_such_field = object()
 
 __all__ = [
-    'Record',
+    'Record', 'getRecord',
     'Field',
+    'IOScanListBlock',
+    'IOScanListThread',
 ]
 
 def getRecord(name):
@@ -20,7 +26,100 @@ def getRecord(name):
         _rec_cache[name] = rec
         return rec
 
-class Record(_Record):
+class IOScanListBlock(object):
+    def __init__(self):
+        super(IOScanListBlock,self).__init__()
+        self._recs, self._recs_add, self._recs_remove = set(), set(), set()
+        self._running = False
+
+    def add(self, rec):
+        assert isinstance(rec, Record)
+
+        if self._running:
+            self._recs_remove.discard(rec)
+            self._recs_add.add(rec)
+
+        else:
+            self._recs.add(rec)
+
+        return self._remove
+
+    def _remove(self, rec):
+        if self._running:
+            self._recs_add.discard(rec)
+            self._recs_add._recs_remove(rec)
+
+        else:
+            self._recs.discard(rec)
+
+    def interrupt(self, reason=None, mask=None):
+        self._running = True
+        try:
+            for R in self._recs:
+                if mask and R in mask:
+                    continue
+                R.scan(sync=True, reason=reason, force=2)
+        finally:
+            self._running = False
+            if self._recs_add or self._recs_remove:
+                assert len(self._recs_add.interaction(self._recs_remove))==0
+            
+                self._recs.update(self._recs_add)
+                self._recs_add.clear()
+                self._recs.difference_update(self._recs_remove)
+                self._recs_remove.clear()
+            
+
+def _default_whendone(type, val, tb):
+    if type or val or tb:
+        traceback.print_exception(type, val, tb)
+
+class IOScanListThread(IOScanListBlock):
+    _worker = None
+    queuelength=100
+    @classmethod
+    def getworker(cls):
+        if cls._worker:
+            return cls._worker
+        import hooks
+        T = Worker(max=cls.queuelength)
+        hooks.addHook('AtIocExit', T.stop)
+        T.start()
+        cls._worker = T
+        return T
+
+    def __init__(self):
+        super(IOScanListThread,self).__init__()
+        self._lock = threading.Lock()
+
+    def add(self, rec):
+        print self,'add',rec
+        with self._lock:
+            return super(IOScanListThread,self).add(rec)
+
+    def _remove(self, rec):
+        print self,'remove',rec
+        with self._lock:
+            return super(IOScanListThread,self)._remove(rec)
+
+    def interrupt(self, reason=None, mask=None, whendone=_default_whendone):
+        W = self.getworker()
+        try:
+            W.add(self._X, (reason, mask, whendone))
+            return True
+        except RuntimeError:
+            return False
+
+    def _X(self, reason, mask, whendone):
+        try:
+            #print 'XXXXX',self
+            with self._lock:
+                super(IOScanListThread,self).interrupt(reason, mask)
+        finally:
+            #print 'YYYYY',self,sys.exc_info()
+            whendone(*sys.exc_info())
+
+class Record(_dbapi._Record):
     def __init__(self, *args, **kws):
         super(Record, self).__init__(*args, **kws)
         super(Record, self).__setattr__('_fld_cache', {})
@@ -64,7 +163,7 @@ class Record(_Record):
     def __repr__(self):
         return 'Record("%s")'%self.name()
 
-class Field(_Field):
+class Field(_dbapi._Field):
     @property
     def record(self):
         """Fetch the record associated with this field