diff --git a/trytond/ir/cron.py b/trytond/ir/cron.py
index e2ff0e8da5..c666714f78 100644
--- a/trytond/ir/cron.py
+++ b/trytond/ir/cron.py
@@ -96,16 +96,55 @@ class Cron(OSV):
     def check_xml_record(self, cursor, user, ids, values, context=None):
         return True
 
-    def _callback(self, cursor, user, job_id, model, func, args):
-        args = (args or []) and eval(args)
-        obj = self.pool.get(model)
-        if obj and hasattr(obj, func):
-            fct = getattr(obj, func)
-            fct(cursor, user, *args)
+    def _callback(self, cursor, cron):
+        try:
+            args = (cron['args'] or []) and eval(cron['args'])
+            obj = self.pool.get(cron['model'])
+            if not obj and hasattr(obj, cron['function']):
+                return False
+            fct = getattr(obj, cron['function'])
+            fct(cursor, cron['user'], *args)
+        except Exception, error:
+            cursor.rollback()
+
+            tb_s = ''
+            for line in traceback.format_exception(*sys.exc_info()):
+                try:
+                    line = line.encode('utf-8', 'ignore')
+                except:
+                    continue
+                tb_s += line
+            try:
+                tb_s += error.message.decode('utf-8', 'ignore')
+            except:
+                pass
+
+            request_obj = self.pool.get('res.request')
+            try:
+                rid = request_obj.create(
+                    cursor, cron['user'],
+                    {'name': self.raise_user_error(
+                            cursor, 'request_title', raise_exception=False),
+                     'priority': '2',
+                     'act_from': cron['user'],
+                     'act_to': cron['request_user'],
+                     'body': self.raise_user_error(
+                            cursor, 'request_body', (cron['name'], tb_s),
+                            raise_exception=False),
+                     'date_sent': DateTime.now(),
+                     'references': [
+                            ('create',{'reference': "ir.cron,%s"%cron['id']})],
+                     'state': 'waiting',
+                     'trigger_date': DateTime.now(),
+                     })
+                cursor.commit()
+            except:
+                cursor.rollback()
 
     def pool_jobs(self, db_name):
         now = DateTime.now()
         cursor = pooler.get_db(db_name).cursor()
+        cursor.execute('LOCK TABLE ir_cron')
         cursor.execute('SELECT * FROM ir_cron ' \
                 'WHERE numbercall <> 0 ' \
                     'AND active ' \
@@ -115,68 +154,32 @@ class Cron(OSV):
         crons = cursor.dictfetchall()
 
         for cron in crons:
-            try:
-                cursor.execute('UPDATE ir_cron SET running = True ' \
-                        'WHERE id = %s' % cron['id'])
-                nextcall = DateTime.strptime(str(cron['nextcall']),
-                        '%Y-%m-%d %H:%M:%S')
-                numbercall = cron['numbercall']
-                done = False
-                while nextcall < now and numbercall:
-                    if numbercall > 0:
-                        numbercall -= 1
-                    if not done or cron['doall']:
-                        self._callback(cursor, cron['user'], cron['id'], cron['model'],
-                                       cron['function'], cron['args'])
-                    if numbercall:
-                        nextcall += _INTERVALTYPES[cron['interval_type']](
-                                cron['interval_number'])
-                    done = True
-                addsql = ''
-                if not numbercall:
-                    addsql = ', active=False'
-                cursor.execute("UPDATE ir_cron SET nextcall = %s, " \
-                            "running = False, numbercall = %s" + addsql + " " \
-                            "WHERE id = %s",
-                            (nextcall.strftime('%Y-%m-%d %H:%M:%S'),
-                                numbercall, cron['id']))
-                cursor.commit()
+            cursor.execute('UPDATE ir_cron SET running = True ' \
+                               'WHERE id = %s' % cron['id'])
+            nextcall = DateTime.strptime(str(cron['nextcall']),
+                                         '%Y-%m-%d %H:%M:%S')
+            numbercall = cron['numbercall']
+            done = False
 
-            except Exception, error:
-                cursor.rollback()
+            while nextcall < now and numbercall:
+                if numbercall > 0:
+                    numbercall -= 1
+                if not done or cron['doall']:
+                    self._callback(cursor, cron)
+                if numbercall:
+                    nextcall += _INTERVALTYPES[cron['interval_type']](
+                            cron['interval_number'])
+                done = True
 
-                tb_s = ''
-                for line in traceback.format_exception(*sys.exc_info()):
-                    try:
-                        line = line.encode('utf-8', 'ignore')
-                    except:
-                        continue
-                    tb_s += line
-                try:
-                    tb_s += error.message.decode('utf-8', 'ignore')
-                except:
-                    continue
+            addsql = ''
+            if not numbercall:
+                addsql = ', active=False'
+            cursor.execute("UPDATE ir_cron SET nextcall = %s, " \
+                        "running = False, numbercall = %s" + addsql + " " \
+                        "WHERE id = %s",
+                        (nextcall.strftime('%Y-%m-%d %H:%M:%S'),
+                            numbercall, cron['id']))
+            cursor.commit()
 
-                request_obj = self.pool.get('res.request')
-                try:
-                    request_obj.create(
-                        cursor, cron['user'],
-                        {'name': self.raise_user_error(
-                                cursor, 'request_title', raise_exception=False),
-                         'priority': '2',
-                         'act_from': cron['user'],
-                         'act_to': cron['request_user'],
-                         'body': self.raise_user_error(
-                                cursor, 'request_body', (cron['name'], tb_s),
-                                raise_exception=False),
-                         'date_sent': now,
-                         'references': [
-                                ('create',{'reference': "ir.cron,%s"%cron['id']})],
-                         'state': 'waiting',
-                         'trigger_date': now,
-                         })
-                    cursor.commit()
-                except:
-                    cursor.rollback()
         cursor.close()
 Cron()