OK, I've spent some more time trying to understand this part of syncprov.c. From what I understand : - the assert failure in ldap_pvt_runqueue_resched is caused by the fact syncprov_qstart is trying to "reschedule" a task that is no longer in the task_list - the only time the task is removed from the task_list (via ldap_pvt_runqueue_remove) is when the task is being run, in syncprov_qtask, if syncprov_qplay returns !=0 - the next time syncprov_qstart is called, it finds "so->s_qtask" is not NULL, and tries to reschedule the task, but it's no longer in the task_list. I've written a patch that sets "so->s_qtask" to NULL in syncprov_qtask, just after removing the task from the task_list. So that when syncprov_qstart is called again, it goes into ldap_pvt_runqueue_insert... The patch is attached. Unfortunately, I can't confirm it fixes the bug since I can't reproduce it... For those who understand the logic behind this, does this make any sense? :)