Author: marek Date: 2009-12-17 13:23:35 +0000 (Thu, 17 Dec 2009) New Revision: 1504
Modified: trunk/batman-adv-kernelland/send.c Log: batman-adv: Use forw_bcast_list_lock always in disabled interrupt context
forw_bcast_list_lock is spin_locked in both process and softirq context. SoftIRQ calls the spinlock with disabled IRQ and normal process context with enabled IRQs.
When process context is inside an spin_locked area protected by forw_bcast_list_lock and gets interrupted by an IRQ, it could happen that something tries to lock forw_bcast_list_lock again in SoftIRQ context. It cannot proceed further since the lock is already taken somewhere else, but no reschedule will happen inside the SoftIRQ context. This leads to an complete kernel hang without any chance of resurrection.
All functions called in process context must disable IRQs when they try to get get that lock to to prevent any reschedule due to IRQs.
Signed-off-by: Sven Eckelmann sven.eckelmann@gmx.de Acked-by: Marek Lindner lindner_marek@yahoo.de
Modified: trunk/batman-adv-kernelland/send.c =================================================================== --- trunk/batman-adv-kernelland/send.c 2009-12-17 11:53:38 UTC (rev 1503) +++ trunk/batman-adv-kernelland/send.c 2009-12-17 13:23:35 UTC (rev 1504) @@ -338,12 +338,13 @@ static void _add_bcast_packet_to_list(struct forw_packet *forw_packet, unsigned long send_time) { + unsigned long flags; INIT_HLIST_NODE(&forw_packet->list);
/* add new packet to packet list */ - spin_lock(&forw_bcast_list_lock); + spin_lock_irqsave(&forw_bcast_list_lock, flags); hlist_add_head(&forw_packet->list, &forw_bcast_list); - spin_unlock(&forw_bcast_list_lock); + spin_unlock_irqrestore(&forw_bcast_list_lock, flags);
/* start timer for this packet */ INIT_DELAYED_WORK(&forw_packet->delayed_work, @@ -382,10 +383,11 @@ container_of(work, struct delayed_work, work); struct forw_packet *forw_packet = container_of(delayed_work, struct forw_packet, delayed_work); + unsigned long flags;
- spin_lock(&forw_bcast_list_lock); + spin_lock_irqsave(&forw_bcast_list_lock, flags); hlist_del(&forw_packet->list); - spin_unlock(&forw_bcast_list_lock); + spin_unlock_irqrestore(&forw_bcast_list_lock, flags);
/* rebroadcast packet */ rcu_read_lock(); @@ -436,24 +438,25 @@ { struct forw_packet *forw_packet; struct hlist_node *tmp_node, *safe_tmp_node; + unsigned long flags;
bat_dbg(DBG_BATMAN, "purge_outstanding_packets()\n");
/* free bcast list */ - spin_lock(&forw_bcast_list_lock); + spin_lock_irqsave(&forw_bcast_list_lock, flags); hlist_for_each_entry_safe(forw_packet, tmp_node, safe_tmp_node, &forw_bcast_list, list) {
- spin_unlock(&forw_bcast_list_lock); + spin_unlock_irqrestore(&forw_bcast_list_lock, flags);
/** * send_outstanding_bcast_packet() will lock the list to * delete the item from the list */ cancel_delayed_work_sync(&forw_packet->delayed_work); - spin_lock(&forw_bcast_list_lock); + spin_lock_irqsave(&forw_bcast_list_lock, flags); } - spin_unlock(&forw_bcast_list_lock); + spin_unlock_irqrestore(&forw_bcast_list_lock, flags);
/* free batman packet list */ spin_lock(&forw_bat_list_lock);