From: Ingo Molnar Date: Mon, 3 Jul 2006 07:25:14 +0000 (-0700) Subject: [PATCH] lockdep: annotate ieee1394 skb-queue-head locking X-Git-Url: http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=d378834840907326ac9d448056d957d13cc3718f [PATCH] lockdep: annotate ieee1394 skb-queue-head locking ieee1394 reuses the skb infrastructure of the networking code, and uses two skb-head queues: ->pending_packet_queue and hpsbpkt_queue. The latter is used in the usual fashion: processed from a kernel thread. The other one, ->pending_packet_queue is also processed from hardirq context (f.e. in hpsb_bus_reset()), which is not what the networking code usually does (which completes from softirq or process context). This locking assymetry can be totally correct if done carefully, but it can also be dangerous if networking helper functions are reused, which could assume traditional networking use. It would probably be more robust to push this completion into a workqueue - but technically the code can be 100% correct, and lockdep has to be taught about it. The solution is to split the ->pending_packet_queue skb-head->lock class from the networking lock-class by using a private lock-validator key. Has no effect on non-lockdep kernels. Signed-off-by: Ingo Molnar Cc: Stefan Richter Cc: Jody McIntyre Cc: Ben Collins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- --- a/drivers/ieee1394/hosts.c +++ b/drivers/ieee1394/hosts.c @@ -107,6 +107,14 @@ static int alloc_hostnum_cb(struct hpsb_ */ static DEFINE_MUTEX(host_num_alloc); +/* + * The pending_packet_queue is special in that it's processed + * from hardirq context too (such as hpsb_bus_reset()). Hence + * split the lock class from the usual networking skb-head + * lock class by using a separate key for it: + */ +static struct lock_class_key pending_packet_queue_key; + struct hpsb_host *hpsb_alloc_host(struct hpsb_host_driver *drv, size_t extra, struct device *dev) { @@ -128,6 +136,8 @@ struct hpsb_host *hpsb_alloc_host(struct h->driver = drv; skb_queue_head_init(&h->pending_packet_queue); + lockdep_set_class(&h->pending_packet_queue.lock, + &pending_packet_queue_key); INIT_LIST_HEAD(&h->addr_space); for (i = 2; i < 16; i++)