Hi,
I get a recursice lock warning from usbnet (asix adapter) with lockdep
checking on:
=============================================
[ INFO: possible recursive locking detected ]
2.6.37-rc4+ #1695
---------------------------------------------
ifconfig/536 is trying to acquire lock:
(&(&list->lock)->rlock#2){-.-...}, at: [<401a63bc>] _defer_bh+0x24/0x124
but task is already holding lock:
(&(&list->lock)->rlock#2){-.-...}, at: [<401a5f28>] _unlink_urbs+0x1c/0xa8
other info that might help us debug this:
2 locks held by ifconfig/536:
#0: (rtnl_mutex){+.+.+.}, at: [<4026b4f8>] _rtnl_lock+0x1c/0x2c
#1: (&(&list->lock)->rlock#2){-.-...}, at: [<401a5f28>] _unlink_urbs+0x1c/0xa8
this occurs on bring the interface down.
I think this is due to unlink_urbs():
static int unlink_urbs (struct usbnet *dev, struct sk_buff_head *q)
{
unsigned long flags;
struct sk_buff *skb, *skbnext;
int count = 0;
spin_lock_irqsave (&q->lock, flags);
skb_queue_walk_safe(q, skb, skbnext) {
struct skb_data *entry;
struct urb *urb;
int retval;
entry = (struct skb_data *) skb->cb;
urb = entry->urb;
// during some PM-driven resume scenarios,
// these (async) unlinks complete immediately
retval = usb_unlink_urb (urb);
if (retval != -EINPROGRESS && retval != 0)
netdev_dbg(dev->net, "unlink urb err, %d\n", retval);
else
count++;
}
spin_unlock_irqrestore (&q->lock, flags);
return count;
}
I dont think this should hold the list lock when calling usb_unlink_urb (urb).
The completion for the URBs takes the lock as required in its bottom half:
If people agree I will submit a patch.
Cheers
Neil
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