[PATCH v2 4/4] net: macb: Add hardware PTP support

On Wed, Jun 07, 2017 at 11:13:36AM +0000, Rafal Ozieblo wrote:

Please look at following call-stack:

1. macb_interrupt()   // spin_lock(&bp->lock) is taken
2. macb_tx_interrupt()
3. macb_handle_txtstamp()
4. skb_tstamp_tx()
5. __skb_tstamp_tx()
6. skb_may_tx_timestamp()
7. read_lock_bh() // second lock is taken

Well, you can always drop the lock, or postpone the call to
skb_tstamp_tx() until after the spin lock is released...

I know that those are different locks and different types. But this could lead 
to deadlocks. This is the reason of warning I could see.

Can you please post the lockdep splat?

Thanks,
Richard