On Mon, 17 Mar 2014 23:27:52 -0700
ebiederm@xmission.com (Eric W. Biederman) wrote:

Add a test skb_irq_freeable to report when it is safe to free a skb
from irq context.

It is not safe to free an skb from irq context when:
- The skb has a destructor as some skb destructors call local_bh_disable
  or spin_lock_bh.
- There is xfrm state as __xfrm_state_destroy calls spin_lock_bh.
- There is netfilter conntrack state as destroy_conntrack calls
  spin_lock_bh.
- If there is a refcounted dst entry on the skb, as __dst_free
  calls spin_lock_bh.
- If there is a frag_list, which could be a list of any skbs.
Otherwise it appears safe to free a skb from interrupt context.

- Update the warning in skb_releae_head_state to warn about freeing
  skb's in the wrong context.

- Update __dev_kfree_skb_irq to free all skbs that it can immediately

- Kill zap_completion_queue because there is no point going through
  a queue of packets that are not safe to free and looking for packets
  that are safe to free.

Signed-off-by: "Eric W. Biederman" <redacted>

Why introduce the additional complexity for so little gain?
It looks like you are only optimizing for the corner case where netpoll
is cleaning up on Tx.

-1