Re: [PATCH 1/2] xfrm: Force a dst refcount before entering the xfrm type handlers

From: Steffen Klassert <steffen.klassert@secunet.com>
Date: Wed, 16 Mar 2011 08:43:06 +0100

On Wed, Mar 16, 2011 at 12:17:32AM -0700, David Miller wrote:

quoted

Steffen we really need to find another way to fix these problems.

We already make way too many expensive atomic operations in these code
paths modified by your 3 patches, we should strive to not add new
ones.

I know that it is exspensive, but we have to take a refcount if
the crypto layer returns asyncronous. Unfortunately it is too
late to take the refcount when the crypto layer notifies us about
that as the skb might be already gone.

We can pass around an atomic_t for the crypto layer to bump when
it decides to take an async path, bump it on entry and upon event
wakeup decrement it.

Actually, a plain atomic_t is a bad idea because we might have to
release the object.  So callbacks with private void pointer arg is
better.