Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t

[Peter Zijlstra]

On Mon, Mar 20, 2017 at 02:10:24PM +0000, David Laight wrote:
> On x86 the cpu flags from the 'lock inc/dec' could be used to reasonably
> cheaply detect errors - provided you actually generate a forwards branch.

Note that currently there is no arch specific implementation. We could
of course cure this.

But note that the thing you propose; using the overflow flag, can only
reasonably be done on PREEMPT=n kernels, otherwise we have an incredible
number of contexts that can nest.

Sure; getting all starts aligned to double overflow is incredibly rare,
but I don't want to be the one to have to debug that.