> On Mon, Nov 21, 2016 at 04:49:15PM +0100, Peter Zijlstra wrote: > > > Speaking of non-fitting patterns. This one is quite common in > > > networking code for refcounters: > > > > > > if (atomic_cmpxchg(&cur->refcnt, 1, 0) == 1) {} This is from > > > net/netfilter/nfnetlink_acct.c, but there are similar ones in other > > > places. > > > > Cute, but weird it doesn't actually decrement if not 1. > > Hurgh.. creative refcounting that. The question is how much of that do > we want to support? It really must not decrement there.
And one more creative usage: http://lxr.free-electrons.com/source/net/ipv4/udp.c#L1940 if (!sk || !atomic_inc_not_zero_hint(&sk->sk_refcnt, 2)) return; I didn't even guess anyone is using atomic_inc_not_zero_hint... But network code keeps surprising me today :) So, yes, I guess the question is what to do with these cases really?