remote_credits
atomic_t remote_credits;
#define remote_credits(ssk) (atomic_read(&ssk->remote_credits))
c = remote_credits(ssk);
atomic_set(&sdp_sk(sk)->remote_credits,
atomic_set(&ssk->remote_credits, rx_ring_posted(ssk));
atomic_dec(&ssk->remote_credits);
atomic_set(&ssk->remote_credits, rx_ring_posted(ssk));