On Wed, 2016-06-22 at 15:20 -0400, Jason Baron wrote:
> hmm, I think we need the smp_mb() there. From > tcp_poll() we have: > > 1) set_bit(SOCK_NOSPACE, ...) (write) > 2) smp_mb__after_atomic(); > 3) if (sk_stream_is_writeable(sk)) (read) > > while in tcp_check_space() its: > > 1) the state that sk_stream_is_writeable() cares about (write) > 2) smp_mb(); > 3) if (sk->sk_socket && test_bit(SOCK_NOSPACE,...) (read) Oh right, thanks for checking. > > So if we can show that there are sufficient barriers > for #1 (directly above), maybe it can be down-graded or > eliminated. But it would still seem somewhat fragile. > > Note I didn't observe any missing wakeups here, but I > just wanted to make sure we didn't miss any, since they > can be quite hard to debug. x
