Jason Baron <jba...@akamai.com> wrote:
> From: Jason Baron <jba...@akamai.com>
>
> sock_reset_flag() maps to __clear_bit() not the atomic version clear_bit().
> Thus, we need smp_mb(), smp_mb__after_atomic() is not sufficient.
>
> Fixes: 3c7151275c0c ("tcp: add memory barriers to write space paths")
> Cc: Eric Dumazet <eric.duma...@gmail.com>
> Cc: Oleg Nesterov <o...@redhat.com>
> Signed-off-by: Jason Baron <jba...@akamai.com>
This patch makes no sense.
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index bfa165cc455a..1e22ae4a5b38 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -5028,7 +5028,7 @@ static void tcp_check_space(struct sock *sk)
> if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
> sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
> /* pairs with tcp_poll() */
> - smp_mb__after_atomic();
> + smp_mb();
> if (sk->sk_socket &&
> test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
> tcp_new_space(sk);
The comment says that it's pairing with an mb in tcp_poll, but
tcp_poll doesn't touch QUEUE_SHRUNK at all. So what exactly is
this barrier for?
Cheers,
--
Email: Herbert Xu <herb...@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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