On Wed, 2020-07-15 at 17:20 -0700, Mat Martineau wrote:
> The MPTCP socket's write_seq member can be read without the msk lock
> held, so use WRITE_ONCE() to store it.
> 
> Signed-off-by: Mat Martineau <mathew.j.martineau(a)linux.intel.com>
> ---
>  net/mptcp/protocol.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 30c5810771dd..ed3ca80d72f8 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -797,7 +797,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
>  out:
>  	if (!retransmission)
>  		pfrag->offset += frag_truesize;
> -	*write_seq += ret;
> +	WRITE_ONCE(*write_seq, *write_seq + ret);
>  	mptcp_subflow_ctx(ssk)->rel_write_seq += ret;

I think the msk lock should be already held here ?!?

/P