Re: [PATCH mptcp-next v6 07/13] mptcp: don't delegate sending repeatedly

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Tue, 11 Oct 2022, Geliang Tang wrote:

> Do not delegate sending to a subflow repeatedly. Only do it to the subflow
> without delegated action.
>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
> net/mptcp/protocol.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 86ac38d10bc4..6f55b51e10eb 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1600,6 +1600,7 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk,
> 					 bool first)
> {
> 	struct mptcp_sock *msk = mptcp_sk(sk);
> +	struct mptcp_subflow_context *subflow;
> 	struct mptcp_sendmsg_info info = {
> 		.data_lock_held = true,
> 	};
> @@ -1622,7 +1623,10 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk,
> 			if (!xmit_ssk)
> 				goto out;
> 			if (xmit_ssk != ssk) {
> -				mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk),
> +				subflow = mptcp_subflow_ctx(xmit_ssk);
> +				if (mptcp_subflow_has_delegated_action(subflow))
> +					goto out;
> +				mptcp_subflow_delegate(subflow,
> 						       MPTCP_DELEGATE_SEND);

Hi Geliang -

Did this patch fix a problem you were seeing? It seems like it isn't 
needed, and might introduce a bug.

mptcp_subflow_delegate() does a test_and_set_bit() to see if the specific 
action is already scheduled. This new code will skip the delegated send if 
*any* delegated action is set on the subflow.

> 				goto out;
> 			}
> -- 
> 2.35.3
>
>
>

--
Mat Martineau
Intel