[MPTCP] [PATCH v2] protocol: add comment to smb mb

[MPTCP] [PATCH v2] protocol: add comment to smb mb

[Florian Westphal]

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squashto: mptcp: add subflow write space signalling and mptcp_poll

v2: also add comment to subflow_write_space.

Signed-off-by: Florian Westphal <fw(a)strlen.de>
---
 net/mptcp/protocol.c | 1 +
 net/mptcp/subflow.c  | 1 +
 2 files changed, 2 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 6df4eb20916c..5dfca0aa7ce4 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -547,6 +547,7 @@ static void ssk_check_wmem(struct mptcp_sock *msk, struct sock *ssk)
 	if (sock) {
 		clear_bit(MPTCP_SEND_SPACE, &msk->flags);
 		smp_mb__after_atomic();
+		/* set NOSPACE only after clearing SEND_SPACE flag */
 		set_bit(SOCK_NOSPACE, &sock->flags);
 	}
 }
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index ae9173040f17..3461789ee605 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -727,6 +727,7 @@ static void subflow_write_space(struct sock *sk)
 	if (parent && sk_stream_is_writeable(sk)) {
 		set_bit(MPTCP_SEND_SPACE, &mptcp_sk(parent)->flags);
 		smp_mb__after_atomic();
+		/* set SEND_SPACE before sk_stream_write_space clears NOSPACE */
 		sk_stream_write_space(parent);
 	}
 }
-- 
2.24.1