[PATCH mptcp 2/2] mptcp: make the locking tx schema more readable

[Paolo Abeni <pabeni@redhat.com>]

Florian noted the locking schema used by __mptcp_push_pending()
is hard to follow, let's add some more descriptive comments
and drop an unneeded and confusing check.

Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/protocol.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 84aa11a0b2d5..cd690794e22b 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1525,15 +1525,19 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
 			mptcp_flush_join_list(msk);
 			ssk = mptcp_subflow_get_send(msk);
 
-			/* try to keep the subflow socket lock across
-			 * consecutive xmit on the same socket
+			/* First check. If the ssk has changed since
+			 * the last round, release prev_ssk
 			 */
 			if (ssk != prev_ssk && prev_ssk)
 				mptcp_push_release(sk, prev_ssk, &info);
 			if (!ssk)
 				goto out;
 
-			if (ssk != prev_ssk || !prev_ssk)
+			/* Need to lock the new subflow only if different
+			 * from the previous one, otherwise we are still
+			 * helding the relevant lock
+			 */
+			if (ssk != prev_ssk)
 				lock_sock(ssk);
 
 			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
-- 
2.26.3