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From: gang.yan@linux.dev Message-ID: <311f0492cc7283f6888451425cdb25fdfeca5185@linux.dev> TLS-Required: No Subject: Re: [PATCH mptcp-next v5 1/6] mptcp: replace lock_sock_fast with lock_sock in sockopt To: "MPTCP Linux" Cc: "Gang Yan" , pabeni@redhat.com, matttbe@kernel.org In-Reply-To: <20260522-sockopt_lock-v5-1-108629a46e98@kylinos.cn> References: <20260522-sockopt_lock-v5-0-108629a46e98@kylinos.cn> <20260522-sockopt_lock-v5-1-108629a46e98@kylinos.cn> X-Migadu-Flow: FLOW_OUT May 22, 2026 at 5:12 PM, "Gang Yan" wrote: Hi Matt, Paolo: I have a question about this patch. My plan is to take patches 2~6 as a new series that focuses on fixing MPTCP setsockopt issues under BPF context in the next version. This patch 1 is separate =E2=80=94 it addresses a potential sleeping-in-a= tomic problem in the normal (non-BPF) setsockopt call path, similar to=20 b5c52908d5("mptcp:=20fix scheduling with atomic in timestamp sockopt"). Could you please take a look and let me know if this patch is needed? If it is, I'd appreciate it if you could review it separately and potentially apply it directly, or I can spin a new version based on your feedback. If it's not required, I'll just drop it. Thanks, Gang=20 >=20 > From: Gang Yan >=20 >=20Replace lock_sock_fast()/unlock_sock_fast() with lock_sock()/ > release_sock() in the MPTCP sockopt handlers to avoid accidentally > introducing sleeping operations inside the lock_sock_fast() critical > section. >=20 >=20This is consistent with how other sockopt handlers in the Net code > already use lock_sock()/release_sock(). >=20 >=20Signed-off-by: Gang Yan > --- > net/mptcp/sockopt.c | 18 ++++++++---------- > 1 file changed, 8 insertions(+), 10 deletions(-) >=20 >=20diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c > index 1cf608e7357b..35a74e44a500 100644 > --- a/net/mptcp/sockopt.c > +++ b/net/mptcp/sockopt.c > @@ -77,8 +77,8 @@ static void mptcp_sol_socket_sync_intval(struct mptcp= _sock *msk, int optname, in >=20=20 >=20 mptcp_for_each_subflow(msk, subflow) { > struct sock *ssk =3D mptcp_subflow_tcp_sock(subflow); > - bool slow =3D lock_sock_fast(ssk); >=20=20 >=20+ lock_sock(ssk); > switch (optname) { > case SO_DEBUG: > sock_valbool_flag(ssk, SOCK_DBG, !!val); > @@ -114,7 +114,7 @@ static void mptcp_sol_socket_sync_intval(struct mpt= cp_sock *msk, int optname, in > } >=20=20 >=20 subflow->setsockopt_seq =3D msk->setsockopt_seq; > - unlock_sock_fast(ssk, slow); > + release_sock(ssk); > } >=20=20 >=20 release_sock(sk); > @@ -270,8 +270,8 @@ static int mptcp_setsockopt_sol_socket_linger(struc= t mptcp_sock *msk, sockptr_t > sockopt_seq_inc(msk); > mptcp_for_each_subflow(msk, subflow) { > struct sock *ssk =3D mptcp_subflow_tcp_sock(subflow); > - bool slow =3D lock_sock_fast(ssk); >=20=20 >=20+ lock_sock(ssk); > if (!ling.l_onoff) { > sock_reset_flag(ssk, SOCK_LINGER); > } else { > @@ -280,7 +280,7 @@ static int mptcp_setsockopt_sol_socket_linger(struc= t mptcp_sock *msk, sockptr_t > } >=20=20 >=20 subflow->setsockopt_seq =3D msk->setsockopt_seq; > - unlock_sock_fast(ssk, slow); > + release_sock(ssk); > } >=20=20 >=20 release_sock(sk); > @@ -749,11 +749,10 @@ static int mptcp_setsockopt_v4_set_tos(struct mpt= cp_sock *msk, int optname, > val =3D READ_ONCE(inet_sk(sk)->tos); > mptcp_for_each_subflow(msk, subflow) { > struct sock *ssk =3D mptcp_subflow_tcp_sock(subflow); > - bool slow; >=20=20 >=20- slow =3D lock_sock_fast(ssk); > + lock_sock(ssk); > __ip_sock_set_tos(ssk, val); > - unlock_sock_fast(ssk, slow); > + release_sock(ssk); > } > release_sock(sk); >=20=20 >=20@@ -1647,12 +1646,11 @@ int mptcp_set_rcvlowat(struct sock *sk, int v= al) > WRITE_ONCE(sk->sk_rcvbuf, space); > mptcp_for_each_subflow(mptcp_sk(sk), subflow) { > struct sock *ssk =3D mptcp_subflow_tcp_sock(subflow); > - bool slow; >=20=20 >=20- slow =3D lock_sock_fast(ssk); > + lock_sock(ssk); > WRITE_ONCE(ssk->sk_rcvbuf, space); > WRITE_ONCE(tcp_sk(ssk)->window_clamp, val); > - unlock_sock_fast(ssk, slow); > + release_sock(ssk); > } > return 0; > } >=20 >=20--=20 >=202.43.0 >