From: Sebastian Andrzej Siewior Date: Tue, 24 Oct 2023 09:38:48 +0200 Subject: [PATCH 06/15] net/ipv4: Use nested-BH locking for ipv4_tcp_sk. Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz ipv4_tcp_sk is a per-CPU variable and relies on disabled BH for its locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT this data structure requires explicit locking. Make a struct with a sock member (original ipv4_tcp_sk) and a local_lock_t and use local_lock_nested_bh() for locking. This change adds only lockdep coverage and does not alter the functional behaviour for !PREEMPT_RT. Cc: David Ahern Signed-off-by: Sebastian Andrzej Siewior --- include/net/sock.h | 5 +++++ net/ipv4/tcp_ipv4.c | 15 +++++++++++---- 2 files changed, 16 insertions(+), 4 deletions(-) --- a/include/net/sock.h +++ b/include/net/sock.h @@ -544,6 +544,11 @@ struct sock { netns_tracker ns_tracker; }; +struct sock_bh_locked { + struct sock *sock; + local_lock_t bh_lock; +}; + enum sk_pacing { SK_PACING_NONE = 0, SK_PACING_NEEDED = 1, --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -93,7 +93,9 @@ static int tcp_v4_md5_hash_hdr(char *md5 struct inet_hashinfo tcp_hashinfo; EXPORT_SYMBOL(tcp_hashinfo); -static DEFINE_PER_CPU(struct sock *, ipv4_tcp_sk); +static DEFINE_PER_CPU(struct sock_bh_locked, ipv4_tcp_sk) = { + .bh_lock = INIT_LOCAL_LOCK(bh_lock), +}; static u32 tcp_v4_init_seq(const struct sk_buff *skb) { @@ -885,7 +887,9 @@ static void tcp_v4_send_reset(const stru arg.tos = ip_hdr(skb)->tos; arg.uid = sock_net_uid(net, sk && sk_fullsock(sk) ? sk : NULL); local_bh_disable(); - ctl_sk = this_cpu_read(ipv4_tcp_sk); + local_lock_nested_bh(&ipv4_tcp_sk.bh_lock); + ctl_sk = this_cpu_read(ipv4_tcp_sk.sock); + sock_net_set(ctl_sk, net); if (sk) { ctl_sk->sk_mark = (sk->sk_state == TCP_TIME_WAIT) ? @@ -910,6 +914,7 @@ static void tcp_v4_send_reset(const stru sock_net_set(ctl_sk, &init_net); __TCP_INC_STATS(net, TCP_MIB_OUTSEGS); __TCP_INC_STATS(net, TCP_MIB_OUTRSTS); + local_unlock_nested_bh(&ipv4_tcp_sk.bh_lock); local_bh_enable(); #ifdef CONFIG_TCP_MD5SIG @@ -1005,7 +1010,8 @@ static void tcp_v4_send_ack(const struct arg.tos = tos; arg.uid = sock_net_uid(net, sk_fullsock(sk) ? sk : NULL); local_bh_disable(); - ctl_sk = this_cpu_read(ipv4_tcp_sk); + local_lock_nested_bh(&ipv4_tcp_sk.bh_lock); + ctl_sk = this_cpu_read(ipv4_tcp_sk.sock); sock_net_set(ctl_sk, net); ctl_sk->sk_mark = (sk->sk_state == TCP_TIME_WAIT) ? inet_twsk(sk)->tw_mark : READ_ONCE(sk->sk_mark); @@ -1020,6 +1026,7 @@ static void tcp_v4_send_ack(const struct sock_net_set(ctl_sk, &init_net); __TCP_INC_STATS(net, TCP_MIB_OUTSEGS); + local_unlock_nested_bh(&ipv4_tcp_sk.bh_lock); local_bh_enable(); } @@ -3620,7 +3627,7 @@ void __init tcp_v4_init(void) */ inet_sk(sk)->pmtudisc = IP_PMTUDISC_DO; - per_cpu(ipv4_tcp_sk, cpu) = sk; + per_cpu(ipv4_tcp_sk.sock, cpu) = sk; } if (register_pernet_subsys(&tcp_sk_ops)) panic("Failed to create the TCP control socket.\n");