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net/ipv4: Use nested-BH locking for ipv4_tcp_sk.

Browse source 
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 <dsahern@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20240620132727.660738-7-bigeasy@linutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Sebastian Andrzej Siewior 2024-06-20 15:21:56 +02:00 • committed by Jakub Kicinski
parent 585aa621af
commit ebad6d0334
2 changed files with 16 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
include/net/sock.h
View file

@ -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,

15
net/ipv4/tcp_ipv4.c
View file

@ -93,7 +93,9 @@ static int tcp_v4_md5_hash_hdr(char *md5_hash, const struct tcp_md5sig_key *key,
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)
{
@ -882,7 +884,9 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb,
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) ?
@ -907,6 +911,7 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb,
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
@ -1002,7 +1007,8 @@ static void tcp_v4_send_ack(const struct sock *sk,
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);
@ -1017,6 +1023,7 @@ static void tcp_v4_send_ack(const struct sock *sk,
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();
}
@ -3615,7 +3622,7 @@ void __init tcp_v4_init(void)
sk->sk_clockid = CLOCK_MONOTONIC;
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");