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tcp: annotate tp->snd_nxt lockless reads 

There are few places where we fetch tp->snd_nxt while
this field can change from IRQ or other cpu.

We need to add READ_ONCE() annotations, and also make
sure write sides use corresponding WRITE_ONCE() to avoid
store-tearing.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2019-10-10 20:17:42 -07:00 committed by David S. Miller
parent 0f31746452
commit e0d694d638
4 changed files with 13 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/net/tcp.h
View File

@ -1917,7 +1917,8 @@ static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
static inline bool tcp_stream_memory_free(const struct sock *sk, int wake)
{
const struct tcp_sock *tp = tcp_sk(sk);
u32 notsent_bytes = READ_ONCE(tp->write_seq) - tp->snd_nxt;
u32 notsent_bytes = READ_ONCE(tp->write_seq) -
READ_ONCE(tp->snd_nxt);
return (notsent_bytes << wake) < tcp_notsent_lowat(tp);
}

3
net/ipv4/tcp.c
View File

@ -625,7 +625,8 @@ int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
answ = 0;
else
answ = READ_ONCE(tp->write_seq) - tp->snd_nxt;
answ = READ_ONCE(tp->write_seq) -
READ_ONCE(tp->snd_nxt);
break;
default:
return -ENOIOCTLCMD;

6
net/ipv4/tcp_minisocks.c
View File

@ -482,8 +482,10 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
WRITE_ONCE(newtp->rcv_nxt, seq);
newtp->segs_in = 1;
newtp->snd_sml = newtp->snd_una =
newtp->snd_nxt = newtp->snd_up = treq->snt_isn + 1;
seq = treq->snt_isn + 1;
newtp->snd_sml = newtp->snd_una = seq;
WRITE_ONCE(newtp->snd_nxt, seq);
newtp->snd_up = seq;
INIT_LIST_HEAD(&newtp->tsq_node);
INIT_LIST_HEAD(&newtp->tsorted_sent_queue);

10
net/ipv4/tcp_output.c
View File

@ -67,7 +67,7 @@ static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
struct tcp_sock *tp = tcp_sk(sk);
unsigned int prior_packets = tp->packets_out;
tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);
__skb_unlink(skb, &sk->sk_write_queue);
tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
@ -3142,7 +3142,7 @@ void tcp_send_fin(struct sock *sk)
* if FIN had been sent. This is because retransmit path
* does not change tp->snd_nxt.
*/
tp->snd_nxt++;
WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1);
return;
}
} else {
@ -3426,7 +3426,7 @@ static void tcp_connect_init(struct sock *sk)
tp->snd_una = tp->write_seq;
tp->snd_sml = tp->write_seq;
tp->snd_up = tp->write_seq;
tp->snd_nxt = tp->write_seq;
WRITE_ONCE(tp->snd_nxt, tp->write_seq);
if (likely(!tp->repair))
tp->rcv_nxt = 0;
@ -3586,11 +3586,11 @@ int tcp_connect(struct sock *sk)
/* We change tp->snd_nxt after the tcp_transmit_skb() call
* in order to make this packet get counted in tcpOutSegs.
*/
tp->snd_nxt = tp->write_seq;
WRITE_ONCE(tp->snd_nxt, tp->write_seq);
tp->pushed_seq = tp->write_seq;
buff = tcp_send_head(sk);
if (unlikely(buff)) {
tp->snd_nxt = TCP_SKB_CB(buff)->seq;
WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq);
tp->pushed_seq = TCP_SKB_CB(buff)->seq;
}
TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);