[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <9d951e81-2051-5b67-a394-2cb819e5bf57@ya.ru>
Date: Sat, 14 Jan 2023 03:20:54 +0300
From: Kirill Tkhai <tkhai@...ru>
To: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, kuniyu@...zon.com, netdev@...r.kernel.org,
tkhai@...ru
Subject: [PATCH net-next] unix: Improve locking scheme in unix_show_fdinfo()
After switching to TCP_ESTABLISHED or TCP_LISTEN sk_state, alive SOCK_STREAM
and SOCK_SEQPACKET sockets can't change it anymore (since commit 3ff8bff704f4
"unix: Fix race in SOCK_SEQPACKET's unix_dgram_sendmsg()").
Thus, we do not need to take lock here.
Signed-off-by: Kirill Tkhai <tkhai@...ru>
---
net/unix/af_unix.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index f0c2293f1d3b..f98d03fe3942 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -807,23 +807,23 @@ static int unix_count_nr_fds(struct sock *sk)
static void unix_show_fdinfo(struct seq_file *m, struct socket *sock)
{
struct sock *sk = sock->sk;
+ unsigned char s_state;
struct unix_sock *u;
int nr_fds;
if (sk) {
+ s_state = READ_ONCE(sk->sk_state);
u = unix_sk(sk);
- if (sock->type == SOCK_DGRAM) {
- nr_fds = atomic_read(&u->scm_stat.nr_fds);
- goto out_print;
- }
- unix_state_lock(sk);
- if (sk->sk_state != TCP_LISTEN)
+ /* SOCK_STREAM and SOCK_SEQPACKET sockets never change their
+ * sk_state after switching to TCP_ESTABLISHED or TCP_LISTEN.
+ * SOCK_DGRAM is ordinary. So, no lock is needed.
+ */
+ if (sock->type == SOCK_DGRAM || s_state == TCP_ESTABLISHED)
nr_fds = atomic_read(&u->scm_stat.nr_fds);
- else
+ else if (s_state == TCP_LISTEN)
nr_fds = unix_count_nr_fds(sk);
- unix_state_unlock(sk);
-out_print:
+
seq_printf(m, "scm_fds: %u\n", nr_fds);
}
}
Powered by blists - more mailing lists