diff options
| author | Kirill Tkhai <tkhai@ya.ru> | 2023-01-14 12:35:02 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2023-01-16 11:21:11 +0000 |
| commit | b27401a30ee466c4476b035487be0580767ba1fb (patch) | |
| tree | d2e97d34aecaddbddb5fe2cc4c5f7449c09a07db /net/unix | |
| parent | 40ea3ee2ced1a6eb3d6b22ecda40f5f6179fd990 (diff) | |
| download | lwn-b27401a30ee466c4476b035487be0580767ba1fb.tar.gz lwn-b27401a30ee466c4476b035487be0580767ba1fb.zip | |
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@ya.ru>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/unix')
| -rw-r--r-- | net/unix/af_unix.c | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index f0c2293f1d3b..009616fa0256 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; + int nr_fds = 0; 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); } } |