On Tue, Mar 10, 2026 at 9:17 PM Kuniyuki Iwashima <[email protected]> wrote: > > On Fri, Mar 6, 2026 at 6:05 AM Michal Luczaj <[email protected]> wrote: > > > > On 3/6/26 06:44, Kuniyuki Iwashima wrote: > > > On Thu, Mar 5, 2026 at 3:32 PM Michal Luczaj <[email protected]> wrote: > > >> > > >> Instead of repeating the same (un)locking pattern, reuse > > >> sock_map_sk_{acquire,release}(). This centralizes the code and makes it > > >> easier to adapt sockmap to af_unix-specific locking. > > >> > > >> Signed-off-by: Michal Luczaj <[email protected]> > > >> --- > > >> net/core/sock_map.c | 21 +++++++-------------- > > >> 1 file changed, 7 insertions(+), 14 deletions(-) > > >> > > >> diff --git a/net/core/sock_map.c b/net/core/sock_map.c > > >> index 02a68be3002a..7ba6a7f24ccd 100644 > > >> --- a/net/core/sock_map.c > > >> +++ b/net/core/sock_map.c > > >> @@ -353,11 +353,9 @@ static void sock_map_free(struct bpf_map *map) > > >> sk = xchg(psk, NULL); > > >> if (sk) { > > >> sock_hold(sk); > > >> - lock_sock(sk); > > >> - rcu_read_lock(); > > >> + sock_map_sk_acquire(sk); > > >> sock_map_unref(sk, psk); > > >> - rcu_read_unlock(); > > >> - release_sock(sk); > > >> + sock_map_sk_release(sk); > > >> sock_put(sk); > > >> } > > >> } > > >> @@ -1176,11 +1174,9 @@ static void sock_hash_free(struct bpf_map *map) > > >> */ > > >> hlist_for_each_entry_safe(elem, node, &unlink_list, > > >> node) { > > >> hlist_del(&elem->node); > > >> - lock_sock(elem->sk); > > >> - rcu_read_lock(); > > >> + sock_map_sk_acquire(elem->sk); > > >> sock_map_unref(elem->sk, elem); > > >> - rcu_read_unlock(); > > >> - release_sock(elem->sk); > > >> + sock_map_sk_release(elem->sk); > > >> sock_put(elem->sk); > > >> sock_hash_free_elem(htab, elem); > > >> } > > >> @@ -1676,8 +1672,7 @@ void sock_map_close(struct sock *sk, long timeout) > > >> void (*saved_close)(struct sock *sk, long timeout); > > >> struct sk_psock *psock; > > >> > > >> - lock_sock(sk); > > >> - rcu_read_lock(); > > >> + sock_map_sk_acquire(sk); > > >> psock = sk_psock(sk); > > >> if (likely(psock)) { > > >> saved_close = psock->saved_close; > > >> @@ -1685,16 +1680,14 @@ void sock_map_close(struct sock *sk, long > > >> timeout) > > >> psock = sk_psock_get(sk); > > >> if (unlikely(!psock)) > > >> goto no_psock; > > >> - rcu_read_unlock(); > > >> sk_psock_stop(psock); > > >> - release_sock(sk); > > >> + sock_map_sk_release(sk); > > > > > > I think sk_psock_stop() was intentionally put outside > > > of rcu_read_lock() to not extend the grace period > > > unnecessarily. e.g. while + __sk_msg_free(). > > > > > > Maybe add __sock_map_sk_release() without > > > rcu_read_unlock() ? > > > > How about dropping this patch completely? The more I stare at it, I see no > > reason why af_unix state lock would matter in any of these places. > > I agree. Actually, once it's held, it can be released right away. > The lock is only to ensure that peer is set after checking > TCP_ESTABLISHED, but it continues holding unix_state_lock() > unnecessarily long. > > Honestly I prefer Martin's idea, using unix_peer_get() in > unix_stream_bpf_update_proto().
Pondering again, I'm leaning to towards my initial approach, just null check for peer, which allows bpf_iter to acquire unix_state_lock() and make sure the socket is alive. (still lock_sock() is needed for bpf_setsockopt()) The check is lightweight and SOCKMAP does not need to hold the lock unnecessarily, and we can provide stable result to bpf_iter. IOW, if we hold unix_state_lock() in the SOCKMAP path (even unix_peer_get()), we cannot use unix_state_lock() for bpf_iter and lose stability since it will trigger dead lock.
