Revert "udp: avoid calling sock_def_readable() if possible"

This reverts commit 612b1c0dec5bc7367f90fc508448b8d0d7c05414. On a
scenario with multiple threads blocking on a recvfrom(), we need to call
sock_def_readable() on every __udp_enqueue_schedule_skb() otherwise the
threads won't be woken up as __skb_wait_for_more_packets() is using
prepare_to_wait_exclusive().

Link: https://bugzilla.redhat.com/2308477
Fixes: 612b1c0dec5b ("udp: avoid calling sock_def_readable() if possible")
Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241202155620.1719-1-ffmancera@riseup.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 6a01905d379fdd5c1815c3a71694071f6e5e06d3..e8953e88efef987c5125094b3c7c7385fd7444ab 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1674,7 +1674,6 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
        struct sk_buff_head *list = &sk->sk_receive_queue;
        int rmem, err = -ENOMEM;
        spinlock_t *busy = NULL;
-       bool becomes_readable;
        int size, rcvbuf;
 
        /* Immediately drop when the receive queue is full.
@@ -1715,19 +1714,12 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
         */
        sock_skb_set_dropcount(sk, skb);
 
-       becomes_readable = skb_queue_empty(list);
        __skb_queue_tail(list, skb);
        spin_unlock(&list->lock);
 
-       if (!sock_flag(sk, SOCK_DEAD)) {
-               if (becomes_readable ||
-                   sk->sk_data_ready != sock_def_readable ||
-                   READ_ONCE(sk->sk_peek_off) >= 0)
-                       INDIRECT_CALL_1(sk->sk_data_ready,
-                                       sock_def_readable, sk);
-               else
-                       sk_wake_async_rcu(sk, SOCK_WAKE_WAITD, POLL_IN);
-       }
+       if (!sock_flag(sk, SOCK_DEAD))
+               INDIRECT_CALL_1(sk->sk_data_ready, sock_def_readable, sk);
+
        busylock_release(busy);
        return 0;