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udp: fix busy polling

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Generic sk_busy_loop_end() only looks at sk->sk_receive_queue
for presence of packets.

Problem is that for UDP sockets after blamed commit, some packets
could be present in another queue: udp_sk(sk)->reader_queue

In some cases, a busy poller could spin until timeout expiration,
even if some packets are available in udp_sk(sk)->reader_queue.

v3: - make sk_busy_loop_end() nicer (Willem)

v2: - add a READ_ONCE(sk->sk_family) in sk_is_inet() to avoid KCSAN splats.
    - add a sk_is_inet() check in sk_is_udp() (Willem feedback)
    - add a sk_is_inet() check in sk_is_tcp().

Fixes: 2276f58ac5 ("udp: use a separate rx queue for packet reception")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2024-01-18 20:17:49 +00:00 committed by David S. Miller
parent e3f9bed9be
commit a54d51fb2d
4 changed files with 26 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/skmsg.h
View File

@ -505,12 +505,6 @@ static inline bool sk_psock_strp_enabled(struct sk_psock *psock)
return !!psock->saved_data_ready;
}
static inline bool sk_is_udp(const struct sock *sk)
{
return sk->sk_type == SOCK_DGRAM &&
sk->sk_protocol == IPPROTO_UDP;
}
#if IS_ENABLED(CONFIG_NET_SOCK_MSG)
#define BPF_F_STRPARSER (1UL << 1)

5
include/net/inet_sock.h
View File

@ -307,11 +307,6 @@ static inline unsigned long inet_cmsg_flags(const struct inet_sock *inet)
#define inet_assign_bit(nr, sk, val) \
assign_bit(INET_FLAGS_##nr, &inet_sk(sk)->inet_flags, val)
static inline bool sk_is_inet(struct sock *sk)
{
return sk->sk_family == AF_INET || sk->sk_family == AF_INET6;
}
/**
* sk_to_full_sk - Access to a full socket
* @sk: pointer to a socket

18
include/net/sock.h
View File

@ -2765,9 +2765,25 @@ static inline void skb_setup_tx_timestamp(struct sk_buff *skb, __u16 tsflags)
&skb_shinfo(skb)->tskey);
}
static inline bool sk_is_inet(const struct sock *sk)
{
int family = READ_ONCE(sk->sk_family);
return family == AF_INET || family == AF_INET6;
}
static inline bool sk_is_tcp(const struct sock *sk)
{
return sk->sk_type == SOCK_STREAM && sk->sk_protocol == IPPROTO_TCP;
return sk_is_inet(sk) &&
sk->sk_type == SOCK_STREAM &&
sk->sk_protocol == IPPROTO_TCP;
}
static inline bool sk_is_udp(const struct sock *sk)
{
return sk_is_inet(sk) &&
sk->sk_type == SOCK_DGRAM &&
sk->sk_protocol == IPPROTO_UDP;
}
static inline bool sk_is_stream_unix(const struct sock *sk)

11
net/core/sock.c
View File

@ -107,6 +107,7 @@
#include <linux/interrupt.h>
#include <linux/poll.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/init.h>
#include <linux/highmem.h>
#include <linux/user_namespace.h>
@ -4144,8 +4145,14 @@ bool sk_busy_loop_end(void *p, unsigned long start_time)
{
struct sock *sk = p;
return !skb_queue_empty_lockless(&sk->sk_receive_queue) ||
sk_busy_loop_timeout(sk, start_time);
if (!skb_queue_empty_lockless(&sk->sk_receive_queue))
return true;
if (sk_is_udp(sk) &&
!skb_queue_empty_lockless(&udp_sk(sk)->reader_queue))
return true;
return sk_busy_loop_timeout(sk, start_time);
}
EXPORT_SYMBOL(sk_busy_loop_end);
#endif /* CONFIG_NET_RX_BUSY_POLL */