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Message-ID: <20240118201749.4148681-1-edumazet@google.com>
Date: Thu, 18 Jan 2024 20:17:49 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH v3 net] udp: fix busy polling
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: 2276f58ac589 ("udp: use a separate rx queue for packet reception")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reviewed-by: Paolo Abeni <pabeni@...hat.com>
Reviewed-by: Willem de Bruijn <willemb@...gle.com>
---
include/linux/skmsg.h | 6 ------
include/net/inet_sock.h | 5 -----
include/net/sock.h | 18 +++++++++++++++++-
net/core/sock.c | 11 +++++++++--
4 files changed, 26 insertions(+), 14 deletions(-)
diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 888a4b217829fd4d6baf52f784ce35e9ad6bd0ed..e65ec3fd27998a5b82fc2c4597c575125e653056 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -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)
diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index aa86453f6b9ba367f772570a7b783bb098be6236..d94c242eb3ed20b2c5b2e5ceea3953cf96341fb7 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -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
diff --git a/include/net/sock.h b/include/net/sock.h
index a7f815c7cfdfdf1296be2967fd100efdb10cdd63..54ca8dcbfb4335d657b5cea323aa7d8c4316d49e 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -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)
diff --git a/net/core/sock.c b/net/core/sock.c
index 158dbdebce6a3693deb63e557e856d9cdd7500ae..0a7f46c37f0cfc169e11377107c8342c229da0de 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -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 */
--
2.43.0.429.g432eaa2c6b-goog
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