tcp: annotate lockless access to tcp_memory_pressure

BugLink: https://bugs.launchpad.net/bugs/1863019
[ Upstream commit 1f142c17d19a5618d5a633195a46f2c8be9bf232 ]

tcp_memory_pressure is read without holding any lock,
and its value could be changed on other cpus.

Use READ_ONCE() to annotate these lockless reads.

The write side is already using atomic ops.

Fixes: b8da51ebb1aa ("tcp: introduce tcp_under_memory_pressure()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 493b948cff440d1c3e1494d870ddf706908190cd..88b7c5f1039aa508c6365000e47c1a04790ec593 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -259,7 +259,7 @@ static inline bool tcp_under_memory_pressure(const struct sock *sk)
            mem_cgroup_under_socket_pressure(sk->sk_memcg))
                return true;
 
-       return tcp_memory_pressure;
+       return READ_ONCE(tcp_memory_pressure);
 }
 /*
  * The next routines deal with comparing 32 bit unsigned ints

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index d946137b5b85150f222f59e830282b34f4af8f4b..7fb0edc4b60650ea38379858f9eaf9f8e9c6610b 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -327,7 +327,7 @@ void tcp_enter_memory_pressure(struct sock *sk)
 {
        unsigned long val;
 
-       if (tcp_memory_pressure)
+       if (READ_ONCE(tcp_memory_pressure))
                return;
        val = jiffies;
 
@@ -342,7 +342,7 @@ void tcp_leave_memory_pressure(struct sock *sk)
 {
        unsigned long val;
 
-       if (!tcp_memory_pressure)
+       if (!READ_ONCE(tcp_memory_pressure))
                return;
        val = xchg(&tcp_memory_pressure, 0);
        if (val)