From: Eric Dumazet <edumazet@google.com>
Date: Wed, 9 Oct 2019 15:10:15 -0700
Subject: tcp: annotate lockless access to tcp_memory_pressure
Patch-mainline: v5.4-rc4
Git-commit: 1f142c17d19a5618d5a633195a46f2c8be9bf232
References: bsc#1154353

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/net/tcp.h |    2 +-
 net/ipv4/tcp.c    |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -258,7 +258,7 @@ static inline bool tcp_under_memory_pres
 	    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
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -326,7 +326,7 @@ void tcp_enter_memory_pressure(struct so
 {
 	unsigned long val;
 
-	if (tcp_memory_pressure)
+	if (READ_ONCE(tcp_memory_pressure))
 		return;
 	val = jiffies;
 
@@ -341,7 +341,7 @@ void tcp_leave_memory_pressure(struct so
 {
 	unsigned long val;
 
-	if (!tcp_memory_pressure)
+	if (!READ_ONCE(tcp_memory_pressure))
 		return;
 	val = xchg(&tcp_memory_pressure, 0);
 	if (val)