[PATCH AUTOSEL 4.19 591/671] tcp: annotate lockless access to tcp_memory_pressure
From: Sasha Levin <sashal@kernel.org>
Date: 2020-01-16 18:37:17
Also in:
lkml, stable
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
From: Eric Dumazet <edumazet@google.com>
[ 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 <redacted>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/tcp.h | 2 +-
net/ipv4/tcp.c | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index ac4ffe8013d8..918bfd0d7d1f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h@@ -261,7 +261,7 @@ 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 7561fa1bcc3e..3c181ca714d0 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c@@ -325,7 +325,7 @@ void tcp_enter_memory_pressure(struct sock *sk) { unsigned long val; - if (tcp_memory_pressure) + if (READ_ONCE(tcp_memory_pressure)) return; val = jiffies;
@@ -340,7 +340,7 @@ 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)
--
2.20.1