[PATCH AUTOSEL 4.19 34/59] net: avoid possible false sharing in sk_leave_memory_pressure()
From: Sasha Levin <sashal@kernel.org>
Date: 2019-10-26 13:20:35
Also in:
lkml, stable
Subsystem:
networking [general], networking [sockets], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Willem de Bruijn, Linus Torvalds
From: Eric Dumazet <edumazet@google.com> [ Upstream commit 503978aca46124cd714703e180b9c8292ba50ba7 ] As mentioned in https://github.com/google/ktsan/wiki/READ_ONCE-and-WRITE_ONCE#it-may-improve-performance a C compiler can legally transform : if (memory_pressure && *memory_pressure) *memory_pressure = 0; to : if (memory_pressure) *memory_pressure = 0; Fixes: 0604475119de ("tcp: add TCPMemoryPressuresChrono counter") Fixes: 180d8cd942ce ("foundations of per-cgroup memory pressure controlling.") Fixes: 3ab224be6d69 ("[NET] CORE: Introducing new memory accounting interface.") Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Jakub Kicinski <redacted> Signed-off-by: Sasha Levin <sashal@kernel.org> --- net/core/sock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/core/sock.c b/net/core/sock.c
index f881eea1c4a47..fa38a2d3cb106 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c@@ -2179,8 +2179,8 @@ static void sk_leave_memory_pressure(struct sock *sk) } else { unsigned long *memory_pressure = sk->sk_prot->memory_pressure; - if (memory_pressure && *memory_pressure) - *memory_pressure = 0; + if (memory_pressure && READ_ONCE(*memory_pressure)) + WRITE_ONCE(*memory_pressure, 0); } }
--
2.20.1