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tcp: annotate lockless access to tcp_memory_pressure 

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: b8da51ebb1 ("tcp: introduce tcp_under_memory_pressure()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
This commit is contained in:
Eric Dumazet 2019-10-09 15:10:15 -07:00 committed by Jakub Kicinski
parent 60b173ca3d
commit 1f142c17d1
2 changed files with 3 additions and 3 deletions
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2
include/net/tcp.h
View File

@ -258,7 +258,7 @@ 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

4
net/ipv4/tcp.c
View File

@ -326,7 +326,7 @@ void tcp_enter_memory_pressure(struct sock *sk)
{
unsigned long val;
if (tcp_memory_pressure)
if (READ_ONCE(tcp_memory_pressure))
return;
val = jiffies;
@ -341,7 +341,7 @@ 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)