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Commit a92c895e authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman
Browse files

tcp: annotate lockless access to tcp_memory_pressure 



[ 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: b8da51eb ("tcp: introduce tcp_under_memory_pressure()")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent b0fb910b

include/net/tcp.h

+1 −1
Original line number Original line Diff line number Diff line
@@ -261,7 +261,7 @@ static inline bool tcp_under_memory_pressure(const struct sock *sk) 
	    mem_cgroup_under_socket_pressure(sk->sk_memcg))

	    mem_cgroup_under_socket_pressure(sk->sk_memcg))

		return true;

		return true;





	return tcp_memory_pressure;

	return READ_ONCE(tcp_memory_pressure);

}

}

/*

/*

 * The next routines deal with comparing 32 bit unsigned ints

 * The next routines deal with comparing 32 bit unsigned ints

net/ipv4/tcp.c

+2 −2
Original line number Original line Diff line number Diff line
@@ -325,7 +325,7 @@ void tcp_enter_memory_pressure(struct sock *sk) 
{

{

	unsigned long val;

	unsigned long val;





	if (tcp_memory_pressure)

	if (READ_ONCE(tcp_memory_pressure))

		return;

		return;

	val = jiffies;

	val = jiffies;
@@ -340,7 +340,7 @@ void tcp_leave_memory_pressure(struct sock *sk) 
{

{

	unsigned long val;

	unsigned long val;





	if (!tcp_memory_pressure)

	if (!READ_ONCE(tcp_memory_pressure))

		return;

		return;

	val = xchg(&tcp_memory_pressure, 0);

	val = xchg(&tcp_memory_pressure, 0);

	if (val)

	if (val)