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net: annotate lockless accesses to sk->sk_pacing_shift

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sk->sk_pacing_shift can be read and written without lock
synchronization. This patch adds annotations to
document this fact and avoid future syzbot complains.

This might also avoid unexpected false sharing
in sk_pacing_shift_update(), as the compiler
could remove the conditional check and always
write over sk->sk_pacing_shift :

if (sk->sk_pacing_shift != val)
	sk->sk_pacing_shift = val;

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2019-12-16 18:51:03 -08:00
committed by David S. Miller
parent cad46039e4
commit 7c68fa2bdd
4 changed files with 7 additions and 6 deletions
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4
include/net/sock.h
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@@ -2588,9 +2588,9 @@ static inline int sk_get_rmem0(const struct sock *sk, const struct proto *proto)
*/
static inline void sk_pacing_shift_update(struct sock *sk, int val)
{
if (!sk || !sk_fullsock(sk) || sk->sk_pacing_shift == val)
if (!sk || !sk_fullsock(sk) || READ_ONCE(sk->sk_pacing_shift) == val)
return;
sk->sk_pacing_shift = val;
WRITE_ONCE(sk->sk_pacing_shift, val);
}
/* if a socket is bound to a device, check that the given device