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tcp: annotate sk->sk_sndbuf lockless reads

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For the sake of tcp_poll(), there are few places where we fetch
sk->sk_sndbuf while this field can change from IRQ or other cpu.

We need to add READ_ONCE() annotations, and also make sure write
sides use corresponding WRITE_ONCE() to avoid store-tearing.

Note that other transports probably need similar fixes.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2019-10-10 20:17:45 -07:00
committed by David S. Miller
parent ebb3b78db7
commit e292f05e0d
5 changed files with 25 additions and 16 deletions
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18
include/net/sock.h
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@@ -883,7 +883,7 @@ static inline int sk_stream_min_wspace(const struct sock *sk)
static inline int sk_stream_wspace(const struct sock *sk)
{
return sk->sk_sndbuf - sk->sk_wmem_queued;
return READ_ONCE(sk->sk_sndbuf) - sk->sk_wmem_queued;
}
void sk_stream_write_space(struct sock *sk);
@@ -1207,7 +1207,7 @@ static inline void sk_refcnt_debug_release(const struct sock *sk)
static inline bool __sk_stream_memory_free(const struct sock *sk, int wake)
{
if (sk->sk_wmem_queued >= sk->sk_sndbuf)
if (sk->sk_wmem_queued >= READ_ONCE(sk->sk_sndbuf))
return false;
return sk->sk_prot->stream_memory_free ?
@@ -2220,10 +2220,14 @@ static inline void sk_wake_async(const struct sock *sk, int how, int band)
static inline void sk_stream_moderate_sndbuf(struct sock *sk)
{
if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) {
sk->sk_sndbuf = min(sk->sk_sndbuf, sk->sk_wmem_queued >> 1);
sk->sk_sndbuf = max_t(u32, sk->sk_sndbuf, SOCK_MIN_SNDBUF);
}
u32 val;
if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
return;
val = min(sk->sk_sndbuf, sk->sk_wmem_queued >> 1);
WRITE_ONCE(sk->sk_sndbuf, max_t(u32, val, SOCK_MIN_SNDBUF));
}
struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp,
@@ -2251,7 +2255,7 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag);
*/
static inline bool sock_writeable(const struct sock *sk)
{
return refcount_read(&sk->sk_wmem_alloc) < (sk->sk_sndbuf >> 1);
return refcount_read(&sk->sk_wmem_alloc) < (READ_ONCE(sk->sk_sndbuf) >> 1);
}
static inline gfp_t gfp_any(void)