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tcp: fix lockdep splat in tcp_snd_una_update()

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tcp_snd_una_update() and tcp_rcv_nxt_update() call
u64_stats_update_begin() either from process context or BH handler.

This triggers a lockdep splat on 32bit & SMP builds.

We could add u64_stats_update_begin_bh() variant but this would
slow down 32bit builds with useless local_disable_bh() and
local_enable_bh() pairs, since we own the socket lock at this point.

I add sock_owned_by_me() helper to have proper lockdep support
even on 64bit builds, and new u64_stats_update_begin_raw()
and u64_stats_update_end_raw methods.

Fixes: c10d9310ed ("tcp: do not assume TCP code is non preemptible")
Reported-by: Fabio Estevam <festevam@gmail.com>
Diagnosed-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-05-03 16:56:03 -07:00 committed by David S. Miller
parent 5332174a83
commit 46cc6e4976
3 changed files with 26 additions and 5 deletions
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14
include/linux/u64_stats_sync.h
View File

@ -89,6 +89,20 @@ static inline void u64_stats_update_end(struct u64_stats_sync *syncp)
#endif
}
static inline void u64_stats_update_begin_raw(struct u64_stats_sync *syncp)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
raw_write_seqcount_begin(&syncp->seq);
#endif
}
static inline void u64_stats_update_end_raw(struct u64_stats_sync *syncp)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
raw_write_seqcount_end(&syncp->seq);
#endif
}
static inline unsigned int u64_stats_fetch_begin(const struct u64_stats_sync *syncp)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)

7
include/net/sock.h
View File

@ -1421,11 +1421,16 @@ static inline void unlock_sock_fast(struct sock *sk, bool slow)
* accesses from user process context.
*/
static inline bool sock_owned_by_user(const struct sock *sk)
static inline void sock_owned_by_me(const struct sock *sk)
{
#ifdef CONFIG_LOCKDEP
WARN_ON_ONCE(!lockdep_sock_is_held(sk) && debug_locks);
#endif
}
static inline bool sock_owned_by_user(const struct sock *sk)
{
sock_owned_by_me(sk);
return sk->sk_lock.owned;
}

10
net/ipv4/tcp_input.c
View File

@ -3355,9 +3355,10 @@ static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
{
u32 delta = ack - tp->snd_una;
u64_stats_update_begin(&tp->syncp);
sock_owned_by_me((struct sock *)tp);
u64_stats_update_begin_raw(&tp->syncp);
tp->bytes_acked += delta;
u64_stats_update_end(&tp->syncp);
u64_stats_update_end_raw(&tp->syncp);
tp->snd_una = ack;
}
@ -3366,9 +3367,10 @@ static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq)
{
u32 delta = seq - tp->rcv_nxt;
u64_stats_update_begin(&tp->syncp);
sock_owned_by_me((struct sock *)tp);
u64_stats_update_begin_raw(&tp->syncp);
tp->bytes_received += delta;
u64_stats_update_end(&tp->syncp);
u64_stats_update_end_raw(&tp->syncp);
tp->rcv_nxt = seq;
}