Commit 46cc6e49 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: fix lockdep splat in tcp_snd_una_update() 



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: c10d9310 ("tcp: do not assume TCP code is non preemptible")
Reported-by: default avatarFabio Estevam <festevam@gmail.com>
Diagnosed-by: default avatarFrancois Romieu <romieu@fr.zoreil.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Tested-by: default avatarFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5332174a

include/linux/u64_stats_sync.h

+14 −0
Original line number Diff line number Diff line
@@ -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)

include/net/sock.h

+6 −1
Original line number Diff line number Diff line
@@ -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;

}

net/ipv4/tcp_input.c

+6 −4
Original line number Diff line number Diff line
@@ -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;

}

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