Return-Path: Received: from mail-pf0-f176.google.com ([209.85.192.176]:36256 "EHLO mail-pf0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756295AbcECX4I (ORCPT ); Tue, 3 May 2016 19:56:08 -0400 Message-ID: <1462319763.5535.329.camel@edumazet-glaptop3.roam.corp.google.com> Subject: [PATCH net-next] tcp: fix lockdep splat in tcp_snd_una_update() From: Eric Dumazet To: Francois Romieu , David Miller Cc: Fabio Estevam , Eric Dumazet , Chuck Lever , Trond Myklebust , "netdev@vger.kernel.org" , Linux NFS Mailing List Date: Tue, 03 May 2016 16:56:03 -0700 In-Reply-To: <1462314901.5535.316.camel@edumazet-glaptop3.roam.corp.google.com> References: <20160503223149.GA19739@electric-eye.fr.zoreil.com> <1462314901.5535.316.camel@edumazet-glaptop3.roam.corp.google.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org List-ID: From: Eric Dumazet 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: c10d9310edf5 ("tcp: do not assume TCP code is non preemptible") Reported-by: Fabio Estevam Diagnosed-by: Francois Romieu Signed-off-by: Eric Dumazet --- include/linux/u64_stats_sync.h | 14 ++++++++++++++ include/net/sock.h | 7 ++++++- net/ipv4/tcp_input.c | 10 ++++++---- 3 files changed, 26 insertions(+), 5 deletions(-) diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h index df89c9bcba7db8dbde3bbf2b99f9af6ed562b112..d3a2bb712af3b9613b98ef9c3219f8dcd31568a5 100644 --- a/include/linux/u64_stats_sync.h +++ b/include/linux/u64_stats_sync.h @@ -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) diff --git a/include/net/sock.h b/include/net/sock.h index 45f5b492c65883cd22e2f615e019fe0d0ba31167..c9c8b19df27c558354687119db60c0716909ea3f 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -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; } diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 6171f92be0903f5a5d17f027dbe6b31829bcc043..a914e0607895dd9321559f93c1008f8de13b73ad 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -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; }