From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7528FC6FD20 for ; Fri, 24 Mar 2023 21:45:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231477AbjCXVpZ (ORCPT ); Fri, 24 Mar 2023 17:45:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50782 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231461AbjCXVpY (ORCPT ); Fri, 24 Mar 2023 17:45:24 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 339D61A679 for ; Fri, 24 Mar 2023 14:45:20 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id g187-20020a2520c4000000b00b74680a7904so2987223ybg.15 for ; Fri, 24 Mar 2023 14:45:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1679694319; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=dbOkGhvYXS9Ka4gC0+dDXm6O6a8TG9MqrjgEhgaFf2g=; b=ruUd5Y7rWctYItXoMs8yOoqVDdunTFcGzIYnW5k3GZL75VoVIVNCIJJcYTvq4Ij1bt HyrJsGhJxOGLumKvtWJGHI9I9C8NvRP699MAhJ3C/p49J4ms91/l4HWr6g2oJuCyqW8A TU2jPRFfhtw11mAFlc6+Tg8dxy0t7CPl9rTDlSLcbhMVE8Jz00d+voNRxEOCDZCCogAG NzQ66AB9bhNx4Z14sbGROye7QbC+b6ScwzWdLkrqxKuD7trVQRvtN+MPT2Y0AYjd/L6c PDMWFYyvHBl/2Ya4DLtHlKZ1zhoyGqEqOxr9AQ0ZtnB4hkNM/AAtaoeamWzsmBmLdWm1 tGAQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679694319; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=dbOkGhvYXS9Ka4gC0+dDXm6O6a8TG9MqrjgEhgaFf2g=; b=wwSSYIMyut9K7DNydzWh3hr2h1mBcBX+w5DDsfYde4HwmCrF1VO6taFoM3XYcIExZm hfwjj9T1BhZGHbSd4kxiqw1x1E2PQU78Eb8El+eVRQmb4vutT+uwUyrgWPoEwOQTYvVG 6jsm8yowbucglR1uhWGHpFRpXHumUhvB3+Avx/Hu4xON6yP/2VO+QY9bFJ5iLcDQBlo1 cBUz4631Ij3WYytHkqAw8pDo0tVzw8/Rvs2F4fk7wHVH1pVnGQIxdGYTNNXH1yrXL7je xhru0PIG1AiXY8xR5JI/tmrUALTJwD3fNsPlzO6Rcd2A+hOAmosdZzAIRVMaPP12ISEv 4B4g== X-Gm-Message-State: AAQBX9caR1DVJqYUMIyNB6YRVPzPPnVfWgtAVftUHaVs9NuQysrEDP5Z cymMWvSh/GZlFh+AWO+qEFtL0oI= X-Google-Smtp-Source: AKy350bEmWQ+Rz5tSCe6HuZhgkGyZwbHP+Io9zds9NBzTOzJI2kZ0fKIHUvXP9Vt9YUcJ+iu8s8V2/0= X-Received: from sdf.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5935]) (user=sdf job=sendgmr) by 2002:a81:a742:0:b0:541:a0cc:2a09 with SMTP id e63-20020a81a742000000b00541a0cc2a09mr1834210ywh.7.1679694319515; Fri, 24 Mar 2023 14:45:19 -0700 (PDT) Date: Fri, 24 Mar 2023 14:45:17 -0700 In-Reply-To: <20230323200633.3175753-4-aditi.ghag@isovalent.com> Mime-Version: 1.0 References: <20230323200633.3175753-1-aditi.ghag@isovalent.com> <20230323200633.3175753-4-aditi.ghag@isovalent.com> Message-ID: Subject: Re: [PATCH v4 bpf-next 3/4] bpf,tcp: Avoid taking fast sock lock in iterator From: Stanislav Fomichev To: Aditi Ghag Cc: bpf@vger.kernel.org, kafai@fb.com, edumazet@google.com Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 03/23, Aditi Ghag wrote: > Previously, BPF TCP iterator was acquiring fast version of sock lock that > disables the BH. This introduced a circular dependency with code paths > that > later acquire sockets hash table bucket lock. > Replace the fast version of sock lock with slow that faciliates BPF > programs executed from the iterator to destroy TCP listening sockets > using the bpf_sock_destroy kfunc. > Here is a stack trace that motivated this change: > ``` > 1) sock_lock with BH disabled + bucket lock > lock_acquire+0xcd/0x330 > _raw_spin_lock_bh+0x38/0x50 > inet_unhash+0x96/0xd0 > tcp_set_state+0x6a/0x210 > tcp_abort+0x12b/0x230 > bpf_prog_f4110fb1100e26b5_iter_tcp6_server+0xa3/0xaa > bpf_iter_run_prog+0x1ff/0x340 > bpf_iter_tcp_seq_show+0xca/0x190 > bpf_seq_read+0x177/0x450 > vfs_read+0xc6/0x300 > ksys_read+0x69/0xf0 > do_syscall_64+0x3c/0x90 > entry_SYSCALL_64_after_hwframe+0x72/0xdc > 2) sock lock with BH enable > [ 1.499968] lock_acquire+0xcd/0x330 > [ 1.500316] _raw_spin_lock+0x33/0x40 > [ 1.500670] sk_clone_lock+0x146/0x520 > [ 1.501030] inet_csk_clone_lock+0x1b/0x110 > [ 1.501433] tcp_create_openreq_child+0x22/0x3f0 > [ 1.501873] tcp_v6_syn_recv_sock+0x96/0x940 > [ 1.502284] tcp_check_req+0x137/0x660 > [ 1.502646] tcp_v6_rcv+0xa63/0xe80 > [ 1.502994] ip6_protocol_deliver_rcu+0x78/0x590 > [ 1.503434] ip6_input_finish+0x72/0x140 > [ 1.503818] __netif_receive_skb_one_core+0x63/0xa0 > [ 1.504281] process_backlog+0x79/0x260 > [ 1.504668] __napi_poll.constprop.0+0x27/0x170 > [ 1.505104] net_rx_action+0x14a/0x2a0 > [ 1.505469] __do_softirq+0x165/0x510 > [ 1.505842] do_softirq+0xcd/0x100 > [ 1.506172] __local_bh_enable_ip+0xcc/0xf0 > [ 1.506588] ip6_finish_output2+0x2a8/0xb00 > [ 1.506988] ip6_finish_output+0x274/0x510 > [ 1.507377] ip6_xmit+0x319/0x9b0 > [ 1.507726] inet6_csk_xmit+0x12b/0x2b0 > [ 1.508096] __tcp_transmit_skb+0x549/0xc40 > [ 1.508498] tcp_rcv_state_process+0x362/0x1180 > ``` > Signed-off-by: Aditi Ghag Acked-by: Stanislav Fomichev Don't need fixes because it doesn't trigger without your new bpf_sock_destroy? > --- > net/ipv4/tcp_ipv4.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c > index ea370afa70ed..f2d370a9450f 100644 > --- a/net/ipv4/tcp_ipv4.c > +++ b/net/ipv4/tcp_ipv4.c > @@ -2962,7 +2962,6 @@ static int bpf_iter_tcp_seq_show(struct seq_file > *seq, void *v) > struct bpf_iter_meta meta; > struct bpf_prog *prog; > struct sock *sk = v; > - bool slow; > uid_t uid; > int ret; > @@ -2970,7 +2969,7 @@ static int bpf_iter_tcp_seq_show(struct seq_file > *seq, void *v) > return 0; > if (sk_fullsock(sk)) > - slow = lock_sock_fast(sk); > + lock_sock(sk); > if (unlikely(sk_unhashed(sk))) { > ret = SEQ_SKIP; > @@ -2994,7 +2993,7 @@ static int bpf_iter_tcp_seq_show(struct seq_file > *seq, void *v) > unlock: > if (sk_fullsock(sk)) > - unlock_sock_fast(sk, slow); > + release_sock(sk); > return ret; > } > -- > 2.34.1