Re: [REGRESSION] Warning in tcp_fastretrans_alert() of net/ipv4/tcp_input.c

Actually, same warning was just triggered with RACK enabled. But main warning 
was not triggered in this case.

===
Sep 18 22:44:32 defiant kernel: ------------[ cut here ]------------
Sep 18 22:44:32 defiant kernel: WARNING: CPU: 1 PID: 702 at net/ipv4/
tcp_input.c:2392 tcp_undo_cwnd_reduction+0xbd/0xd0
Sep 18 22:44:32 defiant kernel: Modules linked in: netconsole ctr ccm cls_bpf 
sch_htb act_mirred cls_u32 sch_ingress sit tunnel4 ip_tunnel 8021q mrp 
nf_conntrack_ipv6 nf_defrag_ipv6 nft_ct nft_set_bitmap nft_set_hash 
nft_set_rbtree nf_tables_inet nf_tables_ipv6 nft_masq_ipv4 
nf_nat_masquerade_ipv4 nft_masq nft_nat nft_counter nft_meta 
nft_chain_nat_ipv4 nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat 
nf_conntrack libcrc32c crc32c_generic nf_tables_ipv4 nf_tables tun nct6775 
nfnetlink hwmon_vid nls_iso8859_1 nls_cp437 vfat fat ext4 snd_hda_codec_hdmi 
mbcache jbd2 snd_hda_codec_realtek snd_hda_codec_generic f2fs arc4 fscrypto 
intel_rapl iTCO_wdt ath9k iTCO_vendor_support intel_powerclamp ath9k_common 
ath9k_hw coretemp kvm_intel ath mac80211 kvm irqbypass intel_cstate cfg80211 
pcspkr snd_hda_intel snd_hda_codec r8169
Sep 18 22:44:32 defiant kernel:  joydev evdev mii snd_hda_core mousedev 
mei_txe input_leds i2c_i801 mac_hid i915 lpc_ich mei shpchp snd_hwdep 
snd_intel_sst_acpi snd_intel_sst_core snd_soc_rt5670 
snd_soc_sst_atom_hifi2_platform battery snd_soc_sst_match snd_soc_rl6231 
drm_kms_helper hci_uart ov5693(C) ov2722(C) lm3554(C) btbcm btqca v4l2_common 
snd_soc_core btintel snd_compress videodev snd_pcm_dmaengine snd_pcm video 
bluetooth snd_timer drm media tpm_tis snd i2c_hid soundcore tpm_tis_core 
rfkill_gpio ac97_bus soc_button_array ecdh_generic rfkill crc16 tpm 8250_dw 
intel_gtt syscopyarea sysfillrect acpi_pad sysimgblt intel_int0002_vgpio 
fb_sys_fops pinctrl_cherryview i2c_algo_bit button sch_fq_codel tcp_bbr ifb 
ip_tables x_tables btrfs xor raid6_pq algif_skcipher af_alg hid_logitech_hidpp 
hid_logitech_dj usbhid hid uas
Sep 18 22:44:32 defiant kernel:  usb_storage dm_crypt dm_mod dax raid10 md_mod 
sd_mod crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel pcbc 
ahci aesni_intel xhci_pci libahci aes_x86_64 crypto_simd glue_helper xhci_hcd 
cryptd libata usbcore scsi_mod usb_common serio sdhci_acpi sdhci led_class 
mmc_core
Sep 18 22:44:32 defiant kernel: CPU: 1 PID: 702 Comm: irq/123-enp3s0 Tainted: 
G        WC      4.13.0-pf4 #1
Sep 18 22:44:32 defiant kernel: Hardware name: To Be Filled By O.E.M. To Be 
Filled By O.E.M./J3710-ITX, BIOS P1.30 03/30/2016
Sep 18 22:44:32 defiant kernel: task: ffff88923a738000 task.stack: 
ffff958001500000
Sep 18 22:44:32 defiant kernel: RIP: 0010:tcp_undo_cwnd_reduction+0xbd/0xd0
Sep 18 22:44:32 defiant kernel: RSP: 0018:ffff88927fc83a48 EFLAGS: 00010202
Sep 18 22:44:32 defiant kernel: RAX: 0000000000000001 RBX: ffff8892412d9800 
RCX: ffff88927fc83b0c
Sep 18 22:44:32 defiant kernel: RDX: 000000007fffffff RSI: 0000000000000001 
RDI: ffff8892412d9800
Sep 18 22:44:32 defiant kernel: RBP: ffff88927fc83a50 R08: 0000000000000000 
R09: 0000000018dfb063
Sep 18 22:44:32 defiant kernel: R10: 0000000018dfd223 R11: 0000000018dfb063 
R12: 0000000000005320
Sep 18 22:44:32 defiant kernel: R13: ffff88927fc83b10 R14: 0000000000000001 
R15: ffff88927fc83b0c
Sep 18 22:44:32 defiant kernel: FS:  0000000000000000(0000) 
GS:ffff88927fc80000(0000) knlGS:0000000000000000
Sep 18 22:44:32 defiant kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 
0000000080050033
Sep 18 22:44:32 defiant kernel: CR2: 00007f1cd1a43620 CR3: 0000000114a09000 
CR4: 00000000001006e0
Sep 18 22:44:32 defiant kernel: Call Trace:
Sep 18 22:44:32 defiant kernel:  <IRQ>
Sep 18 22:44:32 defiant kernel:  tcp_try_undo_loss+0xb3/0xf0
Sep 18 22:44:32 defiant kernel:  tcp_fastretrans_alert+0x746/0x990
Sep 18 22:44:32 defiant kernel:  tcp_ack+0x741/0x1110
Sep 18 22:44:32 defiant kernel:  tcp_rcv_established+0x325/0x770
Sep 18 22:44:32 defiant kernel:  ? sk_filter_trim_cap+0xd4/0x1a0
Sep 18 22:44:32 defiant kernel:  tcp_v4_do_rcv+0x90/0x1e0
Sep 18 22:44:32 defiant kernel:  tcp_v4_rcv+0x950/0xa10
Sep 18 22:44:32 defiant kernel:  ? nf_ct_deliver_cached_events+0xb8/0x110 
[nf_conntrack]
Sep 18 22:44:32 defiant kernel:  ip_local_deliver_finish+0x68/0x210
Sep 18 22:44:32 defiant kernel:  ip_local_deliver+0xfa/0x110
Sep 18 22:44:32 defiant kernel:  ? ip_rcv_finish+0x410/0x410
Sep 18 22:44:32 defiant kernel:  ip_rcv_finish+0x120/0x410
Sep 18 22:44:32 defiant kernel:  ip_rcv+0x28e/0x3b0
Sep 18 22:44:32 defiant kernel:  ? inet_del_offload+0x40/0x40
Sep 18 22:44:32 defiant kernel:  __netif_receive_skb_core+0x39b/0xb00
Sep 18 22:44:32 defiant kernel:  ? netif_receive_skb_internal+0xa0/0x480
Sep 18 22:44:32 defiant kernel:  ? dev_gro_receive+0x2eb/0x4a0
Sep 18 22:44:32 defiant kernel:  __netif_receive_skb+0x18/0x60
Sep 18 22:44:32 defiant kernel:  netif_receive_skb_internal+0x98/0x480
Sep 18 22:44:32 defiant kernel:  netif_receive_skb+0x1c/0x80
Sep 18 22:44:32 defiant kernel:  ifb_ri_tasklet+0x109/0x26a [ifb]
Sep 18 22:44:32 defiant kernel:  tasklet_action+0x63/0x120
Sep 18 22:44:32 defiant kernel:  __do_softirq+0xdf/0x2e5
Sep 18 22:44:32 defiant kernel:  ? irq_finalize_oneshot.part.39+0xe0/0xe0
Sep 18 22:44:32 defiant kernel:  do_softirq_own_stack+0x1c/0x30
Sep 18 22:44:32 defiant kernel:  </IRQ>
Sep 18 22:44:32 defiant kernel:  do_softirq.part.17+0x4e/0x60
Sep 18 22:44:32 defiant kernel:  __local_bh_enable_ip+0x77/0x80
Sep 18 22:44:32 defiant kernel:  irq_forced_thread_fn+0x5c/0x70
Sep 18 22:44:32 defiant kernel:  irq_thread+0x131/0x1a0
Sep 18 22:44:32 defiant kernel:  ? wake_threads_waitq+0x30/0x30
Sep 18 22:44:32 defiant kernel:  kthread+0x126/0x140
Sep 18 22:44:32 defiant kernel:  ? irq_thread_check_affinity+0x90/0x90
Sep 18 22:44:32 defiant kernel:  ? kthread_create_on_node+0x70/0x70
Sep 18 22:44:32 defiant kernel:  ret_from_fork+0x25/0x30
Sep 18 22:44:32 defiant kernel: Code: 5d c3 80 60 35 fb 48 8b 00 48 39 c2 74 
85 48 3b 83 50 01 00 00 75 eb e9 77 ff ff ff 89 83 48 06 00 00 80 a3 1e 06 00 
00 fb eb b3 <0f> ff 5b 5d c3 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 
Sep 18 22:44:32 defiant kernel: ---[ end trace 1aea180efeedb474 ]---
===

On pondělí 18. září 2017 20:01:42 CEST Yuchung Cheng wrote:

On Mon, Sep 18, 2017 at 10:59 AM, Oleksandr Natalenko

[off-list ref] wrote:

quoted

OK. Should I keep FACK disabled?

Yes since it is disabled in the upstream by default. Although you can
experiment FACK enabled additionally.

Do we know the crash you first experienced is tied to this issue?

quoted

On pondělí 18. září 2017 19:51:21 CEST Yuchung Cheng wrote:

quoted

Can you try this patch to verify my theory with tcp_recovery=0 and 1?
thanks

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 5af2f04f8859..9253d9ee7d0e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c

@@ -2381,6 +2381,7 @@ static void tcp_undo_cwnd_reduction(struct sock

*sk, bool unmark_loss)

        }
        tp->snd_cwnd_stamp = tcp_time_stamp;
        tp->undo_marker = 0;

+       WARN_ON(tp->retrans_out);

 }