Kernel lockup with (debian) 4.16.0-2-rt-amd64

[Paul Hedderly]

On Tue, 2018-06-12 at 21:00 +0100, Paul Hedderly wrote:
> Loving wireguard but I'm getting failures running the Debian realtime
> kernel. I first noticed that the wg link was freezing for 20-30
> seconds
> at a time, and then the machine would freeze.


Sorry I meant to add this info:

prh at brix:~$ sudo modinfo wireguard
filename:       /lib/modules/4.16.0-2-rt-
amd64/updates/dkms/wireguard.ko
alias:          net-pf-16-proto-16-family-wireguard
alias:          rtnl-link-wireguard
version:        0.0.20180531-1
author:         Jason A. Donenfeld <Jason at zx2c4.com>
description:    Fast, secure, and modern VPN tunnel
license:        GPL v2
srcversion:     6ED5AE02FC2B8D8E9EA3A3D
depends:        udp_tunnel,ip6_udp_tunnel
retpoline:      Y
name:           wireguard
vermagic:       4.16.0-2-rt-amd64 SMP preempt mod_unload modversions
prh at brix:~$ dpkg -l|grep wireg
ii  wireguard                                     0.0.20180531-
1                             all          fast, modern, secure kernel
VPN tunnel (metapackage)
ii  wireguard-dkms                                0.0.20180531-
1                             all          fast, modern, secure kernel
VPN tunnel (DKMS version)
ii  wireguard-tools                               0.0.20180531-
1                             amd64        fast, modern, secure kernel
VPN tunnel (userland utilities)
> 

I think that is the latest release.

I can raise this with the realtime folk too if that would help - I'm
not sure where the problem would lie really.

Thanks


> For example now, before the innevitable freeze:
> 
> http://dpaste.com/1WFGS46
> 
> from 3820.516865 seconds in
> 
> [ 3820.516865] BUG: scheduling while atomic:
> kworker/1:2/17295/0x00000002
> [ 3820.516865] Modules linked ...
> [ 3820.516926] Preemption disabled at:
> [ 3820.516932] [<ffffffffbda3366f>] kernel_fpu_begin+0xf/0x20
> [ 3820.516934] CPU: 1 PID: 17295 Comm: kworker/1:2 Tainted:
> G     U     O     4.16.0-2-rt-amd64 #1 Debian 4.16.12-1
> [ 3820.516935] Hardware name: Dell Inc. PowerEdge T20/0VD5HY, BIOS
> A06
> 01/27/2015
> [ 3820.516940] Workqueue: wg-crypt-wg0 packet_encrypt_worker
> [wireguard]
> [ 3820.516940] Call Trace:
> [ 3820.516946]  dump_stack+0x5c/0x85
> [ 3820.516948]  ? kernel_fpu_begin+0xf/0x20
> [ 3820.516950]  __schedule_bug+0x73/0xc0
> [ 3820.516953]  __schedule+0x5a1/0x6e0
> <etc - see paste>
> 
> Is there any more info needed? I think I'm going to drop the rt
> kernel
> for now because I've had 4 lockups in 24hrs (since moving to the rt
> kernel)
> 
> Is this a known problem? I'm guessing that wg hasnt been tested much
> with the rt patchset.
> 
> With a previous freeze it was preceeded by thousands of :
> 
> Jun 12 18:11:40 brix /usr/lib/gdm3/gdm-x-session[9135]: ERROR
> block_reap:328: [bandwidth] bad exit code 1
> Jun 12 18:11:45 brix /usr/lib/gdm3/gdm-x-session[9135]: ERROR
> block_reap:328: [bandwidth] bad exit code 1
> Jun 12 18:11:50 brix /usr/lib/gdm3/gdm-x-session[9135]: ERROR
> block_reap:328: [bandwidth] bad exit code 1
> Jun 12 18:11:55 brix /usr/lib/gdm3/gdm-x-session[9135]: ERROR
> block_reap:328: [bandwidth] bad exit code 1
> Jun 12 18:12:00 brix /usr/lib/gdm3/gdm-x-session[9135]: ERROR
> block_reap:328: [bandwidth] bad exit code 1
> Jun 12 18:12:05 brix /usr/lib/gdm3/gdm-x-session[9135]: ERROR
> block_reap:328: [bandwidth] bad exit code 1
> Jun 12 18:12:10 brix /usr/lib/gdm3/gdm-x-session[9135]: ERROR
> block_reap:328: [bandwidth] bad exit code 1
> Jun 12 18:12:15 brix /usr/lib/gdm3/gdm-x-session[9135]: ERROR
> block_reap:328: [bandwidth] bad exit code 1
> 
> then:
> 
> Jun 12 18:16:01 brix kernel: [16507.893206] CPU: 2 PID: 18331 Comm:
> kworker/2:2 Tainted: G     U     O     4.16.0-2-rt-amd64 #1 Debian
> 4.16.12-1
> Jun 12 18:16:01 brix kernel: [16507.893206] Hardware name: Dell Inc.
> PowerEdge T20/0VD5HY, BIOS A06 01/27/2015
> Jun 12 18:16:01 brix kernel: [16507.893211] Workqueue: wg-crypt-wg0
> packet_encrypt_worker [wireguard]
> Jun 12 18:16:01 brix kernel: [16507.893212] Call Trace:
> Jun 12 18:16:01 brix kernel: [16507.893218]  dump_stack+0x5c/0x85
> Jun 12 18:16:01 brix kernel: [16507.893220]  ?
> kernel_fpu_begin+0xf/0x20
> Jun 12 18:16:01 brix kernel: [16507.893222]  __schedule_bug+0x73/0xc0
> Jun 12 18:16:01 brix kernel: [16507.893224]  __schedule+0x5a1/0x6e0
> 
> And this was all interspersed with the network going up and down. A
> log
> of the previous failure:
> 
> https://pastebin.com/eFPHXaYk
> 
> Many thanks.
> 
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