PREEMPT SMP - cgroup_procs_show

[Xavier]

Hello,

Ever since kernel 4.14, I've experienced an issue with erratic kernel
panics, which all trace back to cgroup_procs_show. They are seemingly
triggered by systemd or systemd command-line utilities at complete
random. Downgrading the kernel to a version prior to 4.14 seems to
rectify the issue.

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Nov 30 18:22:23 kernel: Oops: 0000 [#2] PREEMPT SMP
Nov 30 18:22:23 kernel: PGD 0 P4D 0
Nov 30 18:22:23 kernel: IP: pids_free+0x11/0x40
Nov 30 18:22:23 kernel: BUG: unable to handle kernel NULL pointer
dereference at 00000000000000b0
Nov 30 18:22:23 kernel: ---[ end trace abcb55e9159eabe0 ]---
Nov 30 18:22:23 kernel: CR2: ffffffffffffffde
Nov 30 18:22:23 kernel: RIP: __task_pid_nr_ns+0x60/0xd0 RSP:
ffffb256ce567dc8
Nov 30 18:22:23 kernel: Code: 74 0d 48 8d 44 6d 00 48 8d 3c c5 a0 05 00
00 48 8b 9b 68 05 00 00 48 01 fb 48 8b 0b 31 db 48 85 c9 74 1a 41 8b 94
24 30 08 00 00 <3b> 51 04 77 0d 48 c1 e2 05 48 01 d1 4c 3b 61 38 74 45
e8 69 a5
Nov 30 18:22:23 kernel: R13: 00007ffe7905058c R14: 0000000000000000 R15:
0000000000000000
Nov 30 18:22:23 kernel: R10: 0000000000001000 R11: 0000000000000246 R12:
0000000000000000
Nov 30 18:22:23 kernel: RBP: 00007f82bbf2f240 R08: 0000000000000003 R09:
ffffffffffffffb0
Nov 30 18:22:23 kernel: RDX: 0000000000001000 RSI: 00005598ca705e40 RDI:
0000000000000008
Nov 30 18:22:23 kernel: RAX: ffffffffffffffda RBX: 00005598ca6f0260 RCX:
00007f82bbc67a11
Nov 30 18:22:23 kernel: RSP: 002b:00007ffe7904fd18 EFLAGS: 00000246
ORIG_RAX: 0000000000000000
Nov 30 18:22:23 kernel: RIP: 0033:0x7f82bbc67a11
Nov 30 18:22:23 kernel:Â entry_SYSCALL_64_fastpath+0x1a/0xa5
Nov 30 18:22:23 kernel:Â SyS_read+0x52/0xc0
Nov 30 18:22:23 kernel:Â vfs_read+0x89/0x130
Nov 30 18:22:23 kernel:Â __vfs_read+0x33/0x150
Nov 30 18:22:23 kernel:Â seq_read+0x331/0x440
Nov 30 18:22:23 kernel:Â cgroup_procs_show+0x15/0x30
Nov 30 18:22:23 kernel: Call Trace:
Nov 30 18:22:23 kernel: DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7:
0000000000000400
Nov 30 18:22:23 kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
Nov 30 18:22:23 kernel: CR2: ffffffffffffffde CR3: 0000000cb0e81005 CR4:
00000000003626e0
Nov 30 18:22:23 kernel: CS:Â 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Nov 30 18:22:23 kernel: FS:Â 00007f82bc33d8c0(0000)
GS:ffff952d3f300000(0000) knlGS:0000000000000000
Nov 30 18:22:23 kernel: R13: 00000000ffffffff R14: ffff952c9a17ba08 R15:
ffff952a2be8d900
Nov 30 18:22:23 kernel: R10: 0000000000001000 R11: ffff952ce831b004 R12:
ffffffffb5c4ca60
Nov 30 18:22:23 kernel: RBP: 0000000000000000 R08: 0000000000001000 R09:
0000000000000005
Nov 30 18:22:23 kernel: RDX: 0000000000000000 RSI: 0000000000000000 RDI:
00000000000005a0
Nov 30 18:22:23 kernel: RAX: ffff952d0a0ffb80 RBX: 0000000000000000 RCX:
ffffffffffffffda
Nov 30 18:22:23 kernel: RSP: 0018:ffffb256ce567dc8 EFLAGS: 00010282
Nov 30 18:22:23 kernel: RIP: 0010:__task_pid_nr_ns+0x60/0xd0
Nov 30 18:22:23 kernel: task: ffff952ced2fbb00 task.stack: ffffb256ce564000
Nov 30 18:22:23 kernel: Hardware name: ASUS All Series/X99-A/USB 3.1,
BIOS 3701 03/31/2017
Nov 30 18:22:23 kernel: CPU: 4 PID: 2891 Comm: systemctl Tainted:
PÂÂÂÂÂÂÂÂÂÂ OÂÂÂ 4.14.3-1-ARCH #1

Nov 30 17:52:17 kernel: Command line: BOOT_IMAGE=/vmlinuz-linux
root=UUID=* rw quiet processor.max_cstate=1 intel_idle.max_cstate=0
scsi_mod.use_blk_mq=1 quiet nvidia-drm.modeset=1
Nov 30 17:52:17 kernel: Linux version 4.14.3-1-ARCH
(builduser@heftig-12222) (gcc version 7.2.1 20171128 (GCC)) #1 SMP
PREEMPT Thu Nov 30 18:33:13 UTC 2017

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/proc/cpuinfo

processorÂÂÂ : 0
vendor_idÂÂÂ : GenuineIntel
cpu familyÂÂÂ : 6
modelÂÂÂ ÂÂÂ : 79
model nameÂÂÂ : Intel(R) Core(TM) i7-6800K CPU @ 3.40GHz
steppingÂÂÂ : 1
microcodeÂÂÂ : 0xb00001c
cpu MHzÂÂÂ ÂÂÂ : 3999.938
cache sizeÂÂÂ : 15360 KB
physical idÂÂÂ : 0
siblingsÂÂÂ : 12
core idÂÂÂ ÂÂÂ : 0
cpu coresÂÂÂ : 6
apicidÂÂÂ ÂÂÂ : 0
initial apicidÂÂÂ : 0
fpuÂÂÂ ÂÂÂ : yes
fpu_exceptionÂÂÂ : yes
cpuid levelÂÂÂ : 20
wpÂÂÂ ÂÂÂ : yes
flagsÂÂÂ ÂÂÂ : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall
nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl
xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor
ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2
x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm
abm 3dnowprefetch epb intel_pt tpr_shadow vnmi flexpriority ept vpid
fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm cqm rdseed
adx smap xsaveopt cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local
dtherm ida arat pln pts
bugsÂÂÂ ÂÂÂ :
bogomipsÂÂÂ : 6783.90
clflush sizeÂÂÂ : 64
cache_alignmentÂÂÂ : 64
address sizesÂÂÂ : 46 bits physical, 48 bits virtual

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