Arch Linux

tomahhunt

Member

Registered: 2011-10-21

Posts: 8

[SOLVED] Skylake Pentium G4400 random restarts

Hi,

I have a new NAS box build I have setup. It's a new skylake cpu Pentium G4400 and a Gigabyte H170N-WIFI motherboard.

I know there is a bug with my CPU in GMP from reading here: https://bugs.archlinux.org/task/47284

Trying to compile stuff from AUR often segfaults with "Illegal instruction" and the "expr 4 \* 4" as shown in the bug also segfaults. Waiting on this to be fixed!

However generally the machine runs fine aside from I get random resets. 1 or 2 times a day when totally idle.

I know that the cpu is not under load or hot. I have run memtest and prime95 and these are both stable.

I don't see anything in any logs that I have tried it just says "-- Reboot --".

My main question is:

Could this problem be caused by the GMP bug? i.e. something that runs 1 or 2 times a day that is important is segfaulting and resetting the system or is something else wrong?

If not then what else can I look at to Debug this issue. I am a bit perplexed. And what extra information can I supply to aid debug.

Thanks in advance,

Tom

Last edited by tomahhunt (2016-01-04 14:56:49)

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 21,764

Re: [SOLVED] Skylake Pentium G4400 random restarts

https://bbs.archlinux.org/viewtopic.php?id=201194

Sounds similar to the issues mentioned here, maybe trying the 4.3 kernel will help

Last edited by V1del (2015-12-15 15:31:19)

tomahhunt

Member

Registered: 2011-10-21

Posts: 8

Re: [SOLVED] Skylake Pentium G4400 random restarts

Thanks for the reply. Not sure if that thread is the same as my issue but will read it through.
I have updated my bios already + installed the intel-ucode updates although there don't seem to be any for my cpu yet.
I can't rebuild glibc due to the GMP bug so I will give the 4.3 kernel a go once I remind myself how to pull stuff from testing!

Cheers.

letni69

Member

Registered: 2015-09-21

Posts: 17

Re: [SOLVED] Skylake Pentium G4400 random restarts

Thanks for the reply. Not sure if that thread is the same as my issue but will read it through.
I have updated my bios already + installed the intel-ucode updates although there don't seem to be any for my cpu yet.
I can't rebuild glibc due to the GMP bug so I will give the 4.3 kernel a go once I remind myself how to pull stuff from testing!

Cheers.

There is no microupdate for skylake cpus which really sucks because there is a known issue in the cpuid instruction which basically returns wrongs flags (BMI1/BMI2).
I have the same cpu but I am not experiencing any freezes (I am using linux-ck 4.3.2-1). To make sure gmp isn't the reason for those crashes you obviously need a working gmp..
Yeah the problem was that one could not rebuild gmp because gcc itself was using gmp, as a workaround you probably have to use a spare computer (or vm ?/digitalocean?) and make a cross build + setting host to sandybridge.
But the good thing is that the upstream gmp lib has already fixes for this bug and the package maintainer should release an new update soon I guess...

tomahhunt

Member

Registered: 2011-10-21

Posts: 8

Re: [SOLVED] Skylake Pentium G4400 random restarts

I think my best bet is to wait for the upstream fix to GMP. Then I can use this to build the latest 4.3 kernel natively.
The cross compiling stuff is a step into the unknown for me. Although probably quite educational.
I may go down that route in a few days if the fix doesn't end up in ARCH soon.
Thanks again.

tomahhunt

Member

Registered: 2011-10-21

Posts: 8

Re: [SOLVED] Skylake Pentium G4400 random restarts

As a follow up to this and semi resolution:

I went away for Christmas and while I was away the power supply failed in this machine.
I have put a new one in and have yet to have any restarts. So I assume the random restarts were in fact the dodgy power supply.
The GMP bug is still present and unfixed but not really a big issue.

Cheers.

tomahhunt

Member

Registered: 2011-10-21

Posts: 8

Re: [SOLVED] Skylake Pentium G4400 random restarts

And another follow up the GMP bug was fixed today.
So all my issues are fixed. I will marks this as SOLVED.