Arch Linux

kode54

Member

Registered: 2013-10-21

Posts: 20

linux-rt-lts enables DEBUG_PREEMPT... why?

I am asking why the linux-rt kernel, specifically the LTS version, enables CONFIG_DEBUG_PREEMPT. The last time I booted and enabled my KVM / libvirt / Qemu VMs on a kernel that enabled DEBUG_PREEMPT, my syslog was flooded with gigantic stack traces at every batch of VM guest code switching into context, due to some KVM function requesting the processor ID during a preemptible block. I attempted to apply a patch to the kernel which would disable preempt for that entire function, but that resulted in VMs that would deadlock instead of executing.

I have instead lived well with a preempt kernel that disables the debug messages. My report to the Liquorix kernel led to them disabling that setting on their kernels as well.

Is there any chance that this option was enabled in error? Or is it even necessary for anything short of full on kernel debugging? I have modified my local copy of the linux-rt-lts PKGCONFIG and config files to disable it for my build, but I'm not even sure if that same preempt + kvm bug exists as far back as the 4.9.x branch.

WorMzy

Forum Moderator

From: Scotland

Registered: 2010-06-16

Posts: 11,845

Website

Re: linux-rt-lts enables DEBUG_PREEMPT... why?

You're more likely to get a response on the AUR page, this sounds like a conscious decision by the package maintainer.

Mod note: moving to AUR issues

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