Ritesh Oedayrajsingh Varma3d ago

New article! A user *cough* @aras *cough* is reporting full system freezes while using Superluminal on Linux. What do you do? Cry? Well, we did a little bit.

But we also dove into the kernel...again, this time finding & fixing several issues in eBPF's spinlock implementation. Read all about it:

https://rovarma.com/articles/a-tale-about-fixing-ebpf-spinlock-issues-in-the-linux-kernel/

A tale about fixing eBPF spinlock issues in the Linux kernel | Ritesh Oedayrajsingh Varma

A system freeze led us deep into Linux spinlock internals, where we helped find not one but three bugs in the kernel's resilient locking code used by eBPF.

Show threadChris Green3d ago
@rovarma @aras Will a cheap rs232 to ethernet adapter + rs232 card work for kernel debuggjng? The advantage would be that you only need this on the target machine to gain access to it from any computer that can see its ip addr.
Show threadRitesh Oedayrajsingh Varma
@aachrisg @aras it might, but honestly a regular rs232 card is not expensive either, so it doesn’t matter much :)
Mar 18 at 8:35amWeb
Show threadChris Green1d ago
@rovarma @aras Its not about $, it's about getting a 1:N connection for kernel-level logs for about the same cost as 1:1. And w/o running any (severely limited length) thick cables. My home office is kind of sprawling :-). I tend to use tablets as log displayers too.
Show threadRitesh Oedayrajsingh Varma1d ago

@aachrisg @aras True! In my case, my machines are right next to each other, so the cable is fine. There is a KGDBOE (“KGDB Over Ethernet”) project that attempts to generically support kernel debugging over ethernet transports, but due to the complexity of the ethernet driver, it’s severely limited, and I never got it to work. If the ethernet driver is “external” to the machine being debugged, it should work in principle I think. One way to find out! ;-)

https://github.com/sysprogs/kgdboe

GitHub - sysprogs/kgdboe: A network interface for GDB for Linux Kernel

A network interface for GDB for Linux Kernel. Contribute to sysprogs/kgdboe development by creating an account on GitHub.

GitHub
Show threadChris Green1d ago
@rovarma @aras Thanks, I'll have to take a look. I had to figure out what was going on with a non-booting mini-pc recently and it sure would have been nice to watch kernel log output on my main desktop (and 200K faster throughput as a bonus).