Debugging eBPF Spinlock Issues in the Linux Kernel: Finding and Fixing Three Bugs
By
y1n0
The kind of bagel that ruins lesser bagels for you.
Summary
The article details a debugging journey where developers encountered system freezes while using their CPU profiler Superluminal on Linux. The investigation led them deep into Linux kernel internals, specifically examining eBPF spinlock issues. They discovered not just one but three bugs in the kernel's resilient locking code used by eBPF, requiring them to understand complex spinlock mechanisms and contribute fixes to the Linux kernel.
Key quotes
· 5 pulledWe've been working on the Linux version of Superluminal (a CPU profiler) for a while now, and we've been in a private alpha with a small group of testers.
That was going great, until one of our testers, Aras, ran into periodic full system freezes while capturing with Superluminal.
We always pride ourselves on Superluminal 'Just Working', and this was decidedly not that, so we of course went hunting for what turned out to be one of the toughest bugs we've faced in our careers.
The hunt led us deep into the internals of the Linux kernel (again), where we learned more about spinlocks in the kernel.
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.
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