December 15, 2025
Kernel panic at the disco
A Kernel Bug Froze My Machine: Debugging an Async-Profiler Deadlock
A tiny tool froze whole PCs; Linux fans split between praise, panic, and “use seL4” chants
TLDR: A new Linux kernel version can freeze PCs when a profiling tool runs, but a safer start option avoids it. Commenters split between praising the detective work, hyping heatmaps, confessing Docker chaos, and arguing Linux vs microkernels—making this a bug fix with maximum drama.
A QuestDB dev tried to profile a slowdown and his Linux machine turned into a statue—multiple times. The culprit? A recent kernel update (6.17) that causes total freeze-ups when the async-profiler tool pokes the system. The workaround—starting the profiler in a safer mode—works, but the comment section? That’s where the sparks fly.
The author pops in, calling the deep-dive “impractical party tricks,” and everyone claps. One crowd cheers the detective work and nerds out about the new heatmap feature, with shout‑outs to the creator and the Netflix write‑ups. Another crowd arrives with sirens blaring: the “Linux is a temporary solution” camp, dropping the spicy claim that high-stress systems should dump Linux for seL4. Cue the flame war.
Then come the confessions: a Docker power‑user casually admits to hoarding nearly a terabyte of containers and hitting mysterious kernel deadlocks “once every couple of weeks,” which had readers joking the profiler didn’t freeze the PC—his lifestyle did. Through it all, the vibe is part admiration, part chaos. People love a good “debugging journey,” but the split is real: Is Linux reliable enough for heavy duty, or do we need stricter microkernels? Meanwhile, practical folks just bookmark the fix and move on: use the safer timer option, keep calm, and profile on. Links: QuestDB, async-profiler
Key Points
- •System-wide freezes occurred when attaching async-profiler while profiling QuestDB on machines running Linux kernel 6.17.
- •The issue reproduced on Ubuntu 25.10 and Fedora, pointing away from QuestDB and toward the system environment.
- •Profiling worked on an older Ubuntu setup, reinforcing a regression tied to newer kernel/distribution versions.
- •A kernel patch exists that addresses the same async-profiler-triggered freeze, indicating a kernel bug.
- •Using async-profiler with the -e ctimer event avoids the problematic kernel feature and prevents the freeze.