16/ Outro: Profiling is powerful — but beware of deep OS interactions. Stay tuned! #QuestDB #Database

15/ Join the #QuestDB community for product updates, help, and performance tips! #QuestDB #Database

Q14: Will kernel updates resolve this problem? A14: Yes — once the patch is merged and shipping kernels include it. #QuestDB #Database

Q13: Should developers be aware of kernel issues when profiling? A13: Absolutely — OS bugs can surface under low-level tooling. #QuestDB #Database

Q12: Does the blog explain the fix? A12: Yes — replacing blocking cancel with non-blocking hrtimer_try_to_cancel(). #QuestDB #Database

Q11: Is this bug specific to QuestDB? A11: No — it's in the Linux kernel perf timer code used by async-profiler. #QuestDB #Database

Q10: What does the workaround do? A10: It uses a different timer mechanism avoiding the buggy path. #QuestDB #Database

Q9: How can the profiler avoid this kernel bug? A9: Run async-profiler with the -e ctimer option instead. #QuestDB #Database

Q8: Why does this deadlock hang CPUs? A8: Timer cancel waits for callback to finish, but it is already active. #QuestDB #Database

Q7: What causes the freeze at the kernel level? A7: hrtimer_cancel() blocking inside its own callback, creating a deadlock. #QuestDB #Database

Q6: Where did the bug occur in the kernel? A6: In the hrtimer handling code, introduced by a recent fix. #QuestDB #Database

Q5: How does async-profiler collect samples? A5: By setting perf_events that fire signals to capture stack traces. #QuestDB #Database

Q4: What subsystem does async-profiler use on Linux? A4: The perf_events subsystem with high-resolution timers. #QuestDB #Database

Q3: What pointed the author toward the system/environment? A3: Ubuntu 25.10 and a matching kernel version on another user’s Fedora. #QuestDB #Database

Q2: Did this happen only with the latest QuestDB? A2: No — older QuestDB builds also froze under the profiler. #QuestDB #Database

Q1: What was the issue encountered when profiling QuestDB? A1: Attaching async-profiler froze the entire machine. #QuestDB #Database

1/ 🧵 Intro: Q&A on the quest to debug a kernel deadlock triggered by async-profiler in Linux. #QuestDB #Database

16/ Whether you’re building trading systems, aerospace telemetry pipelines, energy grids, or real-time analytics platforms — QuestDB has you covered. #QuestDB #database

15/ Join the #QuestDB community to explore more use cases, ask questions, and contribute.

Q14: In short — when should you reach for QuestDB? A14: When your workload demands high-frequency ingestion, real-time analytics on time-series or event data, and you want performance + scalability + portability in one package. #QuestDB #database