RipGrep musl binaries occasionally segfault during very-large searches • Hacker News Board

Re: RipGrep musl binaries occasionally segfault during very-large searches

#61

Post by wizzwizz4 » Sat, Aug 01, 2026, 2:32 PM UTC

im3w1l wrote: post #16

smallerize wrote: post #12

Earlier quoted context omitted.

Then post whatever notes were fed into the AI instead. The verbosity and self-congratulating add negative value.

What will you do when the prompt was "Figure out the bug and write a report for me". Not saying it was in this particular case, but I think at least in other cases, it will be.

It didn't figure out the bug: the report is largely nonsense. It merely did a bad impression of having figured out the bug, by stringing together several observations into something superficially resembling a narrative. Providing those observations without the gibberish framing might be useful.

Re: RipGrep musl binaries occasionally segfault during very-large searches

#62

Post by amluto » Sat, Aug 01, 2026, 2:33 PM UTC

gpm wrote: post #44

Retr0id wrote: post #29

Earlier quoted context omitted.

The part that doesn't make sense to me is that trying to read through a zeroed PTE should be an immediate segfault, not something that reads back zeroes (regardless of whether the zero page is pfn 0 (it isn't)). I think the broad strokes are that, due to bad locking in the kernel, mmap() returns a VA that a concurrent munmap() is still in the middle of unmapping. The specifics beyond that seem murky/speculative/incon…

> Alternatively, it could be a hardware bug, since afaict it's only been repro'd on one hardware config. (I know there are a bunch of ARM cores with erratas around TLB invalidation) Which raises the question of whether any HN readers have successfully reproduced this? I've just tried (using his file generation script and the official rg binary he links) on a Ryzen 7 5800X / 7.1.5-arch1-2 with sufficient free ram as t…

I have never, in my entire personal history of kernel development, successfully reproduced a paging structure cache bug. I have stared at these sorts of bugs and puzzled them out.

With this particular issue, if my theory is right, it will depend on all manner of microarchitectural issues, possibly address spare randomization, context switch and migration timing, random speculative accesses that pull things into cache, etc. Yuck.

Re: RipGrep musl binaries occasionally segfault during very-large searches

#63

Post by masklinn » Sat, Aug 01, 2026, 2:34 PM UTC

Orphis wrote: post #40

I get why people don't bother replacing the default allocator from musl all the time (it's there, convenient). But in an application whose purpose is to be FAST, I find it weird they haven't bothered replacing it with another more performant one. mallocng is bad at dealing with contention during multithreading. I've had applications that usually were I/O bound suddenly become "malloc" bound when building with musl in…

> I get why people don't bother replacing the default allocator from musl all the time (it's there, convenient).

ripgrep actually sets jemalloc as global allocator when built for 64b musl: https://github.com/BurntSushi/ripgrep/blob/435f59fc4b43af3ab...

Re: RipGrep musl binaries occasionally segfault during very-large searches

#64

Post by munch117 » Sat, Aug 01, 2026, 2:42 PM UTC

anorwell wrote: post #15

yawndex wrote: post #4

Earlier quoted context omitted.

soulless unreadable AI slop

I had the opposite reaction. Clear, detailed, well-organized. Pretty close to the ideal writeup.

Perhaps you are talking about the ripgrep issue itself, which is fine. The others are talking about the linked analysis, which is not.

Re: RipGrep musl binaries occasionally segfault during very-large searches

#65

Post by cerved » Sat, Aug 01, 2026, 2:44 PM UTC

smukherjee19 wrote: post #52

hyperpape wrote: post #3

The analysis of the kernel bug may be a better thing to link to: https://github.com/dfoxfranke/ripgrep-3494-analysis .

I tried reading and gave up at the "Headline"... Quoting from the bug analysis: >Headline. The crash is real and reproducible. With musl instrumentation we pin the in-process mechanism precisely: a thread's own store to a freshly- faulted anonymous page becomes invisible to that same thread's reload ~10 instructions later, because the page's backing is replaced mid-function. A pagemap read at the instant of the fault…

I'm becoming increasingly allergic to the performative writing of LLMs.

The worst part is how compulsive LLMs are at writing like this. Like the system prompt instructs it to "reason" and like a college Sophomore it pontificates and quotes Nietzsche to fein intelligence and orginal thought.

Re: RipGrep musl binaries occasionally segfault during very-large searches

#66

Post by jerf » Sat, Aug 01, 2026, 2:45 PM UTC

rfgplk wrote: post #8

yawndex wrote: post #4

Earlier quoted context omitted.

soulless unreadable AI slop

Why is it unreadable? I actually find LLM bug reports/breakdowns to be far more detailed and concise that classical human written ones. If you read the linked repo it clearly goes it depth where the bug was found, how to reproduce it (and in depth). Most disclosures that are human written don't do this at all, they barely even tell you _how_ to reproduce the bug. Just look at the "3.3 The self-store tear", the LLM cl…

I'm reasonably confident that the author has a reproduction case on their hands. That's easy to directly verify. I'm way less confident in that long and rambling analysis. As fwlr observes, it's not clear that this has been reproduced off the original machine: https://news.ycombinator.com/item?id=49134357

If it is the case that the original machine has an intermittent hardware fault, that analysis is exactly what I'd expect of an current AI. Voluminous and confidently wrong. Also interesting that the AI itself doesn't note this... having been biased by the conversation to consider kernel bugs, in the "cross-machine data" [1] it blames the kernel and doesn't appear to consider alternate explanations.

It doesn't get mentioned much around here but one major issue with AIs today is that they fall into tunnel vision very easily and often need some help getting out of it. There's a structural reason for tunnel vision built into their context limits, and there's also situations like this, where if you bias them in a certain direction they can get monomaniacally stuck on it. You can also see it where they do things like try to do something on your system like view a certain file, then if for some reason they fail due to permission issues, if you don't stop them they'll go absolutely insane trying different ways to access the file, rather than just stopping and saying "Hey, I need help". Even if you prompt them directly to do that, it only helps, it doesn't fix the issue. I suspect the RHLF training they get to be better coding agents reinforces this behavior because in the coding quality tests they're rewarded for one-shotting all the various benchmarks, where that "bull in a china shop" approach works better than giving up. But I'd actually like them to give up a bit more often. I've had the same problem with some particularly go-getting junior devs, too... I appreciate the ambition and I look forward to harnessing it in other situations but I'd rather you didn't spend five hours to create a terrible work around to something I could have gotten you in two minutes. For the junior dev, it's OK, they take the feedback and adjust... the AIs never adjust.

[1]: https://github.com/dfoxfranke/ripgrep-3494-analysis#6-cross-...

Re: RipGrep musl binaries occasionally segfault during very-large searches

#67

Post by bentcorner » Sat, Aug 01, 2026, 2:49 PM UTC

BetterThanSober wrote: post #53

oxidant wrote: post #45

Earlier quoted context omitted.

Stopped after > Headline. The crash is real and reproducible.

I really hated that kind of language, feels like speaking to a motivator anyway it's slop, can sense it even before i started reading

The worst thing is that I know there's something interesting in there but I'm too arsed to take the time and decode what data the author must have used to generate that text.

Re: RipGrep musl binaries occasionally segfault during very-large searches

#68

Post by neerajsi » Sat, Aug 01, 2026, 2:54 PM UTC

rfgplk wrote: post #22

skydhash wrote: post #20

Earlier quoted context omitted.

Because any writing needs a core intent they need to convey, which you can summarize down to according to the audience and why it should be important to them. Kinda like the same idea of elevator pitches, “explain like I’m five” and tactical reports when there’s a time constraints. You got none of that here. It’s just realms of text.

Maybe the person writing the report isn't an expert in this domain or doesn't have the time to commit to it? From my point of view as long as the information is accurate and reproducible, it's valuable.

The other part is that almost no one would have the energy to spend hours instrumenting and rebuilding musl, reading the kernel mm code, and thinking hard about how they might interact.

Claude is probably not right about the root cause here and is probably bsing, I agree. But it's collected enough raw data to point some expert humans at the right interaction. I'd take this bs bug report and start asking Claude some questions that would guide it to a more plausible actual answer, but that requires a little more experience in kernel development.

Re: RipGrep musl binaries occasionally segfault during very-large searches

#69

Post by BetterThanSober » Sat, Aug 01, 2026, 2:54 PM UTC

inigyou wrote: post #25

wild_pointer wrote: post #6

Earlier quoted context omitted.

PoC||GTFO, if it reproduces, it's valuable

They have a PoC, we're arguing about the LLM-generated slop explanation of the PoC.

Is it actually reproducible though and do I want to chase and reproduce something that had no human touch? Do you?

Re: RipGrep musl binaries occasionally segfault during very-large searches

#70

Post by Orphis » Sat, Aug 01, 2026, 2:54 PM UTC

vlovich123 wrote: post #59

Orphis wrote: post #40

I get why people don't bother replacing the default allocator from musl all the time (it's there, convenient). But in an application whose purpose is to be FAST, I find it weird they haven't bothered replacing it with another more performant one. mallocng is bad at dealing with contention during multithreading. I've had applications that usually were I/O bound suddenly become "malloc" bound when building with musl in…

It’s a kernel bug. While I agree libc allocators suck for no good reason, it seems like this work of equally likely hit other application code including mimalloc and glibc.

Sure, but the problem isn't that the bug exists, is that it has surfaced in a performance application using musl and exerting code paths in a slow allocator.

mallocng should not be used at all.