Note that these images are made from many exposures that are then processed and combined, and the total exposure time is given. The individual exposure times were probably long, but I'm guessing on the order of minutes, not hours. (Actually, if you photograph stars with an exposure time that is too long, then you get star trails in the image.)

Trails appear very quickly, at focal lengths of around 20mm (typical dslr kit lens) they are obvious in 20-30 seconds, with a 100mm lens (start of telephoto range) they are obvious in 3-5 seconds. This of course depends on the res of your camera (I shoot with an 8MP and a 24MP).

To get rid of the trails you need a tracking mount. The better the mount the smoother and longer it tracks. Astrophotography is expensive...

> if you photograph stars with an exposure time that is too long, then you get star trails in the image

He was using a tracking mount. At 200mm you can't image for more than a few seconds without trailing.

Also if you were slow updating, you could avoid critical security patches (and many people did)

Which affect the OS mostly and not individual apps. Funnily enough OS updates are usually not automatic. Which I think is a good thing because vendors keep mixing them with "feature updates" which end up making things worse (looking at you Samsung).

I'd love for Google to take away the security update channel from the phone vendors and auto-update ONLY security-related things through that.

So what happens if you are on an old version, a security issue is discovered, but they only fix it in the new version?

Yeah and missing security updates was WAY more common, autoupdates is the lesser of the two evils by far ...

I read it as GP arguing we don't do enough of it.

Yes, this was my intent. It's not that security researchers don't publish this kind of thing... it's just that there are a million rabbit holes to explore, and probably only like 0.1% of those dead ends get written about.

My english may be failing me here, but doesn't

> I feel it sets a precedent for research broadly

imply it's some sort of first time?

Generally, precedent means first "well-known" time, or first time by a respected person/institution/company. I don't know enough about this field to know if this is the first time Google has published a negative result.

This is a fair point to consider. Perhaps my claim was a bit overbroad.

Because it works really well (at least from my experience and others I've heard). It has a solid (and really useful) feature set, and I generally have lower latency and less CPU usage than any other video conferencing system I've tried.

This is my first time hearing Apple refurbished meaning old store display model. I always thought refurbished machines were products that other people bought new and returned, and then Apple restored them to like-new condition. There seem to be a lot more refurbs available than I would imagine there are old display models. Now I'm curious, though, does anyone know more about how (Apple official) refurbs are sourced?

He wrote "second hand, refurbished" so it's not entirely clear that it was Apple refurbished.

I made the assumption that he meant refurbished by a third-party, not Apple, because it's pretty common for those sorts of secondhand machines to be refurbished with new screens. Figure they put in the cheapest screen they could source, and no wonder it's dying in 5 years. I doubt any OE screen from Apple would have the same problem he describes.

Hi, I'm the author. To be honest, I'm not sure how the refurbished thing works. That's why the whole paragraph is full of "I think" and "perhaps" and "my theory is". It's all just speculation. The shop where I bought it had it marked as refurbished, that's what I'm sure about, but I don't know what's the exact history of the machine. I've heard rumors those are computers from Apple Store etc., hence the speculation about worn out display, but I've never really investigated it further. Doesn't matter much now, whatever the reason, the display is dead.

I have bought Apple refurbished machines. I always understood them to be more-or-less unused returns. IIRC Apple cannot legally advertise returned machines as "new", hence the "refurbished" designation.

Moreover Apple has an essentially unlimited supply of machines. I can't imagine it would be worth it to actually take in machines and repair them (not least because it would undermine confidence in the refurb store if it was a gamble about whether you'd get a basically-new machine or beat-up machine.)

It is also my understanding that Apple refurbs are returned devices.

Serious question, can someone who downvoted the parent comment please explain why? This sounds in line with what I've heard about treatment of African Americans by the US medical system, so I would love to hear if there is evidence to say this is wrong.

Ah! This would have been really helpful!

Hackernews at its very best.

Concurrency is still hard for me, but I do find it getting much easier over the years :) thanks for the story!

I hadn't considered eBPF because I needed some pretty obscure information from the kernel internals (i.e. the addresses of the `struct file`s) and I didn't realize eBPF was as capable as it is. Another commenter suggested trying it, though, so I'm checking it out now!

I did use printk for debugging, but I (incorrectly) assumed it could block. Another commenter pointed out that this is not the case. TIL!

The gdb link looks very helpful and I'll try that next time. Thanks for linking that.

Yeah, my mind immediately went to eBPF too.

"But when BPF got extended, it allowed users to add code that is executed by the kernel in a safe manner in various points of its execution, not only in the network code."

Read more here:

https://thenewstack.io/how-io_uring-and-ebpf-will-revolution...

This is really good to know. I had assumed it could block when allocating memory for the formatted string buffer, but the rationale explained in that article makes a lot of sense. Being able to use printk simplifes things a lot.

Also: allocating memory with GFP_ATOMIC doesn't sleep.