Except in this case, it was a bunch of old C devs who aren't just resistant but openly hostile to change, and they'd rather bully people into silence than try to progress.
Rust is sufficiently different that you cannot expect C developers to learn rust to the level they have mastered C in order to be working at the kernel level. It's not going to happen.
I don't really know too much about rust. Maybe one day I'll actually mess around with it. But the one time I looked at a rust git repo I couldn't even find where the code to do a thing was. It's just different enough to be problematic that way.
So I think probably, the best way IS to go the way linus did. Just go ahead and write a very basic working kernel in rust. If the project is popular it will gain momentum.
Trying to slowly adapt parts of the kernel to rust and then complain when long term C developers don't want to learn a new language in order to help isn't going to make many friends on that team.
But the one time I looked at a rust git repo I couldn't even find where the code to do a thing was.
IMO that tells more about how the project was organized and names things than the language used.
So I think probably, the best way IS to go the way linus did. Just go ahead and write a very basic working kernel in rust. If the project is popular it will gain momentum.
As the other commenter pointed out, there's Redox. The issue is that this completly disregards an incremental approach: you have to rewrite everything before it comes usable, you can't do it piece by piece. Currently the approach of Rust for Linux is not even to rewrite things, but to allow writing new drivers in Rust.
Trying to slowly adapt parts of the kernel to rust and then complain when long term C developers don't want to learn a new language in order to help isn't going to make many friends on that team.
Have you seen the conference video? That's not just refusal to learn a new language, it's open hostility. And it's not the only instance, for example Asahi Lina also reported unreasonable behaviour by some maintainers just because she wrote Rust code, even when Rust was not involved.
RedoxOS! There's been solid progress too, beyond just having a functional microkernel, they have many of the userspace tools/their version of coreutils, even a desktop environment already mostly implemented!
My understanding is that it shouldn't be too bad to port some other things over as well. The main issue I had was just the lack of drivers, especially since it's still tricky even on Linux, and the microkernel architecture (though more secure) also means there's no way to reuse any of those from Linux
part of the problem is that old-time kernel developers are used to C and don't know Rust," Torvalds said. "They're not exactly excited about having to learn a new language that is, in some respects, very different. So there's been some pushback on Rust."
Linus hit the nail on the head. If you've been a Kernel dev for a decade or more, and have spent decades learning the ins and outs of C, why would you want to switch to something that is similar, but different in a lot of ways, just because a small subset of devs think it's the best way forward? Let them handle Rust and the majority of devs will keep using C, even though Rust is objectively better.
As one of the other quotes suggested: fork the kernel project and rewrite it entirely in Rust, that way there isn't any push back from the C devs. Replacing C with Rust in the upstream kernel is akin to replacing the engine in a car while it's running or being used every day.
This specific talk was about defining shared common interfaces so these different groups could work together and the guy who actually talked him into stepping down essentially said "I'm gonna keep writing C and if that breaks your rust stuff that's not my problem". This isn't about convincing the c devs to write rust it's about convincing them to work together when some of them seem to have made up their mind to sabotage rust support (either through indifference or willful interface regressions). Personally I'm more ashamed what this points to for someone new wanting to come in contribute to Linux.
As one of the other quotes suggested: fork the kernel project and rewrite it entirely in Rust
That's not practically possible given the scale of the kernel. And doing a total rewrite is almost always a recipe for getting stuck and, if you ever create anything, creating something worse.
Replacing C with Rust in the upstream kernel is akin to replacing the engine in a car while it's running or being used every day.
Almost all real-world software development is like this. That's what we do.
The kernel is probably too large to rewrite the whole thing at once. This could lead to a future without any new C kernel devs, leading to stagnation, while the Rust kernel could be many years away from being finished. (Assuming we actually move away from C.)
At that point you might as well just start an entirely new kernel and hope it is good enough to eventually replace the Linux one once all devs are gone. Kinda the X11 and wayland thing.
One detail about Rust in the kernel that often gets overlooked: the Linux kernel supports arches to which Rust has never been ported. Most of these are marginal (hppa, alpha, m68k—itanium was also on this list), but there are people out there who still use them and may be concerned about their future. As long as Rust remains in device drivers only this isn't a major issue, but if it penetrates further into the kernel, these arches will have to be desupported.
(Gentoo has a special profile "feature" called "wd40" for these arches, which is how I was aware of their lack of Rust support. It's interesting to look at the number and types of packages it masks. Lotta python there, and it looks like gnome is effectively a no-go.)
Developers who are not willing to learn something new and not adapt are the worst. Besides that, nobody is forced to learn Rust, only those who want to work on Rust parts.
Developers who are not willing to learn something new and not adapt are the worst.
And this is why COBOL developers are desperately needed these days: because too many people think that "old" was the same thing as "needs a replacement".
"Learning something new" does not mean the thing you are learning is new. It just means it's new to you. One of the best things you can do for yourself as a dev is to learn to be fluid and be able to adapt to new languages, protocols, and technologies.
The situation of COBOL has nothing to do with Rust in Linux. C is not replaced by Rust, first. Secondly, there are legitimate reasons why Rust was introduced, as a secondary language. You are conflicting two different cases that are two different problems. It's not replacing a language.
Not an expert in both the languages but I heard that C developers are trained to use memory smartly, sometimes even reuse a range of allocated memory for completely different purpose to save cycles freeing and reallocating. But for Rust developers, everything is about making sure when one should get the hand away from the memory, and whose memory is allowed to be touched.
Sounds to me like sharing rides that maximise economically but we may have some oops moments sitting on someone's laps vs absolute private rides to make sure no one in your family will be harmed but we have to make sure everyone gets a car only when needed.
It is quite interesting to see how it will work out eventually...
I heard that C developers are trained to use memory smartly
Kernel coders are an entirely different breed, and when I worked with a few of them they were just stunning. The smartest man I know on the planet so far coded on the Unix kernel -- the one that IBM forced back to Novell who'd already fired their staff after selling it, and thus shelved it and killed Unix. He is and was amazing.
So yes, I can confirm that Kernel devs know how to manage their memory -- they use very little, they allocate and free it, and they build very small, tight, optimized kernels by knowing how the optimizer will do things and how to hint it to do what they know needs to happen.
Yeah, it's a skill. Yeah, it takes skilled people. I'd like to one day find out that really big training wheels will let anyone build code that well, but I've seen the goal and I don't expect we're there yet.
They are amazing but at the end of the day they are still humans and they can make mistakes. In the YouTube video referenced one of the C devs is heavily against rust.
Decided to go look for CVEs from code the guy manages (Ted Ts'o) I found these
CVE-2024-42304 — crash from undocumented function parameter invariants
CVE-2024-40955 — out of bounds read
CVE-2024-0775 — use-after-free
CVE-2023-2513 — use-after-free
CVE-2023-1252 — use-after-free
CVE-2022-1184 — use-after-free
CVE-2020-14314 — out of bounds read
CVE-2019-19447 — use-after-free
CVE-2018-10879 — use-after-free
CVE-2018-10878 — out of bounds write
CVE-2018-10881 — out of bounds read
CVE-2015-8324 — null pointer dereference
CVE-2014-8086 — race condition
CVE-2011-2493 — call function pointer in uninitialized struct
CVE-2009-0748 — null pointer dereference
Do you see a pattern in the type of error here? It's pretty much entirely memory related and right in the wheelhouse of something rust would just outright not allow short of just slapping everything into unsafe blocks.
The Old Guard is not perfect, and they are acting as a barrier to new talent coming in. Sometimes change is good and I'm heavily in the camp that rust one of those times. Linus seems to agree as he allowed the code into the kernel which he would never do lightly or just because it's fomo
Adding rust to a massive mature C project that targets lots of architectures and has many contributors is a difficult process. If it succeeds it is going to take a lot more time and patience.
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