zlacker

>>rvz+(OP)
I know next to nothing about kernel programming, but I'm not sure here what Linus' objection to the comment he is responding to here is.

The comment seemed to be making reference to rust's safety guarantees about undefined behaviour like use after free.

Linus' seems to have a completely different definition of "safey" that conflates allocation failures, indexing out of bounds, and division by zero with memory safety. Rust makes no claims about those problems, and the comment clearly refers to undefined behaviour. Obviously, those other problems are real problems, but just not ones that Rust claims to solve.

Edit: Reading the chain further along, it increasingly feels like Linus is aruging against a strawman.

>>a_hume+h4
I am probably wrong but I understood that “safety meaning panic” is noeither “safe” not allowed in the Linux kernel because the kernel must not panic when an error arises.

>>pfortu+Y4
Which is why Rust has been accommodating the kernel by adding non-panic versions of the functions that Linus has been complaining about (namely that memory allocation is infallible, because that isn't an unreasonable thing to assume in applicationc code.). Still doesn't change the fact that "safe" in this context has a technical meaning, and what Linus is describing isn't that.

>>a_hume+i6
maybe his point is that the technical meaning should use a more acurate word in his opinion?

>>Vt71fc+X8
His point seems to be the opposite, that "safety" should have a vaguer meaning in his opinion, and not the well established technical definition that the author clearly meant when he used the word.

>>a_hume+5b
Or, in other words, rust-safety should mean what safety means in every other context, or rust people need to come up with a different word.

>>LtWorf+pe
You don't get to change the definition of a term used by another when it had a clear meaning in its use, and then make an arugment on the basis that the author meant y when they clearly meant x. That is just conflation.

>>a_hume+Yi
>when it had a clear meaning in its use

Thats not the issue though. It's that "safe" means something is actualy safe. My house isn't safe if its on fire, even if the house is in a safe neighborhood. Linus' claim is that "rust people" sometimes themselves conflate memory saftey with general code saftey, simply because "safe" is in the name. So much so that they will at times sacrifice code quality to achieve this goal despite (a) memory saftey not being real saftey and (b) there is no way to guarantee memory saftey in the kernel anyway. What he is saying is that "rust people" (whatever that means) are at times trading off real saftey or real code maintenance/performance for "rust saftey."

>a compiler - or language infrastructure - that says "my rules are so ingrained that I cannot do that" is not one that is valid for kernel work.

And

>I think you are missing just how many things are "unsafe" in certain contexts and cannot be validated.

>This is not some kind of "a few special things".

>This is things like absolutely _anything_ that allocates memory, or takes a lock, or does a number of other things.

>Those things are simply not "safe" if you hold a spinlock, or if you are in a RCU read-locked region.

>And there is literally no way to check for it in certain configurations. None.

You can judge wheter he is correct but he never said rust's saftey implies absolute saftey, only that some rust users are treating it that way by sacrificing the code for it. If that's the case then it makes a lot of sense to start using a more sensible word like "guaranteed" instead of safe. I think part of what contibutes to this idea is that "unsafe" code is written with the keyword "unsafe" as if code written not that way is safe, and code written with "unsafe" is bad. That's not to say that "unsafe" actually implies any of that - all it means is that it's not guaranteed to be memory safe - but according to Linus it creates a certain mentality which is incongruent with the nature of kernel development. And the reason for that is that safe and unsafe are general english words with strong connotations such as:

>protected from or not exposed to danger or risk; not likely to be harmed or lost.

>uninjured; with no harm done.

And for unsafe:

>able or likely to cause harm, damage, or loss