A regression is the kernel not giving the same result with the same user space • Hacker News Board

Re: A regression is the kernel not giving the same result with the same user space

#131

Post by smcl » Thu, Nov 02, 2017, 2:20 PM UTC

jordigh wrote: post #4

Mercurial, made by another (in my opinion) much more well-spoken kernel hacker, is what really introduced me to the concept that you do not break interface for downstream users, no matter how wrongly you may think they are using the interface. It’s an attitude that is difficult to convey because software developers always want to have the freedom to “improve” their own software, even at the possible cost of breaking…

I was about to post that it was funny this URL popped up when I read the Lobste.rs discussion until I saw your username :)

Re: A regression is the kernel not giving the same result with the same user space

#132

Post by tome » Thu, Nov 02, 2017, 2:21 PM UTC

spraak wrote: post #117

tome wrote: post #91

Earlier quoted context omitted.

Oh well, he should try a language with types ... /me runs ...

What are you trying to say? There are already a lot of explanations for why Clojure is dynamically typed and how it fills its role nicely that way.

I know, I know. We've been having some interesting discussions about Clojure, Haskell and dynamic and static typing on these stories

https://news.ycombinator.com/item?id=15602658

https://news.ycombinator.com/item?id=15593069

My comment was intended to be a wry one referencing those very interesting discussions and hinting that if you have types then you can more easily make breaking changes internally that aren't visible externally.

Re: A regression is the kernel not giving the same result with the same user space

#133

Post by catpolice » Thu, Nov 02, 2017, 2:21 PM UTC

chii wrote: post #49

piker wrote: post #38

Earlier quoted context omitted.

Interesting. > Behavioral changes happen, and maybe we don't even support some feature any more. There's a number of fields in /proc/ /stat that are printed out as zeroes, simply because they don't even exist in the kernel any more, or because showing them was a mistake (typically an information leak). But the numbers got replaced by zeroes, so that the code that used to parse the fields still works. The user might n…

> If my application depends on some of those zero'd fields, it seems like that has potential to cause serious debugging problems, as opposed to just causing an error on the parse. if your app didn't used to handle the 'zero' case (assuming zero was a "valid" value for said field), then the app was poorly written and would'be been broken in the first place. However, if the app _did_ handle the 'zero' case, then the ap…

Zero could be a perfectly "valid" value and still break your application if changing the function to always return zero breaks an implicit contract. Suppose the previous behavior of the function returned something you could use as an ID for some internal representation in a database that you could look up and write to. Before, the ID you got back depended on the input, but now it doesn't. And you can't tell you're not getting real IDs back anymore, so you just happily write to the database. Now you're corrupting your database because the implicit behavioral contract you were relying on was broken - I'd MUCH rather the program just crash than for it to continue "working" in a way that irrecoverably corrupts data.

Re: A regression is the kernel not giving the same result with the same user space

#134

Post by fatbird » Thu, Nov 02, 2017, 2:21 PM UTC

Cthulhu_ wrote: post #54

raverbashing wrote: post #47

I'm glad Linus has this attitude and it is unfortunate it's not present in some other places Though it is annoying if you're at the receiving end of it, own up (the opposite of what the patch author was doing)

Annoying and hurtful, yes, but at the same time, he's not wrong - you fucked up, you did bad and you should feel bad. The upside of this rant too is that the author is not "fired", as such, but told to shape up or gtfo. In a lot of companies, mistakes are accepted, fixed, and forgiven without adding a bit of emotion to it. I think adding this kind of emotion will have a bigger impact and will make the receiving end d…

Amongst the emotion, Linus essentially says "I'll reject your kernel patches until you acknowledge my point (rule)". I suspect that had more to do with it than the profanity or the emotion.

Re: A regression is the kernel not giving the same result with the same user space

#135

Post by tome » Thu, Nov 02, 2017, 2:21 PM UTC

pjmlp wrote: post #127

tome wrote: post #91

Earlier quoted context omitted.

Oh well, he should try a language with types ... /me runs ...

All my favorite languages are typed and I do agree with him.

Really? How so? If you have abstract types then you can easily make internal changes without making those changes visible externally.

Re: A regression is the kernel not giving the same result with the same user space

#136

Post by andrestc » Thu, Nov 02, 2017, 2:23 PM UTC

dilap wrote: post #116

_Codemonkeyism wrote: post #15

Earlier quoted context omitted.

For various reasons I would not go back to Java, but that was wonderful, your very old code still worked with newer versions, nothing broke during upgrades (even when behind deprecation one version).

Go is really good about this too. It's great.

It's not as strong as the kernel. Go does not break APIs but may break undocumented behavior.

Re: A regression is the kernel not giving the same result with the same user space

#137

Post by magnetic » Thu, Nov 02, 2017, 2:24 PM UTC

chrisseaton wrote: post #113

emodendroket wrote: post #83

Earlier quoted context omitted.

I mean, is the answer really that hard? If the "refactor" would break the interface, you can't do it. Maybe you deprecate the old method and make a new one.

How do they handle bug fixing though? What if one application wants a bug fixed, but another application is depending on the bug inadvertently?

The bug they fix is the bug that keeps the API contract intact. The first application gets its bug fixed, and the second application breaks because it was relying on a bug that didn't match the API contract. You program to an API, not to an implementation. The second application did the latter, and will therefore pay the price.

Re: A regression is the kernel not giving the same result with the same user space

#138

Post by Beltiras » Thu, Nov 02, 2017, 2:24 PM UTC

santoshalper wrote: post #66

jokoon wrote: post #50

Eli5, What is kernel regression? Does he mean breaking backward compatibility?

A change was made to the kernel that broke some applications - this is called a regression (a bug introduced in an update). The developer who made the change that caused the bug in the downstream application tried to argue that it was the application's fault, not the kernel. Linus then calmly and politely reminded him that the official policy of kernel development is that they never introduce changes that break appli…

You only say "calmly and politely" because Linus is a known pottymouth and frequently "tears people a new one". An email like this might get you demoted or fired in some workplaces.

Re: A regression is the kernel not giving the same result with the same user space

#139

Post by catpolice » Thu, Nov 02, 2017, 2:24 PM UTC

macinjosh wrote: post #129

Linus is right but his choice of words seems unprofessional bordering on harassment. Almost sounds childish in parts, especially the ALL CAPS screaming he does. Its cool to be passionate but also be civil.

I think of the line from the Big Lebowski a lot: "You're not wrong, Walter. You're just an asshole."

Re: A regression is the kernel not giving the same result with the same user space

#140

Post by bischofs » Thu, Nov 02, 2017, 2:24 PM UTC

Someone needs to codify this shit for when he leaves. Its surprising that he still needs to scream at people after two decades of kernel work. I don't have a lot of faith that whoever comes after him will be as proud of the kernel as he is given they just inherited most of it.

Succession is a weird concept with linux but the fact that it has always been more stable than the other OS' is I think the main reason it is been so successful in the internet age.

An example of a failed succession is Tim Cook; the guy is the complete opposite of Jobs. Just take a look at the apple website nowadays. A product guru would not sell three generations of iphones that are all cannibalizing each other and lack any real differences.