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

lkml.iu.edu

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

#51

Post by piker »

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…

I guess that depends on whether or not zeros were valid in the first instance. My post assumed they were. I agree with your point if zero would be outside of the valid range in the first instance.

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

#52

Post by cgdub »

_Codemonkeyism wrote: post #15
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…

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).

There's a great talk about backwards compatibility in Java by Brian Goetz: https://www.youtube.com/watch?v=2y5Pv4yN0b0

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

#53

Post by anon1385 »

vacri wrote: post #35
orcdork wrote: post #14

In any other kind of social/business arrangement he would be politely but firmly escorted out, possibly by security, for this kind of behavior. Being right or wrong is irrelevant.

You need to work in a wider variety of workplaces, if you genuinely believe that. Perhaps put another way: were Jobs or Ballmer ever escorted out for their obnoxious behaviours?

No, but they probably should have been.

The events of the past few weeks should serve as a reminder that what's historically been considered 'normal' behaviour in a workplace just because people have gotten away with it doesn't mean it's morally, ethically or legally justifiable.

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

#54

Post by Cthulhu_ »

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 do better.

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

#56

Post by jokoon »

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)

He can afford to be politically incorrect because he makes all the decision, and because nobody else than him can make decisions. He is the expert.

There are very few places in software where an expert/engineer have full authority on the development/how things are done/specifications. You often see money/markets/trends take over.

I really wonder what linux will become without Torvalds when he will go away. I hope he already thought about it, because it will really require somebody with huge confidence about what to do.

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

#57

Post by Ntrails »

delroth wrote: post #45
wolfwyrd wrote: post #43

Earlier quoted context omitted.

It's laid out further in the thread [1]. The key quote comes from Thorsten: > All that afaics doesn't matter. If a new kernel breaks things for people > (that especially includes people that do not update their userland) > then it's a kernel regression, even if the root of the problem is in > usersland. Linus (CCed) said that often enough [1] http://lkml.iu.edu/hypermail/linux/kernel/1710.3/02487.html

Does that mean the kernel is not allowed to change version number anymore because I could write an app that segfaults if it sees Linux >= 4.14?

You're just being disingenuous, what does that help?

It's clearly an error on the part of the kernel if the owner of said kernel has specific expectations of behaviour on upgrade with respect to user spaces and those are not being met.

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

#59

Post by Cthulhu_ »

orcdork wrote: post #14

In any other kind of social/business arrangement he would be politely but firmly escorted out, possibly by security, for this kind of behavior. Being right or wrong is irrelevant.

Even when he's effectively CEO, visionary, and end-responsible for the business? He's the Big Boss of Linux, there is nobody above him in the chain of command. You're used to traditional businesses when there is no single end-responsible person, and when there is a public face for the company (like Jobs, Gates, etc), there is still a group of faceless shareholders above them that can choose to remove them. Not in this case. I like it myself, a dictatorship is a much more effective form of managing a software product.

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

#60

Post by rkangel »

fdej wrote: post #29
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…

If only compiler developers had this attitude.

I think Rust has done this quite well, managing to have the best of both worlds. Unstable features are only available on the nightly build and need specifically enabling (and their interface may change). Once a feature is considered stable it is carefully maintained. They do have some breaking changes, but they're not common and for unusual edge cases:

https://killercup.github.io/bitrust/

This explains the Rust approach:

https://blog.rust-lang.org/2014/10/30/Stability.html

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