Is preventing misuse that complex?

By: Linus Torvalds (torvalds.delete@this.linux-foundation.org), August 23, 2018 12:46 pm
Room: Moderated Discussions
Paul A. Clayton (paaronclayton.delete@this.gmail.com) on August 23, 2018 5:42 am wrote:
>
> In my ignorance, I thought that the OS could simply check if the thread yielded shortly after
> it was given some extra time and if not penalize the thread (adding the extra time slice to its
> use count would be a light punishment, revoking the privilege would be a heavier punishment).
> The thread would only get one extension when another thread would ordinarily be scheduled.

.. so what about realtime? Just throw that out the window?

What about page faults that need to do IO?

What about any number of things that simply force the process to be scheduled?

And since you have to force-evict at some point anyway, whatever issue you tried to prevent is still there, and so the process can't rely on it anyway.

So it's completely idiotic and pointless. All you added was a grace period non-guarantee that doesn't guarantee anything at all, but that made people perhaps think it did, and probably incorrectly rely on it.

If you don't see why that is stupid, I can't help you.

> (Policed cooperative multitasking seems like a potentially useful design.)

Oh, cooperative scheduling within a group of mutually trusting threads can be great. It means they don't need any locking amongst themselves, and they could have some fixed thread-pool or whatever. I'm all for it, and it's been done (often in user space).

It doesn't have anything to do with percpu state and some general operating system interfaces.

> > Don't do it. There is no upside anyway.
>
> In my ignorance (I am not even a programmer much less an operating systems developer), I thought
> that there were cases where temporary deadlock due to thread scheduling was a significant issue.

Oh yes. Locking is complicated. But "let the processes tell you that they want to run longer" isn't the answer.

Linus
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TopicPosted ByDate
ARM turns to a god and a heroAM2018/08/16 09:32 AM
  ARM turns to a god and a heroMaynard Handley2018/08/16 09:41 AM
    ARM turns to a god and a heroDoug S2018/08/16 11:11 AM
    ARM turns to a god and a heroGeoff Langdale2018/08/16 11:59 PM
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      It's marketing materialMichael S2018/08/17 03:13 AM
        It's marketing materialdmcq2018/08/17 05:23 AM
          It's marketing materialAndrei Frumusanu2018/08/17 07:25 AM
        It's marketing materialLinus Torvalds2018/08/17 11:20 AM
          It's marketing materialGroo2018/08/17 01:44 PM
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              Just by way of clarification Passing Through2018/08/17 03:15 PM
                Just by way of clarification AM2018/08/18 12:49 PM
                  Just by way of clarification Passing Through2018/08/18 01:34 PM
                    This ain't the nineties any longerPassing Through2018/08/18 01:54 PM
                      This ain't the nineties any longerMaynard Handley2018/08/18 02:50 PM
                        This ain't the nineties any longerPassing Through2018/08/18 03:57 PM
                          This ain't the nineties any longerPassing Through2018/09/06 02:42 PM
                            This ain't the nineties any longerMaynard Handley2018/09/07 04:10 PM
                              This ain't the nineties any longerPassing Through2018/09/07 04:48 PM
                                This ain't the nineties any longerMaynard Handley2018/09/07 05:22 PM
                Just by way of clarification Wilco2018/08/18 01:26 PM
                  Just by way of clarification Passing Through2018/08/18 01:39 PM
                  Just by way of clarification none2018/08/18 10:52 PM
                    Just by way of clarification dmcq2018/08/19 08:32 AM
                      Just by way of clarification none2018/08/19 08:54 AM
                        Just by way of clarification dmcq2018/08/19 11:24 AM
                          Just by way of clarification none2018/08/19 11:52 AM
                  Just by way of clarification Gabriele Svelto2018/08/19 06:41 AM
                    Just by way of clarification Passing Through2018/08/19 09:25 AM
                      Whiteboards at Gatwick airport anyone? Passing Through2018/08/20 04:24 AM
          It's marketing materialMichael S2018/08/18 11:12 AM
          It's marketing materialBrett2018/08/18 05:22 PM
            It's marketing materialBrett2018/08/18 05:33 PM
              It's marketing materialAdrian2018/08/19 01:21 AM
        A76AM2018/08/17 02:45 PM
          A76Michael S2018/08/18 11:20 AM
            A76AM2018/08/18 12:39 PM
              A76Michael S2018/08/18 12:49 PM
                A76AM2018/08/18 01:06 PM
                  A76Doug S2018/08/18 01:43 PM
                    A76Maynard Handley2018/08/18 02:42 PM
                      A76Maynard Handley2018/08/18 04:22 PM
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                          Why write zeros when one can use metadata?Maynard Handley2018/08/19 11:12 AM
                            Dictionary compress might apply to memcopyPaul A. Clayton2018/08/19 01:45 PM
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                          Instructions for zeroingMaynard Handley2018/08/30 08:41 AM
                          Instructions for zeroingAdrian2018/08/30 11:37 AM
                            dcbz -> dcbzl (was: Instructions for zeroing)hobold2018/08/31 01:50 AM
                              dcbz -> dcbzl (was: Instructions for zeroing)dmcq2018/09/01 05:28 AM
                      A76Travis2018/08/19 11:36 AM
                        A76Maynard Handley2018/08/19 12:22 PM
                          A76Travis2018/08/19 02:07 PM
                            A76Maynard Handley2018/08/19 06:24 PM
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                          Remote atomicsMichael S2018/08/19 01:58 PM
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                                    Remote atomicsRicardo B2018/08/20 10:05 AM
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                          Remote atomicsTravis2018/08/19 02:32 PM
                            Remote atomicsMichael S2018/08/19 02:46 PM
                              Remote atomicsTravis2018/08/19 05:35 PM
                                Remote atomicsMichael S2018/08/20 03:29 AM
                            Remote atomicsmatthew2018/08/19 07:58 PM
                              Remote atomicsanon2018/08/20 12:59 AM
                                Remote atomicsTravis2018/08/20 10:26 AM
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                                Fitting time slices to execution phasesPaul A. Clayton2018/08/21 09:09 AM
                                  Fitting time slices to execution phasesLinus Torvalds2018/08/21 02:34 PM
                                    Fitting time slices to execution phasesLinus Torvalds2018/08/21 03:31 PM
                                      Fitting time slices to execution phasesGabriele Svelto2018/08/21 03:54 PM
                                        Fitting time slices to execution phasesLinus Torvalds2018/08/21 04:26 PM
                                      Fitting time slices to execution phasesTravis2018/08/21 04:21 PM
                                        Fitting time slices to execution phasesLinus Torvalds2018/08/21 04:39 PM
                                          Fitting time slices to execution phasesTravis2018/08/21 04:59 PM
                                            Fitting time slices to execution phasesLinus Torvalds2018/08/21 05:13 PM
                                      Fitting time slices to execution phasesanon2018/08/21 04:27 PM
                                        Fitting time slices to execution phasesLinus Torvalds2018/08/21 06:02 PM
                                          Fitting time slices to execution phasesEtienne2018/08/22 02:28 AM
                                        Fitting time slices to execution phasesGabriele Svelto2018/08/22 03:07 PM
                                          Fitting time slices to execution phasesTravis2018/08/22 04:00 PM
                                          Fitting time slices to execution phasesanon2018/08/22 06:52 PM
                                    Fitting time slices to execution phasesTravis2018/08/21 04:37 PM
                                    Is preventing misuse that complex?Paul A. Clayton2018/08/23 05:42 AM
                                      Is preventing misuse that complex?Linus Torvalds2018/08/23 12:46 PM
                                        Is preventing misuse that complex?Travis2018/08/23 01:29 PM
                                          Is preventing misuse that complex?Travis2018/08/23 01:33 PM
                                            Is preventing misuse that complex?Jeff S.2018/08/24 07:57 AM
                                              Is preventing misuse that complex?Travis2018/08/24 08:47 AM
                                          Is preventing misuse that complex?Linus Torvalds2018/08/23 02:30 PM
                                            Is preventing misuse that complex?Travis2018/08/23 03:11 PM
                                              Is preventing misuse that complex?Linus Torvalds2018/08/24 01:00 PM
                                                Is preventing misuse that complex?Gabriele Svelto2018/08/24 01:25 PM
                                                  Is preventing misuse that complex?Linus Torvalds2018/08/24 01:33 PM
                                  Fitting time slices to execution phasesTravis2018/08/21 03:54 PM
                                rseq: holy grail rwlock?Travis2018/08/21 03:18 PM
                                  rseq: holy grail rwlock?Linus Torvalds2018/08/21 03:59 PM
                                    rseq: holy grail rwlock?Travis2018/08/21 04:27 PM
                                      rseq: holy grail rwlock?Linus Torvalds2018/08/21 05:10 PM
                                        rseq: holy grail rwlock?Travis2018/08/21 06:21 PM
                  ARM design housesMichael S2018/08/21 05:07 AM
                    ARM design housesWilco2018/08/22 12:38 PM
                      ARM design housesMichael S2018/08/22 02:21 PM
                        ARM design housesWilco2018/08/22 03:23 PM
                          ARM design housesMichael S2018/08/29 01:58 AM
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                  A76Michael S2018/08/18 02:32 PM
                    A76Maynard Handley2018/08/18 02:52 PM
                      A76Michael S2018/08/18 03:04 PM
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      Surprised??Alberto2018/08/17 02:10 AM
      Surprised??none2018/08/17 02:46 AM
      Garbage talkAndrei Frumusanu2018/08/17 07:30 AM
        Garbage talkMichael S2018/08/17 07:43 AM
          Garbage talkAndrei Frumusanu2018/08/17 09:51 AM
            Garbage talkMichael S2018/08/18 11:29 AM
        Garbage talkAdrian2018/08/17 08:28 AM
          Garbage talkAlberto2018/08/17 09:20 AM
          Garbage talkAndrei Frumusanu2018/08/17 09:48 AM
            Garbage talkAdrian2018/08/17 10:17 AM
              Garbage talkAndrei Frumusanu2018/08/17 10:36 AM
                Garbage talkAdrian2018/08/17 02:53 PM
                  Garbage talkAndrei Frumusanu2018/08/18 12:17 AM
        More like a religion he?? ARM has an easy life :)Alberto2018/08/17 09:13 AM
          More like a religion he?? ARM has an easy life :)Andrei Frumusanu2018/08/17 09:34 AM
            More like a religion he?? ARM has an easy life :)Alberto2018/08/17 10:03 AM
              More like a religion he?? ARM has an easy life :)Andrei Frumusanu2018/08/17 10:43 AM
              More like a religion he?? ARM has an easy life :)Doug S2018/08/17 02:17 PM
              15W phone SoCsAM2018/08/17 03:04 PM
          More like a religion he?? ARM has an easy life :)Maynard Handley2018/08/17 12:29 PM
  my future stuff will be better than your old stuff, hey I'm a god at last (NT)Eric Bron2018/08/18 03:34 AM
    my future stuff will be better than your old stuff, hey I'm a god at lastnone2018/08/18 08:34 AM
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