Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality
Date	2015-10-01 00:10 +0200
Message-ID	<qexJv-1cv-3@gated-at.bofh.it> (permalink)
References	(4 earlier) <qdPp8-4Mj-5@gated-at.bofh.it> <qe7m2-5cj-9@gated-at.bofh.it> <qe7m2-5cj-7@gated-at.bofh.it> <qewaK-7gv-15@gated-at.bofh.it> <qexJv-1cv-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, 30 Sep 2015, Chris Metcalf wrote:
> So for now, if a task-isolation thread sets up a timer,
> they're screwed: so, don't do that.  And it's really not part of
> the typical programming model for these kinds of userspace
> drivers anyway, so it's pretty reasonable to forbid it.

There is a difference between forbidding it and looping for 10 minutes
in the kernel.

I have yet to understand WHY this loop is there at all. All I've seen
so far is that things might need to settle and that the indicator for
settlement is that the next expiry time of the per cpu timer is set to
KTIME_MAX.

To be blunt, that just stinks. This is duct tape engineering and not
even close to a reasonable design.

Thanks,

	tglx
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Thread

Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality Andy Lutomirski <luto@amacapital.net> - 2015-09-28 23:00 +0200
  Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality Andy Lutomirski <luto@amacapital.net> - 2015-09-29 00:50 +0200
    Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality Andy Lutomirski <luto@amacapital.net> - 2015-09-29 20:00 +0200
      Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality Thomas Gleixner <tglx@linutronix.de> - 2015-09-30 22:30 +0200
        Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality Thomas Gleixner <tglx@linutronix.de> - 2015-10-01 00:10 +0200
          Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality Andy Lutomirski <luto@amacapital.net> - 2015-10-01 00:20 +0200
            Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality Thomas Gleixner <tglx@linutronix.de> - 2015-10-01 10:20 +0200
              Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality Christoph Lameter <cl@linux.com> - 2015-10-01 11:10 +0200
                Re: [PATCH v7 07/11] arch/x86: enable task isolation functionality Thomas Gleixner <tglx@linutronix.de> - 2015-10-01 12:20 +0200

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