Re: Question regarding RT patches for ARM

From	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: Question regarding RT patches for ARM
Date	2017-05-18 22:20 +0200
Message-ID	<tIA3U-8ln-27@gated-at.bofh.it> (permalink)
References	(4 earlier) <tHpay-Ra-27@gated-at.bofh.it> <tI7uV-3HE-1@gated-at.bofh.it> <tI8r1-4kw-39@gated-at.bofh.it> <tI9Gq-5g6-15@gated-at.bofh.it> <tIrtH-1zL-91@gated-at.bofh.it>
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On 2017-05-18 13:08:32 [+0200], Fawad Lateef wrote:
> Hi Sebastian,
Hi Fawad,

> > Of this "page fault" happens on boot, it has to do something without
> > your .config + hw combination. If it happens at rune-time it is probably
> > triggered by a driver or an application is triggering this.
> >
> 
> Yes, this happens at run-time and not always. Sometimes hardware just
> hangs/stalls.

So this sounds like a race condition.

> As now RT is widely used on ARM so to me seems like it something
> related to hardware design/setting OR application.
> 
> Another question: Is RT user-space application can make kernel/system
> crash? As to me kernel should kill the app but let itself running
> _but_ not sure in the case of RT patched kernel.

This is correct. With RT or without it: a use space should not be able
to crash the kernel.
It is possible that a race within a driver triggers more reliably on RT.
I would recommend to strip down the system to the minimum where the
issue should not trigger. And then slowly increase the "enabled"
hardware components so you might get an idea when or what could cause
it.

> Thanks,
> 
> Fawad Lateef

Sebastian

Thread

Question regarding RT patches for ARM Fawad Lateef <fawadlateef@gmail.com> - 2017-05-15 14:50 +0200
  Re: Question regarding RT patches for ARM Richard Weinberger <richard.weinberger@gmail.com> - 2017-05-15 15:10 +0200
  Re: Question regarding RT patches for ARM Fawad Lateef <fawadlateef@gmail.com> - 2017-05-15 15:20 +0200
    Re: Question regarding RT patches for ARM Sebastian Andrzej Siewior <sebastian.siewior@linutronix.de> - 2017-05-15 15:50 +0200
      Re: Question regarding RT patches for ARM Fawad Lateef <fawadlateef@gmail.com> - 2017-05-15 16:10 +0200
    Re: Question regarding RT patches for ARM Eric Nelson <eric@nelint.com> - 2017-05-15 16:20 +0200
      Re: Question regarding RT patches for ARM Fawad Lateef <fawadlateef@gmail.com> - 2017-05-15 16:30 +0200
        Re: Question regarding RT patches for ARM Fawad Lateef <fawadlateef@gmail.com> - 2017-05-17 15:50 +0200
          Re: Question regarding RT patches for ARM Eric Nelson <eric@nelint.com> - 2017-05-17 16:50 +0200
            Re: Question regarding RT patches for ARM Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-05-17 18:10 +0200
              Re: Question regarding RT patches for ARM Fawad Lateef <fawadlateef@gmail.com> - 2017-05-18 13:10 +0200
                Re: Question regarding RT patches for ARM Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-05-18 22:20 +0200
            Re: Question regarding RT patches for ARM Fawad Lateef <fawadlateef@gmail.com> - 2017-05-18 10:50 +0200

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