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From: Tom Cook <tom.k.cook@gmail.com>
To: RT <linux-rt-users@vger.kernel.org>
Subject: Re: Tracers+cyclictest causing kernel oops
Date: Fri, 21 Jun 2013 15:17:54 +0100	[thread overview]
Message-ID: <CAFSh4Uzjvqsew9yAQafO=nYtV5rOuCSdt3aRXUxDvkUBMOCdXw@mail.gmail.com> (raw)
In-Reply-To: <CAFSh4UyVf18mx3Pf0HbOzLWTGEMNC0rv+7H8etcvsj+R0EgSNA@mail.gmail.com>

On Fri, Jun 21, 2013 at 12:21 PM, Tom Cook <tom.k.cook@gmail.com> wrote:
[snip]
> I think I'm nearly starting to get my head around what's going on
> here.  The USB driver uses FIQs, which normally isn't a problem
> because nothing would interrupt the FIQ handler (or if it did, it
> wouldn't generate a page fault).  But cyclictest runs at a higher
> priority than the USB handler and generates page faults (at least when
> it is initialising).  Eventually it interrupts a USB FIQ handler and
> the memory manager doesn't know what to do with a page fault in a FIQ
> handler, so it oopses.  Does that sound about right?

Or, of course, perhaps the tracer is instrumenting the USB FIQ handler
with a hardware watchpoint.  These turn up as data aborts, which are
unhandled in FIQ mode.  Some evidence for this is that if I use
set_ftrace_filter to restrict the tracing to only a few system
functions then the crash doesn't happen.

Regards,
Tom

  reply	other threads:[~2013-06-21 14:17 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-26  8:04 Tracers+cyclictest causing kernel oops Tom Cook
2013-04-29  7:16 ` Tom Cook
2013-05-03 16:05   ` Sebastian Andrzej Siewior
2013-05-12  5:14     ` Tom Cook
     [not found]     ` <CAFSh4UwD5yyJrtKwUaOX-uiUuzVf7YaDbM4vbZ1EFZBf6F1JHg@mail.gmail.com>
2013-05-21 11:16       ` Sebastian Andrzej Siewior
2013-05-21 15:20         ` Tom Cook
2013-05-27  8:02           ` Uwe Kleine-König
2013-05-27 21:23             ` Tom Cook
2013-05-28  6:53               ` Uwe Kleine-König
2013-06-21 11:01                 ` Tom Cook
2013-05-31  9:23           ` Sebastian Andrzej Siewior
2013-05-31  9:31             ` Tom Cook
2013-06-21 11:21             ` Tom Cook
2013-06-21 14:17               ` Tom Cook [this message]
2013-06-21 14:58                 ` Tom Cook
2013-06-21 15:00               ` Sebastian Andrzej Siewior

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