linux-kernel - Re: scheduling while atomic & hang.

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Message-ID: <20130705100531.GA9562@gmail.com>
Date:	Fri, 5 Jul 2013 12:05:31 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: scheduling while atomic & hang.


* Frederic Weisbecker <fweisbec@...il.com> wrote:

> On Fri, Jul 05, 2013 at 08:51:13AM +0200, Ingo Molnar wrote:
> > 
> > * H. Peter Anvin <hpa@...or.com> wrote:
> > 
> > > On 07/03/2013 07:49 PM, Linus Torvalds wrote:
> > > >> [<ffffffff816f42bf>] __schedule+0x94f/0x9c0
> > > >> [<ffffffff816f487e>] schedule_user+0x2e/0x70
> > > >> [<ffffffff816f6de4>] retint_careful+0x12/0x2e
> > > 
> > > This call trace does indeed indicate that we took a hardware
> > > interrupt which caused a reschedule.  It doesn't necessarily have to
> > > be a quantum expiration interrupt, it could just as easily be an I/O
> > > completion interrupt.
> > 
> > Too bad the kernel stack frame at this point is so small [we are just 
> > before return to userspace], so we don't really get our usual trace of 
> > recent activities via the '?' entries ...
> > 
> > It would be nice to have a full-kernel-stack backtrace printout as an 
> > option, which prints entries 'above' the current RSP.
> > 
> > I've Cc:-ed Frederic, maybe he has interest in implementing that?
> 
> Yeah that sounds interesting. I may give it a try.

Which would be visible clearly in the output, via some clear delineation 
from the 'real' portion of the stack trace - a separator line or so?

Thanks,

	Ingo
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