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Date: Fri, 5 Jul 2013 08:51:13 +0200
From: Ingo Molnar <mingo@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>,
        =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Dave Jones <davej@redhat.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: scheduling while atomic & hang.
Message-ID: <20130705065113.GA6588@gmail.com>
References: <20130704015525.GA8486@redhat.com>
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* H. Peter Anvin <hpa@zytor.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?

Thanks,

	Ingo