linux-kernel - Re: 2.6.18-rc6-mm1: GPF loop on early boot

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Message-Id: <20060910093307.a011b16f.akpm@osdl.org>
Date:	Sun, 10 Sep 2006 09:33:07 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andi Kleen <ak@...e.de>, Laurent Riffard <laurent.riffard@...e.fr>,
	Arjan van de Ven <arjan@...radead.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy@...source.com>
Subject: Re: 2.6.18-rc6-mm1: GPF loop on early boot

On Sun, 10 Sep 2006 15:26:14 +0200
Ingo Molnar <mingo@...e.hu> wrote:

> * Andi Kleen <ak@...e.de> wrote:
> 
> > > Basically, non-atomic setup of basic architecture state _is_ going to be
> > > a nightmare, lockdep or not, especially if it uses common infrastructure
> > > like 'current', spin_lock() or even something as simple as C functions.
> > > (for example the stack-footprint tracer was once hit by this weakness of
> > > the x86_64 code)
> > 
> > I disagree with that.  The nightmare is putting stuff that needs so 
> > much infrastructure into the most basic operations.
> 
> ugh, "having a working current" is "so much infrastructure" ?? Lockdep 
> uses a very low amount of infrastructure, considering its complexity: it 
> has its own allocator, uses raw spinlocks, raw irq flags ops, it 
> basically implements its own infrastructure for everything. Being able 
> to access a per-task data area (current) is a quite fundamental thing 
> for kernel code.

I must say that having an unreliable early-current is going to be quite a
pita for evermore.  Things like mcount-based tricks and
basic-block-profiling-based tricks, for example.

Is it really going to be too messy to fake up some statically-defined gdt
which points at init_task, install that before we call any C at all?
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