From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: start_kernel(): bug: interrupts were enabled early
Date: Wed, 31 Mar 2010 15:49:55 -0700
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To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Christoph Lameter <cl@linux-foundation.org>, Matthew Wilcox <matthew@wil.cx>, Yinghai Lu <yinghai@kernel.org>, Rabin Vincent <rabin@rab.in>, lkml <linux-kernel@vger.kernel.org>, penberg@cs.helsinki.fi, linux-arch@vger.kernel.org

On Thu, 01 Apr 2010 09:37:51 +1100
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> On Wed, 2010-03-31 at 14:57 -0700, H. Peter Anvin wrote:
> > 
> > The question still remains what the incremental cost is of doing
> > irqsave/irqrestore. 
> 
> The only other option is to have local_irq_enable() check a global
> (system_state ?) before enabling. Almost as gross ...
> 

Add an irq-disable-depth counter to the task_struct, fix all the bugs
which that exposes..

But these things are all utterly gross.  The bottom line is that
radix_tree_init() is manifestly unsuited to being called with local
interrupts disabled.  773e3eb7b81e5ba13b5155dfb3bb75b8ce37f8f9 was just
a wrong patch.