Date: Fri, 21 Mar 2008 00:25:02 -0700 (PDT)
Message-Id: <20080321.002502.223136918.davem@davemloft.net>
To: clameter@sgi.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [11/14] vcompound: Fallbacks for order 1 stack allocations on
 IA64 and x86
From: David Miller <davem@davemloft.net>
In-Reply-To: <20080321061726.782068299@sgi.com>
References: <20080321061703.921169367@sgi.com>
	<20080321061726.782068299@sgi.com>
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From: Christoph Lameter <clameter@sgi.com>
Date: Thu, 20 Mar 2008 23:17:14 -0700

> This allows fallback for order 1 stack allocations. In the fallback
> scenario the stacks will be virtually mapped.
> 
> Signed-off-by: Christoph Lameter <clameter@sgi.com>

I would be very careful with this especially on IA64.

If the TLB miss or other low-level trap handler depends upon being
able to dereference thread info, task struct, or kernel stack stuff
without causing a fault outside of the linear PAGE_OFFSET area, this
patch will cause problems.

It will be difficult to debug the kinds of crashes this will cause
too.
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