linux-kernel - Re: [PATCH] [5/8] Fix logic error in 64bit memory hotadd

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Date:	Mon, 11 Feb 2008 14:33:33 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <ak@...e.de>
Cc:	tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [5/8] Fix logic error in 64bit memory hotadd


* Andi Kleen <ak@...e.de> wrote:

> > Also, your fix, while it solves a real bug we want to fix, is not quite 
> > right for upstream integration yet. I can see 3 immediate problems with 
> > it:
> > 
> > > +			if (!pud_present(*pud)) {
> > > +				pud = (pud_t *)get_zeroed_page(GFP_ATOMIC);
> > 
> > the GFP_ATOMIC here can fail.
> 
> The memory hotplug code already uses GFP_ATOMIC elsewhere 
> (spp_getpage)

wrong. The _x86_ memory hotplug code uses GFP_ATOMIC elsewhere.
The generic memory hotplug code does not.

and the x86 memory hotplug code uses GFP_ATOMIC and panic() elsewhere 
because:

> The existing code already panics elsewhere (spp_getpage); i just 
> copied that.

and you had nothing to do with that "existing code"? git-log reveals 
that the GFP_ATOMIC and panic()-ing patch was added 2 years ago and was 
signed off by you:

  commit 44df75e629106efcada087cead6c3f33ed6bcc60
  Author: Matt Tolentino <metolent@...vt.edu>
  Date:   Tue Jan 17 07:03:41 2006 +0100

    [PATCH] x86_64: add x86-64 support for memory hot-add

  [...]
  Signed-off-by: Andi Kleen <ak@...e.de>

We (like most upstream kernel subsystems) generally do not accept 
patches into arch/x86 that spreads a buggy implementation detail 
further. Please submit a patch that cleans up the mess. Thanks,

	Ingo
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