Re: Linux 2.6.20-rc7

[Andrew Morton]

On Wed, 31 Jan 2007 08:04:29 -0800 (PST)
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> 
> 
> On Wed, 31 Jan 2007, Pawe__ Sikora wrote:
> > 
> > The 2.6.20-rcX have the same nasty bug as 2.6.19.x.
> > 
> > [ an oops inside kmem_get_pages ]
> > http://bugzilla.kernel.org/show_bug.cgi?id=7889
> 
> Pabel, can you detail more exactly which kernels don't work, and which do?
> 
> >From bugzilla:
> 
>  - 2.6.18.x does work
>  - 2.6.19.2 doesn't work.
>  - what about plain 2.6.19?
>  - can you please test some of the 2.6.19-rcX kernels? Especially 
>    2.6.19-rc1 would be good to test.
> 
> Since it apparently already happens in 2.6.19 (but it would be really good 
> to know exactly when it starts), and considering _where_ it happens, I'd 
> be inclined to blame commit d2e7b7d0: "fix potential stack overflow in 
> mm/slab.c" by Suresh. 
> 
> When do_tune_cpucache() is called at bootup, I'm not sure how safe it is 
> to do the kzalloc() thing.
> 
> I've added a number of hopefully appropriate people to the Cc. Guys? 
> Apparently it only happens with MEMORY_HOTPLUG (and possibly with just an 
> SMP kernel on UP), which probably explains why it's been around without 
> people really complaining very loudly. 
> 

I discussed this with Yasunori Goto <y-goto@xxxxxxxxxxxxxx> (memory
  hot-add developer):

 "But this config uses CONFIG_MEMORY_HOTPLUG_RESERVE which is made by
  Andi Kleen-san and I don't know very well around here.  And, I couldn't
  reproduce this trouble on my box."

I cannot reproduce it with Pawel's config either.

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