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Subject: Re: [LKML] Re: Infinite loop on boot in free_early_partial due to
 start==end on tip/master
From: Ian Campbell <Ian.Campbell@citrix.com>
To: Yinghai Lu <yinghai@kernel.org>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Tejun Heo <tj@kernel.org>,
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Date: Fri, 19 Mar 2010 21:37:26 +0000
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On Fri, 2010-03-19 at 21:17 +0000, Yinghai Lu wrote: 
> > index ef6370b..89a3205 100644
> > --- a/arch/x86/kernel/setup_percpu.c
> > +++ b/arch/x86/kernel/setup_percpu.c
> > @@ -140,7 +140,8 @@  static void __init pcpu_fc_free(void *ptr, size_t
> > size)
> >  #ifdef CONFIG_NO_BOOTMEM
> >  	u64 start = __pa(ptr);
> >  	u64 end = start + size;
> > -	free_early_partial(start, end);
> > +	if (start < end)
> > +		free_early_partial(start, end);
> 
> it seems we could remove this line

> Tejun, how this could happen? free zero range ?

I was seeing start==end although I never fully understood why. It
happened somewhere within pcpu_embed_first_chunk and/or
pcpu_build_alloc_info. My original posting (in
https://patchwork.kernel.org/patch/83756/) has some speculation.

Ian.

> 
> YH
> 
> >  #else
> >  	free_bootmem(__pa(ptr), size);
> >  #endif
> > diff --git a/kernel/early_res.c b/kernel/early_res.c
> > index 3cb2c66..f3a861b 100644
> > --- a/kernel/early_res.c
> > +++ b/kernel/early_res.c
> > @@ -333,6 +333,11 @@  void __init free_early_partial(u64 start, u64 end)
> >  	struct early_res *r;
> >  	int i;
> >  
> > +	if (WARN_ONCE(start >= end,
> > +		      "free_early_partial got wrong start/end
> > %#llx/%#llx\n",
> > +		      start, end))
> > +		return;
> > +
> >  try_next:
> >  	i = find_overlapped_early(start, end);
> >  	if (i >= max_early_res)
> >