Messages in this thread | | | Date | Wed, 13 Dec 2006 15:17:17 -0800 | From | Mike Kravetz <> | Subject | Re: Bug: early_pfn_in_nid() called when not early |
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On Wed, Dec 13, 2006 at 07:20:57PM +0100, Arnd Bergmann wrote: > After a lot of debugging in spufs, I found that a crash that we encountered > on Cell actually was caused by a change in the memory management. > > The patch that caused it is archived in http://lkml.org/lkml/2006/11/1/43, > and this one has been discussed back and forth, but I fear that the current > version may be broken for all setups that do memory hotplug with sparsemen > and NUMA, at least on powerpc.
I believe you are correct. At least the memory hotplug code for powerpc is currently broken (caused crash!).
> - both early_pfn_{in,to}_nid and early_node_map are in the __init > section and may already have been freed at the time we are calling > memmap_init_zone().
Well that is the root of the problem for powerpc. I believe that __meminit attribute on memmap_init_zone() has no definition if CONFIG_MEMORY_HOTPLUG is defined. This is so that it can be called after boot. But, this also implies that memmap_init_zone() can not call any routines in the __init section.
> The patch below is not a suggested fix that I want to get into mainline > (checking slab_is_available is the wrong here), but it is a quick fix > that you should apply if you want to run a recent (post-2.6.18) kernel > on the IBM QS20 blade. I'm sorry for not having reported this earlier, > but we were always trying to find the problem in my own code...
Thanks for the debug work! Just curious if you really need CONFIG_NODES_SPAN_OTHER_NODES defined for your platform? Can you get those types of memory layouts? If not, an easy/immediate fix for you might be to simply turn off the option.
> --- linux-2.6.orig/mm/page_alloc.c > +++ linux-2.6/mm/page_alloc.c > @@ -1962,7 +1962,8 @@ void __meminit memmap_init_zone(unsigned > for (pfn = start_pfn; pfn < end_pfn; pfn++) { > if (!early_pfn_valid(pfn)) > continue; > - if (!early_pfn_in_nid(pfn, nid)) > + if (!slab_is_available() && > + !early_pfn_in_nid(pfn, nid)) > continue; > page = pfn_to_page(pfn); > set_page_links(page, zone, nid, pfn);
I know you don't recommend this as a fix, but it has the interesting quality of doing exactly what we want for powerpc. When slab_is_available() we are performing a 'memory add' operation and there is no need to do the 'pfn_in_nid' check. We know that the range of added pages will all be on the same (passed) nid.
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