Messages in this thread | | | Subject | Re: Regression - locking (all from 2.6.28) | From | Dave Hansen <> | Date | Fri, 06 Mar 2009 09:26:55 -0800 |
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On Fri, 2009-03-06 at 17:18 +0000, Catalin Marinas wrote: > > > Are the pgdat->node_start_pfn and pgdat->node_spanned_pages always > > > valid? Thanks. > > > > The variables themselves? I'm sure there's a window in early boot where > > they aren't valid, but other than that they should be OK unless you're > > int the middle of a hotplug operation. > > > > See pgdat_resize_(un)lock() in include/linux/memory_hotplug.h. > > I wouldn't hold a lock for that long. It's not really critical to scan > all the page structures at a time as there are subsequent scans as well, > so some can be missed.
I think you should be more worried about consistency rather than missing entries. Take these two lines of code:
start_pfn = node->node_start_pfn; /* hotplug occurs here */ end_pfn = start_pfn + node->node_spanned_pages;
What if someone comes in and adds memory to the node, at the beginning of the node, after you have calculated start_pfn? Try to think of what value you'll get for end_pfn and whether it is consistent and was *ever* valid at all. Would that oops the kernel?
-- Dave
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