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SubjectRe: [Patch](memory hotplug)Allocate usemap on the section with pgdat (take 2)
> > +static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
> > +{
> > + unsigned long usemap_snr, pgdat_snr;
> > + static unsigned long old_usemap_snr = NR_MEM_SECTIONS;
> > + static unsigned long old_pgdat_snr = NR_MEM_SECTIONS;
> > + struct pglist_data *pgdat = NODE_DATA(nid);
> > + int usemap_nid;
> > +
> > + usemap_snr = pfn_to_section_nr(__pa(usemap) >> PAGE_SHIFT);
> > + pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT);
> > + if (usemap_snr == pgdat_snr)
> > + return;
> > +
> > + if (old_usemap_snr == usemap_snr && old_pgdat_snr == pgdat_snr)
> > + /* skip redundant message */
> > + return;
> > +
> > + old_usemap_snr = usemap_snr;
> > + old_pgdat_snr = pgdat_snr;
>
> The pgdat and usemap sections are node specific, but this repeat message
> check is not, so if I add sections alternatly to node 0 and node 1 I
> will recieve the warning for every addition?

Yes. alloc_bootmem_section() may be failed, and usemap may be allocated on
other node. I would like to notice for its dependency case too.

>
> > +
> > + usemap_nid = sparse_early_nid(__nr_to_section(usemap_snr));
> > + if (usemap_nid != nid) {
> > + printk("node %d must be removed before remove section %ld\n",
> > + nid, usemap_snr);
> > + return;
> > + }
> > + /*
> > + * There is a dependency deadlock.
> > + * Some platforms allow un-removable section because they will just
> > + * gather other removable sections for dynamic partitioning.
> > + * Just notify un-removable section's number here.
> > + */
> > + printk(KERN_INFO "section %ld and %ld", usemap_snr, pgdat_snr);
> > + printk(" can't be hotremoved due to dependency each other.\n");
>
> This might be better worded as a circular dependancy. Also it would be
> nice to include the node perhaps:
>
> "Sections %ld and %ld (node %ld) have a circular dependancy on
> usemap and pgdat allocations"

Thanks. I'll change it.


--
Yasunori Goto




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