Messages in this thread | | | Date | Fri, 21 Jun 2013 20:42:49 +0900 | From | Satoru Takeuchi <> | Subject | Re: [ 29/48] mm: migration: add migrate_entry_wait_huge() |
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At Thu, 20 Jun 2013 10:02:13 -0700, Greg Kroah-Hartman wrote: > > On Thu, Jun 20, 2013 at 06:52:43PM +0900, Satoru Takeuchi wrote: > > Hi Naoya, > > > > At Tue, 18 Jun 2013 09:17:55 -0700, > > Greg Kroah-Hartman wrote: > > > > > > From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > > > > 3.9-stable review patch. If anyone has any objections, please let me know. > > > > > > ------------------ > > > > > > From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > > > > > > commit 30dad30922ccc733cfdbfe232090cf674dc374dc upstream. > > > > > > When we have a page fault for the address which is backed by a hugepage > > > under migration, the kernel can't wait correctly and do busy looping on > > > hugepage fault until the migration finishes. As a result, users who try > > > to kick hugepage migration (via soft offlining, for example) occasionally > > > experience long delay or soft lockup. > > > > > > This is because pte_offset_map_lock() can't get a correct migration entry > > > or a correct page table lock for hugepage. This patch introduces > > > migration_entry_wait_huge() to solve this. > > > > I suspect that this code doesn't work correctly on i686 box with CONFIG_HIGHPTE. > > If we call hugetlb_fault() -> migration_entry_wait_huge() -> __migration_entry_wait(), > > this function tries to kunmap pte, in this case pte is not-kmapped pmd, via pte_unmap_unlock(). > > If CONFIG_DEBUG_HIGHMEM is also enabled, it results in BUG_ON() at __kunmap_atomic(). > > Have you tried this?
Not yet. I'm now preparing the kernel to reproduce this problem.
> > Also, the same issue is still in 3.10-rc6, right?
Yes.
Thanks, Satoru
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