Messages in this thread | | | Date | Tue, 27 Dec 2011 15:43:52 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page |
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On Fri, 23 Dec 2011 21:35:25 +0800 Hillf Danton <dhillf@gmail.com> wrote:
> From: Hillf Danton <dhillf@gmail.com> > Subject: [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page > > If huge page is enqueued under the protection of hugetlb_lock, then > the operation is atomic and safe. > > Cc: Michal Hocko <mhocko@suse.cz> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Signed-off-by: Hillf Danton <dhillf@gmail.com> > --- > > --- a/mm/hugetlb.c Tue Dec 20 21:26:30 2011 > +++ b/mm/hugetlb.c Fri Dec 23 21:16:28 2011 > @@ -901,7 +901,6 @@ retry: > h->resv_huge_pages += delta; > ret = 0; > > - spin_unlock(&hugetlb_lock); > /* Free the needed pages to the hugetlb pool */ > list_for_each_entry_safe(page, tmp, &surplus_list, lru) { > if ((--needed) < 0) > @@ -915,6 +914,7 @@ retry: > VM_BUG_ON(page_count(page)); > enqueue_huge_page(h, page); > } > + spin_unlock(&hugetlb_lock); > > /* Free unnecessary surplus pages to the buddy allocator */
btw,
/* Free the needed pages to the hugetlb pool */ list_for_each_entry_safe(page, tmp, &surplus_list, lru) { if ((--needed) < 0) break; list_del(&page->lru); /* * This page is now managed by the hugetlb allocator and has * no users -- drop the buddy allocator's reference. */ put_page_testzero(page); VM_BUG_ON(page_count(page)); enqueue_huge_page(h, page); } spin_unlock(&hugetlb_lock);
That VM_BUG_ON() largely duplicates the one in put_page_testzero().
(Putting a VM_BUG_ON() in put_page_testzero() was pretty expensive, too. I wonder how many people are enabling VM_BUG_ON()? We should be sparing in using these things)
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