* Re: [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page
2011-12-23 13:35 [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page Hillf Danton
@ 2011-12-26 7:24 ` KAMEZAWA Hiroyuki
2011-12-27 12:48 ` Michal Hocko
2011-12-27 23:43 ` Andrew Morton
2 siblings, 0 replies; 4+ messages in thread
From: KAMEZAWA Hiroyuki @ 2011-12-26 7:24 UTC (permalink / raw)
To: Hillf Danton; +Cc: linux-mm, LKML, Andrew Morton, Michal Hocko, stable
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>
Hmm, at reporting this kind of bug...it's better to show when it's broken.
Maybe this commit a9869b837c098732bad84939015c0eb391b23e41
and it's better to cc stable.
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.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 */
> free:
> --
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page
2011-12-23 13:35 [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page Hillf Danton
2011-12-26 7:24 ` KAMEZAWA Hiroyuki
@ 2011-12-27 12:48 ` Michal Hocko
2011-12-27 23:43 ` Andrew Morton
2 siblings, 0 replies; 4+ messages in thread
From: Michal Hocko @ 2011-12-27 12:48 UTC (permalink / raw)
To: Hillf Danton; +Cc: linux-mm, LKML, Andrew Morton, KAMEZAWA Hiroyuki
On Fri 23-12-11 21:35:25, Hillf Danton 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>
Yes, looks correct even though the changelog could be more verbose.
The code is broken since .37
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Thanks
> ---
>
> --- 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 */
> free:
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page
2011-12-23 13:35 [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page Hillf Danton
2011-12-26 7:24 ` KAMEZAWA Hiroyuki
2011-12-27 12:48 ` Michal Hocko
@ 2011-12-27 23:43 ` Andrew Morton
2 siblings, 0 replies; 4+ messages in thread
From: Andrew Morton @ 2011-12-27 23:43 UTC (permalink / raw)
To: Hillf Danton; +Cc: linux-mm, LKML, Michal Hocko, KAMEZAWA Hiroyuki
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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^ permalink raw reply [flat|nested] 4+ messages in thread