Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1537607
| From | Vlastimil Babka <vbabka@suse.cz> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() |
| Date | 2016-12-07 09:40 +0100 |
| Message-ID | <sLFVD-68d-19@gated-at.bofh.it> (permalink) |
| References | <sKWOR-2aU-5@gated-at.bofh.it> <sLdd0-3RU-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 12/06/2016 02:53 AM, Xishi Qiu wrote:
> A compiler could re-read "old_flags" from the memory location after reading
> and calculation "flags" and passes a newer value into the cmpxchg making
> the comparison succeed while it should actually fail.
>
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> Suggested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> mm/mmzone.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/mmzone.c b/mm/mmzone.c
> index 5652be8..e0b698e 100644
> --- a/mm/mmzone.c
> +++ b/mm/mmzone.c
> @@ -102,7 +102,7 @@ int page_cpupid_xchg_last(struct page *page, int cpupid)
> int last_cpupid;
>
> do {
> - old_flags = flags = page->flags;
> + old_flags = flags = READ_ONCE(page->flags);
> last_cpupid = page_cpupid_last(page);
>
> flags &= ~(LAST_CPUPID_MASK << LAST_CPUPID_PGSHIFT);
>
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[RFC PATCH] mm: use ACCESS_ONCE in page_cpupid_xchg_last() Xishi Qiu <qiuxishi@huawei.com> - 2016-12-05 09:30 +0100
Re: [RFC PATCH] mm: use ACCESS_ONCE in page_cpupid_xchg_last() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-12-05 09:40 +0100
Re: [RFC PATCH] mm: use ACCESS_ONCE in page_cpupid_xchg_last() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-12-05 10:00 +0100
Re: [RFC PATCH] mm: use ACCESS_ONCE in page_cpupid_xchg_last() Xishi Qiu <qiuxishi@huawei.com> - 2016-12-05 10:30 +0100
[RFC PATCH v2] mm: use ACCESS_ONCE in page_cpupid_xchg_last() Xishi Qiu <qiuxishi@huawei.com> - 2016-12-05 10:30 +0100
Re: [RFC PATCH v2] mm: use ACCESS_ONCE in page_cpupid_xchg_last() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-12-05 10:50 +0100
[RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Xishi Qiu <qiuxishi@huawei.com> - 2016-12-06 03:00 +0100
Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Vlastimil Babka <vbabka@suse.cz> - 2016-12-07 09:40 +0100
Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Michal Hocko <mhocko@kernel.org> - 2016-12-07 09:50 +0100
Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Vlastimil Babka <vbabka@suse.cz> - 2016-12-07 09:50 +0100
Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Michal Hocko <mhocko@kernel.org> - 2016-12-07 10:00 +0100
Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Vlastimil Babka <vbabka@suse.cz> - 2016-12-07 10:40 +0100
Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-12-07 10:50 +0100
Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-12-07 11:10 +0100
Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-12-07 23:20 +0100
Re: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() Michal Hocko <mhocko@kernel.org> - 2016-12-07 11:10 +0100
csiph-web