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Date: Tue, 6 Dec 2016 09:53:14 +0800 From: Xishi Qiu <qiuxishi@...wei.com> To: Andrew Morton <akpm@...ux-foundation.org>, Mel Gorman <mgorman@...hsingularity.net>, Yaowei Bai <baiyaowei@...s.chinamobile.com>, Christian Borntraeger <borntraeger@...ibm.com> CC: Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Yisheng Xie <xieyisheng1@...wei.com> Subject: [RFC PATCH v3] mm: use READ_ONCE in page_cpupid_xchg_last() 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@...wei.com> Suggested-by: Christian Borntraeger <borntraeger@...ibm.com> --- 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); -- 1.8.3.1
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