[PATCH] khugepaged: Raplace barrier() with READ_ONCE() for a selective variable

[PATCH] khugepaged: Raplace barrier() with READ_ONCE() for a selective variable

[yanfei.xu]

From: Yanfei Xu <yanfei.xu@windriver.com>

READ_ONCE() is more selective and lightweight. It is more appropriate that
using a READ_ONCE() for the certain variable to prevent the compiler from
reordering.

Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
---
 mm/khugepaged.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index b81521dfbb1a..034d05a26cb0 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2202,11 +2202,9 @@ static void khugepaged_do_scan(void)
 {
 	struct page *hpage = NULL;
 	unsigned int progress = 0, pass_through_head = 0;
-	unsigned int pages = khugepaged_pages_to_scan;
+	unsigned int pages = READ_ONCE(khugepaged_pages_to_scan);
 	bool wait = true;
 
-	barrier(); /* write khugepaged_pages_to_scan to local stack */
-
 	lru_add_drain_all();
 
 	while (progress < pages) {
-- 
2.27.0

Re: [PATCH] khugepaged: Raplace barrier() with READ_ONCE() for a selective variable

[Kirill A. Shutemov]

On Tue, Mar 23, 2021 at 05:27:30PM +0800, yanfei.xu@windriver.com wrote:
> From: Yanfei Xu <yanfei.xu@windriver.com>
> 
> READ_ONCE() is more selective and lightweight. It is more appropriate that
> using a READ_ONCE() for the certain variable to prevent the compiler from
> reordering.
> 
> Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
 Kirill A. Shutemov