[028/143] mm/khugepaged.c: replace barrier() with READ_ONCE() for a selective variable

Commit Message

Andrew Morton May 5, 2021, 1:34 a.m. UTC

From: Yanfei Xu <[e-mail]>
Subject: mm/khugepaged.c: replace barrier() with READ_ONCE() for a selective variable

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.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Yanfei Xu <[e-mail]>
Acked-by: Kirill A. Shutemov <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/khugepaged.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Patch

--- a/mm/khugepaged.c~khugepaged-raplace-barrier-with-read_once-for-a-selective-variable
+++ a/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) {