linux-kernel - [PATCH] memtest: use {READ,WRITE}

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Date: Tue, 12 Mar 2024 16:04:23 +0800
From: Qiang Zhang <qiang4.zhang@...el.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev,
	Qiang Zhang <qiang4.zhang@...el.com>,
	Stable@...r.kernel.org
Subject: [PATCH] memtest: use {READ,WRITE}_ONCE in memory scanning

memtest failed to find bad memory when compiled with clang. So use
{WRITE,READ}_ONCE  to access memory to avoid compiler over optimization.

Cc: <Stable@...r.kernel.org>
Signed-off-by: Qiang Zhang <qiang4.zhang@...el.com>
---
 mm/memtest.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memtest.c b/mm/memtest.c
index 32f3e9dda837..c2c609c39119 100644
--- a/mm/memtest.c
+++ b/mm/memtest.c
@@ -51,10 +51,10 @@ static void __init memtest(u64 pattern, phys_addr_t start_phys, phys_addr_t size
 	last_bad = 0;
 
 	for (p = start; p < end; p++)
-		*p = pattern;
+		WRITE_ONCE(*p, pattern);
 
 	for (p = start; p < end; p++, start_phys_aligned += incr) {
-		if (*p == pattern)
+		if (READ_ONCE(*p) == pattern)
 			continue;
 		if (start_phys_aligned == last_bad + incr) {
 			last_bad += incr;
-- 
2.39.2