+ memtest-use-readwrite_once-in-memory-scanning.patch added to mm-unstable branch

+ memtest-use-readwrite_once-in-memory-scanning.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: memtest: use {READ,WRITE}_ONCE in memory scanning
has been added to the -mm mm-unstable branch.  Its filename is
     memtest-use-readwrite_once-in-memory-scanning.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memtest-use-readwrite_once-in-memory-scanning.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Qiang Zhang <qiang4.zhang@intel.com>
Subject: memtest: use {READ,WRITE}_ONCE in memory scanning
Date: Tue, 12 Mar 2024 16:04:23 +0800

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

Link: https://lkml.kernel.org/r/20240312080422.691222-1-qiang4.zhang@intel.com
Signed-off-by: Qiang Zhang <qiang4.zhang@intel.com>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memtest.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/memtest.c~memtest-use-readwrite_once-in-memory-scanning
+++ a/mm/memtest.c
@@ -51,10 +51,10 @@ static void __init memtest(u64 pattern,
 	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;
_

Patches currently in -mm which might be from qiang4.zhang@intel.com are

memtest-use-readwrite_once-in-memory-scanning.patch