On Tue, Mar 12, 2024 at 04:04:23PM +0800, Qiang Zhang wrote:
memtest failed to find bad memory when compiled with clang. So use {WRITE,READ}_ONCE to access memory to avoid compiler over optimization.
This commit message is severely lacking in details in my opinion, especially for a patch marked for stable. Did a kernel or LLVM change cause this (i.e., has this always been an issue or is it a recent regression)? What is the transformation that LLVM does to break the test and why is using READ_ONCE() or WRITE_ONCE() sufficient to resolve it?
Cc: Stable@vger.kernel.org Signed-off-by: Qiang Zhang qiang4.zhang@intel.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;-- 2.39.2