+ atomic-add-option-for-weaker-alignment-check.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: atomic: add option for weaker alignment check
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     atomic-add-option-for-weaker-alignment-check.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/atomic-add-option-for-weaker-alignment-check.patch

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

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------------------------------------------------------
From: Finn Thain <fthain@linux-m68k.org>
Subject: atomic: add option for weaker alignment check
Date: Tue, 13 Jan 2026 16:22:28 +1100

Add a new Kconfig symbol to make CONFIG_DEBUG_ATOMIC more useful on those
architectures which do not align dynamic allocations to 8-byte boundaries.
Without this, CONFIG_DEBUG_ATOMIC produces excessive WARN splats.

Link: https://lkml.kernel.org/r/6d25a12934fe9199332f4d65d17c17de450139a8.1768281748.git.fthain@linux-m68k.org
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Daniel Borkman <daniel@iogearbox.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Gary Guo <gary@garyguo.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Hao Luo <haoluo@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Sasha Levin (Microsoft) <sashal@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Stanislav Fomichev <sdf@fomichev.me>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/instrumented.h |    8 +++++++-
 lib/Kconfig.debug            |    8 ++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

--- a/include/linux/instrumented.h~atomic-add-option-for-weaker-alignment-check
+++ a/include/linux/instrumented.h
@@ -59,7 +59,13 @@ static __always_inline void instrument_r
 static __always_inline void instrument_atomic_check_alignment(const volatile void *v, size_t size)
 {
 #ifndef __DISABLE_EXPORTS
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_DEBUG_ATOMIC) && ((unsigned long)v & (size - 1)));
+	if (IS_ENABLED(CONFIG_DEBUG_ATOMIC)) {
+		unsigned int mask = size - 1;
+
+		if (IS_ENABLED(CONFIG_DEBUG_ATOMIC_LARGEST_ALIGN))
+			mask &= sizeof(struct { long x; } __aligned_largest) - 1;
+		WARN_ON_ONCE((unsigned long)v & mask);
+	}
 #endif
 }
 
--- a/lib/Kconfig.debug~atomic-add-option-for-weaker-alignment-check
+++ a/lib/Kconfig.debug
@@ -1370,6 +1370,14 @@ config DEBUG_ATOMIC
 
 	  This option has potentially significant overhead.
 
+config DEBUG_ATOMIC_LARGEST_ALIGN
+	bool "Check alignment only up to __aligned_largest"
+	depends on DEBUG_ATOMIC
+	help
+	  If you say Y here then the check for natural alignment of
+	  atomic accesses will be constrained to the compiler's largest
+	  alignment for scalar types.
+
 menu "Lock Debugging (spinlocks, mutexes, etc...)"
 
 config LOCK_DEBUGGING_SUPPORT
_

Patches currently in -mm which might be from fthain@linux-m68k.org are

bpf-explicitly-align-bpf_res_spin_lock.patch
atomic-specify-alignment-for-atomic_t-and-atomic64_t.patch
atomic-add-option-for-weaker-alignment-check.patch