linux-kernel - [RFC v4 0/5] Align atomic storage

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Message-ID: <cover.1760999284.git.fthain@linux-m68k.org>
Date: Tue, 21 Oct 2025 09:28:04 +1100
From: Finn Thain <fthain@...ux-m68k.org>
To: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
    Helge Deller <deller@....de>,
    Peter Zijlstra <peterz@...radead.org>,
    Will Deacon <will@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
    Andrii Nakryiko <andrii@...nel.org>,
    Arnd Bergmann <arnd@...db.de>,
    Alexei Starovoitov <ast@...nel.org>,
    Boqun Feng <boqun.feng@...il.com>,
    bpf@...r.kernel.org,
    Daniel Borkmann <daniel@...earbox.net>,
    Geert Uytterhoeven <geert@...ux-m68k.org>,
    linux-arch@...r.kernel.org,
    linux-kernel@...r.kernel.org,
    linux-m68k@...r.kernel.org,
    linux-parisc@...r.kernel.org,
    Mark Rutland <mark.rutland@....com>
Subject: [RFC v4 0/5] Align atomic storage

This series adds the __aligned attribute to atomic_t and atomic64_t
definitions in include/asm-generic.

It also adds Kconfig options to enable a new runtime warning to help
reveal misaligned atomic accesses on platforms which don't trap that.

This patch series is a Request For Comments because the alignment
change is a time/space tradeoff. Its costs and benefits are expected
to vary across platforms and workloads. More measurements are needed.

---

Changed since v3:
 - Rebased on v6.17.
 - New patch to resolve header dependency issue on parisc.
 - Dropped documentation patch.

Changed since v2:
 - Specify natural alignment for atomic64_t.
 - CONFIG_DEBUG_ATOMIC checks for natural alignment again.
 - New patch to add weakened alignment check.
 - New patch for explicit alignment in BPF header.

---

Finn Thain (4):
  bpf: Explicitly align bpf_res_spin_lock
  parisc: Drop linux/kernel.h include from asm/bug.h header
  atomic: Specify alignment for atomic_t and atomic64_t
  atomic: Add option for weaker alignment check

Peter Zijlstra (1):
  atomic: Add alignment check to instrumented atomic operations

 arch/parisc/include/asm/bug.h    |  2 --
 include/asm-generic/atomic64.h   |  2 +-
 include/asm-generic/rqspinlock.h |  2 +-
 include/linux/instrumented.h     | 15 +++++++++++++++
 include/linux/types.h            |  2 +-
 kernel/bpf/rqspinlock.c          |  1 -
 lib/Kconfig.debug                | 18 ++++++++++++++++++
 7 files changed, 36 insertions(+), 6 deletions(-)

-- 
2.49.1