mirror-linux/include
Finn Thain e428b013d9 atomic: specify alignment for atomic_t and atomic64_t
Some recent commits incorrectly assumed 4-byte alignment of locks.  That
assumption fails on Linux/m68k (and, interestingly, would have failed on
Linux/cris also).  The jump label implementation makes a similar alignment
assumption.

The expectation that atomic_t and atomic64_t variables will be naturally
aligned seems reasonable, as indeed they are on 64-bit architectures.  But
atomic64_t isn't naturally aligned on csky, m68k, microblaze, nios2,
openrisc and sh.  Neither atomic_t nor atomic64_t are naturally aligned on
m68k.

This patch brings a little uniformity by specifying natural alignment for
atomic types.  One benefit is that atomic64_t variables do not get split
across a page boundary.  The cost is that some structs grow which leads to
cache misses and wasted memory.

See also, commit bbf2a330d9 ("x86: atomic64: The atomic64_t data type
should be 8 bytes aligned on 32-bit too").

Link: https://lkml.kernel.org/r/a76bc24a4e7c1d8112d7d5fa8d14e4b694a0e90c.1768281748.git.fthain@linux-m68k.org
Link: https://lore.kernel.org/lkml/CAFr9PX=MYUDGJS2kAvPMkkfvH+0-SwQB_kxE4ea0J_wZ_pk=7w@mail.gmail.com
Link: https://lore.kernel.org/lkml/CAMuHMdW7Ab13DdGs2acMQcix5ObJK0O2dG_Fxzr8_g58Rc1_0g@mail.gmail.com/
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Acked-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Cc: Guo Ren <guoren@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
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: Eduard Zingerman <eddyz87@gmail.com>
Cc: Gary Guo <gary@garyguo.net>
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: 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: Sasha Levin (Microsoft) <sashal@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Stanislav Fomichev <sdf@fomichev.me>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-01-26 19:07:14 -08:00
..
acpi ACPI: PCI: IRQ: Fix INTx GSIs signedness 2026-01-05 19:06:40 +01:00
asm-generic atomic: specify alignment for atomic_t and atomic64_t 2026-01-26 19:07:14 -08:00
clocksource
crypto
cxl
drm drm-misc-fixes for v6.19-rc6: 2026-01-16 20:27:21 +01:00
dt-bindings This pull request is entirely SoC clk drivers, not for lack of trying to modify 2025-12-08 09:38:52 +09:00
hyperv hyperv: Avoid -Wflex-array-member-not-at-end warning 2025-12-18 19:42:01 +00:00
keys
kunit kunit: Enforce task execution in {soft,hard}irq contexts 2025-12-22 12:20:08 -08:00
kvm
linux atomic: specify alignment for atomic_t and atomic64_t 2026-01-26 19:07:14 -08:00
math-emu
media
memory
misc
net net: add net.core.qdisc_max_burst 2026-01-13 10:12:11 +01:00
pcmcia
ras Significant patch series in this merge are as follows: 2025-12-05 13:52:43 -08:00
rdma
rv
scsi scsi: core: Fix error handler encryption support 2026-01-04 15:16:20 -05:00
soc This pull request is entirely SoC clk drivers, not for lack of trying to modify 2025-12-08 09:38:52 +09:00
sound ALSA: pcm: Improve the fix for race of buffer access at PCM OSS layer 2026-01-08 08:07:54 +01:00
target
trace nfsd-6.19 fixes: 2026-01-06 09:12:52 -08:00
uapi ipc/shm: uapi: remove dependency on libc 2026-01-26 19:07:10 -08:00
ufs
vdso
video
xen
Kbuild