Re: [PATCH 00/12] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double()

Mark Rutland
2023-05-31T14:47:54Z

On Wed, May 31, 2023 at 03:08:33PM +0200, Peter Zijlstra wrote:
> Hi!
>
> After much breaking of things, find here the improved version.
>
> Since v3:
>
> - unbreak everything that does *NOT* have cmpxchg128()
>
> Notably this_cpu_cmpxchg_double() is used unconditionally by SLUB
> which means that this_cpu_try_cmpxchg128() needs to be unconditionally
> available on all 64bit architectures.
>
> - fixed up x86/x86_64 cmpxchg{8,16}b emulation for this_cpu_cmpxchg{64,128}()
>
> - introduce {raw,this}_cpu_try_cmpxchg*()
>
> - add fallback for !__SIZEOF_INT128__ 64bit architectures
>
> Sadly there are supported 64bit architecture/compiler combinations that do
> not have __SIZEOF_INT128__, specifically it was found that HPPA64 only added
> this with GCC-11.
>
> this is yuck, and ideally we'd simply raise compiler requirements, but this
> 'works'.

The patches look good to me, and I used my local cross-build script to build
test this with the kernel.org GCC 10.3.0 cross toolchain for all of the
following arch/triplet/config combinations:

alpha alpha-linux defconfig
arc arc-linux defconfig
arm arm-linux-gnueabi multi_v4t_defconfig
arm arm-linux-gnueabi multi_v5_defconfig
arm arm-linux-gnueabi multi_v7_defconfig
arm arm-linux-gnueabi omap1_defconfig
arm64 aarch64-linux defconfig
csky csky-linux defconfig
i386 i386-linux defconfig
ia64 ia64-linux defconfig
m68k m68k-linux defconfig
microblaze microblaze-linux defconfig
mips mips-linux 32r1_defconfig
mips mips-linux 32r2_defconfig
mips mips-linux 32r6_defconfig
mips mips64-linux 64r1_defconfig
mips mips64-linux 64r2_defconfig
mips mips64-linux 64r6_defconfig
nios2 nios2-linux defconfig
openrisc or1k-linux defconfig
parisc hppa-linux generic-32bit_defconfig
parisc hppa64-linux generic-64bit_defconfig
powerpc powerpc-linux ppc40x_defconfig
powerpc powerpc64-linux ppc64_defconfig
powerpc powerpc64-linux ppc64e_defconfig
riscv riscv32-linux rv32_defconfig
riscv riscv64-linux defconfig
s390 s390-linux defconfig
sh sh4-linux defconfig
sparc sparc-linux sparc32_defconfig
sparc sparc64-linux sparc64_defconfig
x86_64 x86_64-linux defconfig
xtensa xtensa-linux defconfig

... and everything seemed happy.

I've also boot-tested arm64 defconfig.

So FWIW, for the series:

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>

> My plan is to re-add this to tip/locking/core and thus -next later this week.

I'll need to rebase my kerneldoc series atop this, so getting this into a
stable branch soon would be great!

Thanks,
Mark.

>
> Also available at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/core
>
> ---
> Documentation/core-api/this_cpu_ops.rst | 2 -
> arch/arm64/include/asm/atomic_ll_sc.h | 56 +++---
> arch/arm64/include/asm/atomic_lse.h | 39 ++---
> arch/arm64/include/asm/cmpxchg.h | 48 ++----
> arch/arm64/include/asm/percpu.h | 30 ++--
> arch/s390/include/asm/cmpxchg.h | 32 +---
> arch/s390/include/asm/cpu_mf.h | 2 +-
> arch/s390/include/asm/percpu.h | 34 ++--
> arch/s390/kernel/perf_cpum_sf.c | 16 +-
> arch/x86/include/asm/cmpxchg.h | 25 ---
> arch/x86/include/asm/cmpxchg_32.h | 2 +-
> arch/x86/include/asm/cmpxchg_64.h | 63 ++++++-
> arch/x86/include/asm/percpu.h | 102 ++++++-----
> arch/x86/lib/Makefile | 3 +-
> arch/x86/lib/cmpxchg16b_emu.S | 43 +++--
> arch/x86/lib/cmpxchg8b_emu.S | 67 ++++++--
> drivers/iommu/amd/amd_iommu_types.h | 9 +-
> drivers/iommu/amd/iommu.c | 10 +-
> drivers/iommu/intel/irq_remapping.c | 8 +-
> include/asm-generic/percpu.h | 257 ++++++++++++++++++++++------
> include/crypto/b128ops.h | 14 +-
> include/linux/atomic/atomic-arch-fallback.h | 95 +++++++++-
> include/linux/atomic/atomic-instrumented.h | 93 ++++++++--
> include/linux/dmar.h | 125 +++++++-------
> include/linux/percpu-defs.h | 45 ++---
> include/linux/slub_def.h | 12 +-
> include/linux/types.h | 12 ++
> include/uapi/linux/types.h | 4 +
> lib/crypto/curve25519-hacl64.c | 2 -
> lib/crypto/poly1305-donna64.c | 2 -
> mm/slab.h | 53 +++++-
> mm/slub.c | 139 +++++++++------
> scripts/atomic/gen-atomic-fallback.sh | 4 +-
> scripts/atomic/gen-atomic-instrumented.sh | 19 +-
> 34 files changed, 952 insertions(+), 515 deletions(-)
>