linux-toradex.git/include/asm-generic/atomic64.h, branch v7.0-rc5

atomic: specify alignment for atomic_t and atomic64_t

2026-01-27T03:07:14+00:00

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 bbf2a330d92c ("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 
Acked-by: Guo Ren 
Reviewed-by: Arnd Bergmann 
Cc: Guo Ren 
Cc: Geert Uytterhoeven 
Cc: Dinh Nguyen 
Cc: Jonas Bonn 
Cc: Stefan Kristiansson 
Cc: Stafford Horne 
Cc: Yoshinori Sato 
Cc: Rich Felker 
Cc: John Paul Adrian Glaubitz 
Cc: Alexei Starovoitov 
Cc: Andrii Nakryiko 
Cc: Ard Biesheuvel 
Cc: Boqun Feng 
Cc: "Borislav Petkov (AMD)" 
Cc: Daniel Borkman 
Cc: Dave Hansen 
Cc: Eduard Zingerman 
Cc: Gary Guo 
Cc: Hao Luo 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Jiri Olsa 
Cc: John Fastabend 
Cc: KP Singh 
Cc: Marc Rutland 
Cc: Martin KaFai Lau 
Cc: Peter Zijlstra 
Cc: Sasha Levin (Microsoft) 
Cc: Song Liu 
Cc: Stanislav Fomichev 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Cc: Yonghong Song 
Signed-off-by: Andrew Morton

locking/atomic: delete !ARCH_ATOMIC remnants

2021-05-26T11:20:52+00:00

Now that all architectures implement ARCH_ATOMIC, we can make it
mandatory, removing the Kconfig symbol and logic for !ARCH_ATOMIC.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland 
Acked-by: Geert Uytterhoeven 
Cc: Boqun Feng 
Cc: Peter Zijlstra 
Cc: Will Deacon 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20210525140232.53872-33-mark.rutland@arm.com

locking/atomic: atomic64: support ARCH_ATOMIC

2021-05-26T11:20:50+00:00

We'd like all architectures to convert to ARCH_ATOMIC, as this will
enable functionality, and once all architectures are converted it will
be possible to make significant cleanups to the atomic headers.

A number of architectures use asm-generic/atomic64.h, and it's
impractical to convert the header and all these architectures in one go.
To make it possible to convert them one-by-one, let's make the
asm-generic implementation function as either atomic64_*() or
arch_atomic64_*() depending on whether ARCH_ATOMIC is selected. To do
this, the generic implementations are prefixed as generic_atomic64_*(),
and preprocessor definitions map atomic64_*()/arch_atomic64_*() onto
these as appropriate.

Once all users are moved over to ARCH_ATOMIC the ifdeffery in the header
can be simplified and/or removed entirely.

For existing users (none of which select ARCH_ATOMIC), there should be
no functional change as a result of this patch.

Signed-off-by: Mark Rutland 
Cc: Arnd Bergmann 
Cc: Boqun Feng 
Cc: Peter Zijlstra 
Cc: Will Deacon 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20210525140232.53872-11-mark.rutland@arm.com

locking/atomic: Use s64 for atomic64

2019-06-03T10:32:56+00:00

As a step towards making the atomic64 API use consistent types treewide,
let's have the generic atomic64 implementation use s64 as the underlying
type for atomic64_t, rather than long long, matching the generated
headers.

Otherwise, there should be no functional change as a result of this
patch.

Signed-off-by: Mark Rutland 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Arnd Bergmann 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Cc: aou@eecs.berkeley.edu
Cc: bp@alien8.de
Cc: catalin.marinas@arm.com
Cc: davem@davemloft.net
Cc: fenghua.yu@intel.com
Cc: heiko.carstens@de.ibm.com
Cc: herbert@gondor.apana.org.au
Cc: ink@jurassic.park.msu.ru
Cc: jhogan@kernel.org
Cc: linux@armlinux.org.uk
Cc: mattst88@gmail.com
Cc: mpe@ellerman.id.au
Cc: palmer@sifive.com
Cc: paul.burton@mips.com
Cc: paulus@samba.org
Cc: ralf@linux-mips.org
Cc: rth@twiddle.net
Cc: tony.luck@intel.com
Cc: vgupta@synopsys.com
Link: https://lkml.kernel.org/r/20190522132250.26499-4-mark.rutland@arm.com
Signed-off-by: Ingo Molnar

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

2019-05-30T18:26:32+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Allison Randal 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman

atomics/treewide: Make conditional inc/dec ops optional

2018-06-21T12:25:24+00:00

The conditional inc/dec ops differ for atomic_t and atomic64_t:

- atomic_inc_unless_positive() is optional for atomic_t, and doesn't exist for atomic64_t.
- atomic_dec_unless_negative() is optional for atomic_t, and doesn't exist for atomic64_t.
- atomic_dec_if_positive is optional for atomic_t, and is mandatory for atomic64_t.

Let's make these consistently optional for both. At the same time, let's
clean up the existing fallbacks to use atomic_try_cmpxchg().

The instrumented atomics are updated accordingly.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Acked-by: Peter Zijlstra (Intel) 
Cc: Boqun Feng 
Cc: Linus Torvalds 
Cc: Thomas Gleixner 
Link: https://lore.kernel.org/lkml/20180621121321.4761-18-mark.rutland@arm.com
Signed-off-by: Ingo Molnar

atomics/treewide: Make unconditional inc/dec ops optional

2018-06-21T12:25:24+00:00

Many of the inc/dec ops are mandatory, but for most architectures inc/dec are
simply trivial wrappers around their corresponding add/sub ops.

Let's make all the inc/dec ops optional, so that we can get rid of these
boilerplate wrappers.

The instrumented atomics are updated accordingly.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Acked-by: Peter Zijlstra (Intel) 
Acked-by: Palmer Dabbelt 
Cc: Boqun Feng 
Cc: Linus Torvalds 
Cc: Thomas Gleixner 
Link: https://lore.kernel.org/lkml/20180621121321.4761-17-mark.rutland@arm.com
Signed-off-by: Ingo Molnar

atomics/treewide: Make test ops optional

2018-06-21T12:25:24+00:00

Some of the atomics return the result of a test applied after the atomic
operation, and almost all architectures implement these as trivial
wrappers around the underlying atomic. Specifically:

 * _inc_and_test(v)    is (_inc_return(v)    == 0)
 * _dec_and_test(v)    is (_dec_return(v)    == 0)
 * _sub_and_test(i, v) is (_sub_return(i, v) == 0)
 * _add_negative(i, v) is (_add_return(i, v)  < 0)

Rather than have these definitions duplicated in all architectures, with
minor inconsistencies in formatting and documentation, let's make these
operations optional, with default fallbacks as above. Implementations
must now provide a preprocessor symbol.

The instrumented atomics are updated accordingly.

Both x86 and m68k have custom implementations, which are left as-is,
given preprocessor symbols to avoid being overridden.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Acked-by: Geert Uytterhoeven 
Acked-by: Peter Zijlstra (Intel) 
Acked-by: Palmer Dabbelt 
Cc: Boqun Feng 
Cc: Linus Torvalds 
Cc: Thomas Gleixner 
Link: https://lore.kernel.org/lkml/20180621121321.4761-16-mark.rutland@arm.com
Signed-off-by: Ingo Molnar

atomics/generic: Define atomic64_fetch_add_unless()

2018-06-21T12:25:21+00:00

As a step towards unifying the atomic/atomic64/atomic_long APIs, this
patch converts the generic implementation of atomic64_add_unless() into
a generic implementation of atomic64_fetch_add_unless().

A wrapper in  will build atomic_add_unless() atop of
this, provided it is given a preprocessor definition.

No functional change is intended as a result of this patch.

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Acked-by: Peter Zijlstra (Intel) 
Cc: Arnd Bergmann 
Cc: Boqun Feng 
Cc: Linus Torvalds 
Cc: Thomas Gleixner 
Link: https://lore.kernel.org/lkml/20180621121321.4761-9-mark.rutland@arm.com
Signed-off-by: Ingo Molnar

atomics/treewide: Make atomic64_inc_not_zero() optional

2018-06-21T12:22:33+00:00

We define a trivial fallback for atomic_inc_not_zero(), but don't do
the same for atomic64_inc_not_zero(), leading most architectures to
define the same boilerplate.

Let's add a fallback in , and remove the redundant
implementations. Note that atomic64_add_unless() is always defined in
, and promotes its arguments to the requisite types, so
we need not do this explicitly.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Acked-by: Peter Zijlstra (Intel) 
Acked-by: Palmer Dabbelt 
Cc: Boqun Feng 
Cc: Linus Torvalds 
Cc: Thomas Gleixner 
Link: https://lore.kernel.org/lkml/20180621121321.4761-6-mark.rutland@arm.com
Signed-off-by: Ingo Molnar