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Date:   Wed, 22 Mar 2023 13:20:51 +0000
From:   Mark Rutland <mark.rutland@arm.com>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linuxfoundation.org>, x86@kernel.org,
        Wangyang Guo <wangyang.guo@intel.com>,
        Arjan van De Ven <arjan@linux.intel.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
        Will Deacon <will@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        Marc Zyngier <maz@kernel.org>
Subject: Re: [patch V2 2/4] atomics: Provide atomic_add_and_negative()
 variants
Message-ID: <ZBsAs8MKbD0o5Xlm@FVFF77S0Q05N>
References: <20230307125358.772287565@linutronix.de>
 <20230307125538.877037764@linutronix.de>
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In-Reply-To: <20230307125538.877037764@linutronix.de>
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On Tue, Mar 07, 2023 at 01:57:43PM +0100, Thomas Gleixner wrote:
> atomic_add_and_negative() does not provide the relaxed/acquire/release
             ^^^^

Spurious 'and_' above.

> variants.
> 
> Provide them in preparation for a new scalable reference count algorithm.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Other than the typo, this looks reasonable to me, so FWIW:

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

Mark.

> ---
> V2: New patch
> ---
>  include/linux/atomic/atomic-arch-fallback.h |  200 +++++++++++++++++++++++++++-
>  include/linux/atomic/atomic-instrumented.h  |   68 +++++++++
>  include/linux/atomic/atomic-long.h          |   38 +++++
>  scripts/atomic/atomics.tbl                  |    2 
>  scripts/atomic/fallbacks/add_negative       |    4 
>  5 files changed, 306 insertions(+), 6 deletions(-)
> 
> --- a/include/linux/atomic/atomic-arch-fallback.h
> +++ b/include/linux/atomic/atomic-arch-fallback.h
> @@ -1208,6 +1208,13 @@ arch_atomic_inc_and_test(atomic_t *v)
>  #define arch_atomic_inc_and_test arch_atomic_inc_and_test
>  #endif
>  
> +#ifndef arch_atomic_add_negative_relaxed
> +#ifdef arch_atomic_add_negative
> +#define arch_atomic_add_negative_acquire arch_atomic_add_negative
> +#define arch_atomic_add_negative_release arch_atomic_add_negative
> +#define arch_atomic_add_negative_relaxed arch_atomic_add_negative
> +#endif /* arch_atomic_add_negative */
> +
>  #ifndef arch_atomic_add_negative
>  /**
>   * arch_atomic_add_negative - add and test if negative
> @@ -1226,6 +1233,98 @@ arch_atomic_add_negative(int i, atomic_t
>  #define arch_atomic_add_negative arch_atomic_add_negative
>  #endif
>  
> +#ifndef arch_atomic_add_negative_acquire
> +/**
> + * arch_atomic_add_negative - add and test if negative
> + * @i: integer value to add
> + * @v: pointer of type atomic_t
> + *
> + * Atomically adds @i to @v and returns true
> + * if the result is negative, or false when
> + * result is greater than or equal to zero.
> + */
> +static __always_inline bool
> +arch_atomic_add_negative_acquire(int i, atomic_t *v)
> +{
> +	return arch_atomic_add_return_acquire(i, v) < 0;
> +}
> +#define arch_atomic_add_negative_acquire arch_atomic_add_negative_acquire
> +#endif
> +
> +#ifndef arch_atomic_add_negative_release
> +/**
> + * arch_atomic_add_negative - add and test if negative
> + * @i: integer value to add
> + * @v: pointer of type atomic_t
> + *
> + * Atomically adds @i to @v and returns true
> + * if the result is negative, or false when
> + * result is greater than or equal to zero.
> + */
> +static __always_inline bool
> +arch_atomic_add_negative_release(int i, atomic_t *v)
> +{
> +	return arch_atomic_add_return_release(i, v) < 0;
> +}
> +#define arch_atomic_add_negative_release arch_atomic_add_negative_release
> +#endif
> +
> +#ifndef arch_atomic_add_negative_relaxed
> +/**
> + * arch_atomic_add_negative - add and test if negative
> + * @i: integer value to add
> + * @v: pointer of type atomic_t
> + *
> + * Atomically adds @i to @v and returns true
> + * if the result is negative, or false when
> + * result is greater than or equal to zero.
> + */
> +static __always_inline bool
> +arch_atomic_add_negative_relaxed(int i, atomic_t *v)
> +{
> +	return arch_atomic_add_return_relaxed(i, v) < 0;
> +}
> +#define arch_atomic_add_negative_relaxed arch_atomic_add_negative_relaxed
> +#endif
> +
> +#else /* arch_atomic_add_negative_relaxed */
> +
> +#ifndef arch_atomic_add_negative_acquire
> +static __always_inline bool
> +arch_atomic_add_negative_acquire(int i, atomic_t *v)
> +{
> +	bool ret = arch_atomic_add_negative_relaxed(i, v);
> +	__atomic_acquire_fence();
> +	return ret;
> +}
> +#define arch_atomic_add_negative_acquire arch_atomic_add_negative_acquire
> +#endif
> +
> +#ifndef arch_atomic_add_negative_release
> +static __always_inline bool
> +arch_atomic_add_negative_release(int i, atomic_t *v)
> +{
> +	__atomic_release_fence();
> +	return arch_atomic_add_negative_relaxed(i, v);
> +}
> +#define arch_atomic_add_negative_release arch_atomic_add_negative_release
> +#endif
> +
> +#ifndef arch_atomic_add_negative
> +static __always_inline bool
> +arch_atomic_add_negative(int i, atomic_t *v)
> +{
> +	bool ret;
> +	__atomic_pre_full_fence();
> +	ret = arch_atomic_add_negative_relaxed(i, v);
> +	__atomic_post_full_fence();
> +	return ret;
> +}
> +#define arch_atomic_add_negative arch_atomic_add_negative
> +#endif
> +
> +#endif /* arch_atomic_add_negative_relaxed */
> +
>  #ifndef arch_atomic_fetch_add_unless
>  /**
>   * arch_atomic_fetch_add_unless - add unless the number is already a given value
> @@ -2329,6 +2428,13 @@ arch_atomic64_inc_and_test(atomic64_t *v
>  #define arch_atomic64_inc_and_test arch_atomic64_inc_and_test
>  #endif
>  
> +#ifndef arch_atomic64_add_negative_relaxed
> +#ifdef arch_atomic64_add_negative
> +#define arch_atomic64_add_negative_acquire arch_atomic64_add_negative
> +#define arch_atomic64_add_negative_release arch_atomic64_add_negative
> +#define arch_atomic64_add_negative_relaxed arch_atomic64_add_negative
> +#endif /* arch_atomic64_add_negative */
> +
>  #ifndef arch_atomic64_add_negative
>  /**
>   * arch_atomic64_add_negative - add and test if negative
> @@ -2347,6 +2453,98 @@ arch_atomic64_add_negative(s64 i, atomic
>  #define arch_atomic64_add_negative arch_atomic64_add_negative
>  #endif
>  
> +#ifndef arch_atomic64_add_negative_acquire
> +/**
> + * arch_atomic64_add_negative - add and test if negative
> + * @i: integer value to add
> + * @v: pointer of type atomic64_t
> + *
> + * Atomically adds @i to @v and returns true
> + * if the result is negative, or false when
> + * result is greater than or equal to zero.
> + */
> +static __always_inline bool
> +arch_atomic64_add_negative_acquire(s64 i, atomic64_t *v)
> +{
> +	return arch_atomic64_add_return_acquire(i, v) < 0;
> +}
> +#define arch_atomic64_add_negative_acquire arch_atomic64_add_negative_acquire
> +#endif
> +
> +#ifndef arch_atomic64_add_negative_release
> +/**
> + * arch_atomic64_add_negative - add and test if negative
> + * @i: integer value to add
> + * @v: pointer of type atomic64_t
> + *
> + * Atomically adds @i to @v and returns true
> + * if the result is negative, or false when
> + * result is greater than or equal to zero.
> + */
> +static __always_inline bool
> +arch_atomic64_add_negative_release(s64 i, atomic64_t *v)
> +{
> +	return arch_atomic64_add_return_release(i, v) < 0;
> +}
> +#define arch_atomic64_add_negative_release arch_atomic64_add_negative_release
> +#endif
> +
> +#ifndef arch_atomic64_add_negative_relaxed
> +/**
> + * arch_atomic64_add_negative - add and test if negative
> + * @i: integer value to add
> + * @v: pointer of type atomic64_t
> + *
> + * Atomically adds @i to @v and returns true
> + * if the result is negative, or false when
> + * result is greater than or equal to zero.
> + */
> +static __always_inline bool
> +arch_atomic64_add_negative_relaxed(s64 i, atomic64_t *v)
> +{
> +	return arch_atomic64_add_return_relaxed(i, v) < 0;
> +}
> +#define arch_atomic64_add_negative_relaxed arch_atomic64_add_negative_relaxed
> +#endif
> +
> +#else /* arch_atomic64_add_negative_relaxed */
> +
> +#ifndef arch_atomic64_add_negative_acquire
> +static __always_inline bool
> +arch_atomic64_add_negative_acquire(s64 i, atomic64_t *v)
> +{
> +	bool ret = arch_atomic64_add_negative_relaxed(i, v);
> +	__atomic_acquire_fence();
> +	return ret;
> +}
> +#define arch_atomic64_add_negative_acquire arch_atomic64_add_negative_acquire
> +#endif
> +
> +#ifndef arch_atomic64_add_negative_release
> +static __always_inline bool
> +arch_atomic64_add_negative_release(s64 i, atomic64_t *v)
> +{
> +	__atomic_release_fence();
> +	return arch_atomic64_add_negative_relaxed(i, v);
> +}
> +#define arch_atomic64_add_negative_release arch_atomic64_add_negative_release
> +#endif
> +
> +#ifndef arch_atomic64_add_negative
> +static __always_inline bool
> +arch_atomic64_add_negative(s64 i, atomic64_t *v)
> +{
> +	bool ret;
> +	__atomic_pre_full_fence();
> +	ret = arch_atomic64_add_negative_relaxed(i, v);
> +	__atomic_post_full_fence();
> +	return ret;
> +}
> +#define arch_atomic64_add_negative arch_atomic64_add_negative
> +#endif
> +
> +#endif /* arch_atomic64_add_negative_relaxed */
> +
>  #ifndef arch_atomic64_fetch_add_unless
>  /**
>   * arch_atomic64_fetch_add_unless - add unless the number is already a given value
> @@ -2456,4 +2654,4 @@ arch_atomic64_dec_if_positive(atomic64_t
>  #endif
>  
>  #endif /* _LINUX_ATOMIC_FALLBACK_H */
> -// b5e87bdd5ede61470c29f7a7e4de781af3770f09
> +// 63bcc1a53125d4eca5e659892e10615f00f9abf8
> --- a/include/linux/atomic/atomic-instrumented.h
> +++ b/include/linux/atomic/atomic-instrumented.h
> @@ -592,6 +592,28 @@ atomic_add_negative(int i, atomic_t *v)
>  	return arch_atomic_add_negative(i, v);
>  }
>  
> +static __always_inline bool
> +atomic_add_negative_acquire(int i, atomic_t *v)
> +{
> +	instrument_atomic_read_write(v, sizeof(*v));
> +	return arch_atomic_add_negative_acquire(i, v);
> +}
> +
> +static __always_inline bool
> +atomic_add_negative_release(int i, atomic_t *v)
> +{
> +	kcsan_release();
> +	instrument_atomic_read_write(v, sizeof(*v));
> +	return arch_atomic_add_negative_release(i, v);
> +}
> +
> +static __always_inline bool
> +atomic_add_negative_relaxed(int i, atomic_t *v)
> +{
> +	instrument_atomic_read_write(v, sizeof(*v));
> +	return arch_atomic_add_negative_relaxed(i, v);
> +}
> +
>  static __always_inline int
>  atomic_fetch_add_unless(atomic_t *v, int a, int u)
>  {
> @@ -1211,6 +1233,28 @@ atomic64_add_negative(s64 i, atomic64_t
>  	return arch_atomic64_add_negative(i, v);
>  }
>  
> +static __always_inline bool
> +atomic64_add_negative_acquire(s64 i, atomic64_t *v)
> +{
> +	instrument_atomic_read_write(v, sizeof(*v));
> +	return arch_atomic64_add_negative_acquire(i, v);
> +}
> +
> +static __always_inline bool
> +atomic64_add_negative_release(s64 i, atomic64_t *v)
> +{
> +	kcsan_release();
> +	instrument_atomic_read_write(v, sizeof(*v));
> +	return arch_atomic64_add_negative_release(i, v);
> +}
> +
> +static __always_inline bool
> +atomic64_add_negative_relaxed(s64 i, atomic64_t *v)
> +{
> +	instrument_atomic_read_write(v, sizeof(*v));
> +	return arch_atomic64_add_negative_relaxed(i, v);
> +}
> +
>  static __always_inline s64
>  atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
>  {
> @@ -1830,6 +1874,28 @@ atomic_long_add_negative(long i, atomic_
>  	return arch_atomic_long_add_negative(i, v);
>  }
>  
> +static __always_inline bool
> +atomic_long_add_negative_acquire(long i, atomic_long_t *v)
> +{
> +	instrument_atomic_read_write(v, sizeof(*v));
> +	return arch_atomic_long_add_negative_acquire(i, v);
> +}
> +
> +static __always_inline bool
> +atomic_long_add_negative_release(long i, atomic_long_t *v)
> +{
> +	kcsan_release();
> +	instrument_atomic_read_write(v, sizeof(*v));
> +	return arch_atomic_long_add_negative_release(i, v);
> +}
> +
> +static __always_inline bool
> +atomic_long_add_negative_relaxed(long i, atomic_long_t *v)
> +{
> +	instrument_atomic_read_write(v, sizeof(*v));
> +	return arch_atomic_long_add_negative_relaxed(i, v);
> +}
> +
>  static __always_inline long
>  atomic_long_fetch_add_unless(atomic_long_t *v, long a, long u)
>  {
> @@ -2083,4 +2149,4 @@ atomic_long_dec_if_positive(atomic_long_
>  })
>  
>  #endif /* _LINUX_ATOMIC_INSTRUMENTED_H */
> -// 764f741eb77a7ad565dc8d99ce2837d5542e8aee
> +// 1b485de9cbaa4900de59e14ee2084357eaeb1c3a
> --- a/include/linux/atomic/atomic-long.h
> +++ b/include/linux/atomic/atomic-long.h
> @@ -479,6 +479,24 @@ arch_atomic_long_add_negative(long i, at
>  	return arch_atomic64_add_negative(i, v);
>  }
>  
> +static __always_inline bool
> +arch_atomic_long_add_negative_acquire(long i, atomic_long_t *v)
> +{
> +	return arch_atomic64_add_negative_acquire(i, v);
> +}
> +
> +static __always_inline bool
> +arch_atomic_long_add_negative_release(long i, atomic_long_t *v)
> +{
> +	return arch_atomic64_add_negative_release(i, v);
> +}
> +
> +static __always_inline bool
> +arch_atomic_long_add_negative_relaxed(long i, atomic_long_t *v)
> +{
> +	return arch_atomic64_add_negative_relaxed(i, v);
> +}
> +
>  static __always_inline long
>  arch_atomic_long_fetch_add_unless(atomic_long_t *v, long a, long u)
>  {
> @@ -973,6 +991,24 @@ arch_atomic_long_add_negative(long i, at
>  	return arch_atomic_add_negative(i, v);
>  }
>  
> +static __always_inline bool
> +arch_atomic_long_add_negative_acquire(long i, atomic_long_t *v)
> +{
> +	return arch_atomic_add_negative_acquire(i, v);
> +}
> +
> +static __always_inline bool
> +arch_atomic_long_add_negative_release(long i, atomic_long_t *v)
> +{
> +	return arch_atomic_add_negative_release(i, v);
> +}
> +
> +static __always_inline bool
> +arch_atomic_long_add_negative_relaxed(long i, atomic_long_t *v)
> +{
> +	return arch_atomic_add_negative_relaxed(i, v);
> +}
> +
>  static __always_inline long
>  arch_atomic_long_fetch_add_unless(atomic_long_t *v, long a, long u)
>  {
> @@ -1011,4 +1047,4 @@ arch_atomic_long_dec_if_positive(atomic_
>  
>  #endif /* CONFIG_64BIT */
>  #endif /* _LINUX_ATOMIC_LONG_H */
> -// e8f0e08ff072b74d180eabe2ad001282b38c2c88
> +// a194c07d7d2f4b0e178d3c118c919775d5d65f50
> --- a/scripts/atomic/atomics.tbl
> +++ b/scripts/atomic/atomics.tbl
> @@ -33,7 +33,7 @@ try_cmpxchg		B	v	p:old	i:new
>  sub_and_test		b	i	v
>  dec_and_test		b	v
>  inc_and_test		b	v
> -add_negative		b	i	v
> +add_negative		B	i	v
>  add_unless		fb	v	i:a	i:u
>  inc_not_zero		b	v
>  inc_unless_negative	b	v
> --- a/scripts/atomic/fallbacks/add_negative
> +++ b/scripts/atomic/fallbacks/add_negative
> @@ -9,8 +9,8 @@ cat <<EOF
>   * result is greater than or equal to zero.
>   */
>  static __always_inline bool
> -arch_${atomic}_add_negative(${int} i, ${atomic}_t *v)
> +arch_${atomic}_add_negative${order}(${int} i, ${atomic}_t *v)
>  {
> -	return arch_${atomic}_add_return(i, v) < 0;
> +	return arch_${atomic}_add_return${order}(i, v) < 0;
>  }
>  EOF
>