linux-kernel - Re: [PATCH v2 1/7] cpumask: introduce cpumask_first_and

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Date: Tue, 16 Apr 2024 10:45:53 -0700
From: Yury Norov <yury.norov@...il.com>
To: Dawei Li <dawei.li@...ngroup.cn>
Cc: tglx@...utronix.de, rafael@...nel.org, akpm@...ux-foundation.org,
	maz@...nel.org, florian.fainelli@...adcom.com,
	chenhuacai@...nel.org, jiaxun.yang@...goat.com, anup@...infault.org,
	palmer@...belt.com, samuel.holland@...ive.com,
	linux@...musvillemoes.dk, daniel.lezcano@...aro.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] cpumask: introduce cpumask_first_and_and()

On Tue, Apr 16, 2024 at 04:54:48PM +0800, Dawei Li wrote:
> Introduce cpumask_first_and_and() to get intersection between 3 cpumasks,
> free of any intermediate cpumask variable. Instead, cpumask_first_and_and()
> works in-place with all inputs and produce desired output directly.
> 
> Signed-off-by: Dawei Li <dawei.li@...ngroup.cn>

Acked-by: Yury Norov <yury.norov@...il.com>

> ---
>  include/linux/cpumask.h | 17 +++++++++++++++++
>  include/linux/find.h    | 27 +++++++++++++++++++++++++++
>  lib/find_bit.c          | 12 ++++++++++++
>  3 files changed, 56 insertions(+)
> 
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index 1c29947db848..c46f9e9e1d66 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -187,6 +187,23 @@ unsigned int cpumask_first_and(const struct cpumask *srcp1, const struct cpumask
>  	return find_first_and_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), small_cpumask_bits);
>  }
>  
> +/**
> + * cpumask_first_and_and - return the first cpu from *srcp1 & *srcp2 & *srcp3
> + * @srcp1: the first input
> + * @srcp2: the second input
> + * @srcp3: the third input
> + *
> + * Return: >= nr_cpu_ids if no cpus set in all.
> + */
> +static inline
> +unsigned int cpumask_first_and_and(const struct cpumask *srcp1,
> +				   const struct cpumask *srcp2,
> +				   const struct cpumask *srcp3)
> +{
> +	return find_first_and_and_bit(cpumask_bits(srcp1), cpumask_bits(srcp2),
> +				      cpumask_bits(srcp3), small_cpumask_bits);
> +}
> +
>  /**
>   * cpumask_last - get the last CPU in a cpumask
>   * @srcp:	- the cpumask pointer
> diff --git a/include/linux/find.h b/include/linux/find.h
> index c69598e383c1..28ec5a03393a 100644
> --- a/include/linux/find.h
> +++ b/include/linux/find.h
> @@ -29,6 +29,8 @@ unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1, const unsign
>  					unsigned long n);
>  extern unsigned long _find_first_and_bit(const unsigned long *addr1,
>  					 const unsigned long *addr2, unsigned long size);
> +unsigned long _find_first_and_and_bit(const unsigned long *addr1, const unsigned long *addr2,
> +				      const unsigned long *addr3, unsigned long size);
>  extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size);
>  extern unsigned long _find_last_bit(const unsigned long *addr, unsigned long size);
>  
> @@ -345,6 +347,31 @@ unsigned long find_first_and_bit(const unsigned long *addr1,
>  }
>  #endif
>  
> +/**
> + * find_first_and_and_bit - find the first set bit in 3 memory regions
> + * @addr1: The first address to base the search on
> + * @addr2: The second address to base the search on
> + * @addr3: The third address to base the search on
> + * @size: The bitmap size in bits
> + *
> + * Returns the bit number for the first set bit
> + * If no bits are set, returns @size.
> + */
> +static inline
> +unsigned long find_first_and_and_bit(const unsigned long *addr1,
> +				     const unsigned long *addr2,
> +				     const unsigned long *addr3,
> +				     unsigned long size)
> +{
> +	if (small_const_nbits(size)) {
> +		unsigned long val = *addr1 & *addr2 & *addr3 & GENMASK(size - 1, 0);
> +
> +		return val ? __ffs(val) : size;
> +	}
> +
> +	return _find_first_and_and_bit(addr1, addr2, addr3, size);
> +}
> +
>  #ifndef find_first_zero_bit
>  /**
>   * find_first_zero_bit - find the first cleared bit in a memory region
> diff --git a/lib/find_bit.c b/lib/find_bit.c
> index 32f99e9a670e..dacadd904250 100644
> --- a/lib/find_bit.c
> +++ b/lib/find_bit.c
> @@ -116,6 +116,18 @@ unsigned long _find_first_and_bit(const unsigned long *addr1,
>  EXPORT_SYMBOL(_find_first_and_bit);
>  #endif
>  
> +/*
> + * Find the first set bit in three memory regions.
> + */
> +unsigned long _find_first_and_and_bit(const unsigned long *addr1,
> +				      const unsigned long *addr2,
> +				      const unsigned long *addr3,
> +				      unsigned long size)
> +{
> +	return FIND_FIRST_BIT(addr1[idx] & addr2[idx] & addr3[idx], /* nop */, size);
> +}
> +EXPORT_SYMBOL(_find_first_and_and_bit);
> +
>  #ifndef find_first_zero_bit
>  /*
>   * Find the first cleared bit in a memory region.
> -- 
> 2.27.0