RE: [PATCH 4.4 26/65] sched/fair, cpumask: Export for_each_cpu_wrap()

[<nobuhiro1.iwamatsu@toshiba.co.jp>]

Hi,

> -----Original Message-----
> From: stable-owner@vger.kernel.org [mailto:stable-owner@vger.kernel.org] On Behalf Of Greg Kroah-Hartman
> Sent: Wednesday, May 27, 2020 3:53 AM
> To: linux-kernel@vger.kernel.org
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; stable@vger.kernel.org; Peter Zijlstra (Intel)
> <peterz@infradead.org>; Lauro Ramos Venancio <lvenanci@redhat.com>; Linus Torvalds <torvalds@linux-foundation.org>;
> Mike Galbraith <efault@gmx.de>; Rik van Riel <riel@redhat.com>; Thomas Gleixner <tglx@linutronix.de>;
> lwang@redhat.com; Ingo Molnar <mingo@kernel.org>; Daniel Jordan <daniel.m.jordan@oracle.com>; Sasha Levin
> <sashal@kernel.org>
> Subject: [PATCH 4.4 26/65] sched/fair, cpumask: Export for_each_cpu_wrap()	
> 
> From: Peter Zijlstra <peterz@infradead.org>
> 
> [ Upstream commit c743f0a5c50f2fcbc628526279cfa24f3dabe182 ]
> 
> More users for for_each_cpu_wrap() have appeared. Promote the construct
> to generic cpumask interface.
> 
> The implementation is slightly modified to reduce arguments.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: Lauro Ramos Venancio <lvenanci@redhat.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Mike Galbraith <efault@gmx.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: lwang@redhat.com
> Link: http://lkml.kernel.org/r/20170414122005.o35me2h5nowqkxbv@hirez.programming.kicks-ass.net
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> [dj: include only what's added to the cpumask interface, 4.4 doesn't
>      have them in the scheduler]
> Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  include/linux/cpumask.h | 17 +++++++++++++++++
>  lib/cpumask.c           | 32 ++++++++++++++++++++++++++++++++
>  2 files changed, 49 insertions(+)

This commit also needs the following commits:

commit d207af2eab3f8668b95ad02b21930481c42806fd
Author: Michael Kelley <mhkelley@outlook.com>
Date:   Wed Feb 14 02:54:03 2018 +0000

    cpumask: Make for_each_cpu_wrap() available on UP as well
    
    for_each_cpu_wrap() was originally added in the #else half of a
    large "#if NR_CPUS == 1" statement, but was omitted in the #if
    half.  This patch adds the missing #if half to prevent compile
    errors when NR_CPUS is 1.
    
    Reported-by: kbuild test robot <fengguang.wu@intel.com>
    Signed-off-by: Michael Kelley <mhkelley@outlook.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: kys@microsoft.com
    Cc: martin.petersen@oracle.com
    Cc: mikelley@microsoft.com
    Fixes: c743f0a5c50f ("sched/fair, cpumask: Export for_each_cpu_wrap()")
    Link: http://lkml.kernel.org/r/SN6PR1901MB2045F087F59450507D4FCC17CBF50@SN6PR1901MB2045.namprd19.prod.outlook.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>

Please apply this commit.

Best regards,
  Nobuhro

> 
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index bb3a4bb35183..1322883e7b46 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -232,6 +232,23 @@ unsigned int cpumask_local_spread(unsigned int i, int node);
>  		(cpu) = cpumask_next_zero((cpu), (mask)),	\
>  		(cpu) < nr_cpu_ids;)
> 
> +extern int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap);
> +
> +/**
> + * for_each_cpu_wrap - iterate over every cpu in a mask, starting at a specified location
> + * @cpu: the (optionally unsigned) integer iterator
> + * @mask: the cpumask poiter
> + * @start: the start location
> + *
> + * The implementation does not assume any bit in @mask is set (including @start).
> + *
> + * After the loop, cpu is >= nr_cpu_ids.
> + */
> +#define for_each_cpu_wrap(cpu, mask, start)					\
> +	for ((cpu) = cpumask_next_wrap((start)-1, (mask), (start), false);	\
> +	     (cpu) < nr_cpumask_bits;						\
> +	     (cpu) = cpumask_next_wrap((cpu), (mask), (start), true))
> +
>  /**
>   * for_each_cpu_and - iterate over every cpu in both masks
>   * @cpu: the (optionally unsigned) integer iterator
> diff --git a/lib/cpumask.c b/lib/cpumask.c
> index 5a70f6196f57..24f06e7abf92 100644
> --- a/lib/cpumask.c
> +++ b/lib/cpumask.c
> @@ -42,6 +42,38 @@ int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
>  	return i;
>  }
> 
> +/**
> + * cpumask_next_wrap - helper to implement for_each_cpu_wrap
> + * @n: the cpu prior to the place to search
> + * @mask: the cpumask pointer
> + * @start: the start point of the iteration
> + * @wrap: assume @n crossing @start terminates the iteration
> + *
> + * Returns >= nr_cpu_ids on completion
> + *
> + * Note: the @wrap argument is required for the start condition when
> + * we cannot assume @start is set in @mask.
> + */
> +int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
> +{
> +	int next;
> +
> +again:
> +	next = cpumask_next(n, mask);
> +
> +	if (wrap && n < start && next >= start) {
> +		return nr_cpumask_bits;
> +
> +	} else if (next >= nr_cpumask_bits) {
> +		wrap = true;
> +		n = -1;
> +		goto again;
> +	}
> +
> +	return next;
> +}
> +EXPORT_SYMBOL(cpumask_next_wrap);
> +
>  /* These are not inline because of header tangles. */
>  #ifdef CONFIG_CPUMASK_OFFSTACK
>  /**
> --
> 2.25.1
> 	
>