linux-kernel - Re: [PATCH v4 1/2] smp: Fix the comments of smp_call_function

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Date:   Fri, 17 Dec 2021 21:52:28 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Zhen Lei <thunder.leizhen@...wei.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org
Cc:     Nadav Amit <namit@...are.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v4 1/2] smp: Fix the comments of smp_call_function_many()



On 12/16/21 06:40, Zhen Lei wrote:
> As commit a32a4d8a815c ("smp: Run functions concurrently in
> smp_call_function_many_cond()") itself says:
>                   "Keep other smp_call_function_many() semantic as it is
> today for backward compatibility: the called function is not executed in
> this case locally."
> 
> It's clear that, the function header comments of smp_call_function_many()
> does not need to be changed.
> 
> So move the comment about 'scf_flags' to smp_call_function_many_cond(),
> and restore the original comments of smp_call_function_many(). The
> comments have been simplified slightly to avoid duplication. And the
> description of other parameters of smp_call_function_many_cond() is added.
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>

Acked-by: Randy Dunlap <rdunlap@...radead.org>

thanks.

> ---
>  kernel/smp.c | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 01a7c1706a58b1d..1e5221fe200296a 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -853,14 +853,26 @@ int smp_call_function_any(const struct cpumask *mask,
>  EXPORT_SYMBOL_GPL(smp_call_function_any);
>  
>  /*
> - * Flags to be used as scf_flags argument of smp_call_function_many_cond().
> - *
>   * %SCF_WAIT:		Wait until function execution is completed
>   * %SCF_RUN_LOCAL:	Run also locally if local cpu is set in cpumask
>   */
>  #define SCF_WAIT	(1U << 0)
>  #define SCF_RUN_LOCAL	(1U << 1)
>  
> +/**
> + * smp_call_function_many_cond() - Run a function on a set of CPUs.
> + * @mask:	The set of cpus to run on (only runs on online subset).
> + *		Whether to allow execution on the local CPU is also controlled
> + *		by @scf_flags.
> + * @func:	The function to run on all applicable CPUs.
> + * @info:	An arbitrary pointer to pass to @func.
> + * @scf_flags:	Bitmask that controls the operation. Such as SCF_WAIT,
> + *		SCF_RUN_LOCAL.
> + * @cond_func:	A callback function that is passed a cpu id and the info
> + *		parameter. The function should return a blooean value
> + *		indicating whether @func will be executed on the specified CPU.
> + *		If @cond_func is NULL, that means unconditional, always true.
> + */
>  static void smp_call_function_many_cond(const struct cpumask *mask,
>  					smp_call_func_t func, void *info,
>  					unsigned int scf_flags,
> @@ -972,14 +984,12 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
>  }
>  
>  /**
> - * smp_call_function_many(): Run a function on a set of CPUs.
> + * smp_call_function_many() - Run a function on a set of other CPUs.
>   * @mask: The set of cpus to run on (only runs on online subset).
>   * @func: The function to run. This must be fast and non-blocking.
>   * @info: An arbitrary pointer to pass to the function.
> - * @wait: Bitmask that controls the operation. If %SCF_WAIT is set, wait
> - *        (atomically) until function has completed on other CPUs. If
> - *        %SCF_RUN_LOCAL is set, the function will also be run locally
> - *        if the local CPU is set in the @cpumask.
> + * @wait: If true, wait (atomically) until function has completed
> + *        on other CPUs.
>   *
>   * If @wait is true, then returns once @func has returned.
>   *

-- 
~Randy