linux-kernel - Re: [RFC PATCH 1/2] cpumask: Implement cpumask_next

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Message-ID: <48ffca41-da1a-4ee6-b0aa-5ad0be035c7d@efficios.com>
Date: Tue, 3 Sep 2024 20:47:10 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Yury Norov <yury.norov@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 linux-kernel@...r.kernel.org, Valentin Schneider <vschneid@...hat.com>,
 Mel Gorman <mgorman@...e.de>, Steven Rostedt <rostedt@...dmis.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>, Ben Segall
 <bsegall@...gle.com>, Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [RFC PATCH 1/2] cpumask: Implement cpumask_next_andnot

On 2024-09-03 15:28, Yury Norov wrote:
> On Tue, Sep 03, 2024 at 03:06:49PM -0400, Mathieu Desnoyers wrote:
>> Allow finding the next bit within two input cpumasks which is
>> respectively one and zero.
>>
>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
>> Cc: Yury Norov <yury.norov@...il.com>
>> Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
> 
> Acked-by: Yury Norov <yury.norov@...il.com>

Thanks for the ack. However based on our discussion in the other
leg of this thread, I can simply use

+       for_each_cpu_andnot(cpu, cpumask, mm_allowed)
+               nr_set += !cpumask_test_and_set_cpu(cpu, mm_allowed);

which is already present in the API. I will drop this patch from
my series.

Thanks,

Mathieu

> 
>> ---
>>   include/linux/cpumask.h | 17 +++++++++++++++++
>>   1 file changed, 17 insertions(+)
>>
>> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
>> index 23686bed441d..5da1c66cfa65 100644
>> --- a/include/linux/cpumask.h
>> +++ b/include/linux/cpumask.h
>> @@ -246,6 +246,23 @@ static inline unsigned int cpumask_next_zero(int n, const struct cpumask *srcp)
>>   	return find_next_zero_bit(cpumask_bits(srcp), small_cpumask_bits, n+1);
>>   }
>>   
>> +/**
>> + * cpumask_next_andnot - return the next cpu from *srcp1 & ~*srcp2
>> + * @n: the cpu prior to the place to search (ie. return will be > @n)
>> + * @src1p: the first input
>> + * @src2p: the second input
>> + *
>> + * Returns >= nr_cpu_ids if no cpus match in both.
>> + */
>> +static __always_inline
>> +unsigned int cpumask_next_andnot(int n, const struct cpumask *srcp1, const struct cpumask *srcp2)
>> +{
>> +	/* -1 is a legal arg here. */
>> +	if (n != -1)
>> +		cpumask_check(n);
>> +	return find_next_andnot_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), small_cpumask_bits, n+1);
>> +}
>> +
>>   #if NR_CPUS == 1
>>   /* Uniprocessor: there is only one valid CPU */
>>   static inline unsigned int cpumask_local_spread(unsigned int i, int node)
>> -- 
>> 2.39.2

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com