linux-kernel - Re: [PATCH] sched: rewrite SCHED_CPUMASK

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Date:	Fri, 07 Nov 2008 15:17:32 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: rewrite SCHED_CPUMASK_ALLOC

>>  #if	NR_CPUS > 128
>> -#define	SCHED_CPUMASK_ALLOC		1
>> -#define	SCHED_CPUMASK_FREE(v)		kfree(v)
>> -#define	SCHED_CPUMASK_DECLARE(v)	struct allmasks *v
>> +#define SCHED_CPUMASK_DECLARE(v)	struct allmasks *v
>> +#define SCHED_CPUMASK_ALLOC(v)		v = kmalloc(sizeof(*v), GFP_KERNEL)
>> +#define SCHED_CPUMASK_FREE(v)		kfree(v)
>>  #else
>> -#define	SCHED_CPUMASK_ALLOC		0
>> -#define	SCHED_CPUMASK_FREE(v)
>> -#define	SCHED_CPUMASK_DECLARE(v)	struct allmasks _v, *v = &_v
>> +#define SCHED_CPUMASK_DECLARE(v)	struct allmasks _v, *v = &_v
>> +#define SCHED_CPUMASK_ALLOC(v)
>> +#define SCHED_CPUMASK_FREE(v)
>>  #endif
> 
> ok, the #ifdef removal is nice, but we can make it even cleaner: 
> please just change it to a sched_cpumask_alloc() inline. That way 
> SCHED_CPUMASK_DECLARE() can go away as well: just declare the 
> variable, it will be unused in the <128 CPUs case.
> 

I don't catch you. :(

In the <128 CPUs case, SCHED_CPUMASK_DECLARE is needed to declare a local
variable(struct allmasks) and a pointer pointing to it. So I don't know
what you mean by 'unused' and how to remove the DECLARE macro..

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