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

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Date:	Fri, 7 Nov 2008 09:16:27 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: rewrite SCHED_CPUMASK_ALLOC


* Li Zefan <lizf@...fujitsu.com> wrote:

> >>  #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..

Sorry, you are right - keep the SCHED_CPUMASK_DECLARE() macro please. 

But the other macros can become an inline function just fine, correct?

	Ingo
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