linux-kernel - Re: [patch 2/2] x86,fpu: lazy allocation of FPU area

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Date:	Sat, 23 Feb 2008 22:08:52 -0500
From:	Christoph Hellwig <hch@...radead.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	mingo@...e.hu, hpa@...or.com, tglx@...utronix.de,
	andi@...stfloor.org, linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [patch 2/2] x86,fpu: lazy allocation of FPU area

On Sat, Feb 23, 2008 at 06:34:39PM -0800, Suresh Siddha wrote:
> +	if (!tsk->thread.cntxt)
> +                tsk->thread.cntxt = alloc_cntxt_struct();

Please use tabs, not spaces for indentation.

> +union thread_cntxt *alloc_cntxt_struct(void)
> +{
> +	return kmem_cache_alloc(task_cntxt_cachep, GFP_KERNEL);
> +}

Why do you need this wrapper at all?

> +struct task_struct * alloc_task_struct(struct task_struct *src)
>  {
>  	struct task_struct *tsk;
>  	tsk = kmem_cache_alloc(task_struct_cachep, GFP_KERNEL);
> +	if (tsk && src->thread.cntxt) {
> +		tsk->thread.cntxt = alloc_cntxt_struct();
> +		if (!tsk->thread.cntxt) {
> +			kmem_cache_free(task_struct_cachep, tsk);
> +			return NULL;
> +		}
> +		WARN_ON((unsigned long)tsk->thread.cntxt & 15);
> +	} else if (tsk)
> +		tsk->thread.cntxt = NULL;
>  	return tsk;

I think passing the src here doesn't make much sense.  Copying
the fpu context structure should be done by the arch dup_task_struct
hook.  Now if you free the fpu context in free_thread_info that means
you don't have to have your own arch-specific task_struct allocator
which would be a _lot_ cleaner.  Talking about clean I think
the .cntxt field really wants a more descriptive name :)

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