linux-kernel - Re: [PATCH 1/3] switch vector_irq[] from irq number to irq

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Date:	Fri, 19 Sep 2008 18:26:40 -0500
From:	Dean Nelson <dcn@....com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"H. Peter Anvin" <hpa@...or.com>, Jack Steiner <steiner@....com>,
	Alan Mayer <ajm@....com>, jeremy@...p.org,
	rusty@...tcorp.com.au, suresh.b.siddha@...el.com,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <Yinghai.lu@....com>
Subject: Re: [PATCH 1/3] switch vector_irq[] from irq number to irq_desc pointer v2

On Fri, Sep 19, 2008 at 01:40:23PM -0700, Yinghai Lu wrote:
> On Fri, Sep 19, 2008 at 1:04 PM, Dean Nelson <dcn@....com> wrote:
> > Change per_cpu variable vector_irq[] from holding an 'int' irq number to
> > holding a 'struct irq_desc' pointer.
> 
> why?
> 
> Eric wants to change int irq to some struct irq later?

Well, it was my take on what Eric was saying in the following:

On Mon, Aug 11, 2008 at 12:39:22PM -0700, Eric W. Biederman wrote:
>
> We create a common factor of assign_irq_vector that looks something like:
> 
> bool __grab_irq_vector(struct irq_desc *desc, unsigned vector, cpumask_t new_domain)
> {
>         /* Must be called with vector lock */
>         struct irq_cfg *cfg;
>         bool grabbed = false;
>         unsigned int old_vector;
>         cpumask_t mask;
>         int cpu;
> 
>         cfg = get_irqp_cfg(irq);
>         old_vector = cfg->vector;
>         cpus_and(mask, new_domain, cpu_online_map);
> 
>         for_each_cpu_mask_nr(cpu, mask) {
>               if (per_cpu(vector_irq, cpu)[vector])
>                       goto out;
>         }
>         /* Available reserve it */
>         for_each_cpu_mask_nr(cpu, mask)
>             per_cpu(vector_irq, cpu)[vector] = desc;

The previous line made me think that was what he wanted....

>         if (cfg->vector) {
>               cfg->move_in_progress;
>                 cfg->old_domain = cfg->domain;
>         }
>         cfg->vector = vector;
>         cfg->domain = mask;
>         grabbed = true;
>         
> out:
>         return grabbed;
> }

... Along with the following paragraph.

> I think vector_irq should return an irq_desc and have an entry for
> all of the static vectors as well (if we are going to do weird
> things with dynamic high priority vector allocation, and dynamic
> detection of which vectors assign_irq_vector may use).

If that's not what Eric meant, then I got it wrong and you can reject
the patchset.

Dean

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