linux-kernel - Re: [RFC PATCH 1/3] genirq: add support for per-cpu dev

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Message-ID: <alpine.LFD.2.02.1109161138360.2723@ionos>
Date:	Fri, 16 Sep 2011 11:41:00 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Marc Zyngier <marc.zyngier@....com>
cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 1/3] genirq: add support for per-cpu dev_id
 interrupts

On Fri, 16 Sep 2011, Marc Zyngier wrote:
> On 15/09/11 23:49, Thomas Gleixner wrote:
> >> +
> >> +	raw_spin_unlock_irqrestore(&desc->lock, flags);
> >> +
> >> +	unregister_handler_proc(irq, action);
> >> +
> >> +	/* Make sure it's not being used on another CPU: */
> >> +	synchronize_irq(irq);
> > 
> > That's not helping w/o making synchronize_irq() aware of the percpu
> > stuff. Also there is the question whether we need the ability to
> > remove such interrupts in the first place. The target users are low
> > level arch interrupts not some random device drivers.
> 
> Again, there is no need for this at the moment (the timer code runs
> running forever), and this is only there for completeness.
> 
> I'll see if I can come up with a synchronize_percpu_irq() without adding
> too much bloat to irqdesc.

You'd need a PROGRESS flag per cpu, which is overkill. What you can do
is to check whether the percpu enabled cpumask is completely empty and
return with a WARN when not.

Thanks,

	tglx
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