linux-kernel - Re: [PATCH v3 3/4] irq: Allow multiple clients to register for irq affinity notification

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Date:	Fri, 10 Oct 2014 09:11:06 -0600
From:	Lina Iyer <lina.iyer@...aro.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	khilman@...aro.org, ulf.hansson@...aro.org,
	linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, rjw@...ysocki.net,
	daniel.lezcano@...aro.org
Subject: Re: [PATCH v3 3/4] irq: Allow multiple clients to register for irq
 affinity notification

On Wed, Oct 08 2014 at 09:03 -0600, Thomas Gleixner wrote:
>On Thu, 25 Sep 2014, Lina Iyer wrote:
>> > How would a general "keep track of the targets of all interrupts in
>> > the system" mechanism make use of this?
>> Sorry, I do not understand your question.
>> PM QoS is only interested in the IRQs specified in the QoS request. If
>> there are no requests that need to be associated with an IRQ, then PM
>> QoS will not register for an affinity change notification.
>
>Right, and I really hate the whole per irq notifier. It's a rats nest
>of life time issues and other problems.
>
>It also does not tell you whether an irq is disabled, reenabled or
>removed, which will change the qos constraints as well unless you
>plaster all drivers with updates to qos for those cases.
>
>So what about adding a qos field to irq_data itself, have a function
>to update it and let the irq core keep track of the per cpu irq
>relevant qos constraints and provide an evaluation function or a
>notifier for the PM/idle code?
If that isnt intrusive in the IRQ core, then we can make it work for PM
QoS. The issue that I am concerned is that, it might result in back and
forth between IRQ and PM QoS frameworks. If that doesnt happen, then we
are good with this approach.
>
>That's going to need some serious thought as well, but it should avoid
>most of the nasty notifier and lifetime issue which the per irq
>notifiers provide.
Sure. I will look into this.
>
>Thoughts?

Thank you.

Lina
>
>
>
>
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