[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:

quoted

quoted

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