linux-kernel - Re: [RFC][PATCH] irq: Rework IRQF_NO

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Date:	Fri, 25 Jul 2014 07:58:47 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Dmitry Torokhov <dtor@...gle.com>
Subject: Re: [RFC][PATCH] irq: Rework IRQF_NO_SUSPENDED

On Fri, Jul 25, 2014 at 01:10:36AM +0200, Rafael J. Wysocki wrote:
> > There is still enable_irq_wake()/IRQD_WAKEUP_STATE that tries to serve
> > a similar purpose but is equially wrecked for shared interrupts,
> > ideally this would be removed.
> 
> Let me comment about this particular thing.
> 
> I had a discussion with Dmitry about that and his argument was that
> enable_irq_wake() should imply IRQF_NO_SUSPEND, because drivers that
> set up interrupts for system wakeup should expect those interrupts to
> trigger at any time, including system suspend.  Hence the patch that
> added the IRQD_WAKEUP_STATE check to __disable_irq().
> 
> However, in the face of the problem that is being addressed here I'm
> not really sure that this argument is valid, because if the driver
> calling enable_irq_wake() is sharing the IRQ with another one, the
> other driver may not actually know that the IRQ will be a wakeup one
> and still may not expect interrupts to come to it during system
> suspend/resume.
> 
> Yes, drivers using enable_irq_wake() will likely want IRQF_NO_SUSPEND to
> be set for their irqactions, but that should not imply "no suspend" for
> all irqactions sharing the same desc.  So I guess it may be better to go
> forth and use a global "interrupts suspended" state variable instead of the
> IRQS_SUSPENDED flag for each desc and throw away the IRQD_WAKEUP_STATE
> check from suspend_device_irqs() entirely.
> 
> Peter, it looks like you'd prefer that?

My preference would be to shoot enable_irq_wake() in the head, its
fundamentally broken.
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