Re: [RFC PATCH 0/3] genirq: mixing IRQF_NO_SUSPEND and wakeup sources on shared IRQs

Rafael J. Wysocki
2015-02-26T21:32:25Z

On Thursday, February 26, 2015 07:17:24 PM Boris Brezillon wrote:
> On Thu, 26 Feb 2015 19:17:03 +0100
> "Rafael J. Wysocki" <rjw@rjwysocki.net> wrote:
>
> > On Thursday, February 26, 2015 04:47:24 PM Boris Brezillon wrote:
> > > On Thu, 26 Feb 2015 16:44:16 +0100
> > > "Rafael J. Wysocki" <rjw@rjwysocki.net> wrote:
>
> [...]
>
> > > >
> > > > But it is still a bit risky. Namely, if the driver in question is sufficiently
> > > > broken (eg. it may not suspend the device and rely on the fact that its interrupt
> > > > handler will be run just because it is sharing a "no suspend" IRQ), we may get
> > > > an interrupt storm.
> > > >
> > > > Isn't that a problem?
> > >
> > > For me no (I'll fix all the drivers to handle wakeup, and they are all
> > > already masking interrupts coming from their side in the suspend
> > > callback).
> > > I can't talk for other people though.
> > > The only problem I see here is that you're not informing people that
> > > they are erroneously mixing IRQF_NO_SUSPEND and !IRQF_NO_SUSPEND anymore
> > > (you removed the warning backtrace).
> > > Moreover, you are replacing their handler by a stub when entering
> > > suspend, so they might end-up receiving spurious interrupts when
> > > suspended without knowing why ?
> > >
> > > How about checking if the number of actions registered with
> > > IRQF_NO_SUSPEND + those registered with IRQF_COND_SUSPEND (or another
> > > flag stating that the handler can safely be called in suspended state
> > > even if it didn't ask for NO_SUSPEND) are equal to the total number of
> > > registered actions, and complain if it's not the case.
> >
> > The same idea I had while talking to Peter over IRC. So the patch below
> > implements that.
>
> Yep, that's what I had in mind.

OK, thanks.

I'll submit it formally, then.

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.