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

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Message-ID: <20150226191724.0ae4ca4e@bbrezillon>
Date:	Thu, 26 Feb 2015 19:17:24 +0100
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Mark Rutland <mark.rutland@....com>,
	linux-kernel@...r.kernel.org,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 0/3] genirq: mixing IRQF_NO_SUSPEND and wakeup
 sources on shared IRQs

On Thu, 26 Feb 2015 19:17:03 +0100
"Rafael J. Wysocki" <rjw@...ysocki.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@...ysocki.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.


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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