linux-kernel - Re: [PATCH v2 5/6] watchdog: at91sam9: request the irq with IRQF_NO

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Message-ID: <20150305105729.GB13617@leverpostej>
Date:	Thu, 5 Mar 2015 10:57:29 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	"rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	Mike Turquette <mturquette@...aro.org>,
	"linux-kernel@...r.kernel.org" <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" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 5/6] watchdog: at91sam9: request the irq with
 IRQF_NO_SUSPEND

[...]

> > >  		err = request_irq(wdt->irq, wdt_interrupt,
> > > -				  IRQF_SHARED | IRQF_IRQPOLL,
> > > +				  IRQF_SHARED | IRQF_IRQPOLL |
> > > +				  IRQF_NO_SUSPEND,
> > 
> > I'm a little confused by this. What happens if the watchdog fires when
> > we're actually in the suspended state (when IRQF_NO_SUSPEND interrupts
> > aren't guaranteed to be delivered).
> 
> Why wouldn't they be delivered?
> 
> If that's suspend-to-idle, we'll handle them normally.  If that's full suspend,
> they may not be handled at the last stage (when we run on one CPU with interrupts
> off), but that was the case before the wakeup interrupts rework already and I'd
> expect it to be taken into account somehow in the existing code (or if it isn't
> taken into account, we have a bug, but it is not related to this series).

There's no enable_irq_wake(wdt->irq), and I was under the impression this
is for full suspend.

I agree that if problematic, it's an existing bug. Given Boris's
comments in the other thread this may just a minor semantic issue w.r.t.
IRQF_NO_SUSPEND vs IRQF_COND_SUSPEND.

Thanks,
Mark.
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