linux-kernel - Re: [PATCH] clocksource:fix kernel panic due missing event

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Message-ID: <alpine.LNX.2.00.1605310904450.26919@T520.work>
Date:	Tue, 31 May 2016 09:09:29 +0200 (CEST)
From:	Hans Ulli Kroll <ulli.kroll@...glemail.com>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	Hans Ulli Kroll <ulli.kroll@...glemail.com>,
	linux-kernel@...r.kernel.org,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	stable@...r.kernel.org
Subject: Re: [PATCH] clocksource:fix kernel panic due missing event_handler
 in cs5535

HI

On Mon, 30 May 2016, Thomas Gleixner wrote:

> On Mon, 30 May 2016, Hans Ulli Kroll wrote:
> 
> > Missing event_handler in mfgpt_tick() caused a kernel panic.
> 
> So the real problem is that the interrupt in the device is enabled _BEFORE_
> the clock event device is registered.
>  
> > diff --git a/drivers/clocksource/cs5535-clockevt.c b/drivers/clocksource/cs5535-clockevt.c
> > index 9a7e37c..6f186cf 100644
> > --- a/drivers/clocksource/cs5535-clockevt.c
> > +++ b/drivers/clocksource/cs5535-clockevt.c
> > @@ -129,7 +129,9 @@ static irqreturn_t mfgpt_tick(int irq, void *dev_id)
> >  		cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP,
> >  				MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
> >  
> > -	cs5535_clockevent.event_handler(&cs5535_clockevent);
> > +	if (cs5535_clockevent.event_handler)
> > +		cs5535_clockevent.event_handler(&cs5535_clockevent);
> > +
> 
> So what about fixing the above problem instead of having a conditional in the
> interrupt handler fast path?
> 

So there in an default handler for this in the clockevent framework.
OK, for this approach.
I'll send another patch.

Greetings from Cologne
Hans Ulli Kroll