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Date: Mon, 30 May 2016 12:35:52 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Hans Ulli Kroll <ulli.kroll@googlemail.com>
cc: linux-kernel@vger.kernel.org,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	stable@vger.kernel.org
Subject: Re: [PATCH] clocksource:fix kernel panic due missing event_handler
 in cs5535
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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?

Thanks,

	tglx