linux-kernel - Re: [PATCH] rtc: core: Prevent repeated calling of alarm_irq

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Date:	Wed, 6 Feb 2013 13:12:25 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jonghwa Lee <jonghwa3.lee@...sung.com>
Cc:	linux-kernel@...r.kernel.org, a.zummo@...ertech.it,
	rtc-linux@...glegroups.com
Subject: Re: [PATCH] rtc: core: Prevent repeated calling of
 alarm_irq_enable().

On Wed, 06 Feb 2013 20:22:45 +0900
Jonghwa Lee <jonghwa3.lee@...sung.com> wrote:

> This patch removes repeated execution of disabling alarm in
> rtc_alarm_irq_enable() of rtc core interface. It made useless
> call even all alarm had been disabled from rtc_timer_remove().
> We'd better to skip disabling alarm when timer queue is empty.
> 

I fear that patch does more than that.

> --- a/drivers/rtc/interface.c
> +++ b/drivers/rtc/interface.c
> @@ -428,7 +428,7 @@ int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled)
>  			rtc_timer_remove(rtc, &rtc->aie_timer);
>  	}
>  
> -	if (err)
> +	if (err || !rtc->timerqueue.next)
>  		/* nothing */;
>  	else if (!rtc->ops)
>  		err = -ENODEV;

This will prevent the irq from being *enabled*, as well as disabled.

To match your description, we'd need to also check that enabled==0?
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