linux-kernel - Re: [PATCH v2 2/7] rtc: alarmtimer: Use maximum alarm time offset

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Message-ID: <be8d0ac6da08fdb757d4bec365bc8a94.sboyd@kernel.org>
Date:   Wed, 06 Sep 2023 14:06:58 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Guenter Roeck <linux@...ck-us.net>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Benson Leung <bleung@...omium.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <jstultz@...gle.com>, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Brian Norris <briannorris@...omium.org>
Subject: Re: [PATCH v2 2/7] rtc: alarmtimer: Use maximum alarm time offset

Quoting Guenter Roeck (2023-08-30 21:23:54)
> On 8/30/23 14:16, Stephen Boyd wrote:
> > 
> > We fail alarmtimer creation in the case that CONFIG_RTC_CLASS=n or when
> > there isn't an rtc. See alarmtimer_get_rtcdev() and how it is called. I
> > doubt it ever really happens in practice, but it looks possible to
> > simulate by unbinding the rtc device driver.
> 
> Thanks for the clarification. That really makes me wonder what happens
> if an rtc device is unregistered. The .remove_dev callback of
> alarmtimer_rtc_interface is not populated, and rtc_dev is never cleared.
> That means unbinding an rtc device driver should result in a crash.
> Am I missing something ?
> 

Yeah it looks like a potential problem, but most likely nobody actually
removes the rtc device from the system. It would be good to handle this
case in a followup patch anyway though.