Re: [PATCH] rtc: Don't lose a minute-resolution alarm that rounds down into the past

[kernel test robot <lkp@intel.com>]

Hi Arun,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 7485659ecb81d5fce3a3edf2cae9fcb29c17b1cd]

url:    https://github.com/intel-lab-lkp/linux/commits/Arun-Iyengar-via-B4-Relay/rtc-Don-t-lose-a-minute-resolution-alarm-that-rounds-down-into-the-past/20261110-071347
base:   7485659ecb81d5fce3a3edf2cae9fcb29c17b1cd
patch link:    https://lore.kernel.org/r/20261110-rtc-minute-alarm-v1-1-be9d7c5227a1%40gmail.com
patch subject: [PATCH] rtc: Don't lose a minute-resolution alarm that rounds down into the past
config: i386-defconfig (https://download.01.org/0day-ci/archive/20261110/202611102202.ZY3wJ35v-lkp@intel.com/config)
compiler: clang version 22.1.8 (https://github.com/llvm/llvm-project ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261110/202611102202.ZY3wJ35v-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202611102202.ZY3wJ35v-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/rtc/interface.c:562:39: warning: overflow in expression; result is -129'542'144 with type 'long' [-Winteger-overflow]
     562 |                         alarm_time = ktime_add_ns(down, 60 * NSEC_PER_SEC);
         |                                      ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
   include/linux/ktime.h:60:43: note: expanded from macro 'ktime_add_ns'
      60 | #define ktime_add_ns(kt, nsval)         ((kt) + (nsval))
         |                                                  ^~~~~
   1 warning generated.


vim +562 drivers/rtc/interface.c

   512	
   513	int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
   514	{
   515		ktime_t alarm_time;
   516		int err;
   517	
   518		if (!rtc->ops)
   519			return -ENODEV;
   520		else if (!test_bit(RTC_FEATURE_ALARM, rtc->features))
   521			return -EINVAL;
   522	
   523		err = rtc_valid_tm(&alarm->time);
   524		if (err != 0)
   525			return err;
   526	
   527		err = rtc_valid_range(rtc, &alarm->time);
   528		if (err)
   529			return err;
   530	
   531		err = mutex_lock_interruptible(&rtc->ops_lock);
   532		if (err)
   533			return err;
   534		if (rtc->aie_timer.enabled)
   535			rtc_timer_remove(rtc, &rtc->aie_timer);
   536	
   537		alarm_time = rtc_tm_to_ktime(alarm->time);
   538		if (test_bit(RTC_FEATURE_ALARM_RES_MINUTE, rtc->features) &&
   539		    alarm->time.tm_sec) {
   540			ktime_t down = ktime_sub_ns(alarm_time,
   541						    (u64)alarm->time.tm_sec * NSEC_PER_SEC);
   542			struct rtc_time tm;
   543			ktime_t now;
   544	
   545			err = __rtc_read_time(rtc, &tm);
   546			if (err)
   547				goto unlock;
   548			now = rtc_tm_to_ktime(tm);
   549	
   550			/*
   551			 * Round down so we never miss a deadline. If that puts an alarm
   552			 * that is still in the future into the past, the timer would
   553			 * expire right away and the hardware alarm would never be
   554			 * armed: whoever relies on it, e.g. to wake the system from
   555			 * suspend, would wait forever. Round up to the next minute
   556			 * instead. An alarm already in the past is left alone, it is
   557			 * handled by __rtc_set_alarm.
   558			 */
   559			if (ktime_after(down, now) || !ktime_after(alarm_time, now))
   560				alarm_time = down;
   561			else
 > 562				alarm_time = ktime_add_ns(down, 60 * NSEC_PER_SEC);
   563		}
   564	
   565		rtc->aie_timer.node.expires = alarm_time;
   566		rtc->aie_timer.period = 0;
   567		if (alarm->enabled)
   568			err = rtc_timer_enqueue(rtc, &rtc->aie_timer);
   569	
   570	unlock:
   571		mutex_unlock(&rtc->ops_lock);
   572	
   573		return err;
   574	}
   575	EXPORT_SYMBOL_GPL(rtc_set_alarm);
   576	

--
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