Commit 579e7fd3 authored by Benjamin Berg's avatar Benjamin Berg Committed by Johannes Berg
Browse files

um: rtc: use RTC time when calculating the alarm 



The kernel realtime and the current RTC time may have a (small) offset.
Should the kernel time be slightly in the future, then the timeout is
zero. This is problematic in time-travel mode, as a zero timeout can be
correctly configured and time never advances.

Replace the kernel realtime read with a read of the actual persistent
RTC clock. Also, for time-travel, calculate the exact nanoseconds needed
for the clock to advance.

Signed-off-by: default avatarBenjamin Berg <benjamin.berg@intel.com>
Co-developed-by: default avatarAvraham Stern <avraham.stern@intel.com>
Link: https://patch.msgid.link/20241217204906.1408011-1-benjamin@sipsolutions.net


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 7ee1e43a

arch/um/drivers/rtc_kern.c

+5 −2
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ static int uml_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm) 


static int uml_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)

{

	struct timespec64 ts;

	unsigned long long secs;



	if (!enable && !uml_rtc_alarm_enabled)
@@ -58,7 +59,8 @@ static int uml_rtc_alarm_irq_enable(struct device *dev, unsigned int enable) 


	uml_rtc_alarm_enabled = enable;



	secs = uml_rtc_alarm_time - ktime_get_real_seconds();

	read_persistent_clock64(&ts);

	secs = uml_rtc_alarm_time - ts.tv_sec;



	if (time_travel_mode == TT_MODE_OFF) {

		if (!enable) {
@@ -73,7 +75,8 @@ static int uml_rtc_alarm_irq_enable(struct device *dev, unsigned int enable) 


		if (enable)

			time_travel_add_event_rel(&uml_rtc_alarm_event,

						  secs * NSEC_PER_SEC);

						  secs * NSEC_PER_SEC -

						  ts.tv_nsec);

	}



	return 0;