On kvm qemu with cmos rtc and mc146818 chip, when the read time jump to a future time after set the uie timer expire with a current RTC time, rtc_timer_do_work() will loop for a while util softlockup because the expiration of the uie timer was way before the current RTC time and a new timer will be enqueued until the current rtc time is reached, as below: Fix it by voluntarily yield the CPU in the loop in rtc_timer_do_work(). RTC_UIE_ON: read now: 2019:04:08:12:32:27, add timer0 (expire: 2019:04:08:12:32:28) ^^^^^^^^^^^^^^^^^^^^ ... rtc_timer_do_work() iterate the list in a loop: read now: 2033:12:02:07:27:15 ^^^^^^^^^^^^^^^^^^^ handle timer0, add timer1 to the list (expire: 2019:04:08:12:32:29) handle timer1, add timer2 to the list (expire: 2019:04:08:12:32:30) handle timer2, add timer3: 2019:04:08:12:32:31 ... -> softlockup Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> --- drivers/rtc/interface.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c index b8b298efd9a9..da4e541e0e1c 100644 --- a/drivers/rtc/interface.c +++ b/drivers/rtc/interface.c @@ -965,6 +965,7 @@ void rtc_timer_do_work(struct work_struct *work) timerqueue_add(&rtc->timerqueue, &timer->node); trace_rtc_timer_enqueue(timer); } + cond_resched(); } /* Set next alarm */ -- 2.34.1