On 2015/10/22 15:43, Thomas Gleixner wrote: > On Thu, 22 Oct 2015, Yang Yingliang wrote: >> I use the kernel-4.1.6 running on arm64. >> My testcase is that it calls clock_settime and clock_adjtime alternately with >> random params on each core. My system has 32 cores. >> >> I found the cpu stalling in hrtimer_intterrupts(). So I added some debug >> info >> in hrtimer_intterrupts() and found that the while loop runs 1020437660 times >> and takes 98761 jiffies(HZ=250). >> >> Some debug log is here: >> ---start--- >> Jan 01 00:03:32 Linux kernel: i:0 basenow.tv64:4809284991830 >> hrtimer_get_softexpires_tv64(timer):4440120000000 ccpu0 >> timer:ffffffdffdec6138, timer->function:ffffffc000129b84 >> Jan 01 00:03:32 Linux kernel: i:0 basenow.tv64:4809284991830 >> hrtimer_get_softexpires_tv64(timer):4440120000000 ccpu0 > > Something is rearming a timer over and over with expiry time in the > past. > > Thanks, > > tglx >
Hi Thomas: This problem could only occur on the system with 32 cores, when I cut the cores to 16, this problem disappeared, so I think there is some parallel problem when the 32 core set clock time together: I try to reproduce the scene: 1.do_settimeofday64 2.update tk time 3.update base time offset 4.update expires_next the 3 and 4 will be called in softirq, but the hrtimer_interrupt may break the order and run before 3, I am not sure whether this could make the problem, do we need to update base time and expires_next in the hrtimer_interrupt? maybe I miss something, thanks for any suggestion. diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 93ef7190..9adab23 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1254,6 +1254,7 @@ void hrtimer_interrupt(struct clock_event_device *dev) raw_spin_lock(&cpu_base->lock); entry_time = now = hrtimer_update_base(cpu_base); + hrtimer_force_reprogram(cpu_base, 0); retry: cpu_base->in_hrtirq = 1; Thanks Ding > _______________________________________________ > linux-arm-kernel mailing list > [email protected] > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
