Re: [PATCH 3/3] LoongArch: Allow to enable PREEMPT_RT

[Sebastian Andrzej Siewior]

On 2024-11-14 19:19:26 [+0800], Huacai Chen wrote:
> > > > Why is ntpd/chronyd service affecting this? Is it running at prio 99?
> > > > Otherwise it should not be noticed.
> > > No, ntpd/chronyd doesn't affect latency. But they may trigger RTC
> > > synchronization every 11 minutes, and RTC synchronization affects
> > > latency. We can keep ntpd/chronyd running but disable RTC
> > > synchronization by configuration, this is the least aggressive method.
> >
> > What is "RTC synchronization" in this context?
> Means the sync_hw_clock() function in kernel/time/ntp.c, it can be
> enabled/disabled by chronyd configuration:

But what exactly is sync_hw_clock() doing that is causing a problem
here? The clock on HW is updated. The access to the RTC clock is
preemptible.

> Huacai

Sebastian