Messages in this thread | | | Date | Fri, 30 Sep 2022 08:38:19 +0800 | From | Feng Tang <> | Subject | Re: [PATCH] x86/PCI: Convert force_disable_hpet() to standard quirk |
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On Thu, Sep 29, 2022 at 11:52:28PM +0800, Yu Liao wrote: > On 2020/12/2 15:28, Zhang Rui wrote: > > On Mon, 2020-11-30 at 20:21 +0100, Thomas Gleixner wrote: > >> Feng, > >> > >> On Fri, Nov 27 2020 at 14:11, Feng Tang wrote: > >>> On Fri, Nov 27, 2020 at 12:27:34AM +0100, Thomas Gleixner wrote: > >>>> On Thu, Nov 26 2020 at 09:24, Feng Tang wrote: > >>>> Yes, that can happen. But OTOH, we should start to think about > >>>> the > >>>> requirements for using the TSC watchdog. > > > > My original proposal is to disable jiffies and refined-jiffies as the > > clocksource watchdog, because they are not reliable and it's better to > > use clocksource that has a hardware counter as watchdog, like the patch > > below, which I didn't sent out for upstream. > > > >>From cf9ce0ecab8851a3745edcad92e072022af3dbd9 Mon Sep 17 00:00:00 2001 > > From: Zhang Rui <rui.zhang@intel.com> > > Date: Fri, 19 Jun 2020 22:03:23 +0800 > > Subject: [RFC PATCH] time/clocksource: do not use refined-jiffies as watchdog > > > > On IA platforms, if HPET is disabled, either via x86 early-quirks, or > > via kernel commandline, refined-jiffies will be used as clocksource > > watchdog in early boot phase, before acpi_pm timer registered. > > > > This is not a problem if jiffies are accurate. > > But in some cases, for example, when serial console is enabled, it may > > take several milliseconds to write to the console, with irq disabled, > > frequently. Thus many ticks may become longer than it should be. > > > > Using refined-jiffies as watchdog in this case breaks the system because > > a) duration calculated by refined-jiffies watchdog is always consistent > > with the watchdog timeout issued using add_timer(), say, around 500ms. > > b) duration calculated by the running clocksource, usually TSC on IA > > platforms, reflects the real time cost, which may be much larger. > > This results in the running clocksource being disabled erroneously. > > > > This is reproduced on ICL because HPET is disabled in x86 early-quirks, > > and also reproduced on a KBL and a WHL platform when HPET is disabled > > via command line. > > > > BTW, commit fd329f276eca > > ("x86/mtrr: Skip cache flushes on CPUs with cache self-snooping") is > > another example that refined-jiffies causes the same problem when ticks > > become slow for some other reason. > > Hi, Zhang Rui, we have met the same problem as you mentioned above. I have > tested the following modification. It can solve the problem. Do you have plan > to push it to upstream ?
Hi Liao Yu,
Could you provoide more details? Like, what ARCH is the platform (x86 or others), client or sever, if sever, how many sockets (2S/4S/8S)?
The error kernel log will also be helpful.
Thanks, Feng
> Thanks, > Liao Yu > > > > > IMO, the right solution is to only use hardware clocksource as watchdog. > > Then even if ticks are slow, both the running clocksource and the watchdog > > returns real time cost, and they still match. > > > > Signed-off-by: Zhang Rui <rui.zhang@intel.com> > > --- > > kernel/time/clocksource.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c > > index 02441ead3c3b..e7e703858fa6 100644 > > --- a/kernel/time/clocksource.c > > +++ b/kernel/time/clocksource.c > > @@ -364,6 +364,10 @@ static void clocksource_select_watchdog(bool fallback) > > watchdog = NULL; > > > > list_for_each_entry(cs, &clocksource_list, list) { > > + /* Do not use refined-jiffies as clocksource watchdog */ > > + if (cs->rating <= 2) > > + continue; > > + > > /* cs is a clocksource to be watched. */ > > if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) > > continue; >
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