On Fri, Sep 30, 2022 at 9:04 PM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Sep 29, 2022 at 4:21 AM Pingfan Liu <kernelfans@xxxxxxxxx> wrote:
> >
> > On Thu, Sep 29, 2022 at 4:19 PM Pingfan Liu <kernelfans@xxxxxxxxx> wrote:
> > >
> > [...]
> > > "
> > >
> > > I have no idea whether this is related to the reverted commit.
> > >
> >
> > I have started another test against clean v6.0-rc7 to see whether this
> > is an issue with the mainline.
>
> I am not sure what exactly you are reverting (you could clarify that),
commit 96926686deab ("rcu: Make CPU-hotplug removal operations enable tick").
But due to conflict, "git revert" can not work directly. So I applied
it by hand.
> but if you are just removing the entire TICK_DEP_BIT_RCU, I do
> remember (and mentioned on IRC to others recently) that without this
> NOHZ_FULL has a hard time ending grace-periods because the forcing of
> tick is needed for this configuration if we are spinning in the kernel
> with the tick turned off. That seems to align with your TREE04
> (NOHZ_FULL) configuration.
>
Yes, that is the scenario.
> Also, the commit Frederic suggested to revert seems to be a cosmetic
> optimization in the interrupt-entry path. That should not change
> functionality I believe. So I did not fully follow why reverting that
> is relevant (maybe Frederic can clarify?).
>
Leave this question to Frederic.
And I schedule a test which reverts three commits
96926686deab ("rcu: Make CPU-hotplug removal operations enable tick").
53e87e3cdc15 (timers/nohz: Last resort update jiffies on nohz_full IRQ entry)
and:
a1ff03cd6fb9 (tick: Detect and fix jiffies update stall)
Let us see the result. (Last time, it failed within an hour)
> Or, are you trying to just remove its use from the hotplug path?
>
Not from the hotplug path. Just revert the commit and run the standard
TREE04 test.
Thanks,
Pingfan
