Re: Problem with commit 31e77c93e432 "sched/fair: Update blocked load when newly idle"

[Dietmar Eggemann]

Hi,

On 03/24/2018 01:47 PM, Heiner Kallweit wrote:
> Am 24.03.2018 um 07:46 schrieb Vincent Guittot:
> > Hi Heiner,
> >
> > Le Friday 23 Mar 2018 Ã 22:28:09 (+0100), Heiner Kallweit a Ãcrit :
> > > Recently I started to get the following problems with linux-next:
> > >
> > > - When working via Putty/SSH on the system the console frequently freezes
> > >    for few seconds. Sometimes only opening a second console makes the
> > >    first one react again.
> > >
> > > - I get "INFO: rcu_sched detected stalls on CPUs/tasks:" warnings as
> > >    described in [1].

I can't catch this issue on my Juno r0 (arm64 big.Little).

root@juno:~# uname -r
4.16.0-rc4-00198-g31e77c93e432

I'm using openssh-client and openssh-server though.

> > > Bisecting the issue resulted in:
> > >
> > > 31e77c93e432dec79c7d90b888bbfc3652592741 is the first bad commit
> > > commit 31e77c93e432dec79c7d90b888bbfc3652592741
> > > Author: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> > > Date:   Wed Feb 14 16:26:46 2018 +0100
> > >
> > >      sched/fair: Update blocked load when newly idle
> > >
> > >      When NEWLY_IDLE load balance is not triggered, we might need to update the
> > >      blocked load anyway. We can kick an ilb so an idle CPU will take care of
> > >      updating blocked load or we can try to update them locally before entering
> > >      idle. In the latter case, we reuse part of the nohz_idle_balance.
> > >
> > > After reversing this commit at least the issue with the freezing console
> > > is gone. The second one appeared only sporadically, I still have to see
> > > whether it pops up again.

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