On 28 March 2018 at 16:01, Vincent Guittot <vincent.guit...@linaro.org> wrote: > Hi, > > On 28 March 2018 at 12:37, Dietmar Eggemann <dietmar.eggem...@arm.com> wrote: >> 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 à 22:28:09 (+0100), Heiner Kallweit a écrit : >>>>> >>>>> 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. > > I think that I have finally been able to reproduce it on my hikey > (octo cortex-A53) after unplugging 6 cores and waiting for almost 2 > hours > This seems to happen only on dual core system as I haven't faced that > before on the hikey which I have used for my tests >
I'm finally not so sure that i have the right set up to reproduce the problem as I haven't been able to reproduce it since. Heiner, How fast the problem happens on your board ? Are you doing anything specific on the console that trigger the problem ? Regards, Vincent >> >>>>> Bisecting the issue resulted in: >>>>> >>>>> 31e77c93e432dec79c7d90b888bbfc3652592741 is the first bad commit >>>>> commit 31e77c93e432dec79c7d90b888bbfc3652592741 >>>>> Author: Vincent Guittot <vincent.guit...@linaro.org> >>>>> 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. >> >> >> [...] >>