Am 29.03.2018 um 09:41 schrieb Vincent Guittot: > 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 ? > Hi Vincent,
the lag when working on the console is constantly there, the "rcu_preempt detected stalls" happens after several hours (so far always within 24h) w/o any triggering event I would be aware of. It occured also when the system was idle at that point in time. Rgds, Heiner > 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. >>> >>> >>> [...] >>> >
