Sebastian Andrzej Siewior (Thu, Dec 14, 2017 at 05:25:03PM +0100):
> On 2017-12-13 20:14:54 [+0100], bert schulze wrote:
> > Yes as timer migration kicked in on boot causing the interrupt storm.
> > Disabling it all together there are no more hangs on boot.
>
> and with the patch I Cced you one we have fix for that but there is
> more…
>
> > This is sleep from coreutils, I'm not setting up anything here.
> > top, cyclictest whatever using nanosleep is broken.
>
> that sleep should be also affected.
>
> > Tried that as mentioned, no interrupt storm and nothing fails to expire.
> > (Add mainline 4.14 upto 4.14.5 to the list of working versions).
> …
>
> > Do you need anything else that would be helpful?
>
> bisect with RT is an exercise of its own.
> It looks that if you set rcu_normal_after_boot to 0 in
> kernel/rcu/update.c then other problem should go away and everything is
> "normal" now, right?
System boots reliable with mentioned patch applied, and nanosleep is
working as well! I do not have to set rcu_normal_after_boot to 0 or what
is its purpose?
> Now I need to figure why that is broken…
Guess you already did :)
root@deb9:~# bash test
# uname -a
Linux deb9.virt 4.14.3-rt5-rt+ #5 SMP PREEMPT RT Thu Dec 14 18:39:27 CET 2017 x86_64 GNU/Linux
# cat /proc/sys/kernel/timer_migration
1
# dmesg | grep hrtimer
# date
Thu Dec 14 18:41:21 CET 2017
# grep LOC /proc/interrupts
LOC: 8002 208 138 68 Local timer interrupts
# for cpu in {0..3} ;do time taskset -ac sleep 0.1 ;done
real 0m0.103s
real 0m0.105s
real 0m0.105s
real 0m0.105s
# date
Thu Dec 14 18:41:22 CET 2017
# grep LOC /proc/interrupts
LOC: 8437 209 139 70 Local timer interrupts
Tested on bare hardware and QEMU, top and cyclictest are working as well
no more interrupt storms can be observed!
>
> Sebastian
Thank you!
Bert
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