(In reply to Michaƫl Colignon from comment #420)
> ...
> I want to add another thing, about fixing it directly from the kernel.
> As typical idle current seems (i am testing it again for see) not needed
> under the other OS, that's because the core parking under this other OS is
> partially disabled by DEFAULT on this OS as i said earlier in this thread.
> 
> So it seems possible to fix it via the kernel, without make use of an uefi
> parameters not enabled by default...

I can perhaps confirm that. But I have to say first, I'm not a developer
and I do not understand anything about Linux.

I use an AMD Ryzen 5 1600 Six-Core @ 12x 3.2GHz with Gentoo as the
operating system. So it's very easy for me to build a kernel just for my
machine. (Without the whole Intel, ARM64, Android and Big-Data stuff.)

I try the kernels with standard bios setup, without kernel parameters
like "idle = nomwait", without OC. My bios only has Global C-states Auto
(which is default) and enable/disable options. There is no "Idle Control
to "Typical Current Idle"" in the BIOS. Only CONFIG_RCU_NOCB_CPU=y is
set in the .config.

BOOT_IMAGE=/boot/kernel-x86_64-4.19.0-rc3 
root=UUID=465f9c93-09d0-441b-9440-8ec7799b557c ro real_root=/dev/sdd4 
resume=/dev/sdd3 init=/usr/lib/systemd/systemd
rootfstype=ext4

./zenstates.py -l
...
C6 State - Package - Enabled
C6 State - Core - Enabled
...
On this basis,
It is to be confirmed by me that the kernel 4.17.14 works really well. But the 
series 4.18.x is cruel. Also the currently as "stable" declarated 4.18.7. Bad. 
Freeze or reboot every 2 - 3 hours.

To my surprise, the 4.19.0-rcX work well. So far no soft lockups.

I do not know why. But these are the subjective results of my playing
with the kernels.

I can also understand that the few kernel developers are working on
priority issues. Please think of Specter and Meltdown.

But a few clarifying information would be very welcome..

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https://bugs.launchpad.net/bugs/1690085

Title:
  Ryzen 1800X freeze - rcu_sched detected stalls on CPUs/tasks

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