Re: ~90s reboot delay with v6.19 and PREEMPT_RT

[Calvin Owens]

On Thursday 02/19 at 17:46 +0100, Bert Karwatzki wrote:
> Since linux v6.19 I noticed that rebooting my MSI Alpha 15 Laptop
> would hang for about ~90s before rebooting. I bisected this (from
> v6.18 to v6.19) and got this as the first bad commit:
> 9311e6c29b34 ("cgroup: Fix sleeping from invalid context warning on PREEMPT_RT")
> 
> Reverting this commit fixes the reboot delay but introduces these error (which
> also seem to make the system crash sometimes):
> [    T0] BUG: scheduling while atomic: swapper/0/0/0x00000002
> 
> Compiling the kernel without PREEMPT_RT also fixes the issue.

Hi Bert,

I'm not seeing this behavior, there must be more to it than just this.

Could you share your kconfig? The dmesg with initcall_debug will be more
verbose during shutdown too, that may also help.

Thanks,
Calvin

> I've test these commits from "git log --oneline v6.19 kernel/cgroup"
> 
> This commit shows the reboot delay:
> 9311e6c29b34 cgroup: Fix sleeping from invalid context warning on PREEMPT_RT
> These commits show no reboot delay, but "scheduling while atomic" warnings
> and instability:
> be04e96ba911 cgroup/cpuset: Globally track isolated_cpus update
> b1034a690129 cgroup/cpuset: Ensure domain isolated CPUs stay in root or isolated partition
> 6cfeddbf4ade cgroup/cpuset: Move up prstate_housekeeping_conflict() helper
> 103b08709e8a cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping
> 55939cf28a48 cgroup/cpuset: Rename update_unbound_workqueue_cpumask() to update_isolation_cpumasks()
> b66c7af4d86d cgroup: use credential guards in cgroup_attach_permissions()
> d245698d727a cgroup: Defer task cgroup unlink until after the task is done switching out
> This commit shows neither the reboot delay nor the "scheduling while atomic" problem:
> 260fbcb92bbe cgroup: Move dying_tasks cleanup from cgroup_task_release() to cgroup_task_free()
> 
> Bert Karwatzki