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

[Sebastian Andrzej Siewior]

On 2026-02-25 17:37:56 [+0100], Bert Karwatzki wrote:
> I've done two testruns with this debug patch (The persistant log buffer works now, thanks
> again to Steven Rostedt):

…
> This if from PREEMPT_RT log, there*s a long pause in which cgroup_task_dead() is not called

Yeah, I don't know why. The irq-work is invoked slightly delayed so that
part is working.

| irq_work-24        0..... 1501734us : cgrp_dead_tasks_iwork_fn: Kill ffff888101588000 (sd-close)-1964
| systemd--1         1..... 1502194us : sched_process_wait: comm=systemd pid=1963 prio=120
| systemd--1         1..... 1502547us : sched_process_wait: comm=systemd pid=0 prio=120
| systemd--1         1..... 1502771us : sched_process_wait: comm=systemd pid=1964 prio=120
| systemd--1         1..... 1502819us : sched_process_wait: comm=systemd pid=0 prio=120
| systemd--1         1..... 1502835us : sched_process_wait: comm=systemd pid=0 prio=120
|   rcuc/1-31        1b...1 1524116us : sched_process_free: comm=(sd-close) pid=1964 prio=120
the gap

| systemd--1         3..... 90610397us : sched_process_wait: comm=systemd pid=0 prio=120
| systemd--1         3..... 90611469us : sched_process_wait: comm=systemd pid=1829 prio=120

So for some reason systemd stops killing tasks. It complains about still
running gpg-agent and ssh-agent but both are long gone.

Sebastian