Run this and see if there are any large kernel structures.

sudo cat /proc/slabinfo  | sort -k 15n | tail -10

The one I have see a problem with on a filesystem umount (a long
delay) is dentry being greater than 20 million.    The higher dentry
is the longer the delay.


On Thu, Dec 18, 2025 at 7:03 PM George R Goffe via users
<[email protected]> wrote:
>
> Barry,
>
> From the bugzilla.redhat.com website I got some information which I tried. IT 
> WORKED!!! Yay... but, there's more... :(
>
> I ran these commands:
>
> dnf install fedora-repos-rawhide
>
> followed by
>
> dnf update --enablerepo=rawhide kernel
>
>
> These two commands got me to kernel 6.17.12-200.fc42.x86_64+debug
>
> The panic has gone but in its place are some strange error(?) messages that 
> are meaningless to me (see below). I couldn't find much info on the web about 
> these messages. What I did find is vague suggestions(?) like "update your 
> workqueue settings" but just where they are located is STILL a mystery. Sigh.
>
> MSGS:
>
> [Thu Dec 18 16:00:32 2025] workqueue: drm_fb_helper_damage_work hogged CPU 
> for >10000us 4 times, consider switching to WQ_UNBOUND
> [Thu Dec 18 16:00:32 2025] workqueue: drm_fb_helper_damage_work hogged CPU 
> for >10000us 5 times, consider switching to WQ_UNBOUND
> [Thu Dec 18 16:00:33 2025] workqueue: drm_fb_helper_damage_work hogged CPU 
> for >10000us 7 times, consider switching to WQ_UNBOUND
>
>
> I got these messages after a umount of a 24TB btrfs filesystem which took a 
> (relatively) LONG TIME `1 minute. Usually this happens REALLY quickly. Sigh...
>
> A subsequent reboot froze the system (which had trouble finishing shutting 
> down) for several minutes. The system finally "woke up" when I powered off 
> the 24TB external USB connected hard drive.
>
> I'm trying to submit bugs for abrt which produces a REALLY NICE "details" 
> popup... It's NOT "enabled" for copy/paste operations though... Yet another 
> bug report. ARGH!
>
>
>
> --
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