I've also been experiencing this problem, although I have not seen it happening right on startup (probably because my desktop is completely empty). What triggers it for me is navigating around folders with images in Dolphin. The `/usr/lib/kf6/kioworker /usr/lib/qt6/plugins/kf6/kio/thumbnail.so` process will spawn and stay there, constantly consuming 8% of CPU usage and draining my laptop battery faster than normal, not closing itself unless I kill it myself.

This has been happening for a while, and while I didn't pay attention to when it started occurring, I'll make an educated guess that this started happening on KDE Framework version 6.13.x (but take that with a pinch of salt).

So to summarize the reproduction steps:
1. Open Dolphin
2. Navigate around directory with images
3. Observe the kioworker process launching and constantly hogging the CPU

System info:
Operating System: Arch Linux 
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0
Kernel Version: 6.14.6-zen1-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 5600H with Radeon Graphics
Memory: 7.1 GiB of RAM
Graphics Processor 1: AMD Radeon Graphics
Graphics Processor 2: AMD Radeon RX 5500M

I can confirm this is happening. With some images, the thumbnailer seems to get upset by something and keeps logging `qt.gui.imageio: libpng warning: iCCP: known incorrect sRGB profile`

Do you get the same logs if you start Dolphin inside a terminal?

Can you tell me about the file structure a bit too:

Do you have multiple folders in one view with multiple image files inside of them? Or any other items that can potentially have thumbnails?

One more question, what filetypes are they?

Created attachment 181247 [details]
3MF Problematic file

This 3MF file causes kioworker/thumbnail to stuck with 100% CPU Usage. File was previously downloaded from internet. Download at your own risk.

(In reply to Akseli Lahtinen from comment #4)
> One more question, what filetypes are they?

In my case, I've found that the problematic file is a ".3mf" (3D manufacturing) file that I had on Desktop (that's explains why I had problem "on boot"). Dolphin shows others 3mf files correctly, so I think there is something wrong with this specific one.

3mf is indeed a ZIP file with some metadata, 3D model, and a PNG preview "thumbnail.png". I'm pretty sure Dolphin shows this thumbnail.png as the actual preview. This also would explain why the preview is shown despite only "GIF/PNG" preview is ticked in Dolphin.

However, If I extract this thumbnail.png, Dolphin has no problem with its preview.

I've now attached the file in the report. I'VE DOWNLOADED THE 3MF FILE FROM INTERNET, so I can not guarantee it does not contain some 0-day exploit from NSA, but seems fine to me.

In my case, after investigating for a while, I found out that the images were only a red herring. I was going back to my Home folder to navigate between the different folders with images, which is what actually triggered it. So, now that I know that's the case, I opened Dolphin on my home folder, then looked at the kioworker process's open file descriptors. I quickly narrowed it down to an .exe file of a game made in Godot, that was in a folder inside my Home folder. And sure enough, when I opened Dolphin on that exact folder, the same thing happened. I do have icoutils installed and I do expect Dolphin to generate thumbnails for my Windows .exe files.

The game is publicly available, but just to be sure, I've uploaded the exact version that I currently have: https://pixeldrain.com/u/9sMf3SST (file is too big for bugzilla)

This might be a different issue (or an issue with a different component) with the same symptoms.

Thanks for the information! 

I have not been able to reproduce the exact symptoms after all I'm afraid.. :/ 
For me they create the thumbnail and the worker stops. It stays on though, but with 0% usage.

What I am not sure is if should it stay up and running. I will have to ask around. I guess it makes sense we don't create a new
runner every single time and just use the old one.

But no 100% usage spiking yet with these two files.

I have the same issue after I got a 3D printer. After I create a tar for all my 3mf files and then remove them, the CPU usage has become lower. Then I extract the tar, the problem is not reproduced, weired.

Created attachment 181310 [details]
3mf files exported from fusion360

this tarball contains both a normally behaving and a problematic 3mf. both were exported from the same fusion360 project. (although at different stages of creating the project and containing different components)

the problematic one triggers the bug as soon as i extract the file on the desktop from then on it also bugs on startup. 
I also tested it on my other laptop, and both files behaved the exact same way. I therefore believe that the error is file specific which is why I added a working 3mf file for comparison.

I can eliminate arch as the culprit since I am using aurora (a custom fedora kinoite image) . And my other laptop is intel based, so AMD isn't a common factor in this either.

system infos:
Operating System: Aurora 42
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.13.0
Qt Version: 6.9.0
Kernel Version: 6.14.3-300.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 PRO 7540U w/ Radeon 740M Graphics
Memory: 30,0 GiB of RAM
Graphics Processor: AMD Radeon 740M
Manufacturer: LENOVO
Product Name: 21F8CTO1WW
System Version: ThinkPad T14s Gen 4

Same behaviour with exact same OS and software versions but this hardware:

Processors: 16 × 12th Gen Intel® Core™ i7-1260P
Memory: 31.0 GiB of RAM
Graphics Processor: Intel® Iris® Xe Graphics
Manufacturer: LG Electronics
Product Name: 17Z90Q-G.AD7CG
System Version: 0.1

Hi all.

Just to not that I also have just noticed this issue, but I can't narrow it down to any specific file, but I do know it's unlikely to be caused by a 3mf file on my end as I have confirmed I have none  (at least not judging by extension; I might have if I check headers perhaps?! but I don't use fusion360 though),. I do however have a bunch of exe files:

[root@t480 ~]# fd -e 3mf --exclude '.snapshots' --no-ignore --hidden '.*' / | wc -l 
0
[root@t480 ~]# fd -e exe --exclude '.snapshots' --no-ignore --hidden '.*' / | wc -l 
197

I have however verified that downloading the problematic 3MF file from this bug and opening Dolphin triggers the high CPU usage on kioworker /usr/lib/qt6/plugins/kf6/kio/thumbnail.so which only stops if I kill the process.

System information:

Operating System: Arch Linux 
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.13.0
Qt Version: 6.9.0
Kernel Version: 6.14.5-arch1-1 (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-8550U CPU @ 1.80GHz
Memory: 15,4 GiB of RAM
Graphics Processor: Intel® UHD Graphics 620
Manufacturer: LENOVO
Product Name: 20L6S8FB00
System Version: ThinkPad T480

I have met the same issue. 
Steps to reproduce:
1. Open Dolphin
2. Force delete some files with "shift + del"
3. A high CPU usage process with name "kioworker" will keep on running until I close the Dolphin.

Setting back to confirmed, since Akseli was able to reproduce

I also encountered this problem.It is reproduced in the current KDE beta version.  I also have no 3mf files, this probably affects other file formats as well.

Operating System: Arch Linux / Manjaro
KDE Plasma Version: 6.3.90
KDE Frameworks Version: 6.14
Qt Version: 6.9.0
Kernel Version: 6.14.7
FS: btrfs and bcachefs
Graphics Platform: Wayland

I'm also hit by this bug. It seems to occur when thumbnail.so cannot successfully generate a thumbnail. In my case this always starts with dolphin running and thumbnail.so tries to generate thumbnails on encrypted pdf- or odt-files where it cannot access the content.

Sadly I can't still repro this for some reason. I used encrypted odt and pdf files, but when it fails it stops trying. Even the problematic file in the zip given earlier did not cause thumbnailer to get stuck.

Forgot to add, I thought I had this earlier, but it was not related to this.

Unfortunately I can’t tell which file causes this (because it happens on a disk partition with a lot of different files, but there are no encrypted files), but it still happens in my system.

But I can say that the problem is related to the creation of thumbnails for folders, if you disable this function in the  Dolphin settings everything will work properly

KDE Plasma Version: 6.3.91
KDE Frameworks Version: 6.14
Qt Version: 6.9.1
Kernel Version: 6.15
FS: btrfs and bcachefs
Graphics Platform: Wayland

(In reply to orangeanatola from comment #18)
> Unfortunately I can’t tell which file causes this (because it happens on a
> disk partition with a lot of different files, but there are no encrypted
> files), but it still happens in my system.
> 
> But I can say that the problem is related to the creation of thumbnails for
> folders, if you disable this function in the  Dolphin settings everything
> will work properly
> 
> KDE Plasma Version: 6.3.91
> KDE Frameworks Version: 6.14
> Qt Version: 6.9.1
> Kernel Version: 6.15
> FS: btrfs and bcachefs
> Graphics Platform: Wayland

What filesystem does this partition use? Is your home directory (~/.cache in particular) in different partition than the files?

> What filesystem does this partition use? Is your home directory (~/.cache in
> particular) in different partition than the files?

my root  and the partition where this problem occurs are both on btrfs
yes,  in different partition

It seems I was wrong, the problem in my particular case is causing the creation of a thumbnail not for folders but for specific windows exe
In fact it seems to concern only one exe of all that I have, because this does not happen on other partition.
Unfortunately I cannot send you this file for verification. Maybe other users who have encountered this problem will be able to provide you with a file for checking.

in case you want to check which file format is causing problems for you - go to the dolphin settings, select create thumbnail, disable all, click apply, close dolphin. Now enable creating thumbnails for each format, then click apply, close dolphin and check until you find the right format.
important after each format is enabled to restart dolphin. 
Hope this can help

(In reply to orangeanatola from comment #21)
> It seems I was wrong, the problem in my particular case is causing the
> creation of a thumbnail not for folders but for specific windows exe
> In fact it seems to concern only one exe of all that I have, because this
> does not happen on other partition.

Can you tell me more details of this exe file?
- Is it on NTFS disk?
- How large is the exe file?
- Does the exe itself contain images? (Some exe files have images bundled within them when built)

> Can you tell me more details of this exe file?
> - Is it on NTFS disk?
> - How large is the exe file?
> - Does the exe itself contain images? (Some exe files have images bundled
> within them when built)

It was a game on the Godot game engine. Build in one exe file with all resources. Although I can’t send you the file, I will try to give you any information I can.
1) No
2) ~ 264 Mib
3) I think yes.

I have extracted the contents of this exe with GDRE_tools , unfortunately it did not help, the recovered files do not cause problems by themselves, now I try to find any other game on Godot that would cause such behavior

At least it didn’t take me too long. This game  (windows) version causes the same problem, I hope the publication of links here is not forbidden. In any case you don’t need to run it, just go to the folder with the downloaded file. 

https://wrenchtype.itch.io/puzzles-house

I only managed to reproduce this in an Arch VM. I still am not sure why exactly, but this does tell me that we need to add a timeout to the previewjob at the very least.

A possibly relevant merge request was started @ https://invent.kde.org/frameworks/kio/-/merge_requests/1914

I noticed that with the 3mf file, something keeps investigating the file for the thumbnail forever. 

Similar thing happens with the window exe files.

So I think this is something that needs to be fixed case-by-case per plugin. Alternatively we throw our plugins into bin and use de-facto-standardized thumbnailers.

Both require bunch of work. But at least with the timeout fix we can avoid the plugins to hang around forever, eating CPU.

Since the MR was closed without being merged, I'm setting back to CONFIRMED

Still got this on Gentoo, kio version 6.13.0, after disabled "Show Previews" in Dolphi, everything is OK