tumblerd uses 100% CPU on directories with MID files for a very long time

[Leonardo Müller]

It was observed that tumblerd can use 100% of a CPU core when there are MIDI files present in the directory, either only MIDI files or together with another file types, and it fails to generate a thumbnail.

If I understood tumblerd, it tries to open/access the file to generate a relevant thumbnail from it and saves it on a hidden directory with the name as a hash of the file. What is so strange on this MIDI situation is that most MIDIs I have are quite small (less than 32 kiB), yet tumberld can easily take 10 minutes to finish running on a directory with 40 MIDI files.

I don't know what tumblerd is trying to do with the MIDI files, but whatever it is doing, it's taking way too long to run. And in the end, there isn't even a thumbnail :(

I'm using the Thunar file manager with Xfce desktop.

Steps to reproduce:

1) Have tumblerd running;
2) Use the Thunar file manager to access a directory full of MIDI files. A way to get a directory full of MIDI files without having to resort to anything other than Ubuntu's repositories is to install simutrans and then go to /usr/share/games/simutrans/music/
3) Notice how it will take minutes trying to generate the thumbnails (7 on my computer and still running);

I suspect there is something going on there. Using gdb, I can notice that it starts and finishes threads multiple times per second when I go to a directory with many MIDI files, which is a different from images, other music files (MP3, OGG, ...) and videos. It's as if it was restarting something over and over.

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: tumbler 4.16.0-1
ProcVersionSignature: Ubuntu 5.15.0-22.22-generic 5.15.19
Uname: Linux 5.15.0-22-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu78
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: XFCE
Date: Sat Feb 26 22:38:49 2022
InstallationDate: Installed on 2017-06-13 (1719 days ago)
InstallationMedia: Xubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
SourcePackage: tumbler
UpgradeStatus: Upgraded to jammy on 2019-12-22 (797 days ago)
modified.conffile..etc.cron.daily.apport: [deleted]