https://bugs.kde.org/show_bug.cgi?id=510525
Bug ID: 510525
Summary: kio_http_cache_cleaner is stealing and hanging on
accessing digital TV tuner files
Classification: Frameworks and Libraries
Product: frameworks-kio
Version First unspecified
Reported In:
Platform: Other
OS: Other
Status: REPORTED
Severity: normal
Priority: NOR
Component: HTTP
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: ---
I have Linux Mint 22 Cinnamon installation set up as a dedicated digital TV
recorder.
This whole system runs just a Python script that looks at TV program guide, and
tunes and launches DVB-T recording. (dvbv5-zap to tune, and ffmpeg to record).
The digital TV recorder hardware (the video stream) is accessed as by opening a
file `/dev/dvb/adapter<num>/frontend0`.
That file is exclusive, so only one process can open it for reading at a time.
Attempting to open the file twice concurrently will yield a `Device or resource
busy` error.
The system has worked well for a days, sometimes weeks at a time. But then
after some days of uptime, the recorder hangs in these `Device or resource
busy` errors, unable to record anything.
When debugging, the TV recorder is unable to proceed because the file
`/dev/dvb/adapter<num>/frontend0` is already in use.
Troubleshooting, it looks like it is the executable `kio_http_cache_cleaner`
that has opened the digital TV recorder device, preventing my digital TV
recorder script from opening the file:
```
$ sudo fuser -v /dev/dvb/adapter2/*
USER PID ACCESS COMMAND
/dev/dvb/adapter2/frontend0:
clb 1805289 F.... kio_http_cache_
$ lsof /dev/dvb/adapter2/*
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
kio_http_ 1805289 clb 44u CHR 212,8 0t0 1358
/dev/dvb/adapter2/frontend0
$ ps -p 1805289 -o pid,ppid,uid,gid,cmd,etime
PID PPID UID GID CMD ELAPSED
1805289 1 1000 1000 /usr/lib/x86_64-linux-gnu/l 3-01:09:20
```
Force-killing with `pkill -f kio_http_cache_cleaner` resolves this situation,
and the digital TV recorder is able to continue again.
It seems like a bug of `kio_http_cache_cleaner` that it would ever attempt to
open these digital TV recorder files.
Further, when `kio_http_cache_cleaner` does so, it seems to get permanently
stuck on them. I.e. it is not just temporarily opening and closing these, but
it seems to steal/hang these file descriptors indefinitely.
Should `kio_http_cache_cleaner` blacklist itself from attempting to access
anything under `/dev/`? Or under `/dev/dvb/`?
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