https://bugs.kde.org/show_bug.cgi?id=481793
Bug ID: 481793
Summary: ddcutil constantly locked by powerdevil
Classification: Plasma
Product: Powerdevil
Version: 5.93.0
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: plasma-b...@kde.org
Reporter: dh_log...@posteo.de
CC: m...@ratijas.tk, natalie_clar...@yahoo.de
Target Milestone: ---
SUMMARY
Running ddcutil version 2.1.3, ddcutil detect and other commands always fail
when Powerdevil is running.
Running ddcutil detect yields the following error messages:
(i2c_open_bus ) busno=9, flock() returned:
EAGAIN(-11): Resource temporarily unavailable
/dev/i2c-9 locked. Retrying...
(i2c_open_bus ) busno=9, flock() returned:
EAGAIN(-11): Resource temporarily unavailable
(i2c_open_bus ) busno=9, flock() returned:
EAGAIN(-11): Resource temporarily unavailable
(i2c_open_bus ) busno=9, flock() returned:
EAGAIN(-11): Resource temporarily unavailable
(i2c_open_bus ) busno=9, flock() returned:
EAGAIN(-11): Resource temporarily unavailable
(i2c_open_bus ) busno=9, flock() returned:
EAGAIN(-11): Resource temporarily unavailable
(i2c_open_bus ) busno=9, flock() returned:
EAGAIN(-11): Resource temporarily unavailable
Max wait exceeded for /dev/i2c-9
Programs holding /dev/i2c-9 open:
lsof: WARNING: can't stat() btrfs file system /var/lib/docker/btrfs
Output information may be incomplete.
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
ddcutil 13315 david 3u CHR 89,9 0t0 744 /dev/i2c-9
sh 13322 david 3u CHR 89,9 0t0 744 /dev/i2c-9
lsof: WARNING: can't stat() btrfs file system /var/lib/docker/btrfs
Output information may be incomplete.
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
ddcutil 13315 david 3u CHR 89,9 0t0 744 /dev/i2c-9
sh 13325 david 3u CHR 89,9 0t0 744 /dev/i2c-9
Processes locking /dev/i2c-9 (inode 744):
11285
11285
egrep: warning: egrep is obsolescent; using grep -E
Name: org_kde_powerde
State: S (sleeping)
Pid: 11285
egrep: warning: egrep is obsolescent; using grep -E
Name: org_kde_powerde
State: S (sleeping)
Pid: 11285
(i2c_open_bus ) Cross instance locking failed
The log indicates that /dev/i2c-* files are locked by powerdevil/libddcutil. I
can reliably reproduce this even if I haven't done a interaction involving
external monitors since starting the plasma session.
A workaround is to run ddcutil with the --disable-cross-instance-locks flag, as
this seems to disable all checking for lock files. However, this obviously
breaks the otherwise helpful feature of locking the currently used files.
STEPS TO REPRODUCE
1. Make sure Powerdevil is running
2. Run for example ddcutil detect in a terminal
OBSERVED RESULT
ddcutil fails to communicate with monitors because locks are present.
EXPECTED RESULT
ddcutil shouldn't reliably fail because dev/i2c files are locked.
Operating System: Arch Linux
KDE Plasma Version: 5.93.0
KDE Frameworks Version: 5.249.0
Qt Version: 6.7.0
Kernel Version: 6.7.5-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 5600 6-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: AMD Radeon RX 6750 XT
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