https://bugs.kde.org/show_bug.cgi?id=528227
Bug ID: 528227
Summary: Sensors stay subscribed when a client leaves the bus
before ksystemstats handles its subscribe call
Classification: Frameworks and Libraries
Product: ksystemstats
Version First 6.8.2
Reported In:
Platform: NixOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: General
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: ---
When a client sends subscribe and leaves the bus before ksystemstats handles
the call, its sensors stay subscribed until ksystemstats exits. On my NVIDIA
laptop this keeps `nvidia-smi dmon` running, so the dGPU does not
runtime-suspend.
Daemon::subscribe() calls m_serviceWatcher->addWatchedService(sender), but
QDBusServiceWatcher only reports names that unregister after that. When the
sender is already gone, onServiceDisconnected() never runs for it, and its
Client is never deleted. src/daemon.cpp is the same on master (abe3da27).
I ran this script in a private session bus with the ksystemstats 6.8.2 binary,
as `dbus-run-session -- bash repro.sh <path to ksystemstats>`:
```
#!/usr/bin/env bash
set -uo pipefail
bin=$1
svc=(org.kde.ksystemstats1 /org/kde/ksystemstats1 org.kde.ksystemstats1)
timeout 60 "$bin" --remain >/dev/null 2>&1 &
wrapper=$!
for _ in $(seq 50); do
busctl --user status org.kde.ksystemstats1 >/dev/null 2>&1 && break
sleep 0.2
done
dmon() {
if ps -eo args= | grep -qE '^(/[^ ]*/)?nvidia-smi dmon'; then echo running;
else echo stopped; fi
}
echo "nvidia-smi dmon at start: $(dmon)"
busctl --user call "${svc[@]}" subscribe as 1 gpu/gpu0/usage
sleep 3
echo "1. busctl call subscribe (waits for the reply), then busctl exits. 3 s
later: $(dmon)"
sleep 7
echo " 10 s later: $(dmon)"
busctl --user --expect-reply=no call "${svc[@]}" subscribe as 1 gpu/gpu0/usage
sleep 3
echo "2. busctl --expect-reply=no call subscribe, so busctl exits at once. 3 s
later: $(dmon)"
sleep 27
echo " 30 s later: $(dmon)"
wait "$wrapper"
sleep 2
echo "after the daemon's 60 s timeout ended it: $(dmon)"
```
Two runs printed the same:
```
nvidia-smi dmon at start: stopped
1. busctl call subscribe (waits for the reply), then busctl exits. 3 s later:
stopped
10 s later: stopped
2. busctl --expect-reply=no call subscribe, so busctl exits at once. 3 s later:
running
30 s later: running
after the daemon's 60 s timeout ended it: stopped
```
With a build whose Daemon::subscribe() checks
connection().interface()->isServiceRegistered(sender) after addWatchedService()
and drops the client when the name is gone, step 2 also prints "stopped".
Is that check the right place for the fix? Bug 526594 has the same symptom from
a different cause (one client subscribing twice).
NixOS 26.11, Plasma 6.8.2, Frameworks 6.31.0, Qt 6.12.0, NVIDIA GeForce RTX
4070 Laptop GPU with runtime D3.
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