https://bugs.kde.org/show_bug.cgi?id=523001
Bug ID: 523001
Summary: Interrupted DPMS-off leaks sleep inhibitor, delaying
subsequent suspends by timeout
Classification: Plasma
Product: kwin
Version First 6.7.2
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
On Plasma Wayland, interrupting the monitor power-off sequence (DPMS) by waking
the screens mid-transition (e.g., jiggling the mouse right as the screen fades
to black) leaks a delay-sleep inhibitor reference in KWin. This causes
subsequent system suspends to hang on the visible lock screen for the full
systemd inhibitor timeout duration (default 5 seconds, or whatever
InhibitDelayMaxSec is set to) before the machine actually goes to sleep.
Detailed Root Cause:
LogindSession::delaySleep() (src/core/session_logind.cpp) caches the logind
inhibitor file descriptor in a weak_ptr (m_suspendLock) and hands the exact
same shared fd to all internal callers. Its two primary callers are the
kscreenlocker integration (wayland_server.cpp) and the "dpms animation"
inhibitor in Workspace::requestDpmsState() (workspace.cpp).
When displays are commanded to turn off, Workspace::requestDpmsState() acquires
this shared inhibitor. However, the DpmsState::On code path completely forgets
to reset m_sleepInhibitor. The reference is only normally released in
maybeUpdateDpmsState() once all outputs successfully report that they have
fully reached the Off state.
If a user wakes the displays mid-transition, Workspace permanently leaks its
reference to that shared fd cache. On the next system suspend, KSldApp
successfully locks the screen and drops its own reference to the inhibitor, but
the underlying file descriptor stays open because of KWin's stale Workspace
reference. As a result, systemd-logind waits out the entire safety timeout,
throwing this log into the journal:
systemd-logind: Delay lock is active (PID .../kwin_wayland) but inhibitor
timeout is reached.
The leak temporarily self-heals the next time the monitor is allowed to
complete a full, uninterrupted screen-off cycle.
STEPS TO REPRODUCE
1. Open a terminal in a Plasma Wayland session.
2. Simulate an interrupted screen-off transition by running:
kscreen-doctor --dpms off; sleep 0.1; kscreen-doctor --dpms on; sleep 1
3. Lock the session: loginctl lock-session
4. Check if the screen-lock sleep inhibitor was correctly released by running:
systemd-inhibit --list | grep -c "screen gets locked"
OBSERVED RESULT
The command returns 1, proving the inhibitor is leaked and still actively held
while the session is locked. When you next attempt to suspend the machine, it
will sit on the lock screen for 5 seconds before sleeping.
EXPECTED RESULT
The command should return 0. Waking the displays should immediately clear the
DPMS animation sleep inhibitor, allowing the system to suspend instantly.
SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux
KDE Plasma Version: 6.7.2
KDE Frameworks Version: 6.27.0
Qt Version: 6.11.1
ADDITIONAL INFORMATION
I have already submitted a tested, one-line merge request fixing this issue on
GitLab by explicitly resetting the inhibitor when switching the DPMS state back
to On.
Merge Request Link: https://invent.kde.org/plasma/kwin/-/merge_requests/9572
Proposed Fix:
--- a/src/workspace.cpp
+++ b/src/workspace.cpp
@@ -572,6 +572,7 @@ void Workspace::requestDpmsState(DpmsState state)
if (m_dpms == DpmsState::On) {
applyOutputConfiguration(cfg);
m_dpmsFilter.reset();
m_dpmsTimer.stop();
+ m_sleepInhibitor.reset();
} else {
applyOutputConfiguration(cfg);
m_dpmsFilter = std::make_unique<DpmsInputEventFilter>();
--
You are receiving this mail because:
You are watching all bug changes.
