https://bugs.kde.org/show_bug.cgi?id=502591
Bug ID: 502591
Summary: Infinite Loop in KScreen When Changing Display
Classification: Plasma
Product: KScreen
Version: 6.3.3
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: common
Assignee: kscreen-bugs-n...@kde.org
Reporter: qq2496424...@gmail.com
Target Milestone: ---
---
### Bug Report: Infinite Loop in KScreen When Changing Display Configuration
via X11 Forwarding
#### System Configuration:
1. **Windows Host** with two monitors in extended mode (`Win + P -> Extend`)
2. X11 server running on Windows via [X410](https://x410.dev/download/) with
TCP X11 service enabled
3. Arch Linux guest accessed via SSH with X11 forwarding
#### Steps to Reproduce:
1. On Windows host, set up dual monitors in extended mode
2. Install and run X410 with TCP X11 service
3. From Linux terminal:
```bash
export DISPLAY=windowshostip:0.0
kstart5 startplasma-x11
```
4. Wait for KDE to display on Windows machine
5. Open two SSH terminals to Arch Linux:
**Terminal 1:**
```bash
kscreen-console monitor
```
*Observed behavior:* Infinite spam of identical output (see full output below)
**Terminal 2:**
```bash
journalctl -n 100 -f
```
*Observed behavior:* Infinite spam of identical error logs (see full output
below)
#### Trigger Condition:
When changing display mode via `Win + P -> "Only one screen"` (disabling one
monitor)
#### Current Workaround:
```bash
pkill -f kscreen_backend_launcher
```
(Process automatically restarts but bug reoccurs when changing display modes
again)
you can get very very very large same error log in tab 1 and tab2
```bash
❯ kscreen-console monitor
START: Requesting Config
Received config. Took 37 milliseconds
Remember to enable KSRandR or KSRandR11 in kdebugdialog
Screen:
maxSize: QSize(32768, 32768)
minSize: QSize(0, 0)
currentSize: QSize(5120, 1452)
-----------------------------------------------------
Id: 62
Name: "default"
Type: "Unknown"
Connected: true
Enabled: true
Priority: 1
Rotation: KScreen::Output::None
Pos: QPoint(0,0)
MMSize: QSize(1355, 384)
FollowPreferredMode: false
Size: QSize(5120, 1452)
Scale: 1
Clones: None
Mode: "63"
Preferred Mode: "63"
Preferred modes: QList()
Modes:
"63" "" QSize(5120, 1452) 0
EDID Info:
Unavailable
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
Priorities changed: QMap((62, KScreen::Output(62, "default", connected enabled
priority 1, pos: QPoint(0,0), res: QSize(5120, 1452), modeId: "63", scale: 1,
clone: no, rotation: KScreen::Output::None, followPreferredMode: false)))
..... Excessive repeated output of identical content
..... Generates thousands of identical lines per second
```
new ssh tab 2 and run
```
❯ journalctl -n 100 -f
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
XRandR::setConfig
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Requested screen size is QSize(2560, 1380)
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Needed CRTCs: 1
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Actions to perform:
Priorities:
false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Change Screen Size: false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Disable outputs: false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Change outputs: true
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
QList(62)
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Enable outputs: false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr: Error
on logical size transformation!
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
RRSetCrtcConfig (change output)
Output: 62 (
"default" )
CRTC: 61
Pos:
QPoint(0,0)
Mode:
KScreen::Mode(Id: "362" , Size: QSize(2560, 1380) @ 0 ) Preferred: "362"
Rotation:
KScreen::Output::None
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Result: 0 timestamp: 50696718
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
XRandROutput 62 update
m_connected:
0
m_crtc
XRandRCrtc(0x5c1035e84380)
CRTC: 61
MODE: 362
Connection:
0
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
RRSetOutputPrimary
New
priority: 1
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
XRandR::setConfig done!
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
XRandR::setConfig
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Requested screen size is QSize(2560, 1380)
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Needed CRTCs: 1
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Actions to perform:
Priorities:
false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Change Screen Size: false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Disable outputs: false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Change outputs: true
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
QList(62)
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Enable outputs: false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr: Error
on logical size transformation!
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
RRSetCrtcConfig (change output)
Output: 62 (
"default" )
CRTC: 61
Pos:
QPoint(0,0)
Mode:
KScreen::Mode(Id: "362" , Size: QSize(2560, 1380) @ 0 ) Preferred: "362"
Rotation:
KScreen::Output::None
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Result: 0 timestamp: 50696718
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
XRandROutput 62 update
m_connected:
0
m_crtc
XRandRCrtc(0x5c1035e84380)
CRTC: 61
MODE: 362
Connection:
0
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
RRSetOutputPrimary
New
priority: 1
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
XRandR::setConfig done!
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
XRandR::setConfig
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Requested screen size is QSize(2560, 1380)
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Needed CRTCs: 1
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Actions to perform:
Priorities:
false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Change Screen Size: false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Disable outputs: false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Change outputs: true
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
QList(62)
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
Enable outputs: false
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr: Error
on logical size transformation!
Apr 09 13:53:22 archlinux kscreen_backend_launcher[4076]: kscreen.xrandr:
RRSetCrtcConfig (change output)
Output: 62 (
"default" )
CRTC: 61
Pos:
QPoint(0,0)
Mode:
KScreen::Mode(Id: "362" , Size: QSize(2560, 1380) @ 0 ) Preferred: "362"
Rotation:
KScreen::Output::None
..... Excessive repeated output of identical content
..... Generates thousands of identical lines per second
```
#### Error Analysis:
1. The `kscreen_backend_launcher` enters an infinite loop when display
configuration changes
2. Relevant code locations:
-
[xrandr.cpp#L179](https://github.com/KDE/libkscreen/blob/9dad2a26069644d4c42d280d830d42aba66390ef/backends/xrandr/xrandr.cpp#L179)
-
[xrandroutput.cpp#L451](https://github.com/KDE/libkscreen/blob/9dad2a26069644d4c42d280d830d42aba66390ef/backends/xrandr/xrandroutput.cpp#L451)
#### Additional Notes:
- (`sudo pacman -Syu`) do not resolve the issue
---
```bash
❯ kscreen-console json
START: Requesting Config
Received config. Took 4 milliseconds
{
"features": 11,
"outputs": [
{
"clones": [
],
"connected": true,
"currentModeId": "63",
"enabled": true,
"followPreferredMode": false,
"icon": "",
"id": 62,
"modes": [
{
"id": "63",
"name": "",
"refreshRate": 0,
"size": {
"height": 1452,
"width": 5120
}
}
],
"name": "default",
"pos": {
"x": 0,
"y": 0
},
"preferredModes": [
],
"priority": 1,
"replicationSource": 0,
"rotation": 1,
"scale": 1,
"size": {
"height": 1452,
"width": 5120
},
"sizeMM": {
"height": 384,
"width": 1355
},
"type": 0
}
],
"screen": {
"currentSize": {
"height": 1380,
"width": 2560
},
"id": 0,
"maxActiveOutputsCount": 1,
"maxSize": {
"height": 32768,
"width": 32768
},
"minSize": {
"height": 0,
"width": 0
}
},
"tabletModeAvailable": false,
"tabletModeEngaged": false
}
```
OBSERVED RESULT
EXPECTED RESULT
SOFTWARE/OS VERSIONS
Windows: win11
macOS: no
(available in the Info Center app, or by running `kinfo` in a terminal window)
❯ kinfo
─╯
Operating System: Arch Linux
KDE Plasma Version: 6.3.3
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2
Kernel Version: 6.13.6-arch1-1 (64-bit)
Graphics Platform: X11
Processors: 14 × Intel® Core™ i7-14700K
Memory: 6.1 GiB of RAM
Graphics Processor: llvmpipe
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