Bug 410859 - plasmashell hangs for multiple seconds while nmcli is also slow to respond
Summary: plasmashell hangs for multiple seconds while nmcli is also slow to respond
Status: RESOLVED DUPLICATE of bug 409392
Alias: None
Product: plasma-nm
Classification: Plasma
Component: applet (show other bugs)
Version: 5.15.5
Platform: Fedora RPMs Linux
: NOR normal
Target Milestone: ---
Assignee: Jan Grulich
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2019-08-12 19:19 UTC by Alexander Potashev
Modified: 2019-12-20 19:46 UTC (History)
1 user (show)

See Also:
Latest Commit:
Version Fixed In:

Attachments
stacktrace when plasmashell hangs (53.13 KB, text/plain)
2019-12-17 23:23 UTC, Alexander Potashev 		Details
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Description Alexander Potashev 2019-08-12 19:19:34 UTC 
SUMMARY
plasmashell hangs for multiple seconds while nmcli is also slow to respond.

STEPS TO REPRODUCE
1. Somehow get to a situation when "nmcli c" takes multiple seconds to return results.
2. Click on the plasma-nm icon in Plasma system tray.

OBSERVED RESULT
The panel is only opened after several seconds, at the same time when "nmcli c" un-hangs if run in parallel on command line. The whole Plasma panel is unresponsive, IOW it's not only the plasma-nm applet which is affected by this kind of freeze.

EXPECTED RESULT
Plasma shell should be responsive at any point in time. Plasma-nm should also open its popup immediately when clicking on the tray icon, even if networkmanager is slow to respond. The popup window should probably indicate if it's currently showing outdated information, e.g. more than several seconds old.

SOFTWARE/OS VERSIONS
Operating System: Fedora 30
KDE Plasma Version: 5.15.5
KDE Frameworks Version: 5.59.0
Qt Version: 5.12.4
Kernel Version: 5.1.17-300.fc30.x86_64
OS Type: 64-bit
Processors: 8 × Intel® Core™ i7-6700HQ CPU @ 2.60GHz
Memory: 15,4 ГиБ

ADDITIONAL INFORMATION
Comment 1 Alexander Potashev 2019-08-12 19:21:55 UTC 
The nmcli unresponsiveness might be due to horrible problems with my VPN server (DDoS attack against the data center) which I connect to using networkmanager+openvpn.
Comment 2 Alexander Potashev 2019-12-17 23:23:41 UTC 
Created attachment 124557 [details]
stacktrace when plasmashell hangs

how to reproduce:

1. connect to Wi-Fi with pre-configured secondary VPN connection
2. disconnect WAN cable from the Wi-Fi access point
3. click on the NetworkManager icon in system tray -> plasmashell hangs
Comment 3 Nicolas F. 2019-12-20 19:34:06 UTC 
I can confirm this bug, the way I can reproduce it specifically is to use stubby as a local DNS resolver.

1. Install stubby and configure it
2. Set DNS resolver to 127.0.0.1
3. Switch from one wifi to the other
4. The entirety of plasmashell will now freeze as NetworkManager waits for a dns response to time out

Note that restarting stubby unfreezes plasmashell and NetworkManager prematurely (i.e. before the timeout happens)

The general problem here appears to be threefold, 1. plasmashell lets itself get blocked by applets, 2. plasma-nm lets itself get blocked by NetworkManager, 3. NetworkManager is not good.

Ideally plasmashell would not freeze if a widget freezes, and even more ideally plasma-nm won't freeze if NetworkManager decides to pointlessly block.
Comment 4 Alexander Potashev 2019-12-20 19:46:49 UTC 

*** This bug has been marked as a duplicate of bug 409392 ***