System Monitor shows invalid Firefox applications with no CPU / memory data

I started noticing an issue I can’t quite make sense of. I don’t know if this is a general Linux / Manjaro issue, one with KDE and its system monitor, or with Firefox specifically.

After a day or more of uptime, I notice the System Monitor keeps showing a group of invalid Firefox processes, the list of duplicates slowly growing as time goes on. All of their fields are empty, no memory or CPU use or anything: It only shows Firefox with the FF icon and that’s it. I cannot kill them to make them go away using signals, nor does completely shutting down Firefox remove them… it only seems to disappear after a system restart. If I go to the Processes tab I don’t see any extra FF processes there, it only shows those imaginary (?) entries in the Applications section.

Is this normal and has anyone else experienced it? How can there exist multiple Firefox applications with no CPU / memory information? Any way to get rid of them at runtime?

My Firefox on KDE doesn’t do that. Try a fresh profile.

Well, for some values of “normal”, I guess. By this I mean that it’s not supposed to happen, but it’s also not completely unusual.

Those processes are called “zombies”. They are processes of which the parent process has died, but for some reason, the child processes — which should have been killed when the parent died — don’t know about this. They are not consuming any memory or CPU cycles, though, because they are effectively dead.

No, the only way to get rid of them is to reboot, but depending on what you do with your computer, they will probably return at some point.

The cause could be one of your browser add-ons, or a bug in Firefox itself, or it could even be a bug at a lower level, in one of the system libraries that Firefox uses.

Ah: I used to hear about zombie processes a while ago, but remembered they’re something different from this particular scenario. In this case I only get them in applications not the processes tab, plus zombie processes still used memory IIRC they were just stuck waiting for a signal from the parent process. Possibly a bug in Firefox then… a fresh profile might break too much for me, I’ll have to think what could be doing it and maybe report it with Mozilla next.

Try disabling your extensions and re-enabling them one by one. That way you can determine which one — if any — is causing the issue.

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