Applications blocking in inactive session

[krotuss]

I, for many years now, routinely log into two separate KDE sessions, under two different users and use CTR+ALT+Fx to switch between. Some years ago, I have noticed that some applications in "inactive" session started to block, which was not the case before. I have noticed it first when, after switching back to inactive session, gmail in firefox started to display:

[jonys]

This is probably caused by systemd-logind or elogind. I don't know how to configure or disable it, though.

[Goverp]

I've had an issue with emerge hanging at the end of the install phase, usually on long emerges such as libreoffice, qtwebengine. Several emerges in parallel, ("jobs=16 ..."). The hang is a hard I/O wait; if I Ctl+Alt+Fn to a different session and issue "sync" (or "reboot", which I suspect has something equivalent to sync), that session also hangs. "htop" shows the hanging process is executing emerge python code, not any ebuild-specific work such as compilation. I've not noticed messages about "ebuild-ipc" in the emerge.log, but maybe I've different settings or just not looked in the right place.

I've not managed to even work out a strategy as to how to diagnose it.
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Greybeard

[e8root]

Sounds very similar to issue I had recently https://forums.gentoo.org/viewtopic-t-1167704.html
Does it happen in X11 or Wayland (KWin)?

In X11 there is a code to suspend all processes in AIGLX module. If said module is used or not might (as reported by users) have something to do with used GPU. Also from information I gathered few years ago AIGLX was still a module you could disable (or not enable) but this changed and now its the core part of the Xorg server. This issue happens because in 2006 there was a bug noticed with Xorg hanging when compositors were used and people responsible for development of Xorg didn't want to resolve this properly and opted for terrible workaround.

Thankfully for this specific issue as long as you do not use compositors Xorg server can be patched (patch provided in the linked topic). So far I didn't observe any issues with X11 after applying this patch other than enabling compositor and switching to other TTY and back does indeed cause X11 session to freeze.

At the same time Wayland (in this case KWin) should not have this issue. Or at least I didn't notice anything like that happening under Wayland compositors I tried so far and this include KWin.

That said the issue at hand might be caused by other things. Generally unfortunately switching TTYs and especially running multiple graphical sessions on different TTY is considered rare and unimportant use case by majority of Linux users and therefore such things like background processes hanging can happen. That said I am totally against concluding "it is how it is designed to work" because even if then this is a terrible design and completely against idea of having multiple TTYs. There should be no issues like that and we cannot allow issues like that go unresolved.

Please provide more details about your use case and if you use X11 or Wayland, which GPU you use, etc.
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Unix Wars - Episode V: AT&T Strikes Back

[jonys]