Subject: Re: bug#35683: wishlist: addessing statefulness of .cache(s)

From: Julien Lepiller <[email-masked]>
Date: Sat, 11 May 2019 09:43:44 +0200

Le 11 mai 2019 09:32:43 GMT+02:00, Giovanni Biscuolo <[email-masked]> a écrit :
>Hi Guix,
>
>AFAIU issues like the two I point below are becoming a common pattern
>and are *critical*
>
>1. gnome session not starting due to state in $HOME/.cache
>   http://lists.gnu.org/archive/html/guix-devel/2019-04/msg00177.html
>   Message-ID: <[email-masked]>
>
>Ricardo Wurmus:
>--8<---------------cut here---------------start------------->8---
>What should we do about this?  For gdm I think it would make sense to
>add an activation service extension that clears the gdm user’s home
>directory.  And more generally, maybe we should offer a generic cache
>cleaner service.
>--8<---------------cut here---------------end--------------->8---
>
>2. X broken display transitioning from llvm6 to llvm7 in the mesa
>package
>   http://lists.gnu.org/archive/html/guix-devel/2019-05/msg00223.html
>   Message-ID: <20190511022009.nnu6szga6desvfwd@cf0>
>   see also https://debbugs.gnu.org/cgi/bugreport.cgi?bug=35575
>
>ison:
>--8<---------------cut here---------------start------------->8---
>Note that deleting both shader caches was required, and also if the
>caches get
>rebuilt on a new generation and then I try to boot into an older
>previously
>working generation then that generation will display graphics artifacts
>until
>the caches are deleted again.
>
>So switching between mesa compiled with llvm 6 and 7 on AMD RX 580
>either
>backward or forward requires manually deleting the shader caches.
>--8<---------------cut here---------------end--------------->8---
>
>
>AFAIU unfortunately we have application/library state all over
>.cache(s)
>that sometimes crashes software *and* trying to fix this upstream it's
>_not_ an option [1]
>
>often users have to delete something in some .cache by guessing, "just"
>to solve some strange software crash (this is common to all distros)
>
>maybe an activation service extension proposed by Ricardo (see above)
>is the right solution: I'll try to make a summary of prevoius
>discussions on this topic on guix-devel to help address this (class of)
>issue(s)... sorry I cannot help coding it
>
>WDYT?
>
>Thanks! Gio'
>
>
>
>[1] I say this observing this class of issues since I started using
>free
>software: am I wrong?

I wonder if we could mount a tmpfs on .cache? Would that be enough?