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

[Giovanni Biscuolo <g@xelera.eu>]

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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: <87ef68ibfy.fsf@elephly.net>

Ricardo Wurmus:
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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.
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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:
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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.
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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?


-- 
Giovanni Biscuolo

Xelera IT Infrastructures

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