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Krzysztof Rudnicki
79829ec8a2
pacman intermittently freezes at its FIRST PreTransaction hook - 5 abandoned
transactions since 2026-07-29, stalls of 4 minutes to overnight, always fine on
retry. This investigates it and repairs the real defects found on the way.
The stall is NOT fixed, and deliberately so: no verified defect was found, so
nothing pacman-side was changed.
- Not guard-lib. /etc/guard-lib/targets was empty, so that hook script
provably exits in milliseconds. The failures share POSITION (first hook of
the transaction), not identity: one stall hit the hosts hook back when that
one ran first.
- Not reproducible on demand. 65 real transactions (40 idle, 25 under 2.6 GB
of memory pressure) produced zero stalls. Against the historical 4-in-56
rate that is ~0.9% likely, so the trigger is conditional on something a
synthetic load does not recreate. Memory pressure is untested at the load
that actually occurred - not refuted.
So diagnose_pacman_hook_stall.sh drives real transactions with a watchdog, and
its --watch mode passively captures /proc/<pid>/{stack,wchan,syscall}, the
process tree, meminfo and PSI from the next REAL stall. No pacman-side fix
should ship before that dump exists.
Three real defects were found and fixed:
1. The deployed pacman wrapper was 19916 B against a 27510 B source, never
sourcing the shared pacman_lock_lib.sh that makepkg_wrapper already used.
It hid because check_pacman_wrapper() only tested that files EXIST. Both
installers now write a drift manifest covering source AND installed hashes;
the checker replays it with sha256sum -c and fails closed when it cannot
verify. Manifest paths are absolute - relative ones resolve to nothing under
systemd's cwd=/ and would have looped reinstalling forever.
2. The guard-lib migration (
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| .. | ||
| scripts | ||
| .fvmrc | ||
| .pre-commit-config.yaml | ||
| lint_python.sh | ||
| pyproject.toml | ||
| requirements.txt | ||
| run.sh | ||