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systemd: patch freezer stuck-state on kill-while-frozen

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Reset u->freezer_state to FREEZER_RUNNING when a unit transitions to
inactive/failed. Without this, any SIGKILL path to a frozen unit
(systemctl kill, OOM, watchdog SIGABRT-then-KILL, segfault) leaves
the unit stranded at FreezerState=frozen with no recovery short of
a reboot. Complements upstream PR #38528 which covers only the
watchdog path.

xmrig-auto-pause never calls `systemctl freeze` itself (direct
cgroup.freeze writes bypass the bug class entirely), so the patch
is defensive: benefits systemd-homed on lock, user-session freezing
on suspend, or anything else that may freeze units on muffin.

Patching systemd cascades udev-check-hook hash changes into fuse3 -->
e2fsprogs and into fish. Two test-suite workarounds ride along:
drop e2fsprogs m_hugefile (4 GiB sparse file, fails on some build
sandboxes) and fish doCheck=false (cargo pexpect TTY tests). Both
are environmental, unrelated to the patch.
This commit is contained in:
Simon Gardling
2026-04-21 21:37:37 -04:00
parent 018b590e0d
commit a228f61d34
2 changed files with 74 additions and 0 deletions
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48
patches/systemd/0001-core-unit-reset-freezer-state-on-inactive-failed.patch Normal file
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@@ -0,0 +1,48 @@
From: Simon Gardling <titaniumtown@proton.me>
Date: 2026-04-21
Subject: [PATCH] core/unit: reset freezer state when unit becomes inactive/failed
When a frozen unit is killed via anything that delivers SIGKILL outside
systemd's normal deactivation path (`systemctl kill --signal=KILL`,
`kill -9`, the OOM killer, a segfault), the service transitions to
failed or inactive correctly, but `u->freezer_state` is never reset.
This leaves the unit permanently stuck at FreezerState=frozen:
- `systemctl thaw` refuses with "Unit is not active".
- `systemctl start`/`restart` refuses with
"Cannot perform operation on frozen unit".
- `reset-failed`, `daemon-reload`, `daemon-reexec`, and `revert` do
not clear the state.
The only way to recover a persistent unit in this state is to reboot.
Reset the freezer state to FREEZER_RUNNING whenever a unit transitions
to an inactive or failed state, and cancel any pending freeze/thaw dbus
reply that will never complete. The cgroup is pruned immediately after
this point, so there is nothing left to freeze; the "running" state is
the correct neutral state for a dead unit. On restart, the unit will
pick up its freezer state from the cgroup hierarchy again.
This complements PR #38528 (stop/reset watchdog on freeze/thaw) by
addressing the general SIGKILL path instead of just the watchdog-
initiated kill.
---
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -2754,6 +2754,16 @@
SET_FLAG(u->markers,
(1u << UNIT_MARKER_NEEDS_RELOAD)|(1u << UNIT_MARKER_NEEDS_RESTART),
false);
+
+ /* If the unit was frozen (or in a freezer transition) when it became inactive/failed,
+ * reset the freezer state to running. The cgroup is about to be pruned; leaving the
+ * state stuck at frozen would prevent the unit from ever being started, thawed, or
+ * cleared without rebooting PID 1. Also cancel any pending freeze/thaw dbus reply. */
+ if (u->freezer_state != FREEZER_RUNNING) {
+ unit_set_freezer_state(u, FREEZER_RUNNING);
+ (void) bus_unit_send_pending_freezer_message(u, /* canceled= */ true);
+ }
+
unit_prune_cgroup(u);
unit_unlink_state_files(u);
} else if (ns != os && ns == UNIT_RELOADING)