On 3/17/26 3:08 PM, Vasileios Almpanis wrote:
lockdep reports an inconsistent lock state involving css_set_lock,
triggered via cgroup_events_show() -> check_freeze_timeout():
WARNING: inconsistent lock state
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
Possible unsafe locking scenario:
CPU0
----
lock(css_set_lock);
<Interrupt>
lock(css_set_lock);
*** DEADLOCK ***
The lock is currently taken with spin_lock() in check_freeze_timeout(),
which does not disable interrupts. However, css_set_lock is also
acquired from IRQ/softirq context in RCU callbacks during task
teardown, making it unsafe to take the lock with interrupts enabled.
This can lead to a deadlock if an interrupt fires while holding
css_set_lock and attempts to re-acquire it.
Fix this by switching to spin_lock_irq() semantics via
scoped_guard(spinlock_irq, ...), ensuring interrupts are disabled
while holding css_set_lock in this path.
This matches the locking requirements of css_set_lock.
Fixes: 3cc887c3d0faa ("cgroup-v2/freezer: Print information about unfreezable
process")
https://virtuozzo.atlassian.net/browse/VSTOR-127046
Signed-off-by: Vasileios Almpanis <[email protected]>
Feature: cgroup/freeze: enhance logging
---
kernel/cgroup/cgroup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 040e7e36c238..376c9bbd1c41 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4296,7 +4296,7 @@ static void check_freeze_timeout(struct cgroup *cgrp)
u64 freeze_jiffies;
int timeout;
- scoped_guard(spinlock, &css_set_lock) {
+ scoped_guard(spinlock_irq, &css_set_lock) {
Since the lock is only shared between process context and softirqs,
spinlock_bh should be sufficient here. There is no need to disable irq.
if (!test_bit(CGRP_FREEZE, &cgrp->flags) ||
test_bit(CGRP_FROZEN, &cgrp->flags))
return;
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