6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tim Van Patten <timvp@xxxxxxxxxx>
commit cff5f49d433fcd0063c8be7dd08fa5bf190c6c37 upstream.
__thaw_task() was recently updated to warn if the task being thawed was
part of a freezer cgroup that is still currently freezing:
void __thaw_task(struct task_struct *p)
{
...
if (WARN_ON_ONCE(freezing(p)))
goto unlock;
This has exposed a bug in cgroup1 freezing where when CGROUP_FROZEN is
asserted, the CGROUP_FREEZING bits are not also cleared at the same
time. Meaning, when a cgroup is marked FROZEN it continues to be marked
FREEZING as well. This causes the WARNING to trigger, because
cgroup_freezing() thinks the cgroup is still freezing.
There are two ways to fix this:
1. Whenever FROZEN is set, clear FREEZING for the cgroup and all
children cgroups.
2. Update cgroup_freezing() to also verify that FROZEN is not set.
This patch implements option (2), since it's smaller and more
straightforward.
Signed-off-by: Tim Van Patten <timvp@xxxxxxxxxx>
Tested-by: Mark Hasemeyer <markhas@xxxxxxxxxxxx>
Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
Cc: stable@xxxxxxxxxxxxxxx # v6.1+
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup/legacy_freezer.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/kernel/cgroup/legacy_freezer.c
+++ b/kernel/cgroup/legacy_freezer.c
@@ -66,9 +66,15 @@ static struct freezer *parent_freezer(st
bool cgroup_freezing(struct task_struct *task)
{
bool ret;
+ unsigned int state;
rcu_read_lock();
- ret = task_freezer(task)->state & CGROUP_FREEZING;
+ /* Check if the cgroup is still FREEZING, but not FROZEN. The extra
+ * !FROZEN check is required, because the FREEZING bit is not cleared
+ * when the state FROZEN is reached.
+ */
+ state = task_freezer(task)->state;
+ ret = (state & CGROUP_FREEZING) && !(state & CGROUP_FROZEN);
rcu_read_unlock();
return ret;
