6.1-stable review patch. If anyone has any objections, please let me know.
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From: Tim Van Patten timvp@google.com
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@google.com Tested-by: Mark Hasemeyer markhas@chromium.org Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic") Cc: stable@vger.kernel.org # v6.1+ Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/cgroup/legacy_freezer.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/cgroup/legacy_freezer.c b/kernel/cgroup/legacy_freezer.c index 122dacb3a443..66d1708042a7 100644 --- a/kernel/cgroup/legacy_freezer.c +++ b/kernel/cgroup/legacy_freezer.c @@ -66,9 +66,15 @@ static struct freezer *parent_freezer(struct freezer *freezer) 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;