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authorTim Van Patten <timvp@google.com>2023-11-15 19:20:43 +0300
committerTejun Heo <tj@kernel.org>2023-11-28 21:04:03 +0300
commitcff5f49d433fcd0063c8be7dd08fa5bf190c6c37 (patch)
tree8254e9daea0c23693d541d13ce63ea7e58bac370 /kernel/cgroup
parent037266a5f7239ead1530266f7d7af153d2a867fa (diff)
downloadlinux-cff5f49d433fcd0063c8be7dd08fa5bf190c6c37.tar.xz
cgroup_freezer: cgroup_freezing: Check if not frozen
__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>
Diffstat (limited to 'kernel/cgroup')
-rw-r--r--kernel/cgroup/legacy_freezer.c8
1 files changed, 7 insertions, 1 deletions
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;