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cgroup: inline cgroup_task_freeze()

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After the introduction of the cgroup.kill there is only one call site
of cgroup_task_freeze() left: cgroup_exit(). cgroup_task_freeze() is
currently taking rcu_read_lock() to read task's cgroup flags, but
because it's always called with css_set_lock locked, the rcu protection
is excessive.

Simplify the code by inlining cgroup_task_freeze().

v2: fix build

Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Roman Gushchin 2021-05-10 14:39:46 -07:00 committed by Tejun Heo
parent 85e3b86ed0
commit f4f809f66b
2 changed files with 2 additions and 19 deletions
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18
include/linux/cgroup.h
View file

@ -906,20 +906,6 @@ void cgroup_freeze(struct cgroup *cgrp, bool freeze);
void cgroup_freezer_migrate_task(struct task_struct *task, struct cgroup *src,
struct cgroup *dst);
static inline bool cgroup_task_freeze(struct task_struct *task)
{
bool ret;
if (task->flags & PF_KTHREAD)
return false;
rcu_read_lock();
ret = test_bit(CGRP_FREEZE, &task_dfl_cgroup(task)->flags);
rcu_read_unlock();
return ret;
}
static inline bool cgroup_task_frozen(struct task_struct *task)
{
return task->frozen;
@ -929,10 +915,6 @@ static inline bool cgroup_task_frozen(struct task_struct *task)
static inline void cgroup_enter_frozen(void) { }
static inline void cgroup_leave_frozen(bool always_leave) { }
static inline bool cgroup_task_freeze(struct task_struct *task)
{
return false;
}
static inline bool cgroup_task_frozen(struct task_struct *task)
{
return false;

3
kernel/cgroup/cgroup.c
View file

@ -6267,7 +6267,8 @@ void cgroup_exit(struct task_struct *tsk)
cset->nr_tasks--;
WARN_ON_ONCE(cgroup_task_frozen(tsk));
if (unlikely(cgroup_task_freeze(tsk)))
if (unlikely(!(tsk->flags & PF_KTHREAD) &&
test_bit(CGRP_FREEZE, &task_dfl_cgroup(tsk)->flags)))
cgroup_update_frozen(task_dfl_cgroup(tsk));
spin_unlock_irq(&css_set_lock);