cgroup: remove cgroup_lock_is_held()
We don't want controllers to assume that the information is officially
available and do funky things with it.
The only user is task_subsys_state_check() which uses it to verify RCU
access context. We can move cgroup_lock_is_held() inside
CONFIG_PROVE_RCU but that doesn't add meaningful protection compared
to conditionally exposing cgroup_mutex.
Remove cgroup_lock_is_held(), export cgroup_mutex iff CONFIG_PROVE_RCU
and use lockdep_is_held() directly on the mutex in
task_subsys_state_check().
While at it, add parentheses around macro arguments in
task_subsys_state_check().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 63deb70..515927e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -30,7 +30,6 @@
extern int cgroup_init_early(void);
extern int cgroup_init(void);
-extern int cgroup_lock_is_held(void);
extern void cgroup_fork(struct task_struct *p);
extern void cgroup_post_fork(struct task_struct *p);
extern void cgroup_exit(struct task_struct *p, int run_callbacks);
@@ -552,10 +551,16 @@
* rcu_dereference_check() conditions, such as locks used during the
* cgroup_subsys::attach() methods.
*/
+#ifdef CONFIG_PROVE_RCU
+extern struct mutex cgroup_mutex;
#define task_subsys_state_check(task, subsys_id, __c) \
- rcu_dereference_check(task->cgroups->subsys[subsys_id], \
- lockdep_is_held(&task->alloc_lock) || \
- cgroup_lock_is_held() || (__c))
+ rcu_dereference_check((task)->cgroups->subsys[(subsys_id)], \
+ lockdep_is_held(&(task)->alloc_lock) || \
+ lockdep_is_held(&cgroup_mutex) || (__c))
+#else
+#define task_subsys_state_check(task, subsys_id, __c) \
+ rcu_dereference((task)->cgroups->subsys[(subsys_id)])
+#endif
static inline struct cgroup_subsys_state *
task_subsys_state(struct task_struct *task, int subsys_id)