From 2219449a65ace0290cd9c2260ff337e326b8be8a Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Sun, 7 Apr 2013 09:29:51 -0700 Subject: [PATCH] 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 Acked-by: Li Zefan --- include/linux/cgroup.h | 13 +++++++++---- kernel/cgroup.c | 20 ++++++-------------- 2 files changed, 15 insertions(+), 18 deletions(-) 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 @@ struct css_id; 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 @@ static inline struct cgroup_subsys_state *cgroup_subsys_state( * 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) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 1a65958..ba3e24a 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -83,7 +83,13 @@ * B happens only through cgroup_show_options() and using cgroup_root_mutex * breaks it. */ +#ifdef CONFIG_PROVE_RCU +DEFINE_MUTEX(cgroup_mutex); +EXPORT_SYMBOL_GPL(cgroup_mutex); /* only for task_subsys_state_check() */ +#else static DEFINE_MUTEX(cgroup_mutex); +#endif + static DEFINE_MUTEX(cgroup_root_mutex); /* @@ -251,20 +257,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp); static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys, struct cftype cfts[], bool is_add); -#ifdef CONFIG_PROVE_LOCKING -int cgroup_lock_is_held(void) -{ - return lockdep_is_held(&cgroup_mutex); -} -#else /* #ifdef CONFIG_PROVE_LOCKING */ -int cgroup_lock_is_held(void) -{ - return mutex_is_locked(&cgroup_mutex); -} -#endif /* #else #ifdef CONFIG_PROVE_LOCKING */ - -EXPORT_SYMBOL_GPL(cgroup_lock_is_held); - static int css_unbias_refcnt(int refcnt) { return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS; -- 2.7.4