Commit 5b30afc2 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: Expose some cgroup helpers 



Expose the following through cgroup.h:

- cgroup_on_dfl()
- cgroup_is_dead()
- cgroup_for_each_live_child()
- cgroup_for_each_live_descendant_pre()
- cgroup_for_each_live_descendant_post()

Until now, these didn't need to be exposed because controllers only cared
about the css hierarchy. The planned sched_ext hierarchical scheduler
support will be based on the default cgroup hierarchy, which is in line
with the existing BPF cgroup support, and thus needs these exposed.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 5ee8dbf5

include/linux/cgroup.h

+63 −2
Original line number Diff line number Diff line
@@ -42,6 +42,14 @@ struct kernel_clone_args; 


#ifdef CONFIG_CGROUPS



/*

 * To avoid confusing the compiler (and generating warnings) with code

 * that attempts to access what would be a 0-element array (i.e. sized

 * to a potentially empty array when CGROUP_SUBSYS_COUNT == 0), this

 * constant expression can be added.

 */

#define CGROUP_HAS_SUBSYS_CONFIG	(CGROUP_SUBSYS_COUNT > 0)



enum css_task_iter_flags {

	CSS_TASK_ITER_PROCS    = (1U << 0),  /* walk only threadgroup leaders */

	CSS_TASK_ITER_THREADED = (1U << 1),  /* walk all threaded css_sets in the domain */
@@ -76,6 +84,7 @@ enum cgroup_lifetime_events { 
extern struct file_system_type cgroup_fs_type;

extern struct cgroup_root cgrp_dfl_root;

extern struct css_set init_css_set;

extern struct mutex cgroup_mutex;

extern spinlock_t css_set_lock;

extern struct blocking_notifier_head cgroup_lifetime_notifier;
@@ -103,6 +112,8 @@ extern struct blocking_notifier_head cgroup_lifetime_notifier; 
#define cgroup_subsys_on_dfl(ss)						\

	static_branch_likely(&ss ## _on_dfl_key)



bool cgroup_on_dfl(const struct cgroup *cgrp);



bool css_has_online_children(struct cgroup_subsys_state *css);

struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);

struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgroup,
@@ -274,6 +285,32 @@ void css_task_iter_end(struct css_task_iter *it); 
	for ((pos) = css_next_descendant_post(NULL, (css)); (pos);	\

	     (pos) = css_next_descendant_post((pos), (css)))



/* iterate over child cgrps, lock should be held throughout iteration */

#define cgroup_for_each_live_child(child, cgrp)				\

	list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \

		if (({ lockdep_assert_held(&cgroup_mutex);		\

		       cgroup_is_dead(child); }))			\

			;						\

		else



/* walk live descendants in pre order */

#define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)		\

	css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL))	\

		if (({ lockdep_assert_held(&cgroup_mutex);		\

		       (dsct) = (d_css)->cgroup;			\

		       cgroup_is_dead(dsct); }))			\

			;						\

		else



/* walk live descendants in postorder */

#define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp)		\

	css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL))	\

		if (({ lockdep_assert_held(&cgroup_mutex);		\

		       (dsct) = (d_css)->cgroup;			\

		       cgroup_is_dead(dsct); }))			\

			;						\

		else



/**

 * cgroup_taskset_for_each - iterate cgroup_taskset

 * @task: the loop cursor
@@ -336,6 +373,27 @@ static inline u64 cgroup_id(const struct cgroup *cgrp) 
	return cgrp->kn->id;

}



/**

 * cgroup_css - obtain a cgroup's css for the specified subsystem

 * @cgrp: the cgroup of interest

 * @ss: the subsystem of interest (%NULL returns @cgrp->self)

 *

 * Return @cgrp's css (cgroup_subsys_state) associated with @ss.  This

 * function must be called either under cgroup_mutex or rcu_read_lock() and

 * the caller is responsible for pinning the returned css if it wants to

 * keep accessing it outside the said locks.  This function may return

 * %NULL if @cgrp doesn't have @subsys_id enabled.

 */

static inline struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,

						     struct cgroup_subsys *ss)

{

	if (CGROUP_HAS_SUBSYS_CONFIG && ss)

		return rcu_dereference_check(cgrp->subsys[ss->id],

					lockdep_is_held(&cgroup_mutex));

	else

		return &cgrp->self;

}



/**

 * css_is_dying - test whether the specified css is dying

 * @css: target css
@@ -372,6 +430,11 @@ static inline bool css_is_self(struct cgroup_subsys_state *css) 
	return false;

}



static inline bool cgroup_is_dead(const struct cgroup *cgrp)

{

	return !(cgrp->self.flags & CSS_ONLINE);

}



static inline void cgroup_get(struct cgroup *cgrp)

{

	css_get(&cgrp->self);
@@ -387,8 +450,6 @@ static inline void cgroup_put(struct cgroup *cgrp) 
	css_put(&cgrp->self);

}



extern struct mutex cgroup_mutex;



static inline void cgroup_lock(void)

{

	mutex_lock(&cgroup_mutex);

kernel/cgroup/cgroup-internal.h

+0 −6
Original line number Diff line number Diff line
@@ -184,11 +184,6 @@ extern bool cgrp_dfl_visible; 
	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT &&		\

	     (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)



static inline bool cgroup_is_dead(const struct cgroup *cgrp)

{

	return !(cgrp->self.flags & CSS_ONLINE);

}



static inline bool notify_on_release(const struct cgroup *cgrp)

{

	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
@@ -222,7 +217,6 @@ static inline void get_css_set(struct css_set *cset) 
}



bool cgroup_ssid_enabled(int ssid);

bool cgroup_on_dfl(const struct cgroup *cgrp);



struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root);

struct cgroup *task_cgroup_from_root(struct task_struct *task,

kernel/cgroup/cgroup.c

+0 −55
Original line number Diff line number Diff line
@@ -68,14 +68,6 @@ 
/* let's not notify more than 100 times per second */

#define CGROUP_FILE_NOTIFY_MIN_INTV	DIV_ROUND_UP(HZ, 100)



/*

 * To avoid confusing the compiler (and generating warnings) with code

 * that attempts to access what would be a 0-element array (i.e. sized

 * to a potentially empty array when CGROUP_SUBSYS_COUNT == 0), this

 * constant expression can be added.

 */

#define CGROUP_HAS_SUBSYS_CONFIG	(CGROUP_SUBSYS_COUNT > 0)



/*

 * cgroup_mutex is the master lock.  Any modification to cgroup or its

 * hierarchy must be performed while holding it.
@@ -509,27 +501,6 @@ static u32 cgroup_ss_mask(struct cgroup *cgrp) 
	return cgrp->root->subsys_mask;

}



/**

 * cgroup_css - obtain a cgroup's css for the specified subsystem

 * @cgrp: the cgroup of interest

 * @ss: the subsystem of interest (%NULL returns @cgrp->self)

 *

 * Return @cgrp's css (cgroup_subsys_state) associated with @ss.  This

 * function must be called either under cgroup_mutex or rcu_read_lock() and

 * the caller is responsible for pinning the returned css if it wants to

 * keep accessing it outside the said locks.  This function may return

 * %NULL if @cgrp doesn't have @subsys_id enabled.

 */

static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,

					      struct cgroup_subsys *ss)

{

	if (CGROUP_HAS_SUBSYS_CONFIG && ss)

		return rcu_dereference_check(cgrp->subsys[ss->id],

					lockdep_is_held(&cgroup_mutex));

	else

		return &cgrp->self;

}



/**

 * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss

 * @cgrp: the cgroup of interest
@@ -741,32 +712,6 @@ EXPORT_SYMBOL_GPL(of_css); 
	}								\

} while (false)



/* iterate over child cgrps, lock should be held throughout iteration */

#define cgroup_for_each_live_child(child, cgrp)				\

	list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \

		if (({ lockdep_assert_held(&cgroup_mutex);		\

		       cgroup_is_dead(child); }))			\

			;						\

		else



/* walk live descendants in pre order */

#define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)		\

	css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL))	\

		if (({ lockdep_assert_held(&cgroup_mutex);		\

		       (dsct) = (d_css)->cgroup;			\

		       cgroup_is_dead(dsct); }))			\

			;						\

		else



/* walk live descendants in postorder */

#define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp)		\

	css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL))	\

		if (({ lockdep_assert_held(&cgroup_mutex);		\

		       (dsct) = (d_css)->cgroup;			\

		       cgroup_is_dead(dsct); }))			\

			;						\

		else



/*

 * The default css_set - used by init and its children prior to any

 * hierarchies being mounted. It contains a pointer to the root state