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Commit 49d1dc4b authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: implement static_key based cgroup_subsys_enabled() and cgroup_subsys_on_dfl() 



Whether a subsys is enabled and attached to the default hierarchy
seldom changes and may be tested in the hot paths.  This patch
implements static_key based cgroup_subsys_enabled() and
cgroup_subsys_on_dfl() tests.

The following patches will update the users and remove duplicate
mechanisms.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarZefan Li <lizefan@huawei.com>
parent fa128fd7

include/linux/cgroup.h

+21 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/fs.h>

#include <linux/seq_file.h>

#include <linux/kernfs.h>

#include <linux/jump_label.h>



#include <linux/cgroup-defs.h>
@@ -50,6 +51,26 @@ extern struct css_set init_css_set; 
#include <linux/cgroup_subsys.h>

#undef SUBSYS



#define SUBSYS(_x)								\

	extern struct static_key_true _x ## _cgrp_subsys_enabled_key;		\

	extern struct static_key_true _x ## _cgrp_subsys_on_dfl_key;

#include <linux/cgroup_subsys.h>

#undef SUBSYS



/**

 * cgroup_subsys_enabled - fast test on whether a subsys is enabled

 * @ss: subsystem in question

 */

#define cgroup_subsys_enabled(ss)						\

	static_branch_likely(&ss ## _enabled_key)



/**

 * cgroup_subsys_on_dfl - fast test on whether a subsys is on default hierarchy

 * @ss: subsystem in question

 */

#define cgroup_subsys_on_dfl(ss)						\

	static_branch_likely(&ss ## _on_dfl_key)



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_get_e_css(struct cgroup *cgroup,

kernel/cgroup.c

+26 −1
Original line number Diff line number Diff line
@@ -139,6 +139,27 @@ static const char *cgroup_subsys_name[] = { 
};

#undef SUBSYS



/* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */

#define SUBSYS(_x)								\

	DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key);			\

	DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key);			\

	EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key);			\

	EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);

#include <linux/cgroup_subsys.h>

#undef SUBSYS



#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,

static struct static_key_true *cgroup_subsys_enabled_key[] = {

#include <linux/cgroup_subsys.h>

};

#undef SUBSYS



#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,

static struct static_key_true *cgroup_subsys_on_dfl_key[] = {

#include <linux/cgroup_subsys.h>

};

#undef SUBSYS



/*

 * The default hierarchy, reserved for the subsystems that are otherwise

 * unattached - it never has more than a single cgroup, and all tasks are
@@ -1319,9 +1340,12 @@ static int rebind_subsystems(struct cgroup_root *dst_root, 


		/* default hierarchy doesn't enable controllers by default */

		dst_root->subsys_mask |= 1 << ssid;

		if (dst_root != &cgrp_dfl_root) {

		if (dst_root == &cgrp_dfl_root) {

			static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);

		} else {

			dst_root->cgrp.subtree_control |= 1 << ssid;

			cgroup_refresh_child_subsys_mask(&dst_root->cgrp);

			static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);

		}



		if (ss->bind)
@@ -5483,6 +5507,7 @@ static int __init cgroup_disable(char *str) 
			    strcmp(token, ss->legacy_name))

				continue;



			static_branch_disable(cgroup_subsys_enabled_key[i]);

			ss->disabled = 1;

			printk(KERN_INFO "Disabling %s control group subsystem\n",

			       ss->name);