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cgroup: relocate cgroup_enable_task_cg_lists()

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Move it above so that prototype isn't necessary.  Let's also move the
definition of use_task_css_set_links next to it.

This is purely cosmetic.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2014-02-13 06:58:39 -05:00
commit afeb0f9fd4
1 changed files with 48 additions and 55 deletions
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103
kernel/cgroup.c
View file

@ -173,7 +173,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp);
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
bool is_add);
static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
static void cgroup_enable_task_cg_lists(void);
/**
* cgroup_css - obtain a cgroup's css for the specified subsystem
@ -370,14 +369,6 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
return key;
}
/*
* We don't maintain the lists running through each css_set to its task
* until after the first call to css_task_iter_start(). This reduces the
* fork()/exit() overhead for people who have cgroups compiled into their
* kernel but not actually in use.
*/
static bool use_task_css_set_links __read_mostly;
static void __put_css_set(struct css_set *cset, int taskexit)
{
struct cgrp_cset_link *link, *tmp_link;
@ -1307,6 +1298,54 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
return ret;
}
/*
* To reduce the fork() overhead for systems that are not actually using
* their cgroups capability, we don't maintain the lists running through
* each css_set to its tasks until we see the list actually used - in other
* words after the first mount.
*/
static bool use_task_css_set_links __read_mostly;
static void cgroup_enable_task_cg_lists(void)
{
struct task_struct *p, *g;
write_lock(&css_set_lock);
if (use_task_css_set_links)
goto out_unlock;
use_task_css_set_links = true;
/*
* We need tasklist_lock because RCU is not safe against
* while_each_thread(). Besides, a forking task that has passed
* cgroup_post_fork() without seeing use_task_css_set_links = 1
* is not guaranteed to have its child immediately visible in the
* tasklist if we walk through it with RCU.
*/
read_lock(&tasklist_lock);
do_each_thread(g, p) {
task_lock(p);
WARN_ON_ONCE(!list_empty(&p->cg_list) ||
task_css_set(p) != &init_css_set);
/*
* We should check if the process is exiting, otherwise
* it will race with cgroup_exit() in that the list
* entry won't be deleted though the process has exited.
*/
if (!(p->flags & PF_EXITING))
list_add(&p->cg_list, &task_css_set(p)->tasks);
task_unlock(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
out_unlock:
write_unlock(&css_set_lock);
}
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
atomic_set(&cgrp->refcnt, 1);
@ -2364,52 +2403,6 @@ int cgroup_task_count(const struct cgroup *cgrp)
return count;
}
/*
* To reduce the fork() overhead for systems that are not actually using
* their cgroups capability, we don't maintain the lists running through
* each css_set to its tasks until we see the list actually used - in other
* words after the first mount.
*/
static void cgroup_enable_task_cg_lists(void)
{
struct task_struct *p, *g;
write_lock(&css_set_lock);
if (use_task_css_set_links)
goto out_unlock;
use_task_css_set_links = true;
/*
* We need tasklist_lock because RCU is not safe against
* while_each_thread(). Besides, a forking task that has passed
* cgroup_post_fork() without seeing use_task_css_set_links = 1
* is not guaranteed to have its child immediately visible in the
* tasklist if we walk through it with RCU.
*/
read_lock(&tasklist_lock);
do_each_thread(g, p) {
task_lock(p);
WARN_ON_ONCE(!list_empty(&p->cg_list) ||
task_css_set(p) != &init_css_set);
/*
* We should check if the process is exiting, otherwise
* it will race with cgroup_exit() in that the list
* entry won't be deleted though the process has exited.
*/
if (!(p->flags & PF_EXITING))
list_add(&p->cg_list, &task_css_set(p)->tasks);
task_unlock(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
out_unlock:
write_unlock(&css_set_lock);
}
/**
* css_next_child - find the next child of a given css
* @pos_css: the current position (%NULL to initiate traversal)