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Subject[PATCH 04/16] cgroup: relocate cgroup_enable_task_cg_lists()
Date
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>
---
kernel/cgroup.c | 103 ++++++++++++++++++++++++++------------------------------
1 file changed, 48 insertions(+), 55 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index efae7e2..1ebc6e30 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -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;
@@ -1305,6 +1296,54 @@ 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);
@@ -2363,52 +2402,6 @@ 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)
--
1.8.5.3


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