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authorLi Zefan <lizf@cn.fujitsu.com>2008-04-29 12:00:13 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-29 19:06:10 +0400
commite8d55fdeb882cfcb5e8db5a5ce16edfba78aafc5 (patch)
tree0c0a7338d8adb2aaf4310eb89d1679c802ea617d
parent472b1053f3c319cc60bfb2a0bb062fed77a93eb6 (diff)
downloadlinux-e8d55fdeb882cfcb5e8db5a5ce16edfba78aafc5.tar.xz
cgroups: simplify init_subsys()
We are at system boot and there is only 1 cgroup group (i,e, init_css_set), so we don't need to run through the css_set linked list. Neither do we need to run through the task list, since no processes have been created yet. Also referring to a comment in cgroup.h: struct css_set { ... /* * Set of subsystem states, one for each subsystem. This array * is immutable after creation apart from the init_css_set * during subsystem registration (at boot time). */ struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT]; } Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Reviewed-by: Paul Menage <menage@google.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/cgroups.txt3
-rw-r--r--kernel/cgroup.c35
2 files changed, 10 insertions, 28 deletions
diff --git a/Documentation/cgroups.txt b/Documentation/cgroups.txt
index 31d12e21ff8a..c298a6690e0d 100644
--- a/Documentation/cgroups.txt
+++ b/Documentation/cgroups.txt
@@ -500,8 +500,7 @@ post-attachment activity that requires memory allocations or blocking.
void fork(struct cgroup_subsy *ss, struct task_struct *task)
-Called when a task is forked into a cgroup. Also called during
-registration for all existing tasks.
+Called when a task is forked into a cgroup.
void exit(struct cgroup_subsys *ss, struct task_struct *task)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c447c29f8749..b893c8c94858 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2477,7 +2477,6 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
{
struct cgroup_subsys_state *css;
- struct list_head *l;
printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
@@ -2488,35 +2487,19 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
BUG_ON(IS_ERR(css));
init_cgroup_css(css, ss, dummytop);
- /* Update all cgroup groups to contain a subsys
+ /* Update the init_css_set to contain a subsys
* pointer to this state - since the subsystem is
- * newly registered, all tasks and hence all cgroup
- * groups are in the subsystem's top cgroup. */
- write_lock(&css_set_lock);
- l = &init_css_set.list;
- do {
- struct css_set *cg =
- list_entry(l, struct css_set, list);
- cg->subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
- l = l->next;
- } while (l != &init_css_set.list);
- write_unlock(&css_set_lock);
-
- /* If this subsystem requested that it be notified with fork
- * events, we should send it one now for every process in the
- * system */
- if (ss->fork) {
- struct task_struct *g, *p;
-
- read_lock(&tasklist_lock);
- do_each_thread(g, p) {
- ss->fork(ss, p);
- } while_each_thread(g, p);
- read_unlock(&tasklist_lock);
- }
+ * newly registered, all tasks and hence the
+ * init_css_set is in the subsystem's top cgroup. */
+ init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
need_forkexit_callback |= ss->fork || ss->exit;
+ /* At system boot, before all subsystems have been
+ * registered, no tasks have been forked, so we don't
+ * need to invoke fork callbacks here. */
+ BUG_ON(!list_empty(&init_task.tasks));
+
ss->active = 1;
}