sched, autogroup: Stop claiming ownership of the root task group

Disown it, and only display autogroup association if one exists.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Reviewed-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1298383320.8036.5.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched_autogroup.c b/kernel/sched_autogroup.c
index 137a096..5946ac5 100644 (file)
--- a/kernel/sched_autogroup.c
+++ b/kernel/sched_autogroup.c
@@ -12,7 +12,6 @@ static atomic_t autogroup_seq_nr;
 static void __init autogroup_init(struct task_struct *init_task)
 {
        autogroup_default.tg = &root_task_group;
-       root_task_group.autogroup = &autogroup_default;
        kref_init(&autogroup_default.kref);
        init_rwsem(&autogroup_default.lock);
        init_task->signal->autogroup = &autogroup_default;
@@ -130,7 +129,7 @@ task_wants_autogroup(struct task_struct *p, struct task_group *tg)
 
 static inline bool task_group_is_autogroup(struct task_group *tg)
 {
-       return tg != &root_task_group && tg->autogroup;
+       return !!tg->autogroup;
 }
 
 static inline struct task_group *
@@ -251,10 +250,14 @@ void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 {
        struct autogroup *ag = autogroup_task_get(p);
 
+       if (!task_group_is_autogroup(ag->tg))
+               goto out;
+
        down_read(&ag->lock);
        seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
        up_read(&ag->lock);
 
+out:
        autogroup_kref_put(ag);
 }
 #endif /* CONFIG_PROC_FS */
@@ -262,9 +265,7 @@ void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 #ifdef CONFIG_SCHED_DEBUG
 static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
 {
-       int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
-
-       if (!enabled || !tg->autogroup)
+       if (!task_group_is_autogroup(tg))
                return 0;
 
        return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);