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sched, autogroup: Stop going ahead if autogroup is disabled

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when autogroup is disable from the beginning,
sched_autogroup_create_attach()
  autogroup_move_group()                    <== 1
    sched_move_task()                       <== 2
      task_move_group_fair()
        set_task_rq()
          task_group()
            autogroup_task_group()

We go the whole path without doing anything useful.

Then stop going further if autogroup is disabled.

But there will be a race window between 1 and 2, in which
sysctl_sched_autogroup_enabled is enabled. This issue
will be toke by following patch.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <1298185696-4403-4-git-send-email-yong.zhang0@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Yong Zhang 2011-02-20 15:08:14 +08:00 committed by Ingo Molnar
parent 1747b21fec
commit 800d4d30c8
2 changed files with 9 additions and 0 deletions
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4
kernel/sched_autogroup.c
View file

@ -161,11 +161,15 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag)
p->signal->autogroup = autogroup_kref_get(ag);
if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
goto out;
t = p;
do {
sched_move_task(t);
} while_each_thread(p, t);
out:
unlock_task_sighand(p, &flags);
autogroup_kref_put(prev);
}

5
kernel/sched_autogroup.h
View file

@ -1,6 +1,11 @@
#ifdef CONFIG_SCHED_AUTOGROUP
struct autogroup {
/*
* reference doesn't mean how many thread attach to this
* autogroup now. It just stands for the number of task
* could use this autogroup.
*/
struct kref kref;
struct task_group *tg;
struct rw_semaphore lock;