From: Oleg Nesterov <oleg@redhat.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>, Tejun Heo <tj@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Mandeep Singh Baines <msb@chromium.org>,
Containers <containers@lists.linux-foundation.org>,
Cgroups <cgroups@vger.kernel.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Paul Menage <paul@paulmenage.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: Q: cgroup: Questions about possible issues in cgroup locking
Date: Wed, 21 Dec 2011 19:11:01 +0100 [thread overview]
Message-ID: <20111221181101.GA3092@redhat.com> (raw)
In-Reply-To: <20111221175943.GG17668@somewhere>
On 12/21, Frederic Weisbecker wrote:
>
> On Wed, Dec 21, 2011 at 02:08:48PM +0100, Oleg Nesterov wrote:
> > On 12/21, Frederic Weisbecker wrote:
> > > - By the time we call cgroup_post_fork(), it is ready to be woken up
> > > and usable by the scheduler.
> >
> > No, the new child can't run until do_fork()->wake_up_new_task().
>
> Out of curiosity, why is it not possible for a task to kill and wake up the child
> before that happens?
Because it is not possible to wake it up.
Please note that copy_process() creates the "deactivated" child, iow
it is not on rq.
But, at the same time its ->state == TASK_RUNNING. This "fools"
try_to_wake_up() or anything else which in theory could place it
on the runqueue.
Except, of course, wake_up_new_task() does activate_task(). And
note that it does this unconditionally, exactly because we know that
this task can't be woken.
Oleg.
next prev parent reply other threads:[~2011-12-21 18:22 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-21 3:43 Q: cgroup: Questions about possible issues in cgroup locking Frederic Weisbecker
2011-12-21 13:08 ` Oleg Nesterov
2011-12-21 17:56 ` Frederic Weisbecker
2011-12-21 19:01 ` Mandeep Singh Baines
2011-12-21 19:08 ` Frederic Weisbecker
2011-12-21 19:24 ` Mandeep Singh Baines
2011-12-21 20:04 ` Frederic Weisbecker
2011-12-22 15:30 ` Oleg Nesterov
2012-01-04 19:36 ` Mandeep Singh Baines
2012-01-06 15:23 ` Oleg Nesterov
2012-01-06 18:25 ` Mandeep Singh Baines
2012-01-11 16:07 ` Oleg Nesterov
2012-01-12 0:31 ` Mandeep Singh Baines
2012-01-12 17:07 ` Oleg Nesterov
2012-01-12 17:57 ` Mandeep Singh Baines
2012-01-13 15:20 ` Oleg Nesterov
2012-01-13 18:27 ` Mandeep Singh Baines
2012-01-14 17:36 ` Oleg Nesterov
2012-01-18 23:17 ` Mandeep Singh Baines
2012-01-19 15:45 ` Oleg Nesterov
2012-01-19 18:18 ` Mandeep Singh Baines
2012-01-20 15:06 ` Oleg Nesterov
2012-03-20 19:34 ` Oleg Nesterov
2012-03-21 18:59 ` Mandeep Singh Baines
2012-03-23 17:51 ` Oleg Nesterov
2011-12-21 17:59 ` Frederic Weisbecker
2011-12-21 18:11 ` Oleg Nesterov [this message]
2011-12-21 18:23 ` Frederic Weisbecker
2012-02-01 16:28 ` Frederic Weisbecker
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