From: Michal Hocko <mhocko@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: linux-mm@kvack.org,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
David Rientjes <rientjes@google.com>,
Vladimir Davydov <vdavydov@parallels.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 05/10] mm, oom: skip vforked tasks from being selected
Date: Thu, 16 Jun 2016 08:24:34 +0200 [thread overview]
Message-ID: <20160616062433.GA30768@dhcp22.suse.cz> (raw)
In-Reply-To: <20160615145106.GC7944@redhat.com>
On Wed 15-06-16 16:51:06, Oleg Nesterov wrote:
> On 06/09, Michal Hocko wrote:
> >
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -1883,6 +1883,32 @@ extern int arch_task_struct_size __read_mostly;
> > #define TNF_FAULT_LOCAL 0x08
> > #define TNF_MIGRATE_FAIL 0x10
> >
> > +static inline bool in_vfork(struct task_struct *tsk)
> > +{
> > + bool ret;
> > +
> > + /*
> > + * need RCU to access ->real_parent if CLONE_VM was used along with
> > + * CLONE_PARENT.
> > + *
> > + * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
> > + * imply CLONE_VM
> > + *
> > + * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
> > + * ->real_parent is not necessarily the task doing vfork(), so in
> > + * theory we can't rely on task_lock() if we want to dereference it.
> > + *
> > + * And in this case we can't trust the real_parent->mm == tsk->mm
> > + * check, it can be false negative. But we do not care, if init or
> > + * another oom-unkillable task does this it should blame itself.
> > + */
> > + rcu_read_lock();
> > + ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
> > + rcu_read_unlock();
> > +
> > + return ret;
> > +}
>
> ACK, but why sched.h ? It has a single caller in oom_kill.c.
It felt like generally reusable helper to get subtle details about the
vfork right.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-06-16 6:24 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-09 11:52 [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-09 11:52 ` [PATCH 01/10] proc, oom: drop bogus task_lock and mm check Michal Hocko
2016-06-09 11:52 ` [PATCH 02/10] proc, oom: drop bogus sighand lock Michal Hocko
2016-06-09 11:52 ` [PATCH 03/10] proc, oom_adj: extract oom_score_adj setting into a helper Michal Hocko
2016-06-09 11:52 ` [PATCH 04/10] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko
2016-06-15 15:03 ` Oleg Nesterov
2016-06-09 11:52 ` [PATCH 05/10] mm, oom: skip vforked tasks from being selected Michal Hocko
2016-06-15 14:51 ` Oleg Nesterov
2016-06-16 6:24 ` Michal Hocko [this message]
2016-06-09 11:52 ` [PATCH 06/10] mm, oom: kill all tasks sharing the mm Michal Hocko
2016-06-09 11:52 ` [PATCH 07/10] mm, oom: fortify task_will_free_mem Michal Hocko
2016-06-09 13:18 ` Tetsuo Handa
2016-06-09 14:20 ` Michal Hocko
2016-06-11 8:10 ` Tetsuo Handa
2016-06-13 11:27 ` Michal Hocko
2016-06-16 12:54 ` Tetsuo Handa
2016-06-16 14:29 ` Michal Hocko
2016-06-16 15:40 ` Tetsuo Handa
2016-06-16 15:53 ` Michal Hocko
2016-06-17 11:38 ` Tetsuo Handa
2016-06-17 12:26 ` Michal Hocko
2016-06-17 13:12 ` Tetsuo Handa
2016-06-17 13:29 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 08/10] mm, oom: task_will_free_mem should skip oom_reaped tasks Michal Hocko
2016-06-17 11:35 ` Tetsuo Handa
2016-06-17 12:56 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 09/10] mm, oom_reaper: do not attempt to reap a task more than twice Michal Hocko
2016-06-15 14:48 ` Oleg Nesterov
2016-06-16 6:28 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init Michal Hocko
2016-06-09 15:15 ` Tetsuo Handa
2016-06-09 15:41 ` Michal Hocko
2016-06-16 13:15 ` Tetsuo Handa
2016-06-16 13:36 ` Tetsuo Handa
2016-06-15 14:37 ` Oleg Nesterov
2016-06-16 6:31 ` Michal Hocko
2016-06-13 11:23 ` [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-13 14:13 ` Michal Hocko
2016-06-14 20:17 ` Oleg Nesterov
2016-06-14 20:44 ` Oleg Nesterov
2016-06-16 6:33 ` Michal Hocko
2016-06-15 15:09 ` Oleg Nesterov
2016-06-16 6:34 ` Michal Hocko
-- strict thread matches above, loose matches on Subject: below --
2016-06-20 12:43 [PATCH 0/10 -v5] " Michal Hocko
2016-06-20 12:43 ` [PATCH 05/10] mm, oom: skip vforked tasks from being selected Michal Hocko
2016-06-03 9:16 [PATCH 0/10 -v3] Handle oom bypass more gracefully Michal Hocko
2016-06-03 9:16 ` [PATCH 05/10] mm, oom: skip vforked tasks from being selected Michal Hocko
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