From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: David Rientjes <rientjes@google.com>
Cc: kosaki.motohiro@jp.fujitsu.com, Ying Han <yinghan@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Rik van Riel <riel@redhat.com>,
linux-mm@kvack.org
Subject: Re: [patch 1/3 v3] oom: add per-mm oom disable count
Date: Thu, 2 Sep 2010 09:50:26 +0900 (JST) [thread overview]
Message-ID: <20100902092235.D062.A69D9226@jp.fujitsu.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1009011637000.8831@chino.kir.corp.google.com>
> > > > > @@ -1690,6 +1697,10 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
> > > > > active_mm = current->active_mm;
> > > > > current->mm = new_mm;
> > > > > current->active_mm = new_mm;
> > > > > + if (current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
> > > > > + atomic_dec(&mm->oom_disable_count);
> > > > > + atomic_inc(&new_mm->oom_disable_count);
> > > > > + }
> > > > > activate_mm(active_mm, new_mm);
> > > > > new_mm = mm;
> > > > > }
> > > >
> > > > This place, we are grabbing task_lock(), but task_lock don't prevent
> > > > to change signal->oom_score_adj from another thread. This seems racy.
> > > >
> > >
> > > It does, task_lock(current) protects current->signal->oom_score_adj from
> > > changing in oom-add-per-mm-oom-disable-count.patch.
> > >
> > > I'll add the task_lock(p) in mm_init(), thanks for the review!
> >
> > Wait, can you please elabolate more? task_lock() only lock one thread.
> > Why can it protect multi-thread race?
> >
>
> We take task_lock(tsk) whenever we change tsk->signal->oom_score_adj.
example, Process P1 has threads T1 and T2.
oom_score_adj_write() take task_lock(T1) and siglock(P1). unshare() take
task_lock(T2). How protect?
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prev parent reply other threads:[~2010-09-02 0:50 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-20 22:41 David Rientjes
2010-08-20 22:41 ` [patch 2/3 v3] oom: avoid killing a task if a thread sharing its mm cannot be killed David Rientjes
2010-08-22 9:49 ` KOSAKI Motohiro
2010-08-22 23:14 ` David Rientjes
2010-08-20 22:41 ` [patch 3/3 v3] oom: kill all threads sharing oom killed task's mm David Rientjes
2010-08-20 23:52 ` David Rientjes
2010-08-23 23:16 ` Andrew Morton
2010-08-24 0:57 ` David Rientjes
2010-08-23 23:13 ` [patch 1/3 v3] oom: add per-mm oom disable count Andrew Morton
2010-08-24 0:53 ` David Rientjes
2010-08-27 21:48 ` Andrew Morton
2010-08-28 22:25 ` [patch] oom: fix locking for oom_adj and oom_score_adj David Rientjes
2010-08-30 4:39 ` [patch 1/3 v3] oom: add per-mm oom disable count KOSAKI Motohiro
2010-08-30 21:14 ` David Rientjes
2010-08-31 23:54 ` KOSAKI Motohiro
2010-09-01 23:41 ` David Rientjes
2010-09-02 0:50 ` KOSAKI Motohiro [this message]
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