From: Michal Hocko <mhocko@kernel.org>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Oleg Nesterov <oleg@redhat.com>, Hugh Dickins <hughd@google.com>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap
Date: Wed, 26 Jul 2017 07:45:57 +0200 [thread overview]
Message-ID: <20170726054557.GB960@dhcp22.suse.cz> (raw)
In-Reply-To: <20170725191952.GR29716@redhat.com>
On Tue 25-07-17 21:19:52, Andrea Arcangeli wrote:
> On Tue, Jul 25, 2017 at 06:04:00PM +0200, Michal Hocko wrote:
> > - down_write(&mm->mmap_sem);
> > + if (tsk_is_oom_victim(current))
> > + down_write(&mm->mmap_sem);
> > free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
> > tlb_finish_mmu(&tlb, 0, -1);
> >
> > @@ -3012,7 +3014,8 @@ void exit_mmap(struct mm_struct *mm)
> > }
> > mm->mmap = NULL;
> > vm_unacct_memory(nr_accounted);
> > - up_write(&mm->mmap_sem);
> > + if (tsk_is_oom_victim(current))
> > + up_write(&mm->mmap_sem);
>
> How is this possibly safe? mark_oom_victim can run while exit_mmap is
> running.
I believe it cannot. We always call mark_oom_victim (on !current) with
task_lock held and check task->mm != NULL and we call do_exit->mmput after
mm is set to NULL under the same lock.
--
Michal Hocko
SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Oleg Nesterov <oleg@redhat.com>, Hugh Dickins <hughd@google.com>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap
Date: Wed, 26 Jul 2017 07:45:57 +0200 [thread overview]
Message-ID: <20170726054557.GB960@dhcp22.suse.cz> (raw)
In-Reply-To: <20170725191952.GR29716@redhat.com>
On Tue 25-07-17 21:19:52, Andrea Arcangeli wrote:
> On Tue, Jul 25, 2017 at 06:04:00PM +0200, Michal Hocko wrote:
> > - down_write(&mm->mmap_sem);
> > + if (tsk_is_oom_victim(current))
> > + down_write(&mm->mmap_sem);
> > free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
> > tlb_finish_mmu(&tlb, 0, -1);
> >
> > @@ -3012,7 +3014,8 @@ void exit_mmap(struct mm_struct *mm)
> > }
> > mm->mmap = NULL;
> > vm_unacct_memory(nr_accounted);
> > - up_write(&mm->mmap_sem);
> > + if (tsk_is_oom_victim(current))
> > + up_write(&mm->mmap_sem);
>
> How is this possibly safe? mark_oom_victim can run while exit_mmap is
> running.
I believe it cannot. We always call mark_oom_victim (on !current) with
task_lock held and check task->mm != NULL and we call do_exit->mmput after
mm is set to NULL under the same lock.
--
Michal Hocko
SUSE Labs
--
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next prev parent reply other threads:[~2017-07-26 5:46 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-24 7:23 [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko
2017-07-24 7:23 ` Michal Hocko
2017-07-24 14:00 ` Kirill A. Shutemov
2017-07-24 14:00 ` Kirill A. Shutemov
2017-07-24 14:15 ` Michal Hocko
2017-07-24 14:15 ` Michal Hocko
2017-07-24 14:51 ` Kirill A. Shutemov
2017-07-24 14:51 ` Kirill A. Shutemov
2017-07-24 16:11 ` Michal Hocko
2017-07-24 16:11 ` Michal Hocko
2017-07-25 14:17 ` Kirill A. Shutemov
2017-07-25 14:17 ` Kirill A. Shutemov
2017-07-25 14:26 ` Michal Hocko
2017-07-25 14:26 ` Michal Hocko
2017-07-25 15:07 ` Kirill A. Shutemov
2017-07-25 15:07 ` Kirill A. Shutemov
2017-07-25 15:15 ` Michal Hocko
2017-07-25 15:15 ` Michal Hocko
2017-07-25 14:26 ` Michal Hocko
2017-07-25 15:17 ` Kirill A. Shutemov
2017-07-25 15:17 ` Kirill A. Shutemov
2017-07-25 15:23 ` Michal Hocko
2017-07-25 15:23 ` Michal Hocko
2017-07-25 15:31 ` Kirill A. Shutemov
2017-07-25 15:31 ` Kirill A. Shutemov
2017-07-25 16:04 ` Michal Hocko
2017-07-25 16:04 ` Michal Hocko
2017-07-25 19:19 ` Andrea Arcangeli
2017-07-25 19:19 ` Andrea Arcangeli
2017-07-26 5:45 ` Michal Hocko [this message]
2017-07-26 5:45 ` Michal Hocko
2017-07-26 16:29 ` Andrea Arcangeli
2017-07-26 16:29 ` Andrea Arcangeli
2017-07-26 16:43 ` Andrea Arcangeli
2017-07-26 16:43 ` Andrea Arcangeli
2017-07-27 6:50 ` Michal Hocko
2017-07-27 6:50 ` Michal Hocko
2017-07-27 14:55 ` Andrea Arcangeli
2017-07-27 14:55 ` Andrea Arcangeli
2017-07-28 6:23 ` Michal Hocko
2017-07-28 6:23 ` Michal Hocko
2017-07-28 1:58 ` [PATCH 1/1] mm: oom: let oom_reap_task and exit_mmap to run kbuild test robot
2017-08-15 0:20 ` [PATCH] mm, oom: allow oom reaper to race with exit_mmap David Rientjes
2017-08-15 0:20 ` David Rientjes
2017-07-24 15:27 ` Michal Hocko
2017-07-24 15:27 ` Michal Hocko
2017-07-24 16:42 ` kbuild test robot
2017-07-24 18:12 ` Michal Hocko
2017-07-24 18:12 ` Michal Hocko
2017-07-25 15:26 ` Andrea Arcangeli
2017-07-25 15:26 ` Andrea Arcangeli
2017-07-25 15:45 ` Michal Hocko
2017-07-25 15:45 ` Michal Hocko
2017-07-25 18:26 ` Andrea Arcangeli
2017-07-25 18:26 ` Andrea Arcangeli
2017-07-26 5:45 ` Michal Hocko
2017-07-26 5:45 ` Michal Hocko
2017-07-26 16:39 ` Andrea Arcangeli
2017-07-26 16:39 ` Andrea Arcangeli
2017-07-27 6:32 ` Michal Hocko
2017-07-27 6:32 ` Michal Hocko
2017-07-27 8:29 Manish Jaggi
2017-07-27 9:24 ` Michal Hocko
2017-08-10 8:16 Michal Hocko
2017-08-10 8:16 ` Michal Hocko
2017-08-10 18:05 ` Andrea Arcangeli
2017-08-10 18:05 ` Andrea Arcangeli
2017-08-10 18:51 ` Michal Hocko
2017-08-10 18:51 ` Michal Hocko
2017-08-10 20:36 ` Michal Hocko
2017-08-10 20:36 ` Michal Hocko
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