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Groups > linux.kernel > #1228854
| From | Michal Hocko <mhocko@kernel.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: can't oom-kill zap the victim's memory? |
| Date | 2015-09-20 11:40 +0200 |
| Message-ID | <qaJge-4nK-9@gated-at.bofh.it> (permalink) |
| References | <q9LN8-2Wt-13@gated-at.bofh.it> <qarW1-4WN-1@gated-at.bofh.it> <qayNP-6j1-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Sat 19-09-15 15:24:02, Linus Torvalds wrote:
> On Sat, Sep 19, 2015 at 8:03 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> > +
> > +static void oom_unmap_func(struct work_struct *work)
> > +{
> > + struct mm_struct *mm = xchg(&oom_unmap_mm, NULL);
> > +
> > + if (!atomic_inc_not_zero(&mm->mm_users))
> > + return;
> > +
> > + // If this is not safe we can do use_mm() + unuse_mm()
> > + down_read(&mm->mmap_sem);
>
> I don't think this is safe.
>
> What makes you sure that we might not deadlock on the mmap_sem here?
> For all we know, the process that is going out of memory is in the
> middle of a mmap(), and already holds the mmap_sem for writing. No?
>
> So at the very least that needs to be a trylock, I think.
Agreed.
> And I'm not
> sure zap_page_range() is ok with the mmap_sem only held for reading.
> Normally our rule is that you can *populate* the page tables
> concurrently, but you can't tear the down
Actually mmap_sem for reading should be sufficient because we do not
alter the layout. Both MADV_DONTNEED and MADV_FREE require read mmap_sem
for example.
--
Michal Hocko
SUSE Labs
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[PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Kyle Walker <kwalker@redhat.com> - 2015-09-17 20:10 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-17 21:30 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Christoph Lameter <cl@linux.com> - 2015-09-18 17:50 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-18 18:30 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-18 18:50 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-18 19:00 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Christoph Lameter <cl@linux.com> - 2015-09-18 19:10 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-18 21:20 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Christoph Lameter <cl@linux.com> - 2015-09-18 21:20 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Christoph Lameter <cl@linux.com> - 2015-09-19 00:10 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Michal Hocko <mhocko@kernel.org> - 2015-09-19 10:40 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-19 16:40 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Michal Hocko <mhocko@kernel.org> - 2015-09-19 18:00 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks David Rientjes <rientjes@google.com> - 2015-09-22 01:40 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-22 07:40 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-19 16:50 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks David Rientjes <rientjes@google.com> - 2015-09-22 01:30 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Michal Hocko <mhocko@kernel.org> - 2015-09-19 10:30 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Michal Hocko <mhocko@kernel.org> - 2015-09-19 10:30 +0200
Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks David Rientjes <rientjes@google.com> - 2015-09-22 01:10 +0200
can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-19 17:10 +0200
Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-19 17:20 +0200
Re: can't oom-kill zap the victim's memory? Michal Hocko <mhocko@kernel.org> - 2015-09-19 18:00 +0200
Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-20 15:20 +0200
Re: can't oom-kill zap the victim's memory? Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-20 00:30 +0200
Re: can't oom-kill zap the victim's memory? Raymond Jennings <shentino@gmail.com> - 2015-09-20 01:10 +0200
Re: can't oom-kill zap the victim's memory? Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-20 01:20 +0200
Re: can't oom-kill zap the victim's memory? Michal Hocko <mhocko@kernel.org> - 2015-09-20 11:40 +0200
Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-20 15:10 +0200
Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-20 15:10 +0200
Re: can't oom-kill zap the victim's memory? Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-20 20:10 +0200
Re: can't oom-kill zap the victim's memory? Raymond Jennings <shentino@gmail.com> - 2015-09-20 21:10 +0200
Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-21 16:10 +0200
Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-21 15:50 +0200
Re: can't oom-kill zap the victim's memory? Michal Hocko <mhocko@kernel.org> - 2015-09-21 16:30 +0200
Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-21 17:40 +0200
Re: can't oom-kill zap the victim's memory? Michal Hocko <mhocko@kernel.org> - 2015-09-21 18:20 +0200
Re: can't oom-kill zap the victim's memory? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-21 19:00 +0200
Re: can't oom-kill zap the victim's memory? David Rientjes <rientjes@google.com> - 2015-09-22 01:50 +0200
Re: can't oom-kill zap the victim's memory? Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-21 19:00 +0200
Re: can't oom-kill zap the victim's memory? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-20 17:00 +0200
Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-20 17:00 +0200
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