From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Michal Hocko <mhocko@kernel.org>
Cc: Vegard Nossum <vegard.nossum@oracle.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Rik van Riel <riel@redhat.com>,
Matthew Wilcox <mawilcox@microsoft.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>, Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: crash during oom reaper (was: Re: [PATCH 4/4] [RFC!] mm: 'struct mm_struct' reference counting debugging)
Date: Fri, 16 Dec 2016 13:44:38 +0300 [thread overview]
Message-ID: <20161216104438.GD27758@node> (raw)
In-Reply-To: <20161216101113.GE13940@dhcp22.suse.cz>
On Fri, Dec 16, 2016 at 11:11:13AM +0100, Michal Hocko wrote:
> On Fri 16-12-16 10:43:52, Vegard Nossum wrote:
> [...]
> > I don't think it's a bug in the OOM reaper itself, but either of the
> > following two patches will fix the problem (without my understand how or
> > why):
> >
> > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > index ec9f11d4f094..37b14b2e2af4 100644
> > --- a/mm/oom_kill.c
> > +++ b/mm/oom_kill.c
> > @@ -485,7 +485,7 @@ static bool __oom_reap_task_mm(struct task_struct *tsk,
> > struct mm_struct *mm)
> > */
> > mutex_lock(&oom_lock);
> >
> > - if (!down_read_trylock(&mm->mmap_sem)) {
> > + if (!down_write_trylock(&mm->mmap_sem)) {
>
> __oom_reap_task_mm is basically the same thing as MADV_DONTNEED and that
> doesn't require the exlusive mmap_sem. So this looks correct to me.
BTW, shouldn't we filter out all VM_SPECIAL VMAs there? Or VM_PFNMAP at
least.
MADV_DONTNEED doesn't touch VM_PFNMAP, but I don't see anything matching
on __oom_reap_task_mm() side.
Other difference is that you use unmap_page_range() witch doesn't touch
mmu_notifiers. MADV_DONTNEED goes via zap_page_range(), which invalidates
the range. Not sure if it can make any difference here.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2016-12-16 10:46 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-16 8:21 [PATCH 1/4] mm: add new mmgrab() helper Vegard Nossum
2016-12-16 8:22 ` [PATCH 2/4] mm: add new mmget() helper Vegard Nossum
2016-12-16 9:26 ` Michal Hocko
2016-12-16 8:22 ` [PATCH 3/4] mm: use mmget_not_zero() helper Vegard Nossum
2016-12-16 9:27 ` Michal Hocko
2016-12-16 8:22 ` [PATCH 4/4] [RFC!] mm: 'struct mm_struct' reference counting debugging Vegard Nossum
2016-12-16 9:01 ` Michal Hocko
2016-12-16 9:43 ` Vegard Nossum
2016-12-16 10:11 ` crash during oom reaper (was: Re: [PATCH 4/4] [RFC!] mm: 'struct mm_struct' reference counting debugging) Michal Hocko
2016-12-16 10:44 ` Kirill A. Shutemov [this message]
2016-12-16 11:42 ` crash during oom reaper Michal Hocko
2016-12-16 12:12 ` Michal Hocko
2016-12-16 12:35 ` Kirill A. Shutemov
2016-12-16 12:56 ` Michal Hocko
2016-12-16 13:07 ` Kirill A. Shutemov
2016-12-16 13:14 ` Michal Hocko
2016-12-18 13:47 ` Tetsuo Handa
2016-12-18 16:06 ` Michal Hocko
2016-12-16 13:14 ` Vegard Nossum
2016-12-16 14:00 ` Michal Hocko
2016-12-16 14:25 ` Vegard Nossum
2016-12-16 14:32 ` Michal Hocko
2016-12-16 14:53 ` Vegard Nossum
2016-12-16 14:04 ` Vegard Nossum
2016-12-16 9:14 ` [PATCH 1/4] mm: add new mmgrab() helper Michal Hocko
2016-12-16 9:56 ` Peter Zijlstra
2016-12-16 10:19 ` Kirill A. Shutemov
2016-12-16 10:20 ` Vegard Nossum
2016-12-16 10:36 ` Michal Hocko
2016-12-16 11:14 ` Vegard Nossum
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