From: David Rientjes <rientjes@google.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Oleg Nesterov <oleg@redhat.com>,
Andrea Argangeli <andrea@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [RFC PATCH] mm, oom: allow oom reaper to race with exit_mmap
Date: Mon, 10 Jul 2017 16:55:22 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.10.1707101652260.54972@chino.kir.corp.google.com> (raw)
In-Reply-To: <20170626130346.26314-1-mhocko@kernel.org>
On Mon, 26 Jun 2017, Michal Hocko wrote:
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 3bd5ecd20d4d..253808e716dc 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2962,6 +2962,11 @@ void exit_mmap(struct mm_struct *mm)
> /* Use -1 here to ensure all VMAs in the mm are unmapped */
> unmap_vmas(&tlb, vma, 0, -1);
>
> + /*
> + * oom reaper might race with exit_mmap so make sure we won't free
> + * page tables or unmap VMAs under its feet
> + */
> + down_write(&mm->mmap_sem);
> free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
> tlb_finish_mmu(&tlb, 0, -1);
>
> @@ -2974,7 +2979,9 @@ void exit_mmap(struct mm_struct *mm)
> nr_accounted += vma_pages(vma);
> vma = remove_vma(vma);
> }
> + mm->mmap = NULL;
> vm_unacct_memory(nr_accounted);
> + up_write(&mm->mmap_sem);
> }
>
> /* Insert vm structure into process list sorted by address
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 0e2c925e7826..5dc0ff22d567 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -472,36 +472,8 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
> struct vm_area_struct *vma;
> bool ret = true;
>
> - /*
> - * We have to make sure to not race with the victim exit path
> - * and cause premature new oom victim selection:
> - * __oom_reap_task_mm exit_mm
> - * mmget_not_zero
> - * mmput
> - * atomic_dec_and_test
> - * exit_oom_victim
> - * [...]
> - * out_of_memory
> - * select_bad_process
> - * # no TIF_MEMDIE task selects new victim
> - * unmap_page_range # frees some memory
> - */
> - mutex_lock(&oom_lock);
> -
> - if (!down_read_trylock(&mm->mmap_sem)) {
> - ret = false;
> - goto unlock_oom;
> - }
> -
> - /*
> - * increase mm_users only after we know we will reap something so
> - * that the mmput_async is called only when we have reaped something
> - * and delayed __mmput doesn't matter that much
> - */
> - if (!mmget_not_zero(mm)) {
> - up_read(&mm->mmap_sem);
> - goto unlock_oom;
> - }
> + if (!down_read_trylock(&mm->mmap_sem))
> + return false;
I think this should return true if mm->mmap == NULL here.
--
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next prev parent reply other threads:[~2017-07-10 23:55 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-26 13:03 [RFC PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko
2017-06-27 10:52 ` Tetsuo Handa
2017-06-27 11:26 ` Michal Hocko
2017-06-27 11:39 ` Tetsuo Handa
2017-06-27 12:03 ` Michal Hocko
2017-06-27 13:31 ` Tetsuo Handa
2017-06-27 13:55 ` Michal Hocko
2017-06-27 14:26 ` Tetsuo Handa
2017-06-27 14:41 ` Michal Hocko
2017-07-11 0:01 ` David Rientjes
2017-06-29 8:46 ` Michal Hocko
2017-07-19 5:55 ` Michal Hocko
2017-07-20 1:18 ` Hugh Dickins
2017-07-20 13:05 ` Michal Hocko
2017-07-24 6:39 ` Hugh Dickins
2017-07-10 23:55 ` David Rientjes [this message]
2017-07-11 6:58 ` Michal Hocko
2017-07-11 20:40 ` David Rientjes
2017-07-12 7:12 ` Michal Hocko
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