linux-kernel - Re: [PATCH 2/2] oom-clear-tif_memdie-after-oom_reaper-managed-to-unmap-the-address-space-fix

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Date:	Wed, 9 Mar 2016 13:21:42 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	<linux-mm@...ck.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	David Rientjes <rientjes@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 2/2] 
 oom-clear-tif_memdie-after-oom_reaper-managed-to-unmap-the-address-space-fix

On Tue,  8 Mar 2016 14:12:17 +0100 Michal Hocko <mhocko@...nel.org> wrote:

> From: Michal Hocko <mhocko@...e.com>
> 
> fix a left over
> 
> Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Signed-off-by: Michal Hocko <mhocko@...e.com>
> ---
>  mm/oom_kill.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 70fff7e3b1a7..b6228643367b 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -569,7 +569,7 @@ static int __init oom_init(void)
>  }
>  subsys_initcall(oom_init)
>  #else
> -static void wake_oom_reaper(struct task_struct *mm)
> +static void wake_oom_reaper(struct task_struct *tsk)
>  {
>  }
>  #endif

Thanks.

I found the below patch lying around but I didn't queue it properly. 
Is it legit?


From: Johannes Weiner <hannes@...xchg.org>
Subject: oom-clear-tif_memdie-after-oom_reaper-managed-to-unmap-the-address-space-fix

When the OOM killer scans tasks and encounters a PF_EXITING one, it
force-selects that one regardless of the score. Is there a possibility
that the task might hang after it has set PF_EXITING? In that case the
OOM killer should be able to move on to the next task.

Frankly, I don't even know why we check for exiting tasks in the OOM
killer. We've tried direct reclaim at least 15 times by the time we
decide the system is OOM, there was plenty of time to exit and free
memory; and a task might exit voluntarily right after we issue a kill.
This is testing pure noise.

Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Andrea Argangeli <andrea@...nel.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Sasha Levin <sasha.levin@...cle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 mm/oom_kill.c |    3 ---
 1 file changed, 3 deletions(-)

diff -puN mm/oom_kill.c~oom-clear-tif_memdie-after-oom_reaper-managed-to-unmap-the-address-space-fix mm/oom_kill.c
--- a/mm/oom_kill.c~oom-clear-tif_memdie-after-oom_reaper-managed-to-unmap-the-address-space-fix
+++ a/mm/oom_kill.c
@@ -292,9 +292,6 @@ enum oom_scan_t oom_scan_process_thread(
 	if (oom_task_origin(task))
 		return OOM_SCAN_SELECT;
 
-	if (task_will_free_mem(task) && !is_sysrq_oom(oc))
-		return OOM_SCAN_ABORT;
-
 	return OOM_SCAN_OK;
 }
 
_