[PATCH] mm: oom: do not reap task if there are live threads in threadgroup

[PATCH] mm: oom: do not reap task if there are live threads in threadgroup

[Vladimir Davydov]

If the current process is exiting, we don't invoke oom killer, instead
we give it access to memory reserves and try to reap its mm in case
nobody is going to use it. There's a mistake in the code performing this
check - we just ignore any process of the same thread group no matter if
it is exiting or not - see try_oom_reaper. Fix it.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
---
 mm/oom_kill.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index c0e37dd1422f..03bf7a472296 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -618,8 +618,6 @@ void try_oom_reaper(struct task_struct *tsk)
 
 			if (!process_shares_mm(p, mm))
 				continue;
-			if (same_thread_group(p, tsk))
-				continue;
 			if (fatal_signal_pending(p))
 				continue;
 
-- 
2.1.4

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Re: [PATCH] mm: oom: do not reap task if there are live threads in threadgroup

[Michal Hocko]

On Tue 24-05-16 14:00:28, Vladimir Davydov wrote:
> If the current process is exiting, we don't invoke oom killer, instead
> we give it access to memory reserves and try to reap its mm in case
> nobody is going to use it. There's a mistake in the code performing this
> check - we just ignore any process of the same thread group no matter if
> it is exiting or not - see try_oom_reaper. Fix it.

This is not a problem with the current code because of 98748bd72200
("oom: consider multi-threaded tasks in task_will_free_mem") which got
merged later on, however.

The check is not needed so we can indeed drop it.

Fixes: 3ef22dfff239 ("oom, oom_reaper: try to reap tasks which skip
regular OOM killer path")

Just in case somebody wants to backport only 3ef22dfff239.

> Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

> ---
>  mm/oom_kill.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index c0e37dd1422f..03bf7a472296 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -618,8 +618,6 @@ void try_oom_reaper(struct task_struct *tsk)
>  
>  			if (!process_shares_mm(p, mm))
>  				continue;
> -			if (same_thread_group(p, tsk))
> -				continue;
>  			if (fatal_signal_pending(p))
>  				continue;
>  
> -- 
> 2.1.4

-- 
Michal Hocko
SUSE Labs

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Re: [PATCH] mm: oom: do not reap task if there are live threads in threadgroup

[Vladimir Davydov]

On Tue, May 24, 2016 at 01:46:12PM +0200, Michal Hocko wrote:
> On Tue 24-05-16 14:00:28, Vladimir Davydov wrote:
> > If the current process is exiting, we don't invoke oom killer, instead
> > we give it access to memory reserves and try to reap its mm in case
> > nobody is going to use it. There's a mistake in the code performing this
> > check - we just ignore any process of the same thread group no matter if
> > it is exiting or not - see try_oom_reaper. Fix it.
> 
> This is not a problem with the current code because of 98748bd72200
> ("oom: consider multi-threaded tasks in task_will_free_mem") which got
> merged later on, however.

True, I missed that patch.

> 
> The check is not needed so we can indeed drop it.
> 
> Fixes: 3ef22dfff239 ("oom, oom_reaper: try to reap tasks which skip
> regular OOM killer path")
> 
> Just in case somebody wants to backport only 3ef22dfff239.
> 
> > Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
> 
> Acked-by: Michal Hocko <mhocko@suse.com>

Thanks.

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