linux-kernel - Re: [PATCH] sched/core: Don't use dying mm as active

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Message-ID: <b89697ed-a7f0-bb41-25ae-8e9727875d33@redhat.com>
Date:   Fri, 26 Jul 2019 21:58:11 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH] sched/core: Don't use dying mm as active_mm for kernel
 threads

On 7/26/19 7:45 PM, Waiman Long wrote:
> It was found that a dying mm_struct where the owning task has exited can
> stay on as active_mm of kernel threads as long as no other user tasks
> run on those CPUs that use it as active_mm. This prolongs the life time
> of dying mm holding up memory and other resources that cannot be freed.
>
> Fix that by forcing the kernel threads to use init_mm as the active_mm
> if the previous active_mm is dying.
>
> Signed-off-by: Waiman Long <longman@...hat.com>
> ---
>  kernel/sched/core.c | 13 +++++++++++--
>  mm/init-mm.c        |  2 ++
>  2 files changed, 13 insertions(+), 2 deletions(-)


Sorry, I didn't realize that mm->owner depends on CONFIG_MEMCG. I will
need to refresh the patch and send out v2 when I am done testing.

Cheers,
Longman