linux-kernel - Re: [PATCH v2] sched/core: Don't use dying mm as active

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190729081800.qbamrvsf4rjna656@e107158-lin.cambridge.arm.com>
Date:   Mon, 29 Jul 2019 09:18:01 +0100
From:   Qais Yousef <qais.yousef@....com>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH v2] sched/core: Don't use dying mm as active_mm of
 kthreads

On 07/27/19 13:10, 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 like swap
> space 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.
> 
> The determination of a dying mm is based on the absence of an owning
> task. The selection of the owning task only happens with the CONFIG_MEMCG
> option. Without that, there is no simple way to determine the life span
> of a given mm. So it falls back to the old behavior.

I don't really know a lot about this code, but does the owner field has to
depend on CONFIG_MEMCG? ie: can't the owner be always set?

Cheers

--
Qais Yousef