linux-kernel - Re: [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks

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Message-ID: <099aa0db-045a-e5b8-6df7-b7c3fc4d3caa@i-love.sakura.ne.jp>
Date:   Fri, 10 Sep 2021 22:04:55 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Vasily Averin <vvs@...tuozzo.com>
Cc:     cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH memcg] memcg: prohibit unconditional exceeding the limit
 of dying tasks

On 2021/09/10 21:39, Vasily Averin wrote:
> The kernel currently allows dying tasks to exceed the memcg limits.
> The allocation is expected to be the last one and the occupied memory
> will be freed soon.
> This is not always true because it can be part of the huge vmalloc
> allocation. Allowed once, they will repeat over and over again.
> Moreover lifetime of the allocated object can differ from
> In addition the lifetime of the dying task.

Can't we add fatal_signal_pending(current) test to vmalloc() loop?

> Multiple such allocations running concurrently can not only overuse
> the memcg limit, but can lead to a global out of memory and,
> in the worst case, cause the host to panic.
> 
> Signed-off-by: Vasily Averin <vvs@...tuozzo.com>