linux-kernel - Re: [v3 PATCH] mm: introduce arg_lock to protect arg_start|end and env_start|end in mm

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Message-ID: <20180410094047.GB2041@uranus.lan>
Date:   Tue, 10 Apr 2018 12:40:47 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Yang Shi <yang.shi@...ux.alibaba.com>, adobriyan@...il.com,
        willy@...radead.org, mguzik@...hat.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [v3 PATCH] mm: introduce arg_lock to protect arg_start|end and
 env_start|end in mm_struct

On Tue, Apr 10, 2018 at 11:09:17AM +0200, Michal Hocko wrote:
> On Tue 10-04-18 05:52:54, Yang Shi wrote:
> [...]
> > So, introduce a new spinlock in mm_struct to protect the concurrent
> > access to arg_start|end, env_start|end and others except start_brk and
> > brk, which are still protected by mmap_sem to avoid concurrent access
> > from do_brk().
> 
> Is there any fundamental problem with brk using the same lock?

Seems so. Look into mm/mmap.c:brk syscall which reads and writes
brk value under mmap_sem ('cause of do_brk called inside).