linux-kernel - Re: [PATCH 1/3] mm: get_cmdline use arg_lock instead of mmap

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Message-ID: <1a7265fa-610b-1f2a-e55f-b3a307a39bf2@virtuozzo.com>
Date:   Tue, 30 Apr 2019 12:53:51 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     Cyrill Gorcunov <gorcunov@...il.com>
Cc:     Michal Koutný <mkoutny@...e.com>,
        akpm@...ux-foundation.org, arunks@...eaurora.org, brgl@...ev.pl,
        geert+renesas@...der.be, ldufour@...ux.ibm.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        mguzik@...hat.com, mhocko@...nel.org, rppt@...ux.ibm.com,
        vbabka@...e.cz
Subject: Re: [PATCH 1/3] mm: get_cmdline use arg_lock instead of mmap_sem

On 30.04.2019 12:38, Cyrill Gorcunov wrote:
> On Tue, Apr 30, 2019 at 12:09:57PM +0300, Kirill Tkhai wrote:
>>
>> This looks OK for me.
>>
>> But speaking about existing code it's a secret for me, why we ignore arg_lock
>> in binfmt code, e.g. in load_elf_binary().
> 
> Well, strictly speaking we probably should but you know setup of
> the @arg_start by kernel's elf loader doesn't cause any side
> effects as far as I can tell (its been working this lockless
> way for years, mmap_sem is taken later in the loader code).
> Though for consistency sake we probably should set it up
> under the spinlock.

Ok, so elf loader doesn't change these parameters. Thanks for the explanation.