linux-kernel - Re: [PATCH] kernel/fork: stop playing lockless games for exe

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Message-ID: <00dd353b-e5aa-69fb-6b52-cb59028ea90a@redhat.com>
Date:   Mon, 14 Aug 2023 09:55:03 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Mateusz Guzik <mjguzik@...il.com>, linux-kernel@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, brauner@...nel.org,
        ebiederm@...ssion.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, koct9i@...il.com, oleg@...hat.com,
        dave@...olabs.net
Subject: Re: [PATCH] kernel/fork: stop playing lockless games for exe_file
 replacement

On 13.08.23 14:33, Mateusz Guzik wrote:
> xchg originated in 6e399cd144d8 ("prctl: avoid using mmap_sem for
> exe_file serialization"). While the commit message does not explain
> *why* the change, clearly the intent was to use mmap_sem less in this
> codepath. I found the original submission [1] which ultimately claims it
> cleans things up.

More details are apparently in v1 of that patch:

https://lore.kernel.org/lkml/1424979417.10344.14.camel@stgolabs.net/

Regarding your patch: adding more mmap_write_lock() where avoidable, I'm 
not so sure.

Your patch doesn't look (to me) like it is removing a lot of complexity.

-- 
Cheers,

David / dhildenb