linux-kernel - Re: [PATCH 0/3] exec: Transform exec_update_mutex into a rw

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Message-ID: <20201204045401.4njfkrgpbmeak4qw@linux-p48b.lan>
Date:   Thu, 3 Dec 2020 20:54:01 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Waiman Long <longman@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Jann Horn <jannh@...gle.com>,
        Vasiliy Kulikov <segoon@...nwall.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Bernd Edlinger <bernd.edlinger@...mail.de>,
        Oleg Nesterov <oleg@...hat.com>,
        Christopher Yeoh <cyeoh@....ibm.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Sargun Dhillon <sargun@...gun.me>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Arnd Bergmann <arnd@...db.de>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH 0/3] exec: Transform exec_update_mutex into a rw_semaphore

On Thu, 03 Dec 2020, Linus Torvalds wrote:

>On Thu, Dec 3, 2020 at 12:10 PM Eric W. Biederman <ebiederm@...ssion.com> wrote:
>>
>> The simplest and most robust solution appears to be making
>> exec_update_mutex a read/write lock and having everything execept for
>> exec take the lock for read.
>
>Looks sane to me.
>
>I'd like the locking people to look at the down_read_*() functions,
>even if they look simple. Adding Waiman and Davidlohr to the cc just
>in case they would look at that too, since they've worked on that
>code.

rwsem changes look good to me - and 3/3 looks much nicer than the previous
alternatives to the deadlock.

Acked-by: Davidlohr Bueso <dbueso@...e.de>