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Subject: Re: [PATCH 0/3] exec: Transform exec_update_mutex into a rw_semaphore
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Davidlohr Bueso <dave@stgolabs.net>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
        Jann Horn <jannh@google.com>,
        Vasiliy Kulikov <segoon@openwall.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Bernd Edlinger <bernd.edlinger@hotmail.de>,
        Oleg Nesterov <oleg@redhat.com>,
        Christopher Yeoh <cyeoh@au1.ibm.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Sargun Dhillon <sargun@sargun.me>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
References: <87tut2bqik.fsf@x220.int.ebiederm.org>
 <CAHk-=wjocT58h24do391ZFQwAcOd7EBqBB=qOUyHVU=ubU09Yw@mail.gmail.com>
From:   Waiman Long <longman@redhat.com>
Organization: Red Hat
Message-ID: <874ffe6a-628f-e504-037f-ec321565a40c@redhat.com>
Date:   Thu, 3 Dec 2020 20:56:15 -0500
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On 12/3/20 5:42 PM, Linus Torvalds wrote:
> On Thu, Dec 3, 2020 at 12:10 PM Eric W. Biederman <ebiederm@xmission.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.

I have looked at patches 1 & 2 on adding down_read_killable_nested() and 
down_read_interruptible(). They looks good to me.

Cheers,
Longman