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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Mon, 17 Jan 2022 14:24:15 +0100
Message-ID: <CAK8P3a22ntk5fTuk6xjh1pyS-eVbGo7zDQSVkn2VG1xgp01D9g@mail.gmail.com>
Subject: Re: [PATCH 03/10] exit: Move oops specific logic from do_exit into make_task_dead
To:     Christoph Hellwig <hch@infradead.org>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Alexey Gladkov <legion@kernel.org>,
        Kyle Huey <me@kylehuey.com>, Oleg Nesterov <oleg@redhat.com>,
        Kees Cook <keescook@chromium.org>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>
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On Mon, Jan 17, 2022 at 9:05 AM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Fri, Jan 07, 2022 at 12:59:33PM -0600, Eric W. Biederman wrote:
> > Assuming it won't be too much longer before the rest of the arches have
> > set_fs/get_fs removed it looks like it makes sense to leave the
> > force_uaccess_begin where it is, and just let force_uaccess_begin be
> > removed when set_fs/get_fs are removed from the tree.
> >
> > Christoph does it look like the set_fs/get_fs removal work is going
> > to stall indefinitely on some architectures?  If so I think we want to
> > find a way to get kernel threads to run with set_fs(USER_DS) on the
> > stalled architectures.  Otherwise I think we have a real hazard of
> > introducing bugs that will only show up on the stalled architectures.
>
> I really need help from the arch maintainers to finish the set_fs
> removal.  There have been very few arch maintainers helping with that
> work (arm, arm64, parisc, m68k) in addition to the ones I did because
> I have the test setups and knowledge.  I'll send out another ping,
> for necrotic architectures like ia64 and sh I have very little hope.

I did a conversion of microblaze for fun at some point, and I think I never
sent that out. I haven't tested it, but if this looks correct to you and
Michal, it could serve as a model for other trivial conversions.

I also looked into converting ia64 and sh at the same time, but I can't
find those patches now, so I think they were never complete.

       Arnd