linux-kernel - Re: [PATCH 7/7] clone3: ensure copy_thread

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Message-ID: <20200102182439.kzqabfuadph5cvaf@wittgenstein>
Date:   Thu, 2 Jan 2020 19:24:41 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Amanieu d'Antras <amanieu@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Christian Brauner <christian@...uner.io>,
        stable@...r.kernel.org
Subject: Re: [PATCH 7/7] clone3: ensure copy_thread_tls is implemented

On Thu, Jan 02, 2020 at 07:19:11PM +0100, Amanieu d'Antras wrote:
> On Thu, Jan 2, 2020 at 7:09 PM Christian Brauner
> <christian.brauner@...ntu.com> wrote:
> > I'm in favor of this change. But we need to make sure that any arch
> > which now has ARCH_WANTS_SYS_CLONE3 set but doesn't implement
> > copy_thread_tls() is fixed.
> >
> > Once all architectures have clone3() support - and there are
> > just a few by now (IA64 comes to mind) this means we should also be able
> > to get rid of of copy_thread() completely. That seems desirable to me as
> > it makes the codepaths easier to follow.
> 
> I've already implemented copy_thread_tls for all arches that currently
> have ARCH_WANTS_SYS_CLONE3 in the previous 5 patches. The #error is
> there so that any future arches that wire up clone3 don't forget to
> implement copy_thread_tls as well.

Right, my point is: Once _all_ arches have ARCH_WANT_SYS_CLONE3 they
also must implement copy_thread_tls at which point we can remove:
- ARCH_WANT_SYS_CLONE3 ifdefines
- copy_thread()
We can't do this right now because e.g. IA64 does not set
ARCH_WANT_SYS_CLONE3 and also does not select HAVE_COPY_THREAD_TLS.

Christian