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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 29 Apr 2019 14:31:30 -0700
Message-ID: <CAHk-=wiPv4QJBC0qX8xxnT5P2C7S5uDG0HKdvdSpcoXaHG91tQ@mail.gmail.com>
Subject: Re: RFC: on adding new CLONE_* flags [WAS Re: [PATCH 0/4] clone: add CLONE_PIDFD]
To:     Florian Weimer <fweimer@redhat.com>
Cc:     Jann Horn <jannh@google.com>, Kevin Easton <kevin@guarana.org>,
        Andy Lutomirski <luto@kernel.org>,
        Christian Brauner <christian@brauner.io>,
        Aleksa Sarai <cyphar@cyphar.com>,
        "Enrico Weigelt, metux IT consult" <lkml@metux.net>,
        Al Viro <viro@zeniv.linux.org.uk>,
        David Howells <dhowells@redhat.com>,
        Linux API <linux-api@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Arnd Bergmann <arnd@arndb.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Kees Cook <keescook@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        Daniel Colascione <dancol@google.com>
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On Mon, Apr 29, 2019 at 1:38 PM Florian Weimer <fweimer@redhat.com> wrote:
>
> In Linux-as-the-ABI (as opposed to Linux-as-the-implementation), vfork
> is sometimes implemented as fork, so applications cannot rely on the
> vfork behavior regarding the stopped parent and the shared address
> space.

What broken library does that?

Sure, we didn't have a proper vfork() long long long ago. But that
predates both git and BK, so it's some time in the 90's. We've had a
proper vfork() *forever*.

> In fact, it would be nice to have a flag we can check in the posix_spawn
> implementation, so that we can support vfork-as-fork without any run
> time cost to native Linux.

No. Just make a bug-report to whatever broken library you use. What's
the point of having a library that can't even get vfork() right? Why
would you want to have a flag to say "vfork is broken"?

                 Linus