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From:   "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Date:   Sat, 12 Oct 2019 08:53:34 +0200
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Subject: Re: [PATCH 1/2] clone3: add CLONE3_CLEAR_SIGHAND
To:     Aleksa Sarai <cyphar@cyphar.com>
Cc:     Christian Brauner <christian.brauner@ubuntu.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Oleg Nesterov <oleg@redhat.com>,
        Florian Weimer <fweimer@redhat.com>,
        "libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Shuah Khan <shuah@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>,
        Elena Reshetova <elena.reshetova@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Roman Gushchin <guro@fb.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        linux-kselftest@vger.kernel.org
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Hello Aleksa,

On Sat, 12 Oct 2019 at 00:12, Aleksa Sarai <cyphar@cyphar.com> wrote:
>
> On 2019-10-11, Michael Kerrisk <mtk.manpages@gmail.com> wrote:
> > Why CLONE3_CLEAR_SIGHAND rather than just CLONE_CLEAR_SIGHAND?
>
> There are no more flag bits left for the classic clone()/clone2() (the
> last one was used up by CLONE_PIDFD) -- thus this flag is clone3()-only.

Yes, I understand that. But, I'm not sure that the "3" in the prefix
is necessary. "CLONE_" still seems better to me.

Consider this: sometime in the near future we will probably have time
namespaces. The new flag for those namespaces will only be usable with
clone3(). It should NOT be called CLONE3_NEWTIME, but rather
CLONE_NEWTIME (or similar), because that same flag will presumably
also be used in other APIs such as unshare() and setns(). (Hmm -- I
wonder if we are going to need a new unshare2() or some such...)

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/