linux-kernel - Re: [PATCH v4 00/15] Add futex2 syscalls

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Date:   Tue, 8 Jun 2021 13:44:44 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Andrey Semashev <andrey.semashev@...il.com>,
        Nicholas Piggin <npiggin@...il.com>,
        André Almeida <andrealmeid@...labora.com>,
        acme@...nel.org, Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        corbet@....net, Davidlohr Bueso <dave@...olabs.net>,
        Darren Hart <dvhart@...radead.org>, fweimer@...hat.com,
        joel@...lfernandes.org, kernel@...labora.com,
        krisman@...labora.com, libc-alpha@...rceware.org,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, malteskarupke@...tmail.fm,
        Ingo Molnar <mingo@...hat.com>, pgriffais@...vesoftware.com,
        Peter Oskolkov <posk@...k.io>,
        Steven Rostedt <rostedt@...dmis.org>, shuah@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>, z.figura12@...il.com
Subject: Re: [PATCH v4 00/15] Add futex2 syscalls

On Tue, Jun 08, 2021 at 01:13:30PM +0200, Greg KH wrote:
> On Tue, Jun 08, 2021 at 02:03:50PM +0300, Andrey Semashev wrote:
> So what's keeping the futex2 code from doing all that futex1 does so
> that the futex1 code can be deleted internally?

I'd much rather see it the other way around. Much of what futex2 does
can already be done with the futex1 code-base. And then we can add
features on top.

I've been moaning about this for the past many versions, even older
versions actually implemented some of the new features in futex1,
showing it can be done.

We just wanted a saner futex interface because the existing futex
syscall is a monster and making it even worse seemed like a bad idea.

So *again*: please add the new syscalls on top of futex1 and then
extend.  Do not re-implement.