Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 8 Jun 2021 15:27:32 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Andrey Semashev <andrey.semashev@gmail.com>
Cc:     Nicholas Piggin <npiggin@gmail.com>,
        =?iso-8859-1?Q?Andr=E9?= Almeida <andrealmeid@collabora.com>,
        acme@kernel.org, Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        corbet@lwn.net, Davidlohr Bueso <dave@stgolabs.net>,
        Darren Hart <dvhart@infradead.org>, fweimer@redhat.com,
        joel@joelfernandes.org, kernel@collabora.com,
        krisman@collabora.com, libc-alpha@sourceware.org,
        linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, malteskarupke@fastmail.fm,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        pgriffais@valvesoftware.com, Peter Oskolkov <posk@posk.io>,
        Steven Rostedt <rostedt@goodmis.org>, shuah@kernel.org,
        Thomas Gleixner <tglx@linutronix.de>, z.figura12@gmail.com
Subject: Re: [PATCH v4 00/15] Add futex2 syscalls
Message-ID: <YL9wROdz4y/pETA1@kroah.com>
References: <1622853816.mokf23xgnt.astroid@bobo.none>
 <6d8e3bb4-0cef-b991-9a16-1f03d10f131d@gmail.com>
 <1622980258.cfsuodze38.astroid@bobo.none>
 <c6d86db8-4f63-6c57-9a67-6268da266afe@gmail.com>
 <1623114630.pc8fq7r5y9.astroid@bobo.none>
 <b3488d1b-a4ff-8791-d960-a5f7ae2ea8b3@gmail.com>
 <YL9Q2tKLZP6GKbHW@kroah.com>
 <8fa8b7fd-58ae-9467-138d-4ff4f32f68f7@gmail.com>
 <YL9kApyE6FbG/hru@kroah.com>
 <3fca0afa-d9db-a176-aad1-ff7db21ba4a2@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <3fca0afa-d9db-a176-aad1-ff7db21ba4a2@gmail.com>
Precedence: bulk

On Tue, Jun 08, 2021 at 04:18:42PM +0300, Andrey Semashev wrote:
> On 6/8/21 3:35 PM, Greg KH wrote:
> > On Tue, Jun 08, 2021 at 03:06:48PM +0300, Andrey Semashev wrote:
> > > On 6/8/21 2:13 PM, Greg KH wrote:
> > 
> > > > So what's keeping the futex2 code from doing all that futex1 does so
> > > > that the futex1 code can be deleted internally?
> > > 
> > > I think, Andr? will answer this, but my guess is, as stated above, this is a
> > > lot of work and time while the intermediate version is already useful.
> > 
> > useful to who?  I still do not understand what users will be needing
> > this.  All I can tell is a single userspace program wants to use it, and
> > that is a fork from the real project it was based on and that the
> > maintainers have no plan to merge it back.
> > 
> > So who does need/want this?
> 
> I mentioned C++ std::atomic and Boost.Atomic before. Those need variable
> sized futexes.

And has anyone converted them to use this new api to see if it works
well or not?

As was pointed out to me numerous times when I tried to propose
readfile(), you need a real user that can show and prove it is needed
before we can take new syscalls, especially complex beasts like this
one.

thanks,

greg k-h