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From: Andrey Semashev <andrey.semashev@gmail.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: "Nicholas Piggin" <npiggin@gmail.com>,
	"André 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
Date: Tue, 8 Jun 2021 16:41:07 +0300	[thread overview]
Message-ID: <edc30790-e29c-723c-50c8-61e258c6508b@gmail.com> (raw)
In-Reply-To: <YL9wROdz4y/pETA1@kroah.com>

On 6/8/21 4:27 PM, Greg KH wrote:
> 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, André 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.

André has mentioned that he tested the patch set with patched Wine and 
glibc.

I didn't patch Boost.Atomic or std::atomic, but it doesn't look to be 
problematic. The only difference it would make there is to enable 
futex2-based implementation for multiple atomic sizes and set up flags 
to indicate the futex size, instead of only enabling futex-based 
implementation for 32-bit atomics.

  reply	other threads:[~2021-06-08 13:41 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-03 19:59 André Almeida
2021-06-03 19:59 ` [PATCH v4 01/15] futex2: Implement wait and wake functions André Almeida
2021-06-03 19:59 ` [PATCH v4 02/15] futex2: Add support for shared futexes André Almeida
2021-06-03 19:59 ` [PATCH v4 03/15] futex2: Implement vectorized wait André Almeida
2021-06-03 19:59 ` [PATCH v4 04/15] futex2: Implement requeue operation André Almeida
2021-06-03 19:59 ` [PATCH v4 05/15] futex2: Implement support for different futex sizes André Almeida
2021-06-04  0:23   ` kernel test robot
2021-06-06 19:12   ` Davidlohr Bueso
2021-06-06 23:01     ` Andrey Semashev
2021-06-03 19:59 ` [PATCH v4 06/15] futex2: Add compatibility entry point for x86_x32 ABI André Almeida
2021-06-03 19:59 ` [PATCH v4 07/15] docs: locking: futex2: Add documentation André Almeida
2021-06-06 19:23   ` Davidlohr Bueso
2021-06-03 19:59 ` [PATCH v4 08/15] selftests: futex2: Add wake/wait test André Almeida
2021-06-03 19:59 ` [PATCH v4 09/15] selftests: futex2: Add timeout test André Almeida
2021-06-03 19:59 ` [PATCH v4 10/15] selftests: futex2: Add wouldblock test André Almeida
2021-06-03 19:59 ` [PATCH v4 11/15] selftests: futex2: Add waitv test André Almeida
2021-06-03 19:59 ` [PATCH v4 12/15] selftests: futex2: Add requeue test André Almeida
2021-06-03 19:59 ` [PATCH v4 13/15] selftests: futex2: Add futex sizes test André Almeida
2021-06-03 19:59 ` [PATCH v4 14/15] perf bench: Add futex2 benchmark tests André Almeida
2021-06-03 19:59 ` [PATCH v4 15/15] kernel: Enable waitpid() for futex2 André Almeida
2021-06-04  4:51 ` [PATCH v4 00/15] Add futex2 syscalls Zebediah Figura
2021-06-04 17:04   ` André Almeida
2021-06-04 11:36 ` Nicholas Piggin
2021-06-04 20:01   ` André Almeida
2021-06-05  1:09     ` Nicholas Piggin
2021-06-05  8:56       ` Andrey Semashev
2021-06-06 11:57         ` Nicholas Piggin
2021-06-06 13:15           ` Andrey Semashev
2021-06-08  1:25             ` Nicholas Piggin
2021-06-08 11:03               ` Andrey Semashev
2021-06-08 11:13                 ` Greg KH
2021-06-08 11:44                   ` Peter Zijlstra
2021-06-08 14:31                     ` Davidlohr Bueso
2021-06-08 12:06                   ` Andrey Semashev
2021-06-08 12:33                     ` Greg KH
2021-06-08 12:35                     ` Greg KH
2021-06-08 13:18                       ` Andrey Semashev
2021-06-08 13:27                         ` Greg KH
2021-06-08 13:41                           ` Andrey Semashev [this message]
2021-06-08 17:06                         ` Zebediah Figura
2021-06-08 14:14                   ` André Almeida
2021-06-07 15:40       ` André Almeida
2021-06-08  1:31         ` Nicholas Piggin
2021-06-08  2:33         ` Davidlohr Bueso
2021-06-08  4:45           ` Nicholas Piggin
2021-06-08 12:26         ` Sebastian Andrzej Siewior
2021-06-08 14:23           ` Peter Zijlstra
2021-06-08 14:57             ` Sebastian Andrzej Siewior
2021-06-08 15:04             ` André Almeida
2021-06-08 18:08             ` Adhemerval Zanella
2021-06-08 18:19               ` Florian Weimer
2021-06-08 18:22                 ` Adhemerval Zanella
2021-06-09 16:26             ` David Laight

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