linux-kernel - Re: [PATCH v3 00/13] Add futex2 syscalls

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Date:   Wed, 05 May 2021 16:23:52 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>,
        André Almeida <andrealmeid@...labora.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Darren Hart <dvhart@...radead.org>,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        kernel@...labora.com, krisman@...labora.com,
        pgriffais@...vesoftware.com, z.figura12@...il.com,
        joel@...lfernandes.org, malteskarupke@...tmail.fm,
        linux-api@...r.kernel.org, fweimer@...hat.com,
        libc-alpha@...rceware.org, linux-kselftest@...r.kernel.org,
        shuah@...nel.org, acme@...nel.org, corbet@....net,
        Peter Oskolkov <posk@...k.io>
Subject: Re: [PATCH v3 00/13] Add futex2 syscalls

On Wed, May 05 2021 at 14:31, Peter Zijlstra wrote:

> On Tue, Apr 27, 2021 at 08:12:35PM -0300, André Almeida wrote:
>> Hi,
>> 
>> This patch series introduces the futex2 syscalls.
>
> I still utterly detest that this adds a second hash-table for no
> descernable reason.
>
> The new syscall interface does not depend on that in any way, you
> previously implemented the multi-wait thing in the current futex code.
>
> Like I said last time; I'm okay with the new interface, but I don't see
> why you need to reimplement the insides, that's all pointless code
> duplication.

The real question is whether we really need to model all of this along
the existing futex functionality. I wouldn't mind a new infrastructure
which addresses all the other known issues of futexes and makes the
overall design less horrible than what we have now.

But that needs input from futex users (libraries and other horrible
wrappers) to figure out what they really need, hate, like or do not care
about.

Without that we are bound to pile more crap on the existing pile of
horrors forever.

Thanks,

        tglx