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;
From:   Florian Weimer <fweimer@redhat.com>
To:     Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        linux-kselftest@vger.kernel.org, joel@joelfernandes.org,
        Andrey Semashev <andrey.semashev@gmail.com>,
        kernel@collabora.com, shuah@kernel.org,
        Davidlohr Bueso <dave@stgolabs.net>,
        Peter Oskolkov <posk@posk.io>, corbet@lwn.net,
        krisman@collabora.com, malteskarupke@fastmail.fm,
        Ingo Molnar <mingo@redhat.com>,
        Darren Hart <dvhart@infradead.org>, acme@kernel.org,
        Steven Rostedt <rostedt@goodmis.org>,
        =?utf-8?Q?Andr=C3=A9?= Almeida <andrealmeid@collabora.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        libc-alpha@sourceware.org, linux-api@vger.kernel.org,
        z.figura12@gmail.com, Nicholas Piggin <npiggin@gmail.com>,
        linux-kernel@vger.kernel.org, pgriffais@valvesoftware.com
Subject: Re: [PATCH v4 00/15] Add futex2 syscalls
References: <20210603195924.361327-1-andrealmeid@collabora.com>
        <1622799088.hsuspipe84.astroid@bobo.none>
        <fb85fb20-5421-b095-e68b-955afa105467@collabora.com>
        <1622853816.mokf23xgnt.astroid@bobo.none>
        <22137ccd-c5e6-9fcc-a176-789558e9ab1e@collabora.com>
        <20210608122622.oxf662ruaawrtyrd@linutronix.de>
        <YL99cR0H+7xgU8L1@hirez.programming.kicks-ass.net>
        <74c7f1c1-ca15-1e86-a988-a4d349ad16ef@linaro.org>
Date:   Tue, 08 Jun 2021 20:19:21 +0200
In-Reply-To: <74c7f1c1-ca15-1e86-a988-a4d349ad16ef@linaro.org> (Adhemerval
        Zanella's message of "Tue, 8 Jun 2021 15:08:44 -0300")
Message-ID: <878s3k9q3a.fsf@oldenburg.str.redhat.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

* Adhemerval Zanella:

> Also currently we don't have a specific usage.  The proposed patch to
> add the 'pthread_mutex_lock_any' and 'pthreada_timedlock_any' [3] 
> also did not gave much detail in realword usages or how it can be
> leveraged.

The current rwlock implementation in glibc uses a torn 32-bit futex read
which is part of an atomically updated 64-bit word.  That's just really,
really ugly, and I suspect we could make that go away with futex2.

Thanks,
Florian