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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <878s3k9q3a.fsf@oldenburg.str.redhat.com>
Date:   Tue, 08 Jun 2021 20:19:21 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Adhemerval Zanella <adhemerval.zanella@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kselftest@...r.kernel.org, joel@...lfernandes.org,
        Andrey Semashev <andrey.semashev@...il.com>,
        kernel@...labora.com, shuah@...nel.org,
        Davidlohr Bueso <dave@...olabs.net>,
        Peter Oskolkov <posk@...k.io>, corbet@....net,
        krisman@...labora.com, malteskarupke@...tmail.fm,
        Ingo Molnar <mingo@...hat.com>,
        Darren Hart <dvhart@...radead.org>, acme@...nel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        André Almeida <andrealmeid@...labora.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        libc-alpha@...rceware.org, linux-api@...r.kernel.org,
        z.figura12@...il.com, Nicholas Piggin <npiggin@...il.com>,
        linux-kernel@...r.kernel.org, pgriffais@...vesoftware.com
Subject: Re: [PATCH v4 00/15] Add futex2 syscalls

* 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