linux-kernel - Re: [RFC PATCH for 4.18 00/14] Restartable Sequences

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Message-ID: <702933118.10410.1525370664578.JavaMail.zimbra@efficios.com>
Date:   Thu, 3 May 2018 14:04:24 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Daniel Colascione <dancol@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Andy Lutomirski <luto@...capital.net>,
        Dave Watson <davejwatson@...com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>,
        Paul Turner <pjt@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@....linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Andrew Hunter <ahh@...gle.com>,
        Andi Kleen <andi@...stfloor.org>, Chris Lameter <cl@...ux.com>,
        Ben Maurer <bmaurer@...com>, rostedt <rostedt@...dmis.org>,
        Josh Triplett <josh@...htriplett.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [RFC PATCH for 4.18 00/14] Restartable Sequences

----- On May 3, 2018, at 12:22 PM, Daniel Colascione dancol@...gle.com wrote:

> On Thu, May 3, 2018 at 9:12 AM Mathieu Desnoyers <
> mathieu.desnoyers@...icios.com> wrote:
>> By the way, if we eventually find a way to enhance user-space mutexes in
> the
>> fashion you describe here, it would belong to another TLS area, and would
>> be registered by another system call than rseq. I proposed a more generic
>> "TLS area registration" system call a few years ago, but Linus told me he
>> wanted a system call that was specific to rseq. If we need to implement
>> other use-cases in a TLS area shared between kernel and user-space in a
>> similar fashion, the plan is to do it in a distinct system call.
> 
> If we proliferate TLS areas; we'd have to register each one upon thread
> creation, adding to the overall thread creation path. There's already a
> provision for versioning the TLS area. What's the benefit of splitting the
> registration over multiple system calls?

See the original discussion thread at

https://lkml.org/lkml/2016/4/7/502

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com