linux-kernel - Re: [RFC PATCH for 4.15 v12 00/22] Restartable sequences and CPU op vector

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: <CALCETrX84s-WEa5osP0t6CKh8C4Wj7-ARNMpaSp8Eop1_2ycLA@mail.gmail.com>
Date:   Wed, 22 Nov 2017 07:28:22 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Andi Kleen <andi@...stfloor.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        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>,
        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>
Subject: Re: [RFC PATCH for 4.15 v12 00/22] Restartable sequences and CPU op vector

On Tue, Nov 21, 2017 at 2:05 PM, Mathieu Desnoyers
<mathieu.desnoyers@...icios.com> wrote:
> ----- On Nov 21, 2017, at 12:21 PM, Andi Kleen andi@...stfloor.org wrote:
>
>> On Tue, Nov 21, 2017 at 09:18:38AM -0500, Mathieu Desnoyers wrote:
>>> Hi,
>>>
>>> Following changes based on a thorough coding style and patch changelog
>>> review from Thomas Gleixner and Peter Zijlstra, I'm respinning this
>>> series for another RFC.
>>>
>> My suggestion would be that you also split out the opv system call.
>> That seems to be main contention point currently, and the restartable
>> sequences should be useful without it.
>
> I consider rseq to be incomplete and a pain to use in various scenarios
> without cpu_opv.
>
> About the contention point you refer to:
>
> Using vDSO as an example of how things should be done is just wrong: the
> vDSO interaction with debugger instruction single-stepping is broken,
> as I detailed in my previous email.
>

If anyone ever reports that as a problem, I'll gladly fix it in the
kernel.  That's doable without an ABI change.  If rseq-like things
started breaking single-stepping, we can't just fix it in the kernel.

Also, there is one and only one vclock_gettime.  Debuggers can easily
special-case it.  For all I know, they already do.