linux-kernel - Re: [PATCH v2 08/13] powerpc/hw_breakpoint: Avoid relying on caller synchronization

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: <CANpmjNOeyZ0MZ_esOnR7TUE1R5Vf+_Ejt5JRQ1AoAmhkCrVrBA@mail.gmail.com>
Date:   Fri, 1 Jul 2022 11:41:25 +0200
From:   Marco Elver <elver@...gle.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jiri Olsa <jolsa@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v2 08/13] powerpc/hw_breakpoint: Avoid relying on caller synchronization

On Fri, 1 Jul 2022 at 10:54, Christophe Leroy
<christophe.leroy@...roup.eu> wrote:
>
> Hi Marco,
>
> Le 28/06/2022 à 11:58, Marco Elver a écrit :
> > Internal data structures (cpu_bps, task_bps) of powerpc's hw_breakpoint
> > implementation have relied on nr_bp_mutex serializing access to them.
> >
> > Before overhauling synchronization of kernel/events/hw_breakpoint.c,
> > introduce 2 spinlocks to synchronize cpu_bps and task_bps respectively,
> > thus avoiding reliance on callers synchronizing powerpc's hw_breakpoint.
>
> We have an still opened old issue in our database related to
> hw_breakpoint, I was wondering if it could have any link with the
> changes you are doing and whether you could handle it at the same time.
>
> https://github.com/linuxppc/issues/issues/38
>
> Maybe it is completely unrelated, but as your series modifies only
> powerpc and as the issue says that powerpc is the only one to do that, I
> thought it might be worth a hand up.

I see the powerpc issue unrelated to the optimizations in this series;
perhaps by fixing the powerpc issue, it would also become more
optimal. But all I saw is that it just so happens that powerpc relied
on the nr_bp_mutex which is going away.

This series will become even more complex if I decided to add a
powerpc rework on top (notwithstanding the fact I don't have any ppc
hardware at my disposal either). A separate series/patch seems much
more appropriate.

Thanks,
-- Marco