netdev - Re: [PATCH v5 7/9] task_isolation: don't interrupt CPUs with tick_nohz_full_kick

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 for Android: free password hash cracker in your pocket

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

Message-ID: <87360zn1je.fsf@nanos.tec.linutronix.de>
Date:   Mon, 23 Nov 2020 23:36:37 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Alex Belits <abelits@...vell.com>,
        "nitesh\@redhat.com" <nitesh@...hat.com>,
        "frederic\@kernel.org" <frederic@...nel.org>
Cc:     Prasun Kapoor <pkapoor@...vell.com>,
        "linux-api\@vger.kernel.org" <linux-api@...r.kernel.org>,
        "davem\@davemloft.net" <davem@...emloft.net>,
        "trix\@redhat.com" <trix@...hat.com>,
        "mingo\@kernel.org" <mingo@...nel.org>,
        "catalin.marinas\@arm.com" <catalin.marinas@....com>,
        "rostedt\@goodmis.org" <rostedt@...dmis.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterx\@redhat.com" <peterx@...hat.com>,
        "linux-arch\@vger.kernel.org" <linux-arch@...r.kernel.org>,
        "mtosatti\@redhat.com" <mtosatti@...hat.com>,
        "will\@kernel.org" <will@...nel.org>,
        "peterz\@infradead.org" <peterz@...radead.org>,
        "leon\@sidebranch.com" <leon@...ebranch.com>,
        "linux-arm-kernel\@lists.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "pauld\@redhat.com" <pauld@...hat.com>,
        "netdev\@vger.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH v5 7/9] task_isolation: don't interrupt CPUs with tick_nohz_full_kick_cpu()

On Mon, Nov 23 2020 at 17:58, Alex Belits wrote:
> From: Yuri Norov <ynorov@...vell.com>
>
> For nohz_full CPUs the desirable behavior is to receive interrupts
> generated by tick_nohz_full_kick_cpu(). But for hard isolation it's
> obviously not desirable because it breaks isolation.
>
> This patch adds check for it.

git grep 'This patch' Documentation/process/

>   */
>  void tick_nohz_full_kick_cpu(int cpu)
>  {
> -	if (!tick_nohz_full_cpu(cpu))
> +	smp_rmb();

Undocumented smp_rmb() ...

> +	if (!tick_nohz_full_cpu(cpu) || task_isolation_on_cpu(cpu))
>  		return;

I still have to see a convincing argument why task isolation is special
and not just a straight forward extension of NOHZ full cpu isolation.

It's not special as much as you want it to be special.

Thanks,

        tglx