linux-kernel - Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting

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: <874kpgi025.fsf@nanos.tec.linutronix.de>
Date:   Thu, 06 Aug 2020 11:41:06 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     peterz@...radead.org,
        Valentin Schneider <valentin.schneider@....com>
Cc:     Vladimir Oltean <olteanv@...il.com>,
        Kurt Kanzenbach <kurt.kanzenbach@...utronix.de>,
        Alison Wang <alison.wang@....com>, catalin.marinas@....com,
        will@...nel.org, paulmck@...nel.org, mw@...ihalf.com,
        leoyang.li@....com, vladimir.oltean@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Anna-Maria Gleixner <anna-maria@...utronix.de>
Subject: Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting

peterz@...radead.org writes:
> On Wed, Aug 05, 2020 at 02:56:49PM +0100, Valentin Schneider wrote:
>
>> I've been tempted to say the test case is a bit bogus, but am not familiar
>> enough with the RT throttling details to stand that ground. That said, from
>> both looking at the execution and the stress-ng source code, it seems to
>> unconditionally spawn 32 FIFO-50 tasks (there's even an option to make
>> these FIFO-99!!!), which is quite a crowd on monoCPU systems.
>
> Oh, so it's a case of: we do stupid without tuning and the system falls
> over. I can live with that.

It's not a question of whether you can live with that behaviour for a
particular silly test case.

The same happens with a single RT runaway task with enough interrupt
load on a UP machine. Just validated that. And that has nothing to do
with a silly test case. Sporadic runaways due to a bug in a once per
week code path simply can happen and having the safety net working
depending on a config option selected or not is just wrong.

Thanks,

        tglx