linux-kernel - Re: [RFC PATCH 03/13] sched: Core-wide rq->lock

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: <CANaguZDwK6bXvJabt5gS=kLMVsGNf97u50+1-v_t8bJxCrJ6sQ@mail.gmail.com>
Date:   Tue, 14 Apr 2020 17:35:07 -0400
From:   Vineeth Remanan Pillai <vpillai@...italocean.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Turner <pjt@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Frédéric Weisbecker <fweisbec@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Kerr <kerrnel@...gle.com>, Phil Auld <pauld@...hat.com>,
        Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>,
        "Li, Aubrey" <aubrey.li@...ux.intel.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [RFC PATCH 03/13] sched: Core-wide rq->lock

> Aside from the fact that it's probably much saner to write this as:
>
>         rq->core_enabled = static_key_enabled(&__sched_core_enabled);
>
> I'm fairly sure I didn't write this part. And while I do somewhat see
> the point of disabling core scheduling for a core that has only a single
> thread on, I wonder why we care.
>
I think this change was to fix some crashes which happened due to
uninitialized rq->core if a sibling was offline during boot and is
onlined after coresched was enabled.

https://lwn.net/ml/linux-kernel/20190424111913.1386-1-vpillai@digitalocean.com/

I tried to fix it by initializing coresched members during a cpu online
and tearing it down on a cpu offline. This was back in v3 and do not
remember the exact details. I shall revisit this and see if there is a
better way to fix the race condition above.

Thanks,
Vineeth