linux-kernel - Re: [PATCH RFC] cpumask: Randomly distribute the tasks within affinity mask

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: <CABk29NvHx2saNLdYmQgt31R8W28p7=GUtXiiupgE5czXRBAx5g@mail.gmail.com>
Date:   Wed, 11 Oct 2023 16:55:35 -0700
From:   Josh Don <joshdon@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ankit Jain <ankitja@...are.com>, yury.norov@...il.com,
        andriy.shevchenko@...ux.intel.com, linux@...musvillemoes.dk,
        qyousef@...alina.io, pjt@...gle.com, bristot@...hat.com,
        vschneid@...hat.com, linux-kernel@...r.kernel.org,
        namit@...are.com, amakhalov@...are.com, srinidhir@...are.com,
        vsirnapalli@...are.com, vbrahmajosyula@...are.com,
        akaher@...are.com, srivatsa@...il.mit.edu
Subject: Re: [PATCH RFC] cpumask: Randomly distribute the tasks within
 affinity mask

Hey Peter,

> +static struct cpumask *root_domain_allowed(struct cpumask *newmask,
> +                                          struct cpumask *scratch,
> +                                          struct cpumask *valid)
> +{
> +       struct root_domain *rd;
> +       struct cpumask *mask;
> +       struct rq *rq;
> +
> +       int first = cpumask_first_and(newmask, valid);
> +       if (first >= nr_cpu_ids)
> +               return NULL;

This picks the first arbitrarily, but isn't it possible for the mask
to span both isolated and non-isolated cpus? In which case, the rest
of this just boils down to chance (ie. whatever the span happens to be
for the first cpu here)?