linux-kernel - Re: [PATCH v4] sched/core: Use zero length to reset cpumasks in sched

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: <87mswycztd.fsf@oldenburg.str.redhat.com>
Date:   Wed, 04 Oct 2023 14:55:10 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org, Phil Auld <pauld@...hat.com>,
        Brent Rowsell <browsell@...hat.com>,
        Peter Hunt <pehunt@...hat.com>
Subject: Re: [PATCH v4] sched/core: Use zero length to reset cpumasks in
 sched_setaffinity()

* Waiman Long:

> On 10/4/23 08:34, Florian Weimer wrote:
>> * Peter Zijlstra:
>>
>>> Subject: sched: Add CPU_FILL()
>>>
>>> Add the CPU_FILL() macros to easily create an all-set cpumask.
>>>
>>> FreeBSD also provides this macro with this semantic.
>>>
>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>> My main concer is that obtaining the size of the mask, or at least an
>> approximiation is not exactly easy.  If there's an expectation that
>> applications reset the mask more often than they do today (I don't have
>> the full context here), then we'd some decent interface to get the
>> approriate size.
>
> I believe the macro just use sizeof(cpu_set_t) as the size of the
> bitmask. It is the same case as in CPU_ZERO().

I mean the CPU_FILL_S macro also defined in the patch.  Correctly
written applications should not use CPU_FILL and statically sized CPU
sets.

Thanks,
Florian