linux-kernel - Re: [RFC PATCH 03/19] sched/fair: Use rq->nohz_tick_stopped in update_nohz

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: <409bde01-720b-4602-bde9-a04262ea2c73@linux.ibm.com>
Date: Thu, 25 Sep 2025 01:47:29 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: K Prateek Nayak <kprateek.nayak@....com>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>,
        "Gautham R. Shenoy" <gautham.shenoy@....com>,
        Swapnil Sapkal <swapnil.sapkal@....com>,
        Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        Frederic Weisbecker <frederic@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 03/19] sched/fair: Use rq->nohz_tick_stopped in
 update_nohz_stats()



On 9/4/25 9:44 AM, K Prateek Nayak wrote:
> "rq->nohz_tick_stopped" always follows the state of CPU on
> "nohz.idle_cpus_mask". Use the local rq indicator instead of checking
> for the CPU on the "idle_cpus_mask".
> 
> Use READ_ONCE() and WRITE_ONCE() for "rq->nohz_tick_stopped" to ensure
> update_nohz_stats() always sees the latest value.
> 

Is this ever called by remote CPU? If not, is READ/WRITE ONCE is necessary?

> This cleanup is necessary to avoid the number of references to the
> global "nohz.idle_cpus_mask" to ease the transition to a distributed
> nohz idle tracking strategy.
> 
> No functional changes intended.
> 
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
> Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
> ---