linux-kernel - Re: [RFC PATCH 1/3] sched: Make migrate_task

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: <20230621130439.GF2053369@hirez.programming.kicks-ass.net>
Date:   Wed, 21 Jun 2023 15:04:39 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Vernet <void@...ifault.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        rostedt@...dmis.org, dietmar.eggemann@....com, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        joshdon@...gle.com, roman.gushchin@...ux.dev, tj@...nel.org,
        kernel-team@...a.com
Subject: Re: [RFC PATCH 1/3] sched: Make migrate_task_to() take any task

On Tue, Jun 13, 2023 at 12:20:02AM -0500, David Vernet wrote:
> The migrate_task_to() function exposed from kernel/sched/core.c migrates
> the current task, which is silently assumed to also be its first
> argument, to the specified CPU. The function uses stop_one_cpu() to
> migrate the task to the target CPU, which won't work if @p is not the
> current task as the stop_one_cpu() callback isn't invoked on remote
> CPUs.
> 
> While this operation is useful for task_numa_migrate() in fair.c, it
> would be useful if __migrate_task() in core.c was given external
> linkage, as it actually can be used to migrate any task to a CPU.
> 
> This patch therefore:
> 1. Renames the existing migrate_task_to() be called
>    numa_migrate_current_task_to().
> 2. Renames __migrate_task() to migrate_task_to(), gives it global
>    linkage, and updates all callers accordingly.
> 
> A follow-on patch will call the new migrate_task_to() from fair.c when
> migrating a task in a shared wakequeue to a remote CPU.

I would suggest simply exposing move_queued_task(). You can actually do
is_cpu_allowed() before you do the whole lock dance, or even before
pull.

And then you don't have to create silly long function names either.