linux-kernel - Re: [PATCH 0/1] kthread: don't abuse kthread_create_on_cpu() in __kthread_create

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Message-ID: <20161114110955.GA32499@pathway.suse.cz>
Date:   Mon, 14 Nov 2016 12:09:55 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...capital.net>,
        Roman Pen <roman.penyaev@...fitbricks.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Chunming Zhou <David1.Zhou@....com>,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH 0/1] kthread: don't abuse kthread_create_on_cpu() in
 __kthread_create_worker()

On Thu 2016-11-10 18:19:58, Oleg Nesterov wrote:
> On 11/09, Oleg Nesterov wrote:
> >
> > Yes, agreed. Again, I'll write another email. Perhaps we should even keep
> > park/unpark exported and change them to avoid the races with exit/itself,
> > I dunno.
> >
> > My real point was, imo the KTHREAD_IS_PER_CPU/__kthread_bind(kthread->cpu)
> > logic in kthread_unpark() should be private to smpboot.c/cpu.c.
> >
> > I'll send another patch tomorrow. kthread_create_worker_on_cpu() ab-uses
> > this logic too for no reason, but this is trivial.
> 
> After this change we are almost ready to kill kthread->cpu and KTHREAD_IS_PER_CPU.
> (but the change itself doesn't depend on the previous patches).
> 
> Petr, why do we need kthread_create_worker_on_cpu() ? It has no users and
> I can not imagine any "real" use-case for it. Perhaps it can be removed?

kthread_create_worker_on_cpu() is going to have some users. For
example, patches for intel_powerclamp are already flying around,
see
https://lkml.kernel.org/r/1476707572-32215-3-git-send-email-pmladek@suse.com

Best Regards,
Petr