linux-kernel - Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

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Message-ID: <20170406094626.a42cq66ezgq4lohh@linutronix.de>
Date:   Thu, 6 Apr 2017 11:46:33 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Mike Galbraith <efault@....de>, Ingo Molnar <mingo@...e.hu>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>
Subject: Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU
 mask

On 2017-04-06 11:32:24 [+0200], Peter Zijlstra wrote:
> On Tue, Apr 04, 2017 at 08:42:02PM +0200, Sebastian Andrzej Siewior wrote:
> > While converting the existing users I tried to stick with the rules
> > above however… well mostly CPUFREQ tries to temporary switch the CPU
> > mask to do something on a certain CPU and then switches the mask back it
> > its original value.
> 
> 
> There's a bunch of that through ancient and rotten parts of the kernel.
> All those sites are broken.
> 
> Nothing stops userspace from setting a different affinity right after
> the kernel does for those threads.

Good. So you are saying I should convert them to something like
queue_work_on()?

Sebastian