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Date: Thu, 6 Apr 2017 11:32:24 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Mike Galbraith <efault@gmx.de>, Ingo Molnar <mingo@elte.hu>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>
Subject: Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU
 mask
Message-ID: <20170406093224.q3tunb6gdx5a6flr@hirez.programming.kicks-ass.net>
References: <20170404184202.20376-1-bigeasy@linutronix.de>
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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.