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Date: Thu, 6 Apr 2017 11:35:45 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        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
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On Thu, Apr 06, 2017 at 10:01:39AM +0200, Ingo Molnar wrote:
> I.e. just have a counter and these two APIs:
> 
>         static inline void migrate_disable(void)
>         {
>                 current->migration_disabled++;
>         }
> 
>         ...
> 
>         static inline void migrate_enable(void)
>         {
>                 current->migration_disabled--;
>         }
> 
> ... and make sure the scheduler migration code plus the CPU hotplug code considers 
> the counter.
> 
> Would this work, and would this be the simplest all around solution?

If you want to add expensive bits to hot paths like wakeups ... :/