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Date: Thu, 9 Feb 2017 10:08:08 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Mike Galbraith <efault@gmx.de>, Oleg Nesterov <oleg@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 05/10] sched/core: Remove the tsk_cpus_allowed() wrapper
Message-ID: <20170209090808.GA6893@gmail.com>
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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, Feb 08, 2017 at 07:34:18PM +0100, Ingo Molnar wrote:
>
> > So the original intention of tsk_cpus_allowed() was to 'future-proof' the 
> > field - but it's pretty ineffectual at that, because half of the code uses 
> > ->cpus_allowed directly ...
> > 
> > Also, the wrapper makes the code longer than the original expression!
> 
> I still object to taking this out without replacement.

Yeah, that would have been my next suggestion.

> This leaves RT stranded.

Well, no, it leaves -rt with slightly more patching work than it already has...

Because note how the wrappery is _already_ incomplete to a significant degree:

  triton:~/tip> git grep -Ee '->cpus_allowed' | grep -vE 'tsk_|cpuset|core.c' | wc -l
  27
  triton:~/tip> git grep tsk_cpus_allowed | wc -l
  43

I.e. around 40% of the places that use ->cpus_allowed in the upstream kernel are 
not properly wrapped. That fact already 'wrecks' -rt.

Thanks,

	Ingo