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Date: Fri, 2 Oct 2015 14:00:33 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Ingo Molnar <mingo@elte.hu>
Subject: Re: 4.2.2: NR_CPUS effectively being 1 bug
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On Fri, 2 Oct 2015 23:46:59 +0300 Alexey Dobriyan <adobriyan@gmail.com> wrote:

> FYI, I've upgraded from 4.1.7 to 4.2.1 (and retested with 4.2.2) and
> everything is scheduled on 1 CPU out of 4 (i5 760).
> 
> 	$ sudo cat /proc/1/status | grep cpu -i
> 	Cpus_allowed:   1
> 	Cpus_allowed_list:      0
> 
> Every process inherits this tiny cpumask.

Sell the other CPUs on ebay?

I haven't seen such a report before - maybe it rings a bell with Peter
& Ingo?

It should be pretty easy to debug.  I'd guess that the problem is in
the area of x86 SMP bringup and there might even be a nasty message in
the dmesg explaining what went wrong?

> #
> # Automatically generated file; DO NOT EDIT.
> # Linux/x86 4.2.2 Kernel Configuration
> #
> CONFIG_64BIT=y
> ...
>