linux-kernel - Re: [x86-tip] strange nr

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Date:   Mon, 26 Sep 2016 13:36:47 -0400 (EDT)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Mike Galbraith <umgwanakikbuti@...il.com>
cc:     Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>,
        Dou Liyang <douly.fnst@...fujitsu.com>
Subject: Re: [x86-tip] strange nr_cpus= boot regression

CC'ed: Dou Liyang

On Mon, 26 Sep 2016, Mike Galbraith wrote:

> I've encountered a strange regression in tip, symptom is that if you
> boot with nr_cpus=nr_you_have, what actually boots is nr_you_have/2. 
>  Do not pass nr_cpus=, and all is well. 

What's the number of possible cpus in your system?
 
> Bisection repeatedly goes as below, pointing to the nodeid merge,
> despite both timers/core and x86/apic (nodeid) being fine.  Take tip
> HEAD, extract all of the commits from nodeid (plus the fix), and revert
> them in a quilt tree, the tree remains busted. 

So you remove all the nodeid commits from tip/master and it's still broken?

> Checkout the timers/core merge commit, and merge nodeid with that, it is
> indeed bad.

> Bisecting  takes you right the merge commit, with no commit
> being 'bad', see logs.

That's more than strange. An empty merge commit being the culprit.
 
Thanks,

	tglx