linux-kernel - Re: [PATCH] Avoid mask based num_possible_cpus and num_online

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Message-ID: <4F1F06BF.3040605@gmail.com>
Date:	Tue, 24 Jan 2012 14:30:07 -0500
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
CC:	Venkatesh Pallipadi <venki@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mike Travis <travis@....com>,
	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Avoid mask based num_possible_cpus and num_online_cpus
 -v3

> If I am not missing anything obvious, applying this patch can effectively
> convert the above code into an infinite loop, among other damages!
>
> I still feel it would be safer to edit set_cpu_possible() such that
> nr_possible_cpus is updated whenever cpu_possible_mask is altered.

Yup, I agree with you. The important thing is, even if we use set_cpu_possible(),
x86 performance doesn't drop. So, I don't understand why we need to take
current strategy.
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