linux-kernel - Re: [PATCH 0/6] Optimize the cpu hotplug locking -v2

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Message-ID: <20131011121457.25042.qmail@science.horizon.com>
Date:	11 Oct 2013 08:14:57 -0400
From:	"George Spelvin" <linux@...izon.com>
To:	rostedt@...dmis.org
Cc:	linux@...izon.com, linux-kernel@...r.kernel.org,
	paulmck@...ux.vnet.ibm.com, peterz@...radead.org,
	srivatsa.bhat@...ux.vnet.ibm.com, torvalds@...ux-foundation.org
Subject: Re: [PATCH 0/6] Optimize the cpu hotplug locking -v2

> There's places in the kernel that does for_each_cpu() that I'm sure you
> don't want to disable preemption for. Especially when you start having
> 4096 CPU machines!

Er... why not?

Seriously.  If I have 4096 processors, and preemption is disabled on
*one* of them for a long time, can't an urgent task just find a different
processor to preempt?

This seems like a non-problem.  Or am I misunderstanding something about
processor affinity?
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