linux-kernel - Re: [PATCH] perf_events: fix bug in AMD per-cpu initialization

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Date:	Tue, 23 Mar 2010 16:18:26 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo <mingo@...e.hu>,
	paulus@...ba.org, davem@...emloft.net, fweisbec@...il.com,
	robert.richter@....com, perfmon2-devel@...ts.sf.net,
	eranian@...il.com, "hpa@...or.com" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Manfred Spraul <manfred@...orfullife.com>
Subject: Re: [PATCH] perf_events: fix bug in AMD per-cpu initialization

On Tue, 2010-03-23 at 16:12 +0100, Stephane Eranian wrote:
> On Tue, Mar 23, 2010 at 4:07 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Tue, 2010-03-23 at 15:55 +0100, Stephane Eranian wrote:
> >> What's the point of CPU_ONLINE vs. CPU_STARTING if you're saying the
> >> former is never right? Why not move CPU_ONLINE to the right place and
> >> drop CPU_STARTING?
> >
> > Its right for a lot of things, just not for perf, we need to be ready
> > and done by the time the cpu starts scheduling.
> >
> You mean they need to wait until after the cpu starts scheduling?
> As opposed to being called just before it starts scheduling.

As in it doesn't really matter for them, and the CPU_ONLINE call is
convenient in that it allows the callback to schedule too.
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