linux-kernel - Re: [PATCH 1/3] arm/pmu: Reject groups spanning multiple hardware PMUs

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Date:	Tue, 10 Mar 2015 14:00:41 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Suzuki Poulose <Suzuki.Poulose@....com>,
	Will Deacon <Will.Deacon@....com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"acme@...nel.org" <acme@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Punit Agrawal <Punit.Agrawal@....com>,
	Pawel Moll <Pawel.Moll@....com>
Subject: Re: [PATCH 1/3] arm/pmu: Reject groups spanning multiple hardware
 PMUs

On Tue, Mar 10, 2015 at 01:53:51PM +0100, Peter Zijlstra wrote:
> > It would be nicer if we could prevent this in the core so we're not
> > reliant on every PMU driver doing the same verification. My initial
> > thought was that seemed like unnecessary duplication of the ctx checking
> > above, but if we're going to end up shoving it into several drivers
> > anyway perhaps it's the lesser evil.
> 
> Again, agreed, that would be better and less error prone. But I'm not
> entirely sure how to go about doing it :/ I'll have to go think about
> that; and conferences are not the best place for that.
> 
> Suggestions on that are welcome of course ;)

So the problem is that event_init() is what will return the pmu, so we
cannot make decisions on it until after that returns.

Maybe we can pull out the validate step into its own funciton;
pmu->validate() or whatnot, to be called slightly later.
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