linux-kernel - Re: [patch V2 35/67] arm/perf: Convert to hotplug state machine

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Date:	Fri, 15 Jul 2016 17:26:30 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Anna-Maria Gleixner <anna-maria@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>, rt@...utronix.de,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Will Deacon <will.deacon@....com>
Subject: Re: [patch V2 35/67] arm/perf: Convert to hotplug state machine

* Mark Rutland | 2016-07-15 14:08:18 [+0100]:

>Hi,
Hi Mark,

>We may have multiple PMUs (e.g. two in big.LITTLE systems), and
>__oprofile_cpu_pmu only contains one of these. So this conversion is not
>correct.
>
>We were relying on the notifier list implicitly containing a list of
>those PMUs. It seems like we need an explicit list here.
>
>We keep __oprofile_cpu_pmu around for legacy 32-bit users of OProfile
>(on non-hetereogeneous systems), and that's all that the variable should
>be used for.

By the time I'e been looking there was only one node in the .dts. Now
you say it is not only possible but likely to have more than one node.

So what we need is a list which gets extended in cpu_pmu_init() instead
of using the global pointer we have now. Correct?

>Thanks,
>Mark.

Sebastian