linux-kernel - Re: [patch 22/66] bus: arm-ccn: convert to hotplug statemachine

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Date:	Tue, 12 Jul 2016 13:21:57 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Pawel Moll <pawel.moll@....com>,
	Anna-Maria Gleixner <anna-maria@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [patch 22/66] bus: arm-ccn: convert to hotplug statemachine

On 07/12/2016 01:16 PM, Pawel Moll wrote:
> On Mon, 2016-07-11 at 12:28 +0000, Anna-Maria Gleixner wrote:
>> @@ -1270,9 +1262,10 @@ static int arm_ccn_pmu_init(struct arm_c
>>  	 * ... and change the selection when it goes offline.
>> Priority is
>>  	 * picked to have a chance to migrate events before perf is
>> notified.
>>  	 */
>> -	ccn->dt.cpu_nb.notifier_call = arm_ccn_pmu_cpu_notifier;
>> -	ccn->dt.cpu_nb.priority = CPU_PRI_PERF + 1,
>> -	err = register_cpu_notifier(&ccn->dt.cpu_nb);
>> +	cpuhp_armccn_dt = &ccn->dt;
>> +	err = cpuhp_setup_state(CPUHP_AP_PERF_ARM_CCN_ONLINE,
>> +				"AP_PERF_ARM_CCN_ONLINE", NULL,
>> +				arm_ccn_pmu_offline_cpu);
>>  	if (err)
>>  		goto error_cpu_notifier;
> 
> Also, unless I'm missing something obvious, it seems that the callback
> will be executed for CPUs going online? I'm definitely interested in my
> "current" CPU going down, in order to migrate my handlers somewhere
> else.
> 
> Help?

cpuhp_setup_state() gets two callbacks, online followed by offline
(argument three and four). The online callback is NULL so you have only
one offline callback.

> Pawel

Sebastian