From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kevin Hilman <khilman@ti.com>
Subject: Re: [PATCHv2 3/5] cpuidle: add support for states that affect multiple cpus
Date: Thu, 15 Mar 2012 17:04:43 -0700
Message-ID: <87lin18l7o.fsf@ti.com>
References: <1331749794-8056-1-git-send-email-ccross@android.com>
	<1331749794-8056-4-git-send-email-ccross@android.com>
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Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <1331749794-8056-4-git-send-email-ccross@android.com> (Colin
	Cross's message of "Wed, 14 Mar 2012 11:29:52 -0700")
Sender: linux-kernel-owner@vger.kernel.org
To: Colin Cross <ccross@android.com>
Cc: linux-kernel@vger.kernel.org, Len Brown <len.brown@intel.com>, Trinabh Gupta <g.trinabh@gmail.com>, Kay Sievers <kay.sievers@vrfy.org>, Deepthi Dharwar <deepthi@linux.vnet.ibm.com>, Greg Kroah-Hartman <gregkh@suse.de>, Amit Kucheria <amit.kucheria@linaro.org>, Daniel Lezcano <daniel.lezcano@linaro.org>, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>, Santosh Shilimkar <santosh.shilimkar@ti.com>, linux-pm@lists.linux-foundation.org, Arjan van de Ven <arjan@linux.intel.com>, linux-arm-kernel@lists.infradead.org
List-Id: linux-pm@vger.kernel.org

Colin Cross <ccross@android.com> writes:

> +/**
> + * cpuidle_coupled_cpu_set_alive - adjust alive_count during hotplug transitions
> + * @cpu: target cpu number
> + * @alive: whether the target cpu is going up or down
> + *
> + * Run on the cpu that is bringing up the target cpu, before the target cpu
> + * has been booted, or after the target cpu is completely dead.
> + */
> +static void cpuidle_coupled_cpu_set_alive(int cpu, bool alive)
> +{
> +	struct cpuidle_device *dev;
> +	struct cpuidle_coupled *coupled;
> +
> +	mutex_lock(&cpuidle_lock);
> +
> +	dev = per_cpu(cpuidle_devices, cpu);
> +	if (!dev->coupled)
> +		goto out;
> +
> +	coupled = dev->coupled;
> +
> +	/*
> +	 * waiting_count must be at least 1 less than alive_count, because
> +	 * this cpu is not waiting.  Spin until all cpus have noticed this cpu
> +	 * is not idle and exited the ready loop before changing alive_count.
> +	 */
> +	while (atomic_read(&coupled->ready_count))
> +		cpu_relax();
> +
> +	smp_mb__before_atomic_inc();
> +	atomic_inc(&coupled->alive_count);

This doesn't look quite right.  alive_count is incrmented whether the
CPU is going up or down?

Maybe I misunderstood something, but I don't see anywhere where
alive_count is decrmemented after a CPU is removed.

Kevin

> +	smp_mb__after_atomic_inc();
> +
> +	if (alive)
> +		coupled->requested_state[dev->cpu] = CPUIDLE_COUPLED_NOT_IDLE;
> +	else
> +		coupled->requested_state[dev->cpu] = CPUIDLE_COUPLED_DEAD;
> +
> +out:
> +	mutex_unlock(&cpuidle_lock);
> +}
> +

From mboxrd@z Thu Jan  1 00:00:00 1970
From: khilman@ti.com (Kevin Hilman)
Date: Thu, 15 Mar 2012 17:04:43 -0700
Subject: [PATCHv2 3/5] cpuidle: add support for states that affect
 multiple cpus
In-Reply-To: <1331749794-8056-4-git-send-email-ccross@android.com> (Colin
 Cross's message of "Wed, 14 Mar 2012 11:29:52 -0700")
References: <1331749794-8056-1-git-send-email-ccross@android.com>
 <1331749794-8056-4-git-send-email-ccross@android.com>
Message-ID: <87lin18l7o.fsf@ti.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Colin Cross <ccross@android.com> writes:

> +/**
> + * cpuidle_coupled_cpu_set_alive - adjust alive_count during hotplug transitions
> + * @cpu: target cpu number
> + * @alive: whether the target cpu is going up or down
> + *
> + * Run on the cpu that is bringing up the target cpu, before the target cpu
> + * has been booted, or after the target cpu is completely dead.
> + */
> +static void cpuidle_coupled_cpu_set_alive(int cpu, bool alive)
> +{
> +	struct cpuidle_device *dev;
> +	struct cpuidle_coupled *coupled;
> +
> +	mutex_lock(&cpuidle_lock);
> +
> +	dev = per_cpu(cpuidle_devices, cpu);
> +	if (!dev->coupled)
> +		goto out;
> +
> +	coupled = dev->coupled;
> +
> +	/*
> +	 * waiting_count must be at least 1 less than alive_count, because
> +	 * this cpu is not waiting.  Spin until all cpus have noticed this cpu
> +	 * is not idle and exited the ready loop before changing alive_count.
> +	 */
> +	while (atomic_read(&coupled->ready_count))
> +		cpu_relax();
> +
> +	smp_mb__before_atomic_inc();
> +	atomic_inc(&coupled->alive_count);

This doesn't look quite right.  alive_count is incrmented whether the
CPU is going up or down?

Maybe I misunderstood something, but I don't see anywhere where
alive_count is decrmemented after a CPU is removed.

Kevin

> +	smp_mb__after_atomic_inc();
> +
> +	if (alive)
> +		coupled->requested_state[dev->cpu] = CPUIDLE_COUPLED_NOT_IDLE;
> +	else
> +		coupled->requested_state[dev->cpu] = CPUIDLE_COUPLED_DEAD;
> +
> +out:
> +	mutex_unlock(&cpuidle_lock);
> +}
> +