On Tue, Nov 05, 2013 at 06:01:25PM +0100, Stephane Eranian wrote:
> +static DEFINE_SPINLOCK(rapl_hotplug_lock);
> +static void rapl_exit_cpu(int cpu)
> +{
> + int i, phys_id = topology_physical_package_id(cpu);
> +
> + spin_lock(&rapl_hotplug_lock);
> + spin_unlock(&rapl_hotplug_lock);
> +}
> +
> +static void rapl_init_cpu(int cpu)
> +{
> + int i, phys_id = topology_physical_package_id(cpu);
> +
> + spin_lock(&rapl_hotplug_lock);
> + spin_unlock(&rapl_hotplug_lock);
> +}
> +static int rapl_cpu_starting(int cpu)
> +{
> + struct rapl_pmu *pmu2;
> + struct rapl_pmu *pmu1 = per_cpu(rapl_pmu, cpu);
> + int i, phys_id = topology_physical_package_id(cpu);
> +
> + if (pmu1)
> + return 0;
> +
> + spin_lock(&rapl_hotplug_lock);
> + spin_unlock(&rapl_hotplug_lock);
> + return 0;
> +}
> +
> +static int rapl_cpu_dying(int cpu)
> +{
> + struct rapl_pmu *pmu = per_cpu(rapl_pmu, cpu);
> + struct perf_event *event, *tmp;
> +
> + if (!pmu)
> + return 0;
> +
> + spin_lock(&rapl_hotplug_lock);
> + spin_unlock(&rapl_hotplug_lock);
> + return 0;
> +}
> +
> +static int rapl_cpu_notifier(struct notifier_block *self,
> + unsigned long action, void *hcpu)
> +{
> + unsigned int cpu = (long)hcpu;
> +
> + /* allocate/free data structure for uncore box */
> + switch (action & ~CPU_TASKS_FROZEN) {
> + case CPU_UP_PREPARE:
> + rapl_cpu_prepare(cpu);
> + break;
> + case CPU_STARTING:
> + rapl_cpu_starting(cpu);
> + break;
> + case CPU_UP_CANCELED:
> + case CPU_DYING:
> + rapl_cpu_dying(cpu);
> + break;
> + case CPU_ONLINE:
> + kfree(per_cpu(rapl_pmu_kfree, cpu));
> + per_cpu(rapl_pmu_kfree, cpu) = NULL;
> + break;
> + case CPU_DEAD:
> + per_cpu(rapl_pmu, cpu) = NULL;
> + break;
> + default:
> + break;
> + }
> +
> + /* select the cpu that collects uncore events */
> + switch (action & ~CPU_TASKS_FROZEN) {
> + case CPU_DOWN_FAILED:
> + case CPU_STARTING:
> + rapl_init_cpu(cpu);
> + break;
> + case CPU_DOWN_PREPARE:
> + rapl_exit_cpu(cpu);
> + break;
> + default:
> + break;
> + }
> +
> + return NOTIFY_OK;
> +}
What's the point of that rapl_hotplug_lock? It appears all methods its
used from are called from hotplug notifiers and those are fully
serialized by cpu_add_remove_lock.
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