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arm: perf: fold hotplug notifier into arm_pmu 

Handling multiple PMUs using a single hotplug notifier requires a list
of PMUs to be maintained, with synchronisation in the probe, remove, and
notify paths. This is error-prone and makes the code much harder to
maintain.

Instead of using a single notifier, we can dynamically allocate a
notifier block per-PMU. The end result is the same, but the list of PMUs
is implicit in the hotplug notifier list rather than within a perf-local
data structure, which makes the code far easier to handle.

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Mark Rutland 2014-10-23 15:23:35 +01:00 committed by Will Deacon
parent abdf655a30
commit af66abfe2e
2 changed files with 35 additions and 35 deletions
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1
arch/arm/include/asm/pmu.h
View File

@ -116,6 +116,7 @@ struct arm_pmu {
u64 max_period;
struct platform_device *plat_device;
struct pmu_hw_events __percpu *hw_events;
struct notifier_block hotplug_nb;
};
#define to_arm_pmu(p) (container_of(p, struct arm_pmu, pmu))

69
arch/arm/kernel/perf_event_cpu.c
View File

@ -160,8 +160,31 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler)
return 0;
}
/*
* PMU hardware loses all context when a CPU goes offline.
* When a CPU is hotplugged back in, since some hardware registers are
* UNKNOWN at reset, the PMU must be explicitly reset to avoid reading
* junk values out of them.
*/
static int cpu_pmu_notify(struct notifier_block *b, unsigned long action,
void *hcpu)
{
struct arm_pmu *pmu = container_of(b, struct arm_pmu, hotplug_nb);
if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)
return NOTIFY_DONE;
if (pmu->reset)
pmu->reset(pmu);
else
return NOTIFY_DONE;
return NOTIFY_OK;
}
static int cpu_pmu_init(struct arm_pmu *cpu_pmu)
{
int err;
int cpu;
struct pmu_hw_events __percpu *cpu_hw_events;
@ -169,6 +192,11 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu)
if (!cpu_hw_events)
return -ENOMEM;
cpu_pmu->hotplug_nb.notifier_call = cpu_pmu_notify;
err = register_cpu_notifier(&cpu_pmu->hotplug_nb);
if (err)
goto out_hw_events;
for_each_possible_cpu(cpu) {
struct pmu_hw_events *events = per_cpu_ptr(cpu_hw_events, cpu);
raw_spin_lock_init(&events->pmu_lock);
@ -188,37 +216,18 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu)
cpu_pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;
return 0;
out_hw_events:
free_percpu(cpu_hw_events);
return err;
}
static void cpu_pmu_destroy(struct arm_pmu *cpu_pmu)
{
unregister_cpu_notifier(&cpu_pmu->hotplug_nb);
free_percpu(cpu_pmu->hw_events);
}
/*
* PMU hardware loses all context when a CPU goes offline.
* When a CPU is hotplugged back in, since some hardware registers are
* UNKNOWN at reset, the PMU must be explicitly reset to avoid reading
* junk values out of them.
*/
static int cpu_pmu_notify(struct notifier_block *b, unsigned long action,
void *hcpu)
{
if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)
return NOTIFY_DONE;
if (cpu_pmu && cpu_pmu->reset)
cpu_pmu->reset(cpu_pmu);
else
return NOTIFY_DONE;
return NOTIFY_OK;
}
static struct notifier_block cpu_pmu_hotplug_notifier = {
.notifier_call = cpu_pmu_notify,
};
/*
* PMU platform driver and devicetree bindings.
*/
@ -344,16 +353,6 @@ static struct platform_driver cpu_pmu_driver = {
static int __init register_pmu_driver(void)
{
int err;
err = register_cpu_notifier(&cpu_pmu_hotplug_notifier);
if (err)
return err;
err = platform_driver_register(&cpu_pmu_driver);
if (err)
unregister_cpu_notifier(&cpu_pmu_hotplug_notifier);
return err;
return platform_driver_register(&cpu_pmu_driver);
}
device_initcall(register_pmu_driver);