Re: [PATCH V4 2/2] perf/x86: add sysfs entry to freeze counter on SMI

From: Andi Kleen
Date: Wed Mar 29 2017 - 00:18:51 EST


> + if (x86_pmu.attr_freeze_on_smi == val)
> + return count;
> +
> + mutex_lock(&freeze_on_smi_mutex);

I don't think the mutex is really needed, but if it was it would
need to include the previous check too to be atomic.

> +
> + get_online_cpus();
> +
> + flip_smm_bit(&val);
> + smp_call_function(flip_smm_bit, &val, 1);
> +
> + put_online_cpus();

This is on_each_cpu()

> +
> + x86_pmu.attr_freeze_on_smi = val;
> +
> + mutex_unlock(&freeze_on_smi_mutex);


-Andi