Re: [PATCH v2 2/2] perf/x86/intel: force resched when TFA sysctl is modified

[Peter Zijlstra]

On Mon, Apr 08, 2019 at 10:32:52AM -0700, Stephane Eranian wrote:
> +static ssize_t set_sysctl_tfa(struct device *cdev,
> +			      struct device_attribute *attr,
> +			      const char *buf, size_t count)
> +{
> +	bool val;
> +	ssize_t ret;
> +
> +	ret = kstrtobool(buf, &val);
> +	if (ret)
> +		return ret;
> +
> +	/* no change */
> +	if (val == allow_tsx_force_abort)
> +		return count;
> +
> +	allow_tsx_force_abort = val;
> +
> +	get_online_cpus();
> +	on_each_cpu(update_tfa_sched, NULL, 1);
> +	put_online_cpus();
> +
> +	return count;
> +}

So we care about concurrent writing to that file?