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Date:   Mon, 15 Apr 2019 17:57:42 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Stephane Eranian <eranian@google.com>
Cc:     linux-kernel@vger.kernel.org, tglx@linutronix.de,
        ak@linux.intel.com, kan.liang@intel.com, mingo@elte.hu,
        nelson.dsouza@intel.com, jolsa@redhat.com, tonyj@suse.com
Subject: Re: [PATCH v2 2/2] perf/x86/intel: force resched when TFA sysctl is
 modified
Message-ID: <20190415155742.GI12232@hirez.programming.kicks-ass.net>
References: <20190408173252.37932-1-eranian@google.com>
 <20190408173252.37932-3-eranian@google.com>
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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?