linux-kernel - Re: [PATCH 10/10] rcu: Nocb (de)activate through sysfs

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Message-ID: <20200513184229.GX2869@paulmck-ThinkPad-P72>
Date:   Wed, 13 May 2020 11:42:29 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>
Subject: Re: [PATCH 10/10] rcu: Nocb (de)activate through sysfs

On Wed, May 13, 2020 at 06:47:14PM +0200, Frederic Weisbecker wrote:
> Not for merge.
> 
> Make nocb toggable for a given CPU using:
> 	/sys/devices/system/cpu/cpu*/hotplug/nocb
> 
> This is only intended for those who want to test this patchset. The real
> interfaces will be cpuset/isolation and rcutorture.

Makes sense!

Speaking of rcutorture, what level of testing has this series undergone?

							Thanx, Paul

> Not-Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
> Cc: Paul E. McKenney <paulmck@...nel.org>
> Cc: Josh Triplett <josh@...htriplett.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Lai Jiangshan <jiangshanlai@...il.com>
> Cc: Joel Fernandes <joel@...lfernandes.org>
> ---
>  kernel/cpu.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 2371292f30b0..ac6283dcb897 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -2208,10 +2208,33 @@ static ssize_t show_cpuhp_fail(struct device *dev,
>  
>  static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
>  
> +static ssize_t write_nocb(struct device *dev,
> +			  struct device_attribute *attr,
> +			  const char *buf, size_t count)
> +{
> +	int val, ret;
> +
> +	ret = kstrtoint(buf, 10, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val == 0)
> +		rcu_nocb_cpu_deoffload(dev->id);
> +	else if (val == 1)
> +		rcu_nocb_cpu_offload(dev->id);
> +	else
> +		return -EINVAL;
> +
> +	return count;
> +}
> +
> +static DEVICE_ATTR(nocb, 0644, NULL, write_nocb);
> +
>  static struct attribute *cpuhp_cpu_attrs[] = {
>  	&dev_attr_state.attr,
>  	&dev_attr_target.attr,
>  	&dev_attr_fail.attr,
> +	&dev_attr_nocb.attr,
>  	NULL
>  };
>  
> -- 
> 2.25.0
>