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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
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        linux-arch@vger.kernel.org, Tejun Heo <tj@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Rafael Wysocki <rafael.j.wysocki@intel.com>,
        Arjan van de Ven <arjan@linux.intel.com>,
        Rik van Riel <riel@redhat.com>, "Srivatsa S. Bhat" <srivatsa@mit.edu>,
        Sebastian Siewior <bigeasy@linutronix.de>,
        Paul Turner <pjt@google.com>
Subject: Re: [patch 10/20] cpu/hotplug: Make target state writeable
Date: Tue, 01 Mar 2016 02:53:07 +0100
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On Monday, February 29, 2016 04:49:24 PM Thomas Gleixner wrote:
> On Sun, 28 Feb 2016, Thomas Gleixner wrote:
> > 
> > Understood. I'll fix that thing up so that won't happen and I put it on the
> > list of things to look at deeper.
> 
> The below delta patch should do what you need, right?

Yup, thanks!

Rafael


> 8<-------------
> 
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -1461,6 +1461,11 @@ static ssize_t write_cpuhp_target(struct
>  	if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
>  		return -EINVAL;
>  #endif
> +
> +	ret = lock_device_hotplug_sysfs();
> +	if (ret)
> +		return ret;
> +
>  	mutex_lock(&cpuhp_state_mutex);
>  	sp = cpuhp_get_step(target);
>  	ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
> @@ -1472,6 +1477,8 @@ static ssize_t write_cpuhp_target(struct
>  		ret = do_cpu_up(dev->id, target);
>  	else
>  		ret = do_cpu_down(dev->id, target);
> +
> +	unlock_device_hotplug();
>  	return ret ? ret : count;
>  }