linux-kernel - Re: [PATCH 2/4] hotplug, x86: Add hotplug lock to missing places

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Message-ID: <2079659.IbpQLfJuuh@vostro.rjw.lan>
Date:	Sun, 18 Aug 2013 02:59:51 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Toshi Kani <toshi.kani@...com>
Cc:	mingo@...hat.com, hpa@...ux.intel.com, tglx@...utronix.de,
	gregkh@...uxfoundation.org, benh@...nel.crashing.org,
	x86@...nel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, fenghua.yu@...el.com, bp@...e.de,
	srivatsa.bhat@...ux.vnet.ibm.com, isimatu.yasuaki@...fujitsu.com
Subject: Re: [PATCH 2/4] hotplug, x86: Add hotplug lock to missing places

On Saturday, August 17, 2013 01:46:57 PM Toshi Kani wrote:
> lock_device_hotplug() serializes CPU & Memory online/offline and hotplug
> operations.  However, this lock is not held in the debug interfaces below
> that initiate CPU online/offline operations.
> 
>  - _debug_hotplug_cpu(), cpu0 hotplug test interface enabled by
>    CONFIG_DEBUG_HOTPLUG_CPU0.
>  - cpu_probe_store() and cpu_release_store(), cpu hotplug test interface
>    enabled by CONFIG_ARCH_CPU_PROBE_RELEASE.
> 
> This patch changes the above interfaces to hold lock_device_hotplug().
> 
> Signed-off-by: Toshi Kani <toshi.kani@...com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
>  arch/x86/kernel/topology.c |    2 ++
>  drivers/base/cpu.c         |   16 ++++++++++++++--
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
> index 5823bbd..a3f35eb 100644
> --- a/arch/x86/kernel/topology.c
> +++ b/arch/x86/kernel/topology.c
> @@ -65,6 +65,7 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
>  	if (!cpu_is_hotpluggable(cpu))
>  		return -EINVAL;
>  
> +	lock_device_hotplug();
>  	cpu_hotplug_driver_lock();
>  
>  	switch (action) {
> @@ -91,6 +92,7 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
>  	}
>  
>  	cpu_hotplug_driver_unlock();
> +	unlock_device_hotplug();
>  
>  	return ret;
>  }
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 4c358bc..4cc6928 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -88,7 +88,13 @@ static ssize_t cpu_probe_store(struct device *dev,
>  			       const char *buf,
>  			       size_t count)
>  {
> -	return arch_cpu_probe(buf, count);
> +	ssize_t ret;
> +
> +	lock_device_hotplug();
> +	ret = arch_cpu_probe(buf, count);
> +	unlock_device_hotplug();
> +
> +	return ret;
>  }
>  
>  static ssize_t cpu_release_store(struct device *dev,
> @@ -96,7 +102,13 @@ static ssize_t cpu_release_store(struct device *dev,
>  				 const char *buf,
>  				 size_t count)
>  {
> -	return arch_cpu_release(buf, count);
> +	ssize_t ret;
> +
> +	lock_device_hotplug();
> +	ret = arch_cpu_release(buf, count);
> +	unlock_device_hotplug();
> +
> +	return ret;
>  }
>  
>  static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
> --
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-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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