linux-kernel - Re: [PATCH 2/2] cpu: make sure that cpu/online file created before KOBJ

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Date:	Tue, 14 May 2013 09:17:04 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Igor Mammedov <imammedo@...hat.com>
Cc:	linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
	chuck.anderson@...cle.com
Subject: Re: [PATCH 2/2] cpu: make sure that cpu/online file created before
 KOBJ_ADD is emitted

On Tue, May 14, 2013 at 12:05:32AM +0200, Igor Mammedov wrote:
> Fixes race between udev and hotplugged CPU registration, described at
> https://lkml.org/lkml/2012/4/30/198

It would be better if you copy-n-pasted the contents of that URL in here.
> by defining "online" attribute statically so that device_add() would
> create it before notifying udev about new CPU.

> 
> Signed-off-by: Igor Mammedov <imammedo@...hat.com>
> ---
>  drivers/base/cpu.c |   34 +++++++++++++++++++++-------------
>  1 files changed, 21 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 02e4d73..6578030 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -64,18 +64,21 @@ static ssize_t __ref store_online(struct device *dev,
>  }
>  static DEVICE_ATTR(online, 0644, show_online, store_online);
>  
> -static void __cpuinit register_cpu_control(struct cpu *cpu)
> -{
> -	device_create_file(&cpu->dev, &dev_attr_online);
> -}
> +static struct attribute *hotplug_cpu_attrs[] = {
> +	&dev_attr_online.attr,
> +	NULL
> +};
> +
> +static struct attribute_group hotplug_cpu_attr_group = {
> +	.attrs = hotplug_cpu_attrs,
> +};
> +
>  void unregister_cpu(struct cpu *cpu)
>  {
>  	int logical_cpu = cpu->dev.id;
>  
>  	unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
>  
> -	device_remove_file(&cpu->dev, &dev_attr_online);
> -
>  	device_unregister(&cpu->dev);
>  	per_cpu(cpu_sys_devices, logical_cpu) = NULL;
>  	return;
> @@ -101,11 +104,6 @@ static ssize_t cpu_release_store(struct device *dev,
>  static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
>  static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
>  #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
> -
> -#else /* ... !CONFIG_HOTPLUG_CPU */
> -static inline void register_cpu_control(struct cpu *cpu)
> -{
> -}
>  #endif /* CONFIG_HOTPLUG_CPU */
>  
>  #ifdef CONFIG_KEXEC
> @@ -150,6 +148,16 @@ static const struct attribute_group *common_cpu_attr_groups[] = {
>  	NULL
>  };
>  
> +static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
> +#ifdef CONFIG_KEXEC
> +	&crash_note_cpu_attr_group,
> +#endif
> +#ifdef CONFIG_HOTPLUG_CPU
> +	&hotplug_cpu_attr_group,
> +#endif
> +	NULL
> +};
> +
>  /*
>   * Print cpu online, possible, present, and system maps
>   */
> @@ -265,9 +273,9 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
>  	cpu->dev.bus->uevent = arch_cpu_uevent;
>  #endif
>  	cpu->dev.groups = common_cpu_attr_groups;
> +	if (cpu->hotpluggable)
> +		cpu->dev.groups = hotplugable_cpu_attr_groups;
>  	error = device_register(&cpu->dev);
> -	if (!error && cpu->hotpluggable)
> -		register_cpu_control(cpu);
>  	if (!error)
>  		per_cpu(cpu_sys_devices, num) = &cpu->dev;
>  	if (!error)
> -- 
> 1.7.1
> 
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