linux-kernel - Re: [BUGFIX 5/9] ACPI, DOCK: kill redundant spin lock in dock device object

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Date:	Thu, 13 Jun 2013 20:28:40 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Jiang Liu <jiang.liu@...wei.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	"Alexander E . Patrakov" <patrakov@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Yijing Wang <wangyijing@...wei.com>,
	Jiang Liu <liuj97@...il.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Shaohua Li <shaohua.li@...el.com>,
	Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org
Subject: Re: [BUGFIX 5/9] ACPI, DOCK: kill redundant spin lock in dock device object

On Friday, June 14, 2013 12:32:28 AM Jiang Liu wrote:
> All dock device related data structures are created during driver
> initialization, so kill the redundant spin lock in dock device object.

As a cleanup, it definitely makes sense, but does it fix anything?

Rafael


> Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
> Cc: Shaohua Li <shaohua.li@...el.com>
> Cc: Len Brown <lenb@...nel.org>
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> Cc: linux-acpi@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/acpi/dock.c | 15 +++------------
>  1 file changed, 3 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
> index 8e578aa..cd2d5df 100644
> --- a/drivers/acpi/dock.c
> +++ b/drivers/acpi/dock.c
> @@ -57,7 +57,6 @@ struct dock_station {
>  	acpi_handle handle;
>  	unsigned long last_dock_time;
>  	u32 flags;
> -	spinlock_t dd_lock;
>  	struct mutex hp_lock;
>  	struct task_struct *owner;
>  	struct list_head dependent_devices;
> @@ -107,10 +106,7 @@ add_dock_dependent_device(struct dock_station *ds, acpi_handle handle)
>  	dd->handle = handle;
>  	INIT_LIST_HEAD(&dd->list);
>  	INIT_LIST_HEAD(&dd->hotplug_list);
> -
> -	spin_lock(&ds->dd_lock);
>  	list_add_tail(&dd->list, &ds->dependent_devices);
> -	spin_unlock(&ds->dd_lock);
>  
>  	return 0;
>  }
> @@ -168,14 +164,10 @@ find_dock_dependent_device(struct dock_station *ds, acpi_handle handle)
>  {
>  	struct dock_dependent_device *dd;
>  
> -	spin_lock(&ds->dd_lock);
> -	list_for_each_entry(dd, &ds->dependent_devices, list) {
> -		if (handle == dd->handle) {
> -			spin_unlock(&ds->dd_lock);
> +	list_for_each_entry(dd, &ds->dependent_devices, list)
> +		if (handle == dd->handle)
>  			return dd;
> -		}
> -	}
> -	spin_unlock(&ds->dd_lock);
> +
>  	return NULL;
>  }
>  
> @@ -964,7 +956,6 @@ static int __init dock_add(acpi_handle handle)
>  	dock_station->last_dock_time = jiffies - HZ;
>  
>  	mutex_init(&dock_station->hp_lock);
> -	spin_lock_init(&dock_station->dd_lock);
>  	INIT_LIST_HEAD(&dock_station->sibling);
>  	INIT_LIST_HEAD(&dock_station->hotplug_devices);
>  	INIT_LIST_HEAD(&dock_station->dependent_devices);
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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