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

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Date:	Fri, 14 Jun 2013 22:05:47 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Jiang Liu <jiang.liu@...wei.com>,
	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>, 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 06/14/2013 02:28 AM, Rafael J. Wysocki wrote:
> 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
Patch 3-9 are code cleanup only, I will resend them as separate patchset
later.

> 
> 
>> 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);
>>

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