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 16:16:35 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Jiang Liu <liuj97@...il.com>
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 Friday, June 14, 2013 10:05:47 PM Jiang Liu wrote:
> 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.

Cool, thanks!

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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