linux-kernel - Re: [PATCH 1/1] staging: usbip: remove an unnecessary lock in usbip_event_happened. The variable "happened" is local. So I think there is no need to lock here.

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Date:	Mon, 5 Nov 2012 14:34:31 +0800
From:	harvey yang <harvey.huawei.yang@...il.com>
To:	Prashant Shah <kerneldev100@...il.com>
Cc:	Matt Mooney <mfm@...eddisk.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] staging: usbip: remove an unnecessary lock in
 usbip_event_happened. The variable "happened" is local. So I think there is
 no need to lock here.

I think no need to make 'happened' static as we just check 'ud->event'
feild. Maybe making this function inline would make more sense.

inline int usbip_event_happened(struct usbip_device *ud)
{
        return ud->event ? 1 : 0;
}

Thanks
Harvey


On Mon, Nov 5, 2012 at 1:34 PM, Prashant Shah <kerneldev100@...il.com> wrote:
> Hi,
>
>>         int happened = 0;
>>
>> -       spin_lock(&ud->lock);
>>         if (ud->event != 0)
>>                 happened = 1;
>> -       spin_unlock(&ud->lock);
>>
>>         return happened;
>
> I am guessing locking was intended to protect ud->event along with
> happened so that (checking the value of ud->event and setting value of
> happened) was atomic.
>
> return ud->event != 0 ? 1 : 0;
>
> Regards.
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