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 11:04:39 +0530
From:	Prashant Shah <kerneldev100@...il.com>
To:	Harvey Yang <harvey.huawei.yang@...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.

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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