2012-11-05 04:46:41

by Harvey Yang

Subject: [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.

From: harvey.yang <[email protected]>


Signed-off-by: harvey.yang <[email protected]>
---
drivers/staging/usbip/usbip_event.c | 2 --
1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/usbip/usbip_event.c b/drivers/staging/usbip/usbip_event.c
index d332a34..668f8e0 100644
--- a/drivers/staging/usbip/usbip_event.c
+++ b/drivers/staging/usbip/usbip_event.c
@@ -116,10 +116,8 @@ int usbip_event_happened(struct usbip_device *ud)
{
int happened = 0;

- spin_lock(&ud->lock);
if (ud->event != 0)
happened = 1;
- spin_unlock(&ud->lock);

return happened;
}
--
1.7.1

2012-11-05 04:57:39

by Greg Kroah-Hartman

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.

On Mon, Nov 05, 2012 at 12:50:26PM +0800, Harvey Yang wrote:
> From: harvey.yang <[email protected]>
>
>
> Signed-off-by: harvey.yang <[email protected]>
> ---
> drivers/staging/usbip/usbip_event.c | 2 --
> 1 files changed, 0 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/usbip/usbip_event.c b/drivers/staging/usbip/usbip_event.c
> index d332a34..668f8e0 100644
> --- a/drivers/staging/usbip/usbip_event.c
> +++ b/drivers/staging/usbip/usbip_event.c
> @@ -116,10 +116,8 @@ int usbip_event_happened(struct usbip_device *ud)
> {
> int happened = 0;
>
> - spin_lock(&ud->lock);
> if (ud->event != 0)
> happened = 1;
> - spin_unlock(&ud->lock);
>
> return happened;

Are you sure that the real fix for this isn't just making 'happened' a
static variable? That would make more sense here. Well maybe, the code
seems pretty dumb, it's hard to tell what this is supposed to be doing,
any ideas?

thanks,

greg k-h

2012-11-05 05:34:49

by Prashant Shah

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.

2012-11-05 06:34:33

by Harvey Yang

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 <[email protected]> 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.