[PATCH -next] staging: gdm724x: use GFP_ATOMIC under spin lock

[PATCH -next] staging: gdm724x: use GFP_ATOMIC under spin lock

[Wei Yongjun]

From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>

A spin lock is taken here so we should use GFP_ATOMIC.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
---
 drivers/staging/gdm724x/gdm_mux.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/gdm724x/gdm_mux.c b/drivers/staging/gdm724x/gdm_mux.c
index f570bc0..7becf5c 100644
--- a/drivers/staging/gdm724x/gdm_mux.c
+++ b/drivers/staging/gdm724x/gdm_mux.c
@@ -410,7 +410,7 @@ static int gdm_mux_send(void *priv_dev, void *data, int len, int tty_index,
 			  gdm_mux_send_complete,
 			  t);
 
-	ret = usb_submit_urb(t->urb, GFP_KERNEL);
+	ret = usb_submit_urb(t->urb, GFP_ATOMIC);
 
 	spin_unlock_irqrestore(&mux_dev->write_lock, flags);
 

Re: [PATCH -next] staging: gdm724x: use GFP_ATOMIC under spin lock

[Dan Carpenter]

On Fri, Jul 26, 2013 at 10:15:55AM +0800, Wei Yongjun wrote:
> From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
> 
> A spin lock is taken here so we should use GFP_ATOMIC.
> 

Acked-by: Dan Carpenter <dan.carpenter@oracle.com>

But the locking here is really odd and pointless.  usb_submit_urb()
returns asynchronously before the data has been sent, so there is
almost no point in locking around it.

regards,
dan carpenter

Re: [PATCH -next] staging: gdm724x: use GFP_ATOMIC under spin lock

[Greg KH]

On Fri, Jul 26, 2013 at 10:32:33AM +0300, Dan Carpenter wrote:
> On Fri, Jul 26, 2013 at 10:15:55AM +0800, Wei Yongjun wrote:
> > From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
> > 
> > A spin lock is taken here so we should use GFP_ATOMIC.
> > 
> 
> Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> But the locking here is really odd and pointless.  usb_submit_urb()
> returns asynchronously before the data has been sent, so there is
> almost no point in locking around it.

There's no guarantee it will return before the complete() call is made,
so the data could be sent and then received before the call returns.

Not to say that the locking doesn't seem wrong, I agree with that...

thanks,

greg k-h