[PATCH] USB CDC NCM: tx_fixup() race condition fix

[PATCH] USB CDC NCM: tx_fixup() race condition fix

[Alexey Orishko]

- tx_fixup() call be called from either timer callback or from xmit()
  in usbnet, so spinlock is added to avoid concurrency-related problem.
- minor correction due checkpatch warning for some line over 80 chars
  after previous patch was applied.

Signed-off-by: Alexey Orishko <alexey.orishko-0IS4wlFg1OjSUeElwK9/Pw@public.gmane.org>
---
 drivers/net/usb/cdc_ncm.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index d776c4a..bf13fa6 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -54,7 +54,7 @@
 #include <linux/usb/usbnet.h>
 #include <linux/usb/cdc.h>
 
-#define	DRIVER_VERSION				"30-Nov-2010"
+#define	DRIVER_VERSION				"17-Jan-2011"
 
 /* CDC NCM subclass 3.2.1 */
 #define USB_CDC_NCM_NDP16_LENGTH_MIN		0x10
@@ -873,9 +873,11 @@ static void cdc_ncm_tx_timeout(unsigned long arg)
 
 	spin_unlock(&ctx->mtx);
 
-	if (restart)
+	if (restart) {
+		spin_lock(&ctx->mtx);
 		cdc_ncm_tx_timeout_start(ctx);
-	else if (ctx->netdev != NULL)
+		spin_unlock(&ctx->mtx);
+	} else if (ctx->netdev != NULL)
 		usbnet_start_xmit(NULL, ctx->netdev);
 }
 
@@ -900,7 +902,6 @@ cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 	skb_out = cdc_ncm_fill_tx_frame(ctx, skb);
 	if (ctx->tx_curr_skb != NULL)
 		need_timer = 1;
-	spin_unlock(&ctx->mtx);
 
 	/* Start timer, if there is a remaining skb */
 	if (need_timer)
@@ -908,6 +909,8 @@ cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 
 	if (skb_out)
 		dev->net->stats.tx_packets += ctx->tx_curr_frame_num;
+
+	spin_unlock(&ctx->mtx);
 	return skb_out;
 
 error:
@@ -1021,7 +1024,7 @@ static int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in)
 		    (temp > CDC_NCM_MAX_DATAGRAM_SIZE) || (temp < ETH_HLEN)) {
 			pr_debug("invalid frame detected (ignored)"
 				"offset[%u]=%u, length=%u, skb=%p\n",
-							x, offset, temp, skb_in);
+						x, offset, temp, skb_in);
 			if (!x)
 				goto error;
 			break;
-- 
1.7.0.4

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Re: [PATCH] USB CDC NCM: tx_fixup() race condition fix

[Sergei Shtylyov]

Hello.

Alexey Orishko wrote:

> - tx_fixup() call be called from either timer callback or from xmit()

    s/call/can/?

>   in usbnet, so spinlock is added to avoid concurrency-related problem.
> - minor correction due checkpatch warning for some line over 80 chars

    Due to?

>   after previous patch was applied.

> Signed-off-by: Alexey Orishko <alexey.orishko-0IS4wlFg1OjSUeElwK9/Pw@public.gmane.org>
> ---
>  drivers/net/usb/cdc_ncm.c |   13 ++++++++-----
>  1 files changed, 8 insertions(+), 5 deletions(-)

> diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
> index d776c4a..bf13fa6 100644
> --- a/drivers/net/usb/cdc_ncm.c
> +++ b/drivers/net/usb/cdc_ncm.c
> @@ -54,7 +54,7 @@
>  #include <linux/usb/usbnet.h>
>  #include <linux/usb/cdc.h>
>  
> -#define	DRIVER_VERSION				"30-Nov-2010"
> +#define	DRIVER_VERSION				"17-Jan-2011"
>  
>  /* CDC NCM subclass 3.2.1 */
>  #define USB_CDC_NCM_NDP16_LENGTH_MIN		0x10
> @@ -873,9 +873,11 @@ static void cdc_ncm_tx_timeout(unsigned long arg)
>  
>  	spin_unlock(&ctx->mtx);
>  
> -	if (restart)
> +	if (restart) {
> +		spin_lock(&ctx->mtx);
>  		cdc_ncm_tx_timeout_start(ctx);
> -	else if (ctx->netdev != NULL)
> +		spin_unlock(&ctx->mtx);
> +	} else if (ctx->netdev != NULL)

    The 'else' branch should now also have {}, according to 
Documentation/CodingStyle.

>  		usbnet_start_xmit(NULL, ctx->netdev);
>  }
>  
> @@ -1021,7 +1024,7 @@ static int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in)
>  		    (temp > CDC_NCM_MAX_DATAGRAM_SIZE) || (temp < ETH_HLEN)) {
>  			pr_debug("invalid frame detected (ignored)"
>  				"offset[%u]=%u, length=%u, skb=%p\n",
> -							x, offset, temp, skb_in);
> +						x, offset, temp, skb_in);

    Would be good to align uniformly with the previous line...

WBR, Sergei
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RE: [PATCH] USB CDC NCM: tx_fixup() race condition fix

[Alexey ORISHKO]

> > - tx_fixup() call be called from either timer callback or from xmit()
> 
>     s/call/can/?
Yes :-)

> 
> >   in usbnet, so spinlock is added to avoid concurrency-related
> problem.
> > - minor correction due checkpatch warning for some line over 80 chars
> 
>     Due to?
yep

Sorry for typos...

Regards,
alexey
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