Subject: Re: [PATCH] can: ems_usb: Fix possible tx overflow

From: Marc Kleine-Budde <[email-masked]>
Date: Mon, 22 Feb 2016 13:18:38 +0100

On 02/22/2016 01:11 PM, Sergei Shtylyov wrote:
> Hello.
> 
> On 2/21/2016 6:27 PM, Marc Kleine-Budde wrote:
> 
>> From: Gerhard Uttenthaler <[email-masked]>
>>
>> This patch fixes the problem that more CAN messages could be sent to the
>> interface as could be send on the CAN bus. This was more likely for slow baud
>> rates. The sleeping _start_xmit was woken up in the _write_bulk_callback. Under
>> heavy TX load this produced another bulk transfer without checking the
>> free_slots variable and hence caused the overflow in the interface.
>>
>> Signed-off-by: Gerhard Uttenthaler <[email-masked]>
>> Cc: linux-stable <[email-masked]>
>> Signed-off-by: Marc Kleine-Budde <[email-masked]>
>> ---
>>   drivers/net/can/usb/ems_usb.c | 14 ++++++++++----
>>   1 file changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/net/can/usb/ems_usb.c b/drivers/net/can/usb/ems_usb.c
>> index fc5b75675cd8..eb7192fab593 100644
>> --- a/drivers/net/can/usb/ems_usb.c
>> +++ b/drivers/net/can/usb/ems_usb.c
>> @@ -117,6 +117,9 @@ MODULE_LICENSE("GPL v2");
>>    */
>>   #define EMS_USB_ARM7_CLOCK 8000000
>>
>> +#define CPC_TX_QUEUE_TRIGGER_LOW	25
>> +#define CPC_TX_QUEUE_TRIGGER_HIGH	35
>> +
>>   /*
>>    * CAN-Message representation in a CPC_MSG. Message object type is
>>    * CPC_MSG_TYPE_CAN_FRAME or CPC_MSG_TYPE_RTR_FRAME or
>> @@ -278,6 +281,11 @@ static void ems_usb_read_interrupt_callback(struct urb *urb)
>>   	switch (urb->status) {
>>   	case 0:
>>   		dev->free_slots = dev->intr_in_buffer[1];
>> +		if(dev->free_slots > CPC_TX_QUEUE_TRIGGER_HIGH){
>> +			if (netif_queue_stopped(netdev)){
>> +				netif_wake_queue(netdev);
>> +			}
>> +		}
> 
>     Hm, did anyone run scripts/checkpatch.pl on this patch?

Obviously not. :(

David, I can send a patch to clean up the coding style. Do you want it
for net or via net-next?

Marc
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