cansend app will block while it is sending RTR frames

cansend app will block while it is sending RTR frames

[xuewentian]

Hi all,

  I want to test sending a lot of RTR frames, because select/poll is no 
effect on the flow control, I add the usleep in the cansend app.
  
  The code segment is :
  

	while (infinite || loopcount--) {
		
		ret = write(s, &frame, sizeof(frame));
		if (ret == -1) {
			perror("write");
			printf("Please specify a more long delay time!\n");
			break;
		}
		usleep(delay);//flow control
	}

  Here the "delay" is about 200us, and I used "cansend can0 -r -e -l 500 -
i 0x1234567  0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88" command to send 500 
RTR frames.but candump on
the another board could only received the 336 frames,and candump app 
hasn't print the received RTR frames,and only count the received frmaes.
  and I debugged the send process in the kernel, and I found that it sleep 
on the copy_from_user in the memcpy_fromiovec of the raw_sendmsg
  
  err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size);  // in 
the raw_sendmsg function of the net/can/raw.c file.
	if (err < 0)
		goto free_skb;

  What about happens with the write of the cansend app? and I used the 
same way to send the 5000000 data frames, it didn't blocked.

Thanks a lot.

Re: cansend app will block while it is sending RTR frames

[Marc Kleine-Budde]

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On 08/28/2013 11:34 AM, xuewentian wrote:
> Hi all,
> 
>   I want to test sending a lot of RTR frames, because select/poll is no 
> effect on the flow control, I add the usleep in the cansend app.
>   
>   The code segment is :
>   
> 
> 	while (infinite || loopcount--) {
> 		
> 		ret = write(s, &frame, sizeof(frame));
> 		if (ret == -1) {
> 			perror("write");
> 			printf("Please specify a more long delay time!\n");
> 			break;
> 		}
> 		usleep(delay);//flow control
> 	}
> 
>   Here the "delay" is about 200us, and I used "cansend can0 -r -e -l 500 -
> i 0x1234567  0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88" command to send 500 
> RTR frames.but candump on
> the another board could only received the 336 frames,and candump app 
> hasn't print the received RTR frames,and only count the received frmaes.
>   and I debugged the send process in the kernel, and I found that it sleep 
> on the copy_from_user in the memcpy_fromiovec of the raw_sendmsg
>   
>   err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size);  // in 
> the raw_sendmsg function of the net/can/raw.c file.
> 	if (err < 0)
> 		goto free_skb;

How have you measured that the kernel sleeps in that function? How long
does it sleep?

>   What about happens with the write of the cansend app? and I used the 
> same way to send the 5000000 data frames, it didn't blocked.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


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Re: cansend app will block while it is sending RTR frames

[xuewentian]

Marc Kleine-Budde <mkl <at> pengutronix.de> writes:

> 
> On 08/28/2013 11:34 AM, xuewentian wrote:
> > Hi all,
> > 
> >   I want to test sending a lot of RTR frames, because select/poll is no 
> > effect on the flow control, I add the usleep in the cansend app.
> >   
> >   The code segment is :
> >   
> > 
> > 	while (infinite || loopcount--) {
> > 		
> > 		ret = write(s, &frame, sizeof(frame));
> > 		if (ret == -1) {
> > 			perror("write");
> > 			printf("Please specify a more long delay time!\n");
> > 			break;
> > 		}
> > 		usleep(delay);//flow control
> > 	}
> > 
> >   Here the "delay" is about 200us, and I used "cansend can0 -r -e -l 500 
-
> > i 0x1234567  0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88" command to send 
500 
> > RTR frames.but candump on
> > the another board could only received the 336 frames,and candump app 
> > hasn't print the received RTR frames,and only count the received frmaes.
> >   and I debugged the send process in the kernel, and I found that it 
sleep 
> > on the copy_from_user in the memcpy_fromiovec of the raw_sendmsg
> >   
> >   err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size);  // in 
> > the raw_sendmsg function of the net/can/raw.c file.
> > 	if (err < 0)
> > 		goto free_skb;
> 
> How have you measured that the kernel sleeps in that function? How long
> does it sleep?

**************
my reply:

I found the cansend app will always sleep after sending 336 RTR frames by 
using "cansend can0 -r -e -l 500 -i 0x1234567  0x11 0x22 0x33 0x44 0x55 0x66 
0x77 0x88". I must press ctrl+c to cancel it,after cancelling
it,and I ran "cansend can0 -r -e -i 0x1234567  0x11 0x22 0x33 0x44 0x55 0x66 
0x77 0x88" for send another RTR frame, it could be sent successfully.
and I tested "cansend can0 -r -e -l 500 -i 0x1234567  0x11 0x22 0x33 0x44 
0x55 0x66 0x77 0x88 &" to run background, and it still sent 336 RTR frames, 
and the process was pending, and I could still send RTR
frames on the serial terminal.
And I used command "cansend can0 -e -l 5000000 -i 0x1234567  0x11 0x22 0x33 
0x44 0x55 0x66 0x77 0x88" to send 50000000 data frames,the cansend app could 
return to serial terminal. It didn't block.
The problem seemed to has no relationship with can driver because it still 
could send RTR frames after the problem occurred. I didn't know why it was 
always sleeping on the copy_from_user function.
any suggestion for me? 

Thanks a lot for your reply.

Re: cansend app will block while it is sending RTR frames

[Marc Kleine-Budde]

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On 08/30/2013 09:20 AM, xuewt wrote:
> I found that I didn't free the skb buffer for RTR frame. It was resolved.

Please don't top post. Oh, you're writing a new driver. What hardware
are you supporting? If you post it here, we'll review it.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


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