Re: [lwip-users] lwip crashing, apparently in sys_check_timeouts

[Stephen Cowell]

When presented with problems like this I start by replacing all the 
default handlers with handlers that log a hit.  Since you have NVR that 
you can read and write this should be easy... I use my User Page Flash 
for the same purpose.  This will help you divide-and-conquer.
__
Steve
.

On 8/20/2018 1:13 PM, Keith Rubow wrote:
> I am using lwip 2.0.3 with NO_SYS = 1 on a bare metal 386ex processor 
> with a Wiznet IIM7010A ethernet interface operating in MAC RAW mode. 
> Yes, this hardware is REALLY old, but we have lots of hardware out in 
> the field and need to fix a problem, and lwip seems like the best way 
> to fix it.
>
> My hardware has a hardware watchdog timer that will reset the 
> processor if not refreshed at least every 5 seconds. Since 
> implementing lwip I am experiencing extremely infrequent system 
> crashes. My debugging indicates that I call sys_check_timeouts, and 
> then the watchdog timer times out, resetting the system. Normally the 
> watchdog timer is getting refreshed many times per second around the 
> main program loop. It appears that sys_check_timeouts is taking at 
> least 5 seconds to execute.
>
> This crash (or watchdog timer reset) is happening very infrequently. 
> The system will run flawlessly for 2-3 days before crashing. 
> Unfortunately I do not have source level debugging capability on this 
> old hardware. It is possible a memory exception could be vectoring me 
> to a default exception handler that simply hangs in a loop until the 
> watchdog timer resets the system (but proper code should never cause a 
> memory exception). Or the sys_check_timeouts could simply be taking 
> too long to execute. Can it ever take >5 seconds to execute 
> sys_check_timeouts?
>
> My IIM7010A ethernet interface is being operated in polled mode. My 
> main loop operates as follows:
> for (;;) {
>   if (received ethernet frame available in wiznet) {
>     ethernetif_input(&wiznetif);    // this will read and process the 
> ethernet frame for this interface
>   }
>   sys_check_timeouts();
>   if (I have data to send) {
>     size = size of my data to send; // size is never more than 128 bytes
>     if (tcp_sndbuf(userinfo.pcb) >= size) {    // if enough free space 
> to send it
>       if (tcp_write(userinfo.pcb, mybuffer, size, TCP_WRITE_FLAG_COPY) 
> == ERR_OK) { // if send is successful
>         tcp_output(userinfo.pcb);    // initiate sending of data
>       }
>     }
>   }
>   do other stuff not related to lwip or tcp/ip    // none of it is 
> very time consuming, should take only a few 10's of milliseconds
>   reset_watchdog_timer();
> }
>
> I use ipv4 with fixed ip address. I have a single TCP/IP connection 
> up, use callback function for received data, and everything is working 
> perfectly except for the occasional crashes. My debugging ability is 
> limited to setting debug variables to values in a region of memory 
> that is preserved across reboots. My debug variables always show that 
> the last thing I did was call sys_check_timeouts before the restart, 
> and I never returned from sys_check_timeouts. Any ideas?
>
> Keith
>
>
>
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