[lwip-users] FYI, STM32F4xx demo code (and probably others) with FreeRTOS doesn't set SYS_LIGHTWEIGHT_PROT=1

[Mark Lakata]

If you are an advanced LWIP user, this information is "obvious", but if you are just trying to get LWIP to work without understanding the details read on:

The STM32F4xx demo code for LWIP that uses FreeRTOS doesn't set SYS_LIGHTWEIGHT_PROT=1 like it should, so that means that several thread-sensitive parts of the code *will* break if you wait long enough. In my case, I had a

     Assertion "pbuf_free: p->ref > 0" failed at line 650 in C:\...\lwip\src\core\pbuf.c

problem while loading a web page.

The fix is to make sure you have the following in lwipopts.h

   #define SYS_LIGHTWEIGHT_PROT 1

ST wrote the necessary hooks in sys_arch.c, but didn't enable it!

-Mark