Fix polling and IRQ memory corruption

The IRQ callback routine ended up passing in a stack variable address.  For main
app code this is legal because the app blocks until the LWIP call returns.  But
for IRQs, it returns immediately (can't block in IRQ) and the stack pointer we
passed in will be corrupt.  Use a dumb static (heap) variable for now.

W5100 is now running with multiple AdvancedWebServer clients in parallel with
a WiFiClient MOTD process on core 1, in parallel.

Rewriting the CYW43 driver to work with this TBD.

Author: earlephilhower

cores/rp2040/freertos/FreeRTOSConfig.h

@@ -96,8 +96,14 @@
 #define configGENERATE_RUN_TIME_STATS	1
 #endif
 #ifdef configGENERATE_RUN_TIME_STATS
+#ifdef __cplusplus
+extern "C" {
+#endif
 extern void vMainConfigureTimerForRunTimeStats(void);
 extern unsigned long ulMainGetRunTimeCounterValue(void);
+#ifdef __cplusplus
+};
+#endif
 #define portCONFIGURE_TIMER_FOR_RUN_TIME_STATS() //vMainConfigureTimerForRunTimeStats()
 #define portGET_RUN_TIME_COUNTER_VALUE() ulMainGetRunTimeCounterValue()
 #endif

cores/rp2040/lwip_wrap.cpp

@@ -832,7 +832,19 @@ extern "C" {
 #ifdef __FREERTOS
         if (fromISR) {
             // In ISR we can't check what the current thread is
-            __callback_req req = { cb, cbData };
+            static __callback_req req = { cb, cbData }; // TODO HACK HERE
+            // We pass in the address of an unknown sized request to the LWIP work queue
+            // For normal mode that address is on the app stack, which will be frozen until
+            // the callback is performed.  So no problem, that stack address will remain valid.
+            // Here, we're in an ISR and won't block, just put a pointer on the queue and
+            // return from the interrupt.  The stack address, there, is no longer safe and you
+            // will see memory corruption when the actual app thread uses its stack.
+            // We can't allocate memory in an IRQ in FreeRTOS, so for now we'll just have
+            // a single heap-based (static) request which will live forever.  As long as
+            // only a single lwip_callback from IRQ is present we're OK.  Should you have 2
+            // IRQ driver network cards, this will fail.
+            // A more satisfying method might have the NIC driver pass in its own class local
+            // preallocated storage space which we can use.
             __lwip(__callback, &req, fromISR);
             return;
         } else if (!__isLWIPThread()) {

libraries/lwIP_Ethernet/src/LwipEthernet.cpp

@@ -235,11 +235,13 @@ static TaskHandle_t _ethernetTask;;
 
 static void stage2(void *cbData) {
     (void) cbData;
+    ethernet_arch_lwip_gpio_mask();
     // Scan the installed Ethernet drivers
     for (auto handlePacket : _handlePacketList) {
         // Note that each NIC needs to use its own mutex to ensure LWIP isn't doing something with it at the time we want to poll
-//        handlePacket.second();
+        handlePacket.second();
     }
+    ethernet_arch_lwip_gpio_unmask();
     // Do LWIP stuff as needed
     sys_check_timeouts();
 }