Fix CoreMutex infinite recursion crash

Core could crash while Serial debugging was going on and prints were
happening from LWIP/IRQ land and the main app.

Author: earlephilhower

cores/rp2040/CoreMutex.h

@@ -27,16 +27,18 @@
 
 class CoreMutex {
 public:
-    CoreMutex(mutex_t *mutex) {
+    CoreMutex(mutex_t *mutex, bool debugEnable = true) {
         uint32_t owner;
         _mutex = mutex;
         _acquired = false;
         if (!mutex_try_enter(_mutex, &owner)) {
             if (owner == get_core_num()) { // Deadlock!
-                DEBUGCORE("CoreMutex - Deadlock detected!\n");
+                if (debugEnable) {
+                    DEBUGCORE("CoreMutex - Deadlock detected!\n");
+                }
                 return;
             }
-            mutex_enter_blocking(_mutex);
+            // mutex_enter_blocking(_mutex);
         }
         _acquired = true;
     }

cores/rp2040/SerialUSB.cpp

@@ -64,7 +64,7 @@ void SerialUSB::end() {
 }
 
 int SerialUSB::peek() {
-    CoreMutex m(&__usb_mutex);
+    CoreMutex m(&__usb_mutex, false);
     if (!_running || !m) {
         return 0;
     }
@@ -74,7 +74,7 @@ int SerialUSB::peek() {
 }
 
 int SerialUSB::read() {
-    CoreMutex m(&__usb_mutex);
+    CoreMutex m(&__usb_mutex, false);
     if (!_running || !m) {
         return -1;
     }
@@ -86,7 +86,7 @@ int SerialUSB::read() {
 }
 
 int SerialUSB::available() {
-    CoreMutex m(&__usb_mutex);
+    CoreMutex m(&__usb_mutex, false);
     if (!_running || !m) {
         return 0;
     }
@@ -95,7 +95,7 @@ int SerialUSB::available() {
 }
 
 int SerialUSB::availableForWrite() {
-    CoreMutex m(&__usb_mutex);
+    CoreMutex m(&__usb_mutex, false);
     if (!_running || !m) {
         return 0;
     }
@@ -104,7 +104,7 @@ int SerialUSB::availableForWrite() {
 }
 
 void SerialUSB::flush() {
-    CoreMutex m(&__usb_mutex);
+    CoreMutex m(&__usb_mutex, false);
     if (!_running || !m) {
         return;
     }
@@ -117,7 +117,7 @@ size_t SerialUSB::write(uint8_t c) {
 }
 
 size_t SerialUSB::write(const uint8_t *buf, size_t length) {
-    CoreMutex m(&__usb_mutex);
+    CoreMutex m(&__usb_mutex, false);
     if (!_running || !m) {
         return 0;
     }
@@ -155,7 +155,7 @@ size_t SerialUSB::write(const uint8_t *buf, size_t length) {
 }
 
 SerialUSB::operator bool() {
-    CoreMutex m(&__usb_mutex);
+    CoreMutex m(&__usb_mutex, false);
     if (!_running || !m) {
         return false;
     }