improved mutex error handling

- debug message in case of "unexpected" mutex errors
- removed experimental delay() in requestJSONBufferLock

wled00/json.cpp

@@ -100,6 +100,9 @@ bool deserializeSegment(JsonObject elem, byte it, byte presetId)
       id = strip.getSegmentsNum()-1; // segments are added at the end of list
       newSeg = true;
       esp32SemGive(segmentMux);
+    } else {
+      USER_PRINTLN(F("deserializeSegment(): segment not added - failed to acquire segmentMux."));
+      return false;      
     }
   }
 
@@ -358,6 +361,7 @@ bool deserializeSegment(JsonObject elem, byte it, byte presetId)
       strip.waitUntilIdle();
     }
     // WLEDMM protect against parallel drawing
+    bool drawSuccess = false;
     if (esp32SemTake(busDrawMux, 250) == pdTRUE) {      // WLEDMM first acquire draw mutex, start of critical section
     seg.startFrame();
 
@@ -409,11 +413,13 @@ bool deserializeSegment(JsonObject elem, byte it, byte presetId)
         set = 0;
       }
     }
+    drawSuccess = true;
     esp32SemGive(busDrawMux); // release lock
     } // end of critical section
 
     seg.map1D2D = oldMap1D2D; // restore mapping
-    strip.trigger(); // force segment update
+    if (drawSuccess) strip.trigger(); // force segment update
+    else USER_PRINTLN(F("deserializeSegment() image drawing failed, cannot not to acquire busDrawMux.")); // log failure messaage
     suspendStripService = oldLock; // restore previous lock status
   }
   // send UDP/WS if segment options changed (except selection; will also deselect current preset)

wled00/util.cpp

@@ -239,7 +239,6 @@ bool requestJSONBufferLock(uint8_t module)
 
   if (jsonBufferLock || !haveLock) {
     if (haveLock) esp32SemGive(jsonBufferLockMutex);  // we got the mutex, but jsonBufferLock says the opposite -> give up
-    delay(10); // WLEDMM experimental: small extra wait, in case that esp32 cores temporarily disagree on the value of jsonBufferLock
     USER_PRINT(F("ERROR: Locking JSON buffer failed! (still locked by "));
     USER_PRINT(jsonBufferLock);
     USER_PRINTLN(")");

wled00/wled.cpp

@@ -480,6 +480,8 @@ void WLED::setup()
   busDrawMux = xSemaphoreCreateRecursiveMutex();       // WLEDMM prevent concurrent running of strip.show and strip.service
   segmentMux = xSemaphoreCreateRecursiveMutex();       // WLEDMM prevent segment changes while effects are running
   jsonBufferLockMutex = xSemaphoreCreateRecursiveMutex(); // WLEDMM prevent concurrent JSON buffer writing
+  if ((busDrawMux == nullptr) || (segmentMux == nullptr) || (jsonBufferLockMutex == nullptr))
+    USER_PRINTLN(F("setup error: xSemaphoreCreateRecursiveMutex failed.")); // should never happen.
   xSemaphoreGiveRecursive(busDrawMux);                 // init semaphores to initially allow drawing
   xSemaphoreGiveRecursive(segmentMux);
   xSemaphoreGiveRecursive(jsonBufferLockMutex);