fix presets.json corruption, part 2: mutex for presets file writing

prevents concurrent presets.json writes from doSaveState() and savePreset()

wled00/presets.cpp

@@ -38,7 +38,14 @@ static void doSaveState() {
   bool persist = (presetToSave < 251);
   const char *filename = getFileName(persist);
 
-  if (!requestJSONBufferLock(10)) return; // will set fileDoc
+  if (!requestJSONBufferLock(10)) return; // will set fileDoc // async write
+
+  // WLEDMM Acquire file mutex before writing presets.json or tmp.json
+  if (esp32SemTake(presetFileMux, 2500) != pdTRUE) {
+    USER_PRINTLN(F("doSaveState(): preset file busy, cannot write"));
+    releaseJSONBufferLock();
+    return;
+  }
 
   initPresetsFile(); // just in case if someone deleted presets.json using /edit
   JsonObject sObj = doc.to<JsonObject>();
@@ -82,6 +89,8 @@ static void doSaveState() {
   writeObjectToFileUsingId(filename, presetToSave, fileDoc);
 
   if (persist) presetsModifiedTime = toki.second(); //unix time
+
+  esp32SemGive(presetFileMux);  // Release file mutex
   releaseJSONBufferLock();
   updateFSInfo();
 
@@ -316,7 +325,14 @@ void savePreset(byte index, const char* pname, JsonObject sObj)
   } else {
     // this is a playlist or API call
     if (sObj[F("playlist")].isNull()) {
-      // we will save API call immediately (often causes presets.json corruption)
+      // we will save API call immediately (often causes presets.json corruption in the past)
+
+      // WLEDMM Acquire file mutex before writing presets.json, to prevent presets.json corruption
+      if (esp32SemTake(presetFileMux, 2500) != pdTRUE) {
+          USER_PRINTLN(F("doSaveState(): preset file busy, cannot write"));
+          return; // early exit, no change
+      }
+
       presetToSave = 0;
       if (index > 250 || !fileDoc) return; // cannot save API calls to temporary preset (255)
       sObj.remove("o");
@@ -325,8 +341,11 @@ void savePreset(byte index, const char* pname, JsonObject sObj)
       sObj.remove(F("error"));
       sObj.remove(F("psave"));
       if (sObj["n"].isNull()) sObj["n"] = saveName;
+
       initPresetsFile(); // just in case if someone deleted presets.json using /edit
       writeObjectToFileUsingId(getFileName(index<255), index, fileDoc);
+
+      esp32SemGive(presetFileMux);  // Release file mutex
       presetsModifiedTime = toki.second(); //unix time
       updateFSInfo();
     } else {

wled00/wled.cpp

@@ -480,11 +480,14 @@ 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))
+  presetFileMux = xSemaphoreCreateRecursiveMutex();   // WLEDMM prevent concurrent presets.json file writing
+  if ((busDrawMux == nullptr) || (segmentMux == nullptr) || (jsonBufferLockMutex == nullptr) || (presetFileMux == nullptr)) {
     USER_PRINTLN(F("setup error: xSemaphoreCreateRecursiveMutex failed.")); // should never happen.
+  }
   xSemaphoreGiveRecursive(busDrawMux);                 // init semaphores to initially allow drawing
   xSemaphoreGiveRecursive(segmentMux);
   xSemaphoreGiveRecursive(jsonBufferLockMutex);
+  xSemaphoreGiveRecursive(presetFileMux);
   #endif
 
   #ifdef ARDUINO_ARCH_ESP32

wled00/wled.h

@@ -7,7 +7,7 @@
  */
 
 // version code in format yymmddb (b = daily build)
-#define VERSION 2512291
+#define VERSION 2512292
 
 // WLEDMM  - you can check for this define in usermods, to only enabled WLEDMM specific code in the "right" fork. Its not defined in AC WLED.
 #define _MoonModules_WLED_
@@ -771,6 +771,7 @@ WLED_GLOBAL volatile bool OTAisRunning _INIT(false);        // WLEDMM temporaril
 WLED_GLOBAL SemaphoreHandle_t busDrawMux _INIT(nullptr);
 WLED_GLOBAL SemaphoreHandle_t segmentMux _INIT(nullptr);
 WLED_GLOBAL SemaphoreHandle_t jsonBufferLockMutex _INIT(nullptr);
+WLED_GLOBAL SemaphoreHandle_t presetFileMux _INIT(nullptr); // Protects presets.json file writes
 #define esp32SemTake(mux,timeout) xSemaphoreTakeRecursive(mux, pdMS_TO_TICKS(timeout)) // convenience macro that expands to xSemaphoreTakeRecursive - timeout is in milliseconds
 #define esp32SemGive(mux)  xSemaphoreGiveRecursive(mux)                 // convenience macro that expands to xSemaphoreGiveRecursive
 #define WLED_create_spinlock(theSname) static portMUX_TYPE theSname = portMUX_INITIALIZER_UNLOCKED