fix: scope NTP power lock before vTaskDelete, revert clock refresh override

vTaskDelete(nullptr) does not unwind the C++ stack, so the RAII
HalPowerManager::Lock destructor never ran -- permanently holding the
lock and preventing low-power mode. Fix by wrapping the lock in a block
scope that exits before vTaskDelete().

Revert the setPowerSaving(false) calls in the clock refresh block; the
RenderLock already handles CPU frequency during display updates.

Made-with: Cursor

chat-summaries/2026-03-09_06-30-summary.md

@@ -0,0 +1,38 @@
+# Fix Idle Freeze: NTP Power Lock (Corrected)
+
+**Date**: 2026-03-09
+
+## Task Description
+
+Fix device freeze during idle caused by power management issues with NTP sync and clock refresh. This is a correction to the initial fix (commit `6cf212d`) which introduced two new problems.
+
+## Root Cause
+
+The original freeze at the clock minute boundary was caused by the BootNtpSync background task running WiFi/NTP operations without a power lock, allowing the main loop to drop the CPU to 10 MHz during active WiFi/SPI operations.
+
+## Initial Fix Attempt (commit 6cf212d) -- Two Problems
+
+1. **BootNtpSync Lock**: Added `HalPowerManager::Lock` as a local variable in `taskFunc()`. However, `vTaskDelete(nullptr)` at the end of the function kills the FreeRTOS task immediately without C++ stack unwinding, so the lock destructor never ran. The lock was permanently held, preventing the device from ever entering low-power mode.
+
+2. **Clock Refresh Power Override**: Added `setPowerSaving(false)` and `lastActivityTime` reset in the clock refresh block of `main.cpp`. This was unnecessary -- the `RenderLock` inside the render path already handles CPU frequency restoration. The explicit calls prevented the device from entering low-power mode by resetting the idle timer every minute.
+
+## Corrected Fix
+
+### `src/util/BootNtpSync.cpp`
+- Wrapped the `HalPowerManager::Lock` and all WiFi/NTP work in a block scope `{}` that ends before `vTaskDelete(nullptr)`
+- The lock destructor now runs when the block scope exits, properly releasing the power lock
+- `running = false`, `taskHandle = nullptr`, log message, and `vTaskDelete()` remain outside the scope since they don't need full CPU speed
+
+### `src/main.cpp`
+- Reverted the `setPowerSaving(false)` and `lastActivityTime = millis()` additions from both clock refresh branches
+- Clock refresh relies on the existing `RenderLock` mechanism to handle CPU frequency during display updates
+
+## Key Lesson
+
+FreeRTOS `vTaskDelete(nullptr)` does not unwind the C++ stack. RAII objects (like `HalPowerManager::Lock`) placed as local variables in a task function will never have their destructors called. Always use explicit block scoping or manual release before `vTaskDelete()`.
+
+## Follow-up Items
+
+- Verify on device that low-power mode is entered after idle and that NTP sync still completes
+- Verify the clock still updates at minute boundaries without freezing
+- Consider auditing other FreeRTOS task functions in the codebase for similar RAII + `vTaskDelete` issues

src/main.cpp

@@ -416,13 +416,9 @@ void loop() {
       if (lastRenderedMinute < 0) {
         lastRenderedMinute = currentMinute;
         if (sawInvalidTime) {
-          lastActivityTime = millis();
-          powerManager.setPowerSaving(false);
           activityManager.requestUpdate();
         }
       } else if (currentMinute != lastRenderedMinute) {
-        lastActivityTime = millis();
-        powerManager.setPowerSaving(false);
         activityManager.requestUpdate();
         lastRenderedMinute = currentMinute;
       }

src/util/BootNtpSync.cpp

@@ -94,36 +94,39 @@ static bool tryConnectToSavedNetwork(const TaskParams& params) {
 }
 
 static void taskFunc(void* param) {
-  HalPowerManager::Lock powerLock;
-  auto* params = static_cast<TaskParams*>(param);
+  {
+    HalPowerManager::Lock powerLock;
+    auto* params = static_cast<TaskParams*>(param);
 
-  bool connected = tryConnectToSavedNetwork(*params);
+    bool connected = tryConnectToSavedNetwork(*params);
 
-  if (!connected && running) {
-    LOG_DBG("BNTP", "First scan failed, retrying in 3s...");
-    vTaskDelay(3000 / portTICK_PERIOD_MS);
-    if (running) {
-      connected = tryConnectToSavedNetwork(*params);
+    if (!connected && running) {
+      LOG_DBG("BNTP", "First scan failed, retrying in 3s...");
+      vTaskDelay(3000 / portTICK_PERIOD_MS);
+      if (running) {
+        connected = tryConnectToSavedNetwork(*params);
+      }
     }
+
+    if (connected && running) {
+      LOG_DBG("BNTP", "Starting NTP sync...");
+      bool synced = TimeSync::waitForNtpSync(5000);
+      TimeSync::stopNtpSync();
+      if (synced) {
+        LOG_DBG("BNTP", "NTP sync successful");
+      } else {
+        LOG_DBG("BNTP", "NTP sync timed out, continuing without time");
+      }
+    }
+
+    WiFi.disconnect(false);
+    vTaskDelay(100 / portTICK_PERIOD_MS);
+    WiFi.mode(WIFI_OFF);
+    vTaskDelay(100 / portTICK_PERIOD_MS);
+
+    delete params;
   }
 
-  if (connected && running) {
-    LOG_DBG("BNTP", "Starting NTP sync...");
-    bool synced = TimeSync::waitForNtpSync(5000);
-    TimeSync::stopNtpSync();
-    if (synced) {
-      LOG_DBG("BNTP", "NTP sync successful");
-    } else {
-      LOG_DBG("BNTP", "NTP sync timed out, continuing without time");
-    }
-  }
-
-  WiFi.disconnect(false);
-  vTaskDelay(100 / portTICK_PERIOD_MS);
-  WiFi.mode(WIFI_OFF);
-  vTaskDelay(100 / portTICK_PERIOD_MS);
-
-  delete params;
   running = false;
   taskHandle = nullptr;
   LOG_DBG("BNTP", "Boot NTP task complete");