fix: properly implement requestUpdateAndWait() (#1218)

## Summary

Properly implement `requestUpdateAndWait()` using freeRTOS direct task
notification.

FWIW, I think most of the current use cases of `requestUpdateAndWait()`
are redundant, better to be replaced by `requestUpdate(true)`. But just
keeping them in case we can find a proper use case for it in the future.

---

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Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

authored by

Xuan-Son Nguyen

coderabbitai[bot] and committed by

GitHub 3 months ago a57c62f0 3da2cd3c

+49 -6

4 changed files

expand all

src

activities

Activity.cpp

ActivityManager.cpp

ActivityManager.h

network

WifiSelectionActivity.cpp

+1 -5

src/activities/Activity.cpp

··· 8 8 9 9 void Activity::requestUpdate(bool immediate) { activityManager.requestUpdate(immediate); } 10 10 11 - void Activity::requestUpdateAndWait() { 12 - // FIXME @ngxson : properly implement this using freeRTOS notification 13 - activityManager.requestUpdate(true); 14 - delay(100); 15 - } 11 + void Activity::requestUpdateAndWait() { activityManager.requestUpdateAndWait(); } 16 12 17 13 void Activity::onGoHome() { activityManager.goHome(); } 18 14

+39

src/activities/ActivityManager.cpp

··· 38 38 HalPowerManager::Lock powerLock; // Ensure we don't go into low-power mode while rendering 39 39 currentActivity->render(std::move(lock)); 40 40 } 41 + // Notify any task blocked in requestUpdateAndWait() that the render is done. 42 + TaskHandle_t waiter = nullptr; 43 + taskENTER_CRITICAL(nullptr); 44 + waiter = waitingTaskHandle; 45 + waitingTaskHandle = nullptr; 46 + taskEXIT_CRITICAL(nullptr); 47 + if (waiter) { 48 + xTaskNotify(waiter, 1, eIncrement); 49 + } 41 50 } 42 51 } 43 52 ··· 225 234 requestedUpdate = true; 226 235 } 227 236 } 237 + void ActivityManager::requestUpdateAndWait() { 238 + if (!renderTaskHandle) { 239 + return; 240 + } 241 + 242 + // Atomic section to perform checks 243 + taskENTER_CRITICAL(nullptr); 244 + auto currTaskHandler = xTaskGetCurrentTaskHandle(); 245 + auto mutexHolder = xSemaphoreGetMutexHolder(renderingMutex); 246 + bool isRenderTask = (currTaskHandler == renderTaskHandle); 247 + bool alreadyWaiting = (waitingTaskHandle != nullptr); 248 + bool holdingRenderLock = (mutexHolder == currTaskHandler); 249 + if (!alreadyWaiting && !isRenderTask && !holdingRenderLock) { 250 + waitingTaskHandle = currTaskHandler; 251 + } 252 + taskEXIT_CRITICAL(nullptr); 253 + 254 + // Render task cannot call requestUpdateAndWait() or it will cause a deadlock 255 + assert(!isRenderTask && "Render task cannot call requestUpdateAndWait()"); 256 + 257 + // There should never be the case where 2 tasks are waiting for a render at the same time 258 + assert(!alreadyWaiting && "Already waiting for a render to complete"); 259 + 260 + // Cannot call while holding RenderLock or it will cause a deadlock 261 + assert(!holdingRenderLock && "Cannot call requestUpdateAndWait() while holding RenderLock"); 262 + 263 + xTaskNotify(renderTaskHandle, 1, eIncrement); 264 + ulTaskNotifyTake(pdTRUE, portMAX_DELAY); 265 + } 266 + 228 267 // RenderLock 229 268 230 269 RenderLock::RenderLock() {

src/activities/ActivityManager.h

··· 50 50 static void renderTaskTrampoline(void* param); 51 51 [[noreturn]] virtual void renderTaskLoop(); 52 52 53 + // Set by requestUpdateAndWait(); read and cleared by the render task after render completes. 54 + // Note: only one waiting task is supported at a time 55 + TaskHandle_t waitingTaskHandle = nullptr; 56 + 53 57 // Mutex to protect rendering operations from race conditions 54 58 // Must only be used via RenderLock 55 59 SemaphoreHandle_t renderingMutex = nullptr; ··· 98 102 // If immediate is true, the update will be triggered immediately. 99 103 // Otherwise, it will be deferred until the end of the current loop iteration. 100 104 void requestUpdate(bool immediate = false); 105 + 106 + // Trigger a render and block until it completes. 107 + // Must NOT be called from the render task or while holding a RenderLock. 108 + void requestUpdateAndWait(); 101 109 }; 102 110 103 111 extern ActivityManager activityManager; // singleton, to be defined in main.cpp

+1 -1

src/activities/network/WifiSelectionActivity.cpp

··· 201 201 state = WifiSelectionState::NETWORK_LIST; 202 202 } else { 203 203 enteredPassword = std::get<KeyboardResult>(result.data).text; 204 + // state will be updated in next loop iteration 204 205 } 205 206 }); 206 207 } else { ··· 465 466 // Don't render if we're in PASSWORD_ENTRY state - we're just transitioning 466 467 // from the keyboard subactivity back to the main activity 467 468 if (state == WifiSelectionState::PASSWORD_ENTRY) { 468 - requestUpdateAndWait(); 469 469 return; 470 470 } 471 471

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