Merge branch 'bugfix/freertos_event_group_unblock_race_condition_v4.4' into 'release/v4.4'

FreeRTOS: Fix event group task list race condition (v4.4)

See merge request espressif/esp-idf!19103

components/freertos/event_groups.c

@@ -600,6 +600,10 @@ EventBits_t xEventGroupSetBits( EventGroupHandle_t xEventGroup,
     pxListEnd = listGET_END_MARKER( pxList ); /*lint !e826 !e740 !e9087 The mini list structure is used as the list end to save RAM.  This is checked and valid. */
 #ifdef ESP_PLATFORM // IDF-3755
     taskENTER_CRITICAL();
+    /* The critical section above only takes the event groups spinlock. However, we are about to traverse a task list.
+     * Thus we need call the function below to take the task list spinlock located in tasks.c. Not doing so will risk
+     * the task list's being changed while be are traversing it. */
+    vTaskTakeEventListLock();
 #else
     vTaskSuspendAll();
 #endif // ESP_PLATFORM
@@ -675,6 +679,8 @@ EventBits_t xEventGroupSetBits( EventGroupHandle_t xEventGroup,
         pxEventBits->uxEventBits &= ~uxBitsToClear;
     }
 #ifdef ESP_PLATFORM // IDF-3755
+    /* Release the previously held task list spinlock, then release the event group spinlock. */
+    vTaskReleaseEventListLock();
     taskEXIT_CRITICAL();
 #else
     ( void ) xTaskResumeAll();
@@ -693,6 +699,12 @@ void vEventGroupDelete( EventGroupHandle_t xEventGroup )
 
     // IDF-3755
     taskENTER_CRITICAL();
+#ifdef ESP_PLATFORM
+    /* The critical section above only takes the event groups spinlock. However, we are about to traverse a task list.
+     * Thus we need call the function below to take the task list spinlock located in tasks.c. Not doing so will risk
+     * the task list's being changed while be are traversing it. */
+    vTaskTakeEventListLock();
+#endif
     {
         while( listCURRENT_LIST_LENGTH( pxTasksWaitingForBits ) > ( UBaseType_t ) 0 )
         {
@@ -702,6 +714,10 @@ void vEventGroupDelete( EventGroupHandle_t xEventGroup )
             vTaskRemoveFromUnorderedEventList( pxTasksWaitingForBits->xListEnd.pxNext, eventUNBLOCKED_DUE_TO_BIT_SET );
         }
     }
+#ifdef ESP_PLATFORM
+    /* Release the previously held task list spinlock. */
+    vTaskReleaseEventListLock();
+#endif
     taskEXIT_CRITICAL();
 
         #if ( ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) && ( configSUPPORT_STATIC_ALLOCATION == 0 ) )

components/freertos/include/freertos/task.h

@@ -3367,6 +3367,25 @@ void vTaskPlaceOnEventListRestricted( List_t * const pxEventList,
                                       TickType_t xTicksToWait,
                                       const BaseType_t xWaitIndefinitely ) PRIVILEGED_FUNCTION;
 
+#ifdef ESP_PLATFORM
+/*
+ * THIS FUNCTION MUST NOT BE USED FROM APPLICATION CODE.  IT IS AN
+ * INTERFACE WHICH IS FOR THE EXCLUSIVE USE OF THE SCHEDULER.
+ *
+ * This function is a wrapper to take the "xTaskQueueMutex" spinlock of tasks.c.
+ * This lock is taken whenver any of the task lists or event lists are
+ * accessed/modified, such as when adding/removing tasks to/from the delayed
+ * task list or various event lists.
+ *
+ * This functions is meant to be called by xEventGroupSetBits() and
+ * vEventGroupDelete() as both those functions will access event lists (instead
+ * of delegating the entire responsibility to one of vTask...EventList()
+ * functions).
+ */
+void vTaskTakeEventListLock( void );
+void vTaskReleaseEventListLock( void );
+#endif //  ESP_PLATFORM
+
 /*
  * THIS FUNCTION MUST NOT BE USED FROM APPLICATION CODE.  IT IS AN
  * INTERFACE WHICH IS FOR THE EXCLUSIVE USE OF THE SCHEDULER.

components/freertos/tasks.c

@@ -3733,6 +3733,20 @@ BaseType_t xTaskRemoveFromEventList( const List_t * const pxEventList )
 }
 /*-----------------------------------------------------------*/
 
+#ifdef ESP_PLATFORM
+void vTaskTakeEventListLock( void )
+{
+    /* We call the tasks.c critical section macro to take xTaskQueueMutex */
+    taskENTER_CRITICAL();
+}
+
+void vTaskReleaseEventListLock( void )
+{
+    /* We call the tasks.c critical section macro to release xTaskQueueMutex */
+    taskEXIT_CRITICAL();
+}
+#endif // ESP_PLATFORM
+
 void vTaskRemoveFromUnorderedEventList( ListItem_t * pxEventListItem,
                                         const TickType_t xItemValue )
 {

components/freertos/test/test_freertos_eventgroups.c

@@ -7,6 +7,7 @@
 #include "freertos/event_groups.h"
 #include "driver/timer.h"
 #include "unity.h"
+#include "test_utils.h"
 
 #ifdef CONFIG_IDF_TARGET_ESP32S2
 #define int_clr_timers int_clr
@@ -40,7 +41,8 @@ static void task_event_group_call_response(void *param)
 
     printf("Task %d done\n", task_num);
     xSemaphoreGive(done_sem);
-    vTaskDelete(NULL);
+    // Wait to be deleted
+    vTaskSuspend(NULL);
 }
 
 TEST_CASE("FreeRTOS Event Groups", "[freertos]")
@@ -48,6 +50,8 @@ TEST_CASE("FreeRTOS Event Groups", "[freertos]")
     eg = xEventGroupCreate();
     done_sem = xSemaphoreCreateCounting(NUM_TASKS, 0);
 
+    TaskHandle_t task_handles[NUM_TASKS];
+
     /* Note: task_event_group_call_response all have higher priority than this task, so on this core
        they will always preempt this task.
 
@@ -55,7 +59,7 @@ TEST_CASE("FreeRTOS Event Groups", "[freertos]")
        or they get out of sync.
      */
     for (int c = 0; c < NUM_TASKS; c++) {
-        xTaskCreatePinnedToCore(task_event_group_call_response, "tsk_call_resp", 4096, (void *)c, configMAX_PRIORITIES - 1, NULL, c % portNUM_PROCESSORS);
+        xTaskCreatePinnedToCore(task_event_group_call_response, "tsk_call_resp", 4096, (void *)c, configMAX_PRIORITIES - 1, &task_handles[c], c % portNUM_PROCESSORS);
     }
 
     /* Tasks all start instantly, but this task will resume running at the same time as the higher priority tasks on the
@@ -66,15 +70,19 @@ TEST_CASE("FreeRTOS Event Groups", "[freertos]")
         /* signal all tasks with "CALL" bit... */
         xEventGroupSetBits(eg, BIT_CALL);
 
-        /* Only wait for 1 tick, the wakeup should be immediate... */
-        TEST_ASSERT_EQUAL_HEX16(ALL_RESPONSE_BITS, xEventGroupWaitBits(eg, ALL_RESPONSE_BITS, true, true, 1));
+        /* Wait until all tasks have set their respective response bits */
+        TEST_ASSERT_EQUAL_HEX16(ALL_RESPONSE_BITS, xEventGroupWaitBits(eg, ALL_RESPONSE_BITS, true, true, portMAX_DELAY));
     }
 
-    /* Ensure all tasks cleaned up correctly */
+    /* Ensure all tasks have suspend themselves */
     for (int c = 0; c < NUM_TASKS; c++) {
         TEST_ASSERT( xSemaphoreTake(done_sem, 100/portTICK_PERIOD_MS) );
     }
 
+    for (int c = 0; c < NUM_TASKS; c++) {
+        test_utils_task_delete(task_handles[c]);
+    }
+
     vSemaphoreDelete(done_sem);
     vEventGroupDelete(eg);
 }