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freertos: Fix event group task list race condition
FreeRTOS synchronization primitives (e.g., queues, eventgroups) use various event lists (i.e., task lists) to track what tasks are blocked on a current primitive. Usually these event lists are accessed via one of the event lists functions (such as vTask[PlaceOn|RemoveFrom]UnorderedEventList()), which in turn ensure that the global task list spinlock (xTaskQueueMutex) is taken when accessing these lists. However, some functions in event_groups.c manually traverse their event lists. Thus if a tick interrupt occurs on another core during traversal and that tick interrupt unblocks a task on the event list being traversed, the event list will be corrupted. This commit modifies the following event_groups.c functions so that they take the global task list lock before traversing their event list. - xEventGroupSetBits() - vEventGroupDelete()
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@ -600,6 +600,10 @@ EventBits_t xEventGroupSetBits( EventGroupHandle_t xEventGroup,
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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. */
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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. */
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#ifdef ESP_PLATFORM // IDF-3755
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#ifdef ESP_PLATFORM // IDF-3755
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taskENTER_CRITICAL();
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taskENTER_CRITICAL();
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/* The critical section above only takes the event groups spinlock. However, we are about to traverse a task list.
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* Thus we need call the function below to take the task list spinlock located in tasks.c. Not doing so will risk
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* the task list's being changed while be are traversing it. */
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vTaskTakeEventListLock();
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#else
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#else
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vTaskSuspendAll();
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vTaskSuspendAll();
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#endif // ESP_PLATFORM
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#endif // ESP_PLATFORM
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@ -675,6 +679,8 @@ EventBits_t xEventGroupSetBits( EventGroupHandle_t xEventGroup,
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pxEventBits->uxEventBits &= ~uxBitsToClear;
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pxEventBits->uxEventBits &= ~uxBitsToClear;
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}
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}
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#ifdef ESP_PLATFORM // IDF-3755
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#ifdef ESP_PLATFORM // IDF-3755
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/* Release the previously held task list spinlock, then release the event group spinlock. */
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vTaskReleaseEventListLock();
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taskEXIT_CRITICAL();
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taskEXIT_CRITICAL();
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#else
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#else
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( void ) xTaskResumeAll();
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( void ) xTaskResumeAll();
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@ -693,6 +699,12 @@ void vEventGroupDelete( EventGroupHandle_t xEventGroup )
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// IDF-3755
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// IDF-3755
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taskENTER_CRITICAL();
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taskENTER_CRITICAL();
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#ifdef ESP_PLATFORM
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/* The critical section above only takes the event groups spinlock. However, we are about to traverse a task list.
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* Thus we need call the function below to take the task list spinlock located in tasks.c. Not doing so will risk
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* the task list's being changed while be are traversing it. */
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vTaskTakeEventListLock();
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#endif
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{
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{
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while( listCURRENT_LIST_LENGTH( pxTasksWaitingForBits ) > ( UBaseType_t ) 0 )
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while( listCURRENT_LIST_LENGTH( pxTasksWaitingForBits ) > ( UBaseType_t ) 0 )
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{
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{
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@ -702,6 +714,10 @@ void vEventGroupDelete( EventGroupHandle_t xEventGroup )
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vTaskRemoveFromUnorderedEventList( pxTasksWaitingForBits->xListEnd.pxNext, eventUNBLOCKED_DUE_TO_BIT_SET );
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vTaskRemoveFromUnorderedEventList( pxTasksWaitingForBits->xListEnd.pxNext, eventUNBLOCKED_DUE_TO_BIT_SET );
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}
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}
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}
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}
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#ifdef ESP_PLATFORM
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/* Release the previously held task list spinlock. */
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vTaskReleaseEventListLock();
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#endif
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taskEXIT_CRITICAL();
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taskEXIT_CRITICAL();
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#if ( ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) && ( configSUPPORT_STATIC_ALLOCATION == 0 ) )
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#if ( ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) && ( configSUPPORT_STATIC_ALLOCATION == 0 ) )
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@ -3367,6 +3367,25 @@ void vTaskPlaceOnEventListRestricted( List_t * const pxEventList,
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TickType_t xTicksToWait,
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TickType_t xTicksToWait,
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const BaseType_t xWaitIndefinitely ) PRIVILEGED_FUNCTION;
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const BaseType_t xWaitIndefinitely ) PRIVILEGED_FUNCTION;
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#ifdef ESP_PLATFORM
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/*
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* THIS FUNCTION MUST NOT BE USED FROM APPLICATION CODE. IT IS AN
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* INTERFACE WHICH IS FOR THE EXCLUSIVE USE OF THE SCHEDULER.
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*
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* This function is a wrapper to take the "xTaskQueueMutex" spinlock of tasks.c.
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* This lock is taken whenver any of the task lists or event lists are
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* accessed/modified, such as when adding/removing tasks to/from the delayed
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* task list or various event lists.
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*
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* This functions is meant to be called by xEventGroupSetBits() and
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* vEventGroupDelete() as both those functions will access event lists (instead
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* of delegating the entire responsibility to one of vTask...EventList()
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* functions).
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*/
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void vTaskTakeEventListLock( void );
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void vTaskReleaseEventListLock( void );
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#endif // ESP_PLATFORM
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/*
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/*
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* THIS FUNCTION MUST NOT BE USED FROM APPLICATION CODE. IT IS AN
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* THIS FUNCTION MUST NOT BE USED FROM APPLICATION CODE. IT IS AN
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* INTERFACE WHICH IS FOR THE EXCLUSIVE USE OF THE SCHEDULER.
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* INTERFACE WHICH IS FOR THE EXCLUSIVE USE OF THE SCHEDULER.
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@ -3733,6 +3733,20 @@ BaseType_t xTaskRemoveFromEventList( const List_t * const pxEventList )
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}
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}
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/*-----------------------------------------------------------*/
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/*-----------------------------------------------------------*/
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#ifdef ESP_PLATFORM
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void vTaskTakeEventListLock( void )
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{
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/* We call the tasks.c critical section macro to take xTaskQueueMutex */
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taskENTER_CRITICAL();
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}
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void vTaskReleaseEventListLock( void )
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{
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/* We call the tasks.c critical section macro to release xTaskQueueMutex */
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taskEXIT_CRITICAL();
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}
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#endif // ESP_PLATFORM
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void vTaskRemoveFromUnorderedEventList( ListItem_t * pxEventListItem,
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void vTaskRemoveFromUnorderedEventList( ListItem_t * pxEventListItem,
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const TickType_t xItemValue )
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const TickType_t xItemValue )
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{
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{
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