1 创建事件组 xEventGroupCreate
c
EventGroupHandle_t xEventGroupCreate( void )
{
EventGroup_t *pxEventBits;
/* 分配事件组内存。*/
pxEventBits = ( EventGroup_t * ) pvPortMalloc( sizeof( EventGroup_t ) );
if( pxEventBits != NULL )
{
pxEventBits->uxEventBits = 0; // 初始化事件位为0
vListInitialise( &( pxEventBits->xTasksWaitingForBits ) ); // 初始化等待事件的任务列表
traceEVENT_GROUP_CREATE( pxEventBits );
}
else
{
traceEVENT_GROUP_CREATE_FAILED();
}
return ( EventGroupHandle_t ) pxEventBits;
}2 事件置位 xEventGroupSetBits
c
EventBits_t xEventGroupSetBits( EventGroupHandle_t xEventGroup, const EventBits_t uxBitsToSet )
{
ListItem_t *pxListItem, *pxNext;
ListItem_t const *pxListEnd;
List_t *pxList;
EventBits_t uxBitsToClear = 0, uxBitsWaitedFor, uxControlBits;
EventGroup_t *pxEventBits = ( EventGroup_t * ) xEventGroup;
BaseType_t xMatchFound = pdFALSE;
/* Check the user is not attempting to set the bits used by the kernel
itself. */
configASSERT( xEventGroup );
configASSERT( ( uxBitsToSet & eventEVENT_BITS_CONTROL_BYTES ) == 0 );
/* 获取事件列表头 */
pxList = &( pxEventBits->xTasksWaitingForBits );
/* 获取列表尾节点 */
pxListEnd = listGET_END_MARKER( pxList ); /*lint !e826 !e740 The mini list structure is used as the list end to save RAM. This is checked and valid. */
/* 挂起调度器 */
vTaskSuspendAll();
{
traceEVENT_GROUP_SET_BITS( xEventGroup, uxBitsToSet );
/* 获取头结点 */
pxListItem = listGET_HEAD_ENTRY( pxList );
/* Set the bits. */
/* 设置事件标志位 */
pxEventBits->uxEventBits |= uxBitsToSet;
/* See if the new bit value should unblock any tasks. */
/* 循环遍历整个列表项，直到列表头节点等于尾节点（指针） */
while( pxListItem != pxListEnd )
{
pxNext = listGET_NEXT( pxListItem ); //获取下个列表项
/* 获取当前列表项的值 */
uxBitsWaitedFor = listGET_LIST_ITEM_VALUE( pxListItem );
xMatchFound = pdFALSE; //标记是否找到需要处理的节点
/* Split the bits waited for from the control bits. */
/* 拆分 */
uxControlBits = uxBitsWaitedFor & eventEVENT_BITS_CONTROL_BYTES;
uxBitsWaitedFor &= ~eventEVENT_BITS_CONTROL_BYTES;
if( ( uxControlBits & eventWAIT_FOR_ALL_BITS ) == ( EventBits_t ) 0 )
{
/* Just looking for single bit being set. */
/* 或逻辑，等待位已经置位 */
if( ( uxBitsWaitedFor & pxEventBits->uxEventBits ) != ( EventBits_t ) 0 )
{
xMatchFound = pdTRUE;
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
/* 表示所有等待的位都已经触发 */
else if( ( uxBitsWaitedFor & pxEventBits->uxEventBits ) == uxBitsWaitedFor )
{
/* All bits are set. */
xMatchFound = pdTRUE;
}
else
{
/* Need all bits to be set, but not all the bits were set. */
}
if( xMatchFound != pdFALSE )
{
/* The bits match. Should the bits be cleared on exit? */
/* 判断是否需要清除 */
if( ( uxControlBits & eventCLEAR_EVENTS_ON_EXIT_BIT ) != ( EventBits_t ) 0 )
{
uxBitsToClear |= uxBitsWaitedFor;
}
else
{
mtCOVERAGE_TEST_MARKER();
}
/* Store the actual event flag value in the task's event list
item before removing the task from the event list. The
eventUNBLOCKED_DUE_TO_BIT_SET bit is set so the task knows
that is was unblocked due to its required bits matching, rather
than because it timed out. */
/* 把任务从事件列表中移除 */
( void ) xTaskRemoveFromUnorderedEventList( pxListItem, pxEventBits->uxEventBits | eventUNBLOCKED_DUE_TO_BIT_SET );
}
/* Move onto the next list item. Note pxListItem->pxNext is not
used here as the list item may have been removed from the event list
and inserted into the ready/pending reading list. */
pxListItem = pxNext; //当前列表项指向下个，继续遍历
}
/* Clear any bits that matched when the eventCLEAR_EVENTS_ON_EXIT_BIT
bit was set in the control word. */
pxEventBits->uxEventBits &= ~uxBitsToClear; //清除设置后的标志位
}
( void ) xTaskResumeAll(); //开启调度器
return pxEventBits->uxEventBits;
}3 等待标志位 xEventGroupWaitBits
c
EventBits_t xEventGroupWaitBits( EventGroupHandle_t xEventGroup, const EventBits_t uxBitsToWaitFor, const BaseType_t xClearOnExit, const BaseType_t xWaitForAllBits, TickType_t xTicksToWait )
{
EventGroup_t *pxEventBits = ( EventGroup_t * ) xEventGroup;
EventBits_t uxReturn, uxControlBits = 0;
BaseType_t xWaitConditionMet, xAlreadyYielded;
BaseType_t xTimeoutOccurred = pdFALSE;
/* Check the user is not attempting to wait on the bits used by the kernel
itself, and that at least one bit is being requested. */
configASSERT( xEventGroup );
configASSERT( ( uxBitsToWaitFor & eventEVENT_BITS_CONTROL_BYTES ) == 0 );
configASSERT( uxBitsToWaitFor != 0 );
#if ( ( INCLUDE_xTaskGetSchedulerState == 1 ) || ( configUSE_TIMERS == 1 ) )
{
configASSERT( !( ( xTaskGetSchedulerState() == taskSCHEDULER_SUSPENDED ) && ( xTicksToWait != 0 ) ) );
}
#endif
vTaskSuspendAll(); //挂起调度器
{
/* 获取当前的事件标志位 */
const EventBits_t uxCurrentEventBits = pxEventBits->uxEventBits;
/* Check to see if the wait condition is already met or not. */
/* 检查是否触发 */
xWaitConditionMet = prvTestWaitCondition( uxCurrentEventBits, uxBitsToWaitFor, xWaitForAllBits );
if( xWaitConditionMet != pdFALSE )
{
/* The wait condition has already been met so there is no need to
block. */
/* 已经触发 */
uxReturn = uxCurrentEventBits;
xTicksToWait = ( TickType_t ) 0;
/* Clear the wait bits if requested to do so. */
/* 清楚已经触发的标志 */
if( xClearOnExit != pdFALSE )
{
pxEventBits->uxEventBits &= ~uxBitsToWaitFor;
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
else if( xTicksToWait == ( TickType_t ) 0 )
{
/* 不需要超时，直接返回标志位. */
uxReturn = uxCurrentEventBits;
}
else
{
/* 事件没有触发，并且需要超时*/
if( xClearOnExit != pdFALSE )
{
uxControlBits |= eventCLEAR_EVENTS_ON_EXIT_BIT;
}
else
{
mtCOVERAGE_TEST_MARKER();
}
if( xWaitForAllBits != pdFALSE )
{
uxControlBits |= eventWAIT_FOR_ALL_BITS;
}
else
{
mtCOVERAGE_TEST_MARKER();
}
/* 把任务添加到事件列表中 */
vTaskPlaceOnUnorderedEventList( &( pxEventBits->xTasksWaitingForBits ), ( uxBitsToWaitFor | uxControlBits ), xTicksToWait );
uxReturn = 0;
traceEVENT_GROUP_WAIT_BITS_BLOCK( xEventGroup, uxBitsToWaitFor );
}
}
xAlreadyYielded = xTaskResumeAll(); //恢复调度器
if( xTicksToWait != ( TickType_t ) 0 )
{
if( xAlreadyYielded == pdFALSE )
{
portYIELD_WITHIN_API();
}
else
{
mtCOVERAGE_TEST_MARKER();
}
/* 任务已经恢复，则复位列表项中的值 复位为任务有优先级 */
uxReturn = uxTaskResetEventItemValue();
/* 是不是通过事件置位解除的任务 */
if( ( uxReturn & eventUNBLOCKED_DUE_TO_BIT_SET ) == ( EventBits_t ) 0 )
{
taskENTER_CRITICAL(); //进入临界段
{
/* The task timed out, just return the current event bit value. */
uxReturn = pxEventBits->uxEventBits; // 获取当前事件位
/* It is possible that the event bits were updated between this
task leaving the Blocked state and running again. */
/* 判断是否已经置位 */
if( prvTestWaitCondition( uxReturn, uxBitsToWaitFor, xWaitForAllBits ) != pdFALSE )
{
/* 如果需要清除，清除触发后的标志位 */
if( xClearOnExit != pdFALSE )
{
pxEventBits->uxEventBits &= ~uxBitsToWaitFor;
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
taskEXIT_CRITICAL();
/* Prevent compiler warnings when trace macros are not used. */
xTimeoutOccurred = pdFALSE;
}
else
{
/* The task unblocked because the bits were set. */
}
/* The task blocked so control bits may have been set. */
uxReturn &= ~eventEVENT_BITS_CONTROL_BYTES;
}
traceEVENT_GROUP_WAIT_BITS_END( xEventGroup, uxBitsToWaitFor, xTimeoutOccurred );
return uxReturn;
}