mirror of
https://github.com/FreeRTOS/FreeRTOS-Kernel.git
synced 2025-04-20 05:21:59 -04:00
Add xSemaphoreCreateBinary() so vSemaphoreCreate() can be deprecated.
This commit is contained in:
Richard Barry
parent
ca2191c6ee
commit
dcf261a3e6
|
|
@ -1,5 +1,5 @@
|
|||
/*
|
||||
FreeRTOS V7.5.3 - Copyright (C) 2013 Real Time Engineers Ltd.
|
||||
FreeRTOS V7.5.3 - Copyright (C) 2013 Real Time Engineers Ltd.
|
||||
All rights reserved
|
||||
|
||||
VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
|
||||
|
|
@ -83,6 +83,13 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
* semphr. h
|
||||
* <pre>vSemaphoreCreateBinary( xSemaphoreHandle xSemaphore )</pre>
|
||||
*
|
||||
* This old vSemaphoreCreateBinary() macro is now deprecated in favour of the
|
||||
* xSemaphoreCreateBinary() function. Note that binary semaphores created using
|
||||
* the vSemaphoreCreateBinary() macro are created in a state such that the
|
||||
* first call to 'take' the semaphore would pass, whereas binary semaphores
|
||||
* created using xSemaphoreCreateBinary() are created in a state such that the
|
||||
* the semaphore must first be 'given' before it can be 'taken'.
|
||||
*
|
||||
* <i>Macro</i> that implements a semaphore by using the existing queue mechanism.
|
||||
* The queue length is 1 as this is a binary semaphore. The data size is 0
|
||||
* as we don't want to actually store any data - we just want to know if the
|
||||
|
|
@ -99,7 +106,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
*
|
||||
* Example usage:
|
||||
<pre>
|
||||
xSemaphoreHandle xSemaphore;
|
||||
xSemaphoreHandle xSemaphore = NULL;
|
||||
|
||||
void vATask( void * pvParameters )
|
||||
{
|
||||
|
|
@ -110,7 +117,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
if( xSemaphore != NULL )
|
||||
{
|
||||
// The semaphore was created successfully.
|
||||
// The semaphore can now be used.
|
||||
// The semaphore can now be used.
|
||||
}
|
||||
}
|
||||
</pre>
|
||||
|
|
@ -122,15 +129,62 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
( xSemaphore ) = xQueueGenericCreate( ( unsigned portBASE_TYPE ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, queueQUEUE_TYPE_BINARY_SEMAPHORE ); \
|
||||
if( ( xSemaphore ) != NULL ) \
|
||||
{ \
|
||||
( void ) xSemaphoreGive( ( xSemaphore ) ); \
|
||||
( void ) xSemaphoreGive( ( xSemaphore ) ); \
|
||||
} \
|
||||
}
|
||||
|
||||
/**
|
||||
* semphr. h
|
||||
* <pre>xSemaphoreTake(
|
||||
* xSemaphoreHandle xSemaphore,
|
||||
* portTickType xBlockTime
|
||||
* <pre>xSemaphoreHandle xSemaphoreCreateBinary( void )</pre>
|
||||
*
|
||||
* The old vSemaphoreCreateBinary() macro is now deprecated in favour of this
|
||||
* xSemaphoreCreateBinary() function. Note that binary semaphores created using
|
||||
* the vSemaphoreCreateBinary() macro are created in a state such that the
|
||||
* first call to 'take' the semaphore would pass, whereas binary semaphores
|
||||
* created using xSemaphoreCreateBinary() are created in a state such that the
|
||||
* the semaphore must first be 'given' before it can be 'taken'.
|
||||
*
|
||||
* Function that creates a semaphore by using the existing queue mechanism.
|
||||
* The queue length is 1 as this is a binary semaphore. The data size is 0
|
||||
* as nothing is actually stored - all that is important is whether the queue is
|
||||
* empty or full (the binary semaphore is available or not).
|
||||
*
|
||||
* This type of semaphore can be used for pure synchronisation between tasks or
|
||||
* between an interrupt and a task. The semaphore need not be given back once
|
||||
* obtained, so one task/interrupt can continuously 'give' the semaphore while
|
||||
* another continuously 'takes' the semaphore. For this reason this type of
|
||||
* semaphore does not use a priority inheritance mechanism. For an alternative
|
||||
* that does use priority inheritance see xSemaphoreCreateMutex().
|
||||
*
|
||||
* @return Handle to the created semaphore.
|
||||
*
|
||||
* Example usage:
|
||||
<pre>
|
||||
xSemaphoreHandle xSemaphore = NULL;
|
||||
|
||||
void vATask( void * pvParameters )
|
||||
{
|
||||
// Semaphore cannot be used before a call to vSemaphoreCreateBinary ().
|
||||
// This is a macro so pass the variable in directly.
|
||||
xSemaphore = xSemaphoreCreateBinary();
|
||||
|
||||
if( xSemaphore != NULL )
|
||||
{
|
||||
// The semaphore was created successfully.
|
||||
// The semaphore can now be used.
|
||||
}
|
||||
}
|
||||
</pre>
|
||||
* \defgroup vSemaphoreCreateBinary vSemaphoreCreateBinary
|
||||
* \ingroup Semaphores
|
||||
*/
|
||||
#define xSemaphoreCreateBinary() xQueueGenericCreate( ( unsigned portBASE_TYPE ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, queueQUEUE_TYPE_BINARY_SEMAPHORE )
|
||||
|
||||
/**
|
||||
* semphr. h
|
||||
* <pre>xSemaphoreTake(
|
||||
* xSemaphoreHandle xSemaphore,
|
||||
* portTickType xBlockTime
|
||||
* )</pre>
|
||||
*
|
||||
* <i>Macro</i> to obtain a semaphore. The semaphore must have previously been
|
||||
|
|
@ -168,7 +222,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
if( xSemaphore != NULL )
|
||||
{
|
||||
// See if we can obtain the semaphore. If the semaphore is not available
|
||||
// wait 10 ticks to see if it becomes free.
|
||||
// wait 10 ticks to see if it becomes free.
|
||||
if( xSemaphoreTake( xSemaphore, ( portTickType ) 10 ) == pdTRUE )
|
||||
{
|
||||
// We were able to obtain the semaphore and can now access the
|
||||
|
|
@ -176,7 +230,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
|
||||
// ...
|
||||
|
||||
// We have finished accessing the shared resource. Release the
|
||||
// We have finished accessing the shared resource. Release the
|
||||
// semaphore.
|
||||
xSemaphoreGive( xSemaphore );
|
||||
}
|
||||
|
|
@ -195,24 +249,24 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
|
||||
/**
|
||||
* semphr. h
|
||||
* xSemaphoreTakeRecursive(
|
||||
* xSemaphoreHandle xMutex,
|
||||
* portTickType xBlockTime
|
||||
* xSemaphoreTakeRecursive(
|
||||
* xSemaphoreHandle xMutex,
|
||||
* portTickType xBlockTime
|
||||
* )
|
||||
*
|
||||
* <i>Macro</i> to recursively obtain, or 'take', a mutex type semaphore.
|
||||
* The mutex must have previously been created using a call to
|
||||
* <i>Macro</i> to recursively obtain, or 'take', a mutex type semaphore.
|
||||
* The mutex must have previously been created using a call to
|
||||
* xSemaphoreCreateRecursiveMutex();
|
||||
*
|
||||
*
|
||||
* configUSE_RECURSIVE_MUTEXES must be set to 1 in FreeRTOSConfig.h for this
|
||||
* macro to be available.
|
||||
*
|
||||
*
|
||||
* This macro must not be used on mutexes created using xSemaphoreCreateMutex().
|
||||
*
|
||||
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
|
||||
* doesn't become available again until the owner has called
|
||||
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
|
||||
* if a task successfully 'takes' the same mutex 5 times then the mutex will
|
||||
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
|
||||
* doesn't become available again until the owner has called
|
||||
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
|
||||
* if a task successfully 'takes' the same mutex 5 times then the mutex will
|
||||
* not be available to any other task until it has also 'given' the mutex back
|
||||
* exactly five times.
|
||||
*
|
||||
|
|
@ -223,7 +277,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
* available. The macro portTICK_RATE_MS can be used to convert this to a
|
||||
* real time. A block time of zero can be used to poll the semaphore. If
|
||||
* the task already owns the semaphore then xSemaphoreTakeRecursive() will
|
||||
* return immediately no matter what the value of xBlockTime.
|
||||
* return immediately no matter what the value of xBlockTime.
|
||||
*
|
||||
* @return pdTRUE if the semaphore was obtained. pdFALSE if xBlockTime
|
||||
* expired without the semaphore becoming available.
|
||||
|
|
@ -247,14 +301,14 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
if( xMutex != NULL )
|
||||
{
|
||||
// See if we can obtain the mutex. If the mutex is not available
|
||||
// wait 10 ticks to see if it becomes free.
|
||||
// wait 10 ticks to see if it becomes free.
|
||||
if( xSemaphoreTakeRecursive( xSemaphore, ( portTickType ) 10 ) == pdTRUE )
|
||||
{
|
||||
// We were able to obtain the mutex and can now access the
|
||||
// shared resource.
|
||||
|
||||
// ...
|
||||
// For some reason due to the nature of the code further calls to
|
||||
// For some reason due to the nature of the code further calls to
|
||||
// xSemaphoreTakeRecursive() are made on the same mutex. In real
|
||||
// code these would not be just sequential calls as this would make
|
||||
// no sense. Instead the calls are likely to be buried inside
|
||||
|
|
@ -262,7 +316,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 );
|
||||
xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 );
|
||||
|
||||
// The mutex has now been 'taken' three times, so will not be
|
||||
// The mutex has now been 'taken' three times, so will not be
|
||||
// available to another task until it has also been given back
|
||||
// three times. Again it is unlikely that real code would have
|
||||
// these calls sequentially, but instead buried in a more complex
|
||||
|
|
@ -287,15 +341,15 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
#define xSemaphoreTakeRecursive( xMutex, xBlockTime ) xQueueTakeMutexRecursive( ( xMutex ), ( xBlockTime ) )
|
||||
|
||||
|
||||
/*
|
||||
/*
|
||||
* xSemaphoreAltTake() is an alternative version of xSemaphoreTake().
|
||||
*
|
||||
* The source code that implements the alternative (Alt) API is much
|
||||
* simpler because it executes everything from within a critical section.
|
||||
* This is the approach taken by many other RTOSes, but FreeRTOS.org has the
|
||||
* preferred fully featured API too. The fully featured API has more
|
||||
* complex code that takes longer to execute, but makes much less use of
|
||||
* critical sections. Therefore the alternative API sacrifices interrupt
|
||||
* The source code that implements the alternative (Alt) API is much
|
||||
* simpler because it executes everything from within a critical section.
|
||||
* This is the approach taken by many other RTOSes, but FreeRTOS.org has the
|
||||
* preferred fully featured API too. The fully featured API has more
|
||||
* complex code that takes longer to execute, but makes much less use of
|
||||
* critical sections. Therefore the alternative API sacrifices interrupt
|
||||
* responsiveness to gain execution speed, whereas the fully featured API
|
||||
* sacrifices execution speed to ensure better interrupt responsiveness.
|
||||
*/
|
||||
|
|
@ -312,7 +366,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
* This macro must not be used from an ISR. See xSemaphoreGiveFromISR () for
|
||||
* an alternative which can be used from an ISR.
|
||||
*
|
||||
* This macro must also not be used on semaphores created using
|
||||
* This macro must also not be used on semaphores created using
|
||||
* xSemaphoreCreateRecursiveMutex().
|
||||
*
|
||||
* @param xSemaphore A handle to the semaphore being released. This is the
|
||||
|
|
@ -320,7 +374,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
*
|
||||
* @return pdTRUE if the semaphore was released. pdFALSE if an error occurred.
|
||||
* Semaphores are implemented using queues. An error can occur if there is
|
||||
* no space on the queue to post a message - indicating that the
|
||||
* no space on the queue to post a message - indicating that the
|
||||
* semaphore was not first obtained correctly.
|
||||
*
|
||||
* Example usage:
|
||||
|
|
@ -369,18 +423,18 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
* <pre>xSemaphoreGiveRecursive( xSemaphoreHandle xMutex )</pre>
|
||||
*
|
||||
* <i>Macro</i> to recursively release, or 'give', a mutex type semaphore.
|
||||
* The mutex must have previously been created using a call to
|
||||
* The mutex must have previously been created using a call to
|
||||
* xSemaphoreCreateRecursiveMutex();
|
||||
*
|
||||
*
|
||||
* configUSE_RECURSIVE_MUTEXES must be set to 1 in FreeRTOSConfig.h for this
|
||||
* macro to be available.
|
||||
*
|
||||
* This macro must not be used on mutexes created using xSemaphoreCreateMutex().
|
||||
*
|
||||
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
|
||||
* doesn't become available again until the owner has called
|
||||
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
|
||||
* if a task successfully 'takes' the same mutex 5 times then the mutex will
|
||||
*
|
||||
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
|
||||
* doesn't become available again until the owner has called
|
||||
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
|
||||
* if a task successfully 'takes' the same mutex 5 times then the mutex will
|
||||
* not be available to any other task until it has also 'given' the mutex back
|
||||
* exactly five times.
|
||||
*
|
||||
|
|
@ -408,14 +462,14 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
if( xMutex != NULL )
|
||||
{
|
||||
// See if we can obtain the mutex. If the mutex is not available
|
||||
// wait 10 ticks to see if it becomes free.
|
||||
// wait 10 ticks to see if it becomes free.
|
||||
if( xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 ) == pdTRUE )
|
||||
{
|
||||
// We were able to obtain the mutex and can now access the
|
||||
// shared resource.
|
||||
|
||||
// ...
|
||||
// For some reason due to the nature of the code further calls to
|
||||
// For some reason due to the nature of the code further calls to
|
||||
// xSemaphoreTakeRecursive() are made on the same mutex. In real
|
||||
// code these would not be just sequential calls as this would make
|
||||
// no sense. Instead the calls are likely to be buried inside
|
||||
|
|
@ -423,7 +477,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 );
|
||||
xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 );
|
||||
|
||||
// The mutex has now been 'taken' three times, so will not be
|
||||
// The mutex has now been 'taken' three times, so will not be
|
||||
// available to another task until it has also been given back
|
||||
// three times. Again it is unlikely that real code would have
|
||||
// these calls sequentially, it would be more likely that the calls
|
||||
|
|
@ -448,15 +502,15 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
*/
|
||||
#define xSemaphoreGiveRecursive( xMutex ) xQueueGiveMutexRecursive( ( xMutex ) )
|
||||
|
||||
/*
|
||||
/*
|
||||
* xSemaphoreAltGive() is an alternative version of xSemaphoreGive().
|
||||
*
|
||||
* The source code that implements the alternative (Alt) API is much
|
||||
* simpler because it executes everything from within a critical section.
|
||||
* This is the approach taken by many other RTOSes, but FreeRTOS.org has the
|
||||
* preferred fully featured API too. The fully featured API has more
|
||||
* complex code that takes longer to execute, but makes much less use of
|
||||
* critical sections. Therefore the alternative API sacrifices interrupt
|
||||
* The source code that implements the alternative (Alt) API is much
|
||||
* simpler because it executes everything from within a critical section.
|
||||
* This is the approach taken by many other RTOSes, but FreeRTOS.org has the
|
||||
* preferred fully featured API too. The fully featured API has more
|
||||
* complex code that takes longer to execute, but makes much less use of
|
||||
* critical sections. Therefore the alternative API sacrifices interrupt
|
||||
* responsiveness to gain execution speed, whereas the fully featured API
|
||||
* sacrifices execution speed to ensure better interrupt responsiveness.
|
||||
*/
|
||||
|
|
@ -465,8 +519,8 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
/**
|
||||
* semphr. h
|
||||
* <pre>
|
||||
xSemaphoreGiveFromISR(
|
||||
xSemaphoreHandle xSemaphore,
|
||||
xSemaphoreGiveFromISR(
|
||||
xSemaphoreHandle xSemaphore,
|
||||
signed portBASE_TYPE *pxHigherPriorityTaskWoken
|
||||
)</pre>
|
||||
*
|
||||
|
|
@ -500,7 +554,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
{
|
||||
for( ;; )
|
||||
{
|
||||
// We want this task to run every 10 ticks of a timer. The semaphore
|
||||
// We want this task to run every 10 ticks of a timer. The semaphore
|
||||
// was created before this task was started.
|
||||
|
||||
// Block waiting for the semaphore to become available.
|
||||
|
|
@ -511,7 +565,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
// ...
|
||||
|
||||
// We have finished our task. Return to the top of the loop where
|
||||
// we will block on the semaphore until it is time to execute
|
||||
// we will block on the semaphore until it is time to execute
|
||||
// again. Note when using the semaphore for synchronisation with an
|
||||
// ISR in this manner there is no need to 'give' the semaphore back.
|
||||
}
|
||||
|
|
@ -556,13 +610,13 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
/**
|
||||
* semphr. h
|
||||
* <pre>
|
||||
xSemaphoreTakeFromISR(
|
||||
xSemaphoreHandle xSemaphore,
|
||||
xSemaphoreTakeFromISR(
|
||||
xSemaphoreHandle xSemaphore,
|
||||
signed portBASE_TYPE *pxHigherPriorityTaskWoken
|
||||
)</pre>
|
||||
*
|
||||
* <i>Macro</i> to take a semaphore from an ISR. The semaphore must have
|
||||
* previously been created with a call to vSemaphoreCreateBinary() or
|
||||
* <i>Macro</i> to take a semaphore from an ISR. The semaphore must have
|
||||
* previously been created with a call to vSemaphoreCreateBinary() or
|
||||
* xSemaphoreCreateCounting().
|
||||
*
|
||||
* Mutex type semaphores (those created using a call to xSemaphoreCreateMutex())
|
||||
|
|
@ -582,7 +636,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
* running task. If xSemaphoreTakeFromISR() sets this value to pdTRUE then
|
||||
* a context switch should be requested before the interrupt is exited.
|
||||
*
|
||||
* @return pdTRUE if the semaphore was successfully taken, otherwise
|
||||
* @return pdTRUE if the semaphore was successfully taken, otherwise
|
||||
* pdFALSE
|
||||
*/
|
||||
#define xSemaphoreTakeFromISR( xSemaphore, pxHigherPriorityTaskWoken ) xQueueReceiveFromISR( ( xQueueHandle ) ( xSemaphore ), NULL, ( pxHigherPriorityTaskWoken ) )
|
||||
|
|
@ -591,25 +645,25 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
* semphr. h
|
||||
* <pre>xSemaphoreHandle xSemaphoreCreateMutex( void )</pre>
|
||||
*
|
||||
* <i>Macro</i> that implements a mutex semaphore by using the existing queue
|
||||
* <i>Macro</i> that implements a mutex semaphore by using the existing queue
|
||||
* mechanism.
|
||||
*
|
||||
* Mutexes created using this macro can be accessed using the xSemaphoreTake()
|
||||
* and xSemaphoreGive() macros. The xSemaphoreTakeRecursive() and
|
||||
* and xSemaphoreGive() macros. The xSemaphoreTakeRecursive() and
|
||||
* xSemaphoreGiveRecursive() macros should not be used.
|
||||
*
|
||||
* This type of semaphore uses a priority inheritance mechanism so a task
|
||||
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
|
||||
* semaphore it is no longer required.
|
||||
*
|
||||
* Mutex type semaphores cannot be used from within interrupt service routines.
|
||||
* This type of semaphore uses a priority inheritance mechanism so a task
|
||||
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
|
||||
* semaphore it is no longer required.
|
||||
*
|
||||
* See vSemaphoreCreateBinary() for an alternative implementation that can be
|
||||
* used for pure synchronisation (where one task or interrupt always 'gives' the
|
||||
* semaphore and another always 'takes' the semaphore) and from within interrupt
|
||||
* Mutex type semaphores cannot be used from within interrupt service routines.
|
||||
*
|
||||
* See vSemaphoreCreateBinary() for an alternative implementation that can be
|
||||
* used for pure synchronisation (where one task or interrupt always 'gives' the
|
||||
* semaphore and another always 'takes' the semaphore) and from within interrupt
|
||||
* service routines.
|
||||
*
|
||||
* @return xSemaphore Handle to the created mutex semaphore. Should be of type
|
||||
* @return xSemaphore Handle to the created mutex semaphore. Should be of type
|
||||
* xSemaphoreHandle.
|
||||
*
|
||||
* Example usage:
|
||||
|
|
@ -625,7 +679,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
if( xSemaphore != NULL )
|
||||
{
|
||||
// The semaphore was created successfully.
|
||||
// The semaphore can now be used.
|
||||
// The semaphore can now be used.
|
||||
}
|
||||
}
|
||||
</pre>
|
||||
|
|
@ -639,32 +693,32 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
* semphr. h
|
||||
* <pre>xSemaphoreHandle xSemaphoreCreateRecursiveMutex( void )</pre>
|
||||
*
|
||||
* <i>Macro</i> that implements a recursive mutex by using the existing queue
|
||||
* <i>Macro</i> that implements a recursive mutex by using the existing queue
|
||||
* mechanism.
|
||||
*
|
||||
* Mutexes created using this macro can be accessed using the
|
||||
* xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() macros. The
|
||||
* Mutexes created using this macro can be accessed using the
|
||||
* xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() macros. The
|
||||
* xSemaphoreTake() and xSemaphoreGive() macros should not be used.
|
||||
*
|
||||
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
|
||||
* doesn't become available again until the owner has called
|
||||
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
|
||||
* if a task successfully 'takes' the same mutex 5 times then the mutex will
|
||||
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
|
||||
* doesn't become available again until the owner has called
|
||||
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
|
||||
* if a task successfully 'takes' the same mutex 5 times then the mutex will
|
||||
* not be available to any other task until it has also 'given' the mutex back
|
||||
* exactly five times.
|
||||
*
|
||||
* This type of semaphore uses a priority inheritance mechanism so a task
|
||||
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
|
||||
* semaphore it is no longer required.
|
||||
*
|
||||
* Mutex type semaphores cannot be used from within interrupt service routines.
|
||||
* This type of semaphore uses a priority inheritance mechanism so a task
|
||||
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
|
||||
* semaphore it is no longer required.
|
||||
*
|
||||
* See vSemaphoreCreateBinary() for an alternative implementation that can be
|
||||
* used for pure synchronisation (where one task or interrupt always 'gives' the
|
||||
* semaphore and another always 'takes' the semaphore) and from within interrupt
|
||||
* Mutex type semaphores cannot be used from within interrupt service routines.
|
||||
*
|
||||
* See vSemaphoreCreateBinary() for an alternative implementation that can be
|
||||
* used for pure synchronisation (where one task or interrupt always 'gives' the
|
||||
* semaphore and another always 'takes' the semaphore) and from within interrupt
|
||||
* service routines.
|
||||
*
|
||||
* @return xSemaphore Handle to the created mutex semaphore. Should be of type
|
||||
* @return xSemaphore Handle to the created mutex semaphore. Should be of type
|
||||
* xSemaphoreHandle.
|
||||
*
|
||||
* Example usage:
|
||||
|
|
@ -680,7 +734,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
if( xSemaphore != NULL )
|
||||
{
|
||||
// The semaphore was created successfully.
|
||||
// The semaphore can now be used.
|
||||
// The semaphore can now be used.
|
||||
}
|
||||
}
|
||||
</pre>
|
||||
|
|
@ -693,32 +747,32 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
* semphr. h
|
||||
* <pre>xSemaphoreHandle xSemaphoreCreateCounting( unsigned portBASE_TYPE uxMaxCount, unsigned portBASE_TYPE uxInitialCount )</pre>
|
||||
*
|
||||
* <i>Macro</i> that creates a counting semaphore by using the existing
|
||||
* queue mechanism.
|
||||
* <i>Macro</i> that creates a counting semaphore by using the existing
|
||||
* queue mechanism.
|
||||
*
|
||||
* Counting semaphores are typically used for two things:
|
||||
*
|
||||
* 1) Counting events.
|
||||
* 1) Counting events.
|
||||
*
|
||||
* In this usage scenario an event handler will 'give' a semaphore each time
|
||||
* an event occurs (incrementing the semaphore count value), and a handler
|
||||
* task will 'take' a semaphore each time it processes an event
|
||||
* (decrementing the semaphore count value). The count value is therefore
|
||||
* the difference between the number of events that have occurred and the
|
||||
* number that have been processed. In this case it is desirable for the
|
||||
* an event occurs (incrementing the semaphore count value), and a handler
|
||||
* task will 'take' a semaphore each time it processes an event
|
||||
* (decrementing the semaphore count value). The count value is therefore
|
||||
* the difference between the number of events that have occurred and the
|
||||
* number that have been processed. In this case it is desirable for the
|
||||
* initial count value to be zero.
|
||||
*
|
||||
* 2) Resource management.
|
||||
*
|
||||
* In this usage scenario the count value indicates the number of resources
|
||||
* available. To obtain control of a resource a task must first obtain a
|
||||
* available. To obtain control of a resource a task must first obtain a
|
||||
* semaphore - decrementing the semaphore count value. When the count value
|
||||
* reaches zero there are no free resources. When a task finishes with the
|
||||
* resource it 'gives' the semaphore back - incrementing the semaphore count
|
||||
* value. In this case it is desirable for the initial count value to be
|
||||
* equal to the maximum count value, indicating that all resources are free.
|
||||
*
|
||||
* @param uxMaxCount The maximum count value that can be reached. When the
|
||||
* @param uxMaxCount The maximum count value that can be reached. When the
|
||||
* semaphore reaches this value it can no longer be 'given'.
|
||||
*
|
||||
* @param uxInitialCount The count value assigned to the semaphore when it is
|
||||
|
|
@ -726,7 +780,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
*
|
||||
* @return Handle to the created semaphore. Null if the semaphore could not be
|
||||
* created.
|
||||
*
|
||||
*
|
||||
* Example usage:
|
||||
<pre>
|
||||
xSemaphoreHandle xSemaphore;
|
||||
|
|
@ -743,7 +797,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
if( xSemaphore != NULL )
|
||||
{
|
||||
// The semaphore was created successfully.
|
||||
// The semaphore can now be used.
|
||||
// The semaphore can now be used.
|
||||
}
|
||||
}
|
||||
</pre>
|
||||
|
|
@ -774,7 +828,7 @@ typedef xQueueHandle xSemaphoreHandle;
|
|||
* If xMutex is not a mutex type semaphore, or the mutex is available (not held
|
||||
* by a task), return NULL.
|
||||
*
|
||||
* Note: This Is is a good way of determining if the calling task is the mutex
|
||||
* Note: This Is is a good way of determining if the calling task is the mutex
|
||||
* holder, but not a good way of determining the identity of the mutex holder as
|
||||
* the holder may change between the function exiting and the returned value
|
||||
* being tested.
|
||||
|
|
|
|||
Loading…
Reference in a new issue