Introduce the portSOFTWARE_BARRIER macro which thus far is only used by the Win32...

[freertos] / FreeRTOS / Source / portable / MSVC-MingW / port.c

diff --git a/FreeRTOS/Source/portable/MSVC-MingW/port.c b/FreeRTOS/Source/portable/MSVC-MingW/port.c
index c2e2a82acdf4d24fcf9f00bb90fa1e5d82a790fe..3c685b925ba6849ace36b70a015bc5456dae4ac7 100644 (file)
--- a/FreeRTOS/Source/portable/MSVC-MingW/port.c
+++ b/FreeRTOS/Source/portable/MSVC-MingW/port.c
@@ -68,6 +68,15 @@ static void prvProcessSimulatedInterrupts( void );
 static uint32_t prvProcessYieldInterrupt( void );\r
 static uint32_t prvProcessTickInterrupt( void );\r
 \r
 static uint32_t prvProcessYieldInterrupt( void );\r
 static uint32_t prvProcessTickInterrupt( void );\r
 \r

+/*\r
+ * Exiting a critical section will cause the calling task to block on yield\r
+ * event to wait for an interrupt to process if an interrupt was pended while\r
+ * inside the critical section.  This variable protects against a recursive\r
+ * attempt to obtain pvInterruptEventMutex if a critical section is used inside\r
+ * an interrupt handler itself.\r
+ */\r
+volatile BaseType_t xInsideInterrupt = pdFALSE;\r
+\r

 /*\r
  * Called when the process exits to let Windows know the high timer resolution\r
  * is no longer required.\r
 /*\r
  * Called when the process exits to let Windows know the high timer resolution\r
  * is no longer required.\r


@@ -169,20 +178,22 @@ TIMECAPS xTimeCaps;
 \r
                configASSERT( xPortRunning );\r
 \r
 \r
                configASSERT( xPortRunning );\r
 \r

+               /* Can't proceed if in a critical section as pvInterruptEventMutex won't\r
+               be available. */\r

                WaitForSingleObject( pvInterruptEventMutex, INFINITE );\r
 \r
                /* The timer has expired, generate the simulated tick event. */\r
                ulPendingInterrupts |= ( 1 << portINTERRUPT_TICK );\r
 \r
                /* The interrupt is now pending - notify the simulated interrupt\r
                WaitForSingleObject( pvInterruptEventMutex, INFINITE );\r
 \r
                /* The timer has expired, generate the simulated tick event. */\r
                ulPendingInterrupts |= ( 1 << portINTERRUPT_TICK );\r
 \r
                /* The interrupt is now pending - notify the simulated interrupt\r

-               handler thread. */\r
-               if( ulCriticalNesting == portNO_CRITICAL_NESTING )\r
-               {\r
-                       SetEvent( pvInterruptEvent );\r
-               }\r
+               handler thread.  Must be outside of a critical section to get here so\r
+               the handler thread can execute immediately pvInterruptEventMutex is\r
+               released. */\r
+               configASSERT( ulCriticalNesting == 0UL );\r
+               SetEvent( pvInterruptEvent );\r

 \r
                /* Give back the mutex so the simulated interrupt handler unblocks\r
 \r
                /* Give back the mutex so the simulated interrupt handler unblocks\r

-               and can access the interrupt handler variables. */\r
+               and can access the interrupt handler variables. */\r

                ReleaseMutex( pvInterruptEventMutex );\r
        }\r
 \r
                ReleaseMutex( pvInterruptEventMutex );\r
        }\r
 \r


@@ -341,6 +352,7 @@ SYSTEM_INFO xSystemInfo;
 \r
 static uint32_t prvProcessYieldInterrupt( void )\r
 {\r
 \r
 static uint32_t prvProcessYieldInterrupt( void )\r
 {\r

+       /* Always return true as this is a yield. */\r

        return pdTRUE;\r
 }\r
 /*-----------------------------------------------------------*/\r
        return pdTRUE;\r
 }\r
 /*-----------------------------------------------------------*/\r


@@ -379,8 +391,16 @@ CONTEXT xContext;
 \r
        for(;;)\r
        {\r
 \r
        for(;;)\r
        {\r

+               xInsideInterrupt = pdFALSE;\r

                WaitForMultipleObjects( sizeof( pvObjectList ) / sizeof( void * ), pvObjectList, TRUE, INFINITE );\r
 \r
                WaitForMultipleObjects( sizeof( pvObjectList ) / sizeof( void * ), pvObjectList, TRUE, INFINITE );\r
 \r

+               /* Cannot be in a critical section to get here.  Tasks that exist a\r
+               critical section will block on a yield mutex to wait for an interrupt to\r
+               process if an interrupt was set pending while the task was inside the\r
+               critical section.  xInsideInterrupt prevents interrupts that contain\r
+               critical sections from doing the same. */\r
+               xInsideInterrupt = pdTRUE;\r
+\r

                /* Used to indicate whether the simulated interrupt processing has\r
                necessitated a context switch to another task/thread. */\r
                ulSwitchRequired = pdFALSE;\r
                /* Used to indicate whether the simulated interrupt processing has\r
                necessitated a context switch to another task/thread. */\r
                ulSwitchRequired = pdFALSE;\r


@@ -390,14 +410,16 @@ CONTEXT xContext;
                for( i = 0; i < portMAX_INTERRUPTS; i++ )\r
                {\r
                        /* Is the simulated interrupt pending? */\r
                for( i = 0; i < portMAX_INTERRUPTS; i++ )\r
                {\r
                        /* Is the simulated interrupt pending? */\r

-                       if( ulPendingInterrupts & ( 1UL << i ) )\r
+                       if( ( ulPendingInterrupts & ( 1UL << i ) ) != 0 )\r

                        {\r
                                /* Is a handler installed? */\r
                                if( ulIsrHandler[ i ] != NULL )\r
                                {\r
                        {\r
                                /* Is a handler installed? */\r
                                if( ulIsrHandler[ i ] != NULL )\r
                                {\r

-                                       /* Run the actual handler. */\r
+                                       /* Run the actual handler.  Handlers return pdTRUE if they\r
+                                       necessitate a context switch. */\r

                                        if( ulIsrHandler[ i ]() != pdFALSE )\r
                                        {\r
                                        if( ulIsrHandler[ i ]() != pdFALSE )\r
                                        {\r

+                                               /* A bit mask is used purely to help debugging. */\r

                                                ulSwitchRequired |= ( 1 << i );\r
                                        }\r
                                }\r
                                                ulSwitchRequired |= ( 1 << i );\r
                                        }\r
                                }\r


@@ -420,7 +442,15 @@ CONTEXT xContext;
                        that is already in the running state. */\r
                        if( pvOldCurrentTCB != pxCurrentTCB )\r
                        {\r
                        that is already in the running state. */\r
                        if( pvOldCurrentTCB != pxCurrentTCB )\r
                        {\r

-                               /* Suspend the old thread. */\r
+                               /* Suspend the old thread.  In the cases where the (simulated)\r
+                               interrupt is asynchronous (tick event swapping a task out rather\r
+                               than a task blocking or yielding) it doesn't matter if the\r
+                               'suspend' operation doesn't take effect immediately - if it\r
+                               doesn't it would just be like the interrupt occurring slightly\r
+                               later.  In cases where the yield was caused by a task blocking\r
+                               or yielding then the task will block on a yield event after the\r
+                               yield operation in case the 'suspend' operation doesn't take\r
+                               effect immediately.  */\r

                                pxThreadState = ( ThreadState_t *) *( ( size_t * ) pvOldCurrentTCB );\r
                                SuspendThread( pxThreadState->pvThread );\r
 \r
                                pxThreadState = ( ThreadState_t *) *( ( size_t * ) pvOldCurrentTCB );\r
                                SuspendThread( pxThreadState->pvThread );\r
 \r


@@ -451,7 +481,9 @@ CONTEXT xContext;
                (to ensure it does not continue running after the call to\r
                SuspendThread() above as SuspendThread() is asynchronous).\r
                Signal the event to ensure the thread can proceed now it is\r
                (to ensure it does not continue running after the call to\r
                SuspendThread() above as SuspendThread() is asynchronous).\r
                Signal the event to ensure the thread can proceed now it is\r

-               valid for it to do so. */\r
+               valid for it to do so.  Signaling the event is benign in the case that\r
+               the task was switched out asynchronously by an interrupt as the event\r
+               is reset before the task blocks on it. */\r

                pxThreadState = ( ThreadState_t * ) ( *( size_t *) pxCurrentTCB );\r
                SetEvent( pxThreadState->pvYieldEvent );\r
                ReleaseMutex( pvInterruptEventMutex );\r
                pxThreadState = ( ThreadState_t * ) ( *( size_t *) pxCurrentTCB );\r
                SetEvent( pxThreadState->pvYieldEvent );\r
                ReleaseMutex( pvInterruptEventMutex );\r


@@ -527,7 +559,7 @@ uint32_t ulErrorCode;
        /* This is called from a critical section, which must be exited before the\r
        thread stops. */\r
        taskEXIT_CRITICAL();\r
        /* This is called from a critical section, which must be exited before the\r
        thread stops. */\r
        taskEXIT_CRITICAL();\r

-\r
+       CloseHandle( pxThreadState->pvYieldEvent );\r

        ExitThread( 0 );\r
 }\r
 /*-----------------------------------------------------------*/\r
        ExitThread( 0 );\r
 }\r
 /*-----------------------------------------------------------*/\r


@@ -546,39 +578,32 @@ ThreadState_t *pxThreadState = ( ThreadState_t *) *( ( size_t * ) pxCurrentTCB )
 \r
        if( ( ulInterruptNumber < portMAX_INTERRUPTS ) && ( pvInterruptEventMutex != NULL ) )\r
        {\r
 \r
        if( ( ulInterruptNumber < portMAX_INTERRUPTS ) && ( pvInterruptEventMutex != NULL ) )\r
        {\r

-               /* Yield interrupts are processed even when critical nesting is\r
-               non-zero. */\r

                WaitForSingleObject( pvInterruptEventMutex, INFINITE );\r
                ulPendingInterrupts |= ( 1 << ulInterruptNumber );\r
 \r
                /* The simulated interrupt is now held pending, but don't actually\r
                process it yet if this call is within a critical section.  It is\r
                possible for this to be in a critical section as calls to wait for\r
                WaitForSingleObject( pvInterruptEventMutex, INFINITE );\r
                ulPendingInterrupts |= ( 1 << ulInterruptNumber );\r
 \r
                /* The simulated interrupt is now held pending, but don't actually\r
                process it yet if this call is within a critical section.  It is\r
                possible for this to be in a critical section as calls to wait for\r

-               mutexes are accumulative. */\r
+               mutexes are accumulative.  If in a critical section then the event\r
+               will get set when the critical section nesting count is wound back\r
+               down to zero. */\r

                if( ulCriticalNesting == portNO_CRITICAL_NESTING )\r
                {\r
                        SetEvent( pvInterruptEvent );\r
 \r
                if( ulCriticalNesting == portNO_CRITICAL_NESTING )\r
                {\r
                        SetEvent( pvInterruptEvent );\r
 \r

-                       if( ulInterruptNumber == portINTERRUPT_YIELD )\r
-                       {\r
-                               /* Going to wait for an event - make sure the event is not already\r
-                               signaled. */\r
-                               ResetEvent( pxThreadState->pvYieldEvent );\r
-                       }\r
+                       /* Going to wait for an event - make sure the event is not already\r
+                       signaled. */\r
+                       ResetEvent( pxThreadState->pvYieldEvent );\r

                }\r
 \r
                ReleaseMutex( pvInterruptEventMutex );\r
                }\r
 \r
                ReleaseMutex( pvInterruptEventMutex );\r

-\r

                if( ulCriticalNesting == portNO_CRITICAL_NESTING )\r
                {\r
                if( ulCriticalNesting == portNO_CRITICAL_NESTING )\r
                {\r

-                       if( ulInterruptNumber == portINTERRUPT_YIELD )\r
-                       {\r
-                               /* The task was yielding so will be suspended however the\r
-                               SuspendThread() function is asynchronous so this event is used to\r
-                               prevent the task executing further if SuspendThread() does not take\r
-                               effect immediately. */\r
-                               WaitForSingleObject( pxThreadState->pvYieldEvent, INFINITE );\r
-                       }\r
+                       /* An interrupt was pended so ensure to block to alow it to\r
+                       execute.  In most cases the (simulated) interrupt will have\r
+                       executed before the next line is reached - so this is just to make\r
+                       sure. */\r
+                       WaitForSingleObject( pxThreadState->pvYieldEvent, INFINITE );\r

                }\r
        }\r
 }\r
                }\r
        }\r
 }\r


@@ -626,10 +651,12 @@ int32_t lMutexNeedsReleasing, lWaitForYield = pdFALSE;
 \r
        if( ulCriticalNesting > portNO_CRITICAL_NESTING )\r
        {\r
 \r
        if( ulCriticalNesting > portNO_CRITICAL_NESTING )\r
        {\r

-               if( ulCriticalNesting == ( portNO_CRITICAL_NESTING + 1 ) )\r
-               {\r
-                       ulCriticalNesting--;\r
+               ulCriticalNesting--;\r

 \r
 \r

+               /* Don't need to wait for any pending interrupts to execute if the\r
+               critical section was exited from inside an interrupt. */\r
+               if( ( ulCriticalNesting == portNO_CRITICAL_NESTING ) && ( xInsideInterrupt == pdFALSE ) )\r
+               {\r

                        /* Were any interrupts set to pending while interrupts were\r
                        (simulated) disabled? */\r
                        if( ulPendingInterrupts != 0UL )\r
                        /* Were any interrupts set to pending while interrupts were\r
                        (simulated) disabled? */\r
                        if( ulPendingInterrupts != 0UL )\r


@@ -637,37 +664,29 @@ int32_t lMutexNeedsReleasing, lWaitForYield = pdFALSE;
                                ThreadState_t *pxThreadState = ( ThreadState_t *) *( ( size_t * ) pxCurrentTCB );\r
 \r
                                configASSERT( xPortRunning );\r
                                ThreadState_t *pxThreadState = ( ThreadState_t *) *( ( size_t * ) pxCurrentTCB );\r
 \r
                                configASSERT( xPortRunning );\r

-                               SetEvent( pvInterruptEvent );\r

 \r
 \r

-                               if( ( ulPendingInterrupts & ( 1 << portINTERRUPT_YIELD ) ) != 0 )\r
-                               {\r
-                                       /* Going to wait for an event - make sure the event is not already\r
-                                       signaled. */\r
-                                       ResetEvent( pxThreadState->pvYieldEvent );\r
-                                       lWaitForYield = pdTRUE;\r
-                               }\r
+                               /* The interrupt won't actually executed until\r
+                               pvInterruptEventMutex is released as it waits on both\r
+                               pvInterruptEventMutex and pvInterruptEvent.\r
+                               pvInterruptEvent is only set when the simulated\r
+                               interrupt is pendeded if the interrupt is pended\r
+                               from outside a critical section - hence it is set\r
+                               here. */\r
+                               SetEvent( pvInterruptEvent );\r
+                               /* The calling task is going to wait for an event to ensure the\r
+                               interrupt that is pending executes immediately after the\r
+                               critical section is exited - so make sure the event is not\r
+                               already signaled. */\r
+                               ResetEvent( pxThreadState->pvYieldEvent );\r
+                               lWaitForYield = pdTRUE;\r

 \r
 \r

-                               /* Mutex will be released now, so does not require releasing\r
-                               on function exit. */\r
+                               /* Mutex will be released now so the (simulated) interrupt can\r
+                               execute, so does not require releasing on function exit. */\r

                                lMutexNeedsReleasing = pdFALSE;\r
                                ReleaseMutex( pvInterruptEventMutex );\r
                                lMutexNeedsReleasing = pdFALSE;\r
                                ReleaseMutex( pvInterruptEventMutex );\r

-\r
-                               if( lWaitForYield != pdFALSE )\r
-                               {\r
-                                       /* The task was yielding so will be suspended however the\r
-                                       SuspendThread() function is asynchronous so this event is\r
-                                       used to prevent the task executing further if\r
-                                       SuspendThread() does not take effect immediately. */\r
-                                       WaitForSingleObject( pxThreadState->pvYieldEvent, INFINITE );\r
-                               }\r
+                               WaitForSingleObject( pxThreadState->pvYieldEvent, INFINITE );\r

                        }\r
                }\r
                        }\r
                }\r

-               else\r
-               {\r
-                       /* Tick interrupts will still not be processed as the critical\r
-                       nesting depth will not be zero. */\r
-                       ulCriticalNesting--;\r
-               }\r

        }\r
 \r
        if( pvInterruptEventMutex != NULL )\r
        }\r
 \r
        if( pvInterruptEventMutex != NULL )\r