From: rtel <rtel@1d2547de-c912-0410-9cb9-b8ca96c0e9e2>
Date: Tue, 4 Feb 2014 15:51:48 +0000 (+0000)
Subject: Second attempt: Improve how TimerDemo.c manages differences between the tick count... 
X-Git-Tag: V8.0.0~26
X-Git-Url: https://git.sur5r.net/?a=commitdiff_plain;h=3c7b4516d055189bd9923c205f878a1e511b4666;p=freertos

Second attempt: Improve how TimerDemo.c manages differences between the tick count and its own internal tick count, which can temporarily differ when the tick hook is called while the scheduler is suspended.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2192 1d2547de-c912-0410-9cb9-b8ca96c0e9e2
---

diff --git a/FreeRTOS/Demo/Common/Minimal/TimerDemo.c b/FreeRTOS/Demo/Common/Minimal/TimerDemo.c
index 27f5ed923..c4f2ba6bd 100644
--- a/FreeRTOS/Demo/Common/Minimal/TimerDemo.c
+++ b/FreeRTOS/Demo/Common/Minimal/TimerDemo.c
@@ -723,12 +723,26 @@ static portTickType uxTick = ( portTickType ) -1;
 	callback before their expiry time, but a margin is permissible for calling
 	their callback after their expiry time.  If exact timing is required then
 	configTIMER_TASK_PRIORITY must be set to ensure the timer service task
-	is the highest priority task in the system. */
+	is the highest priority task in the system.
+
+	This function is called from the tick hook.  The tick hook is called
+	even when the scheduler is suspended.  Therefore it is possible that the
+	uxTick count maintained in this function is temporarily ahead of the tick
+	count maintained by the kernel.  When this is the case a message posted from
+	this function will assume a time stamp in advance of the real time stamp,
+	which can result in a timer being processed before this function expects it
+	to.  For example, if the kernel's tick count was 100, and uxTick was 102,
+	then this function will not expect the timer to have expired until the
+	kernel's tick count is (102 + xBasePeriod), whereas in reality the timer
+	will expire when the kernel's tick count is (100 + xBasePeriod).  For this
+	reason xMargin is used as an allowable margin for premature timer expiries
+	as well as late timer expiries. */
 	const portTickType xMargin = 5;
 #else
 	const portTickType xMargin = 2;
 #endif
 
+
 	uxTick++;
 
 	if( uxTick == 0 )
@@ -761,7 +775,7 @@ static portTickType uxTick = ( portTickType ) -1;
 			}
 		}
 	}
-	else if( uxTick == xBasePeriod )
+	else if( uxTick == ( xBasePeriod - xMargin ) )
 	{
 		/* Neither timer should have expired yet. */
 		if( ( ucISRAutoReloadTimerCounter != 0 ) || ( ucISROneShotTimerCounter != 0 ) )
@@ -780,7 +794,7 @@ static portTickType uxTick = ( portTickType ) -1;
 			configASSERT( xTestStatus );
 		}
 	}
-	else if( uxTick == ( 2 * xBasePeriod ) )
+	else if( uxTick == ( ( 2 * xBasePeriod ) - xMargin ) )
 	{
 		/* The auto reload timer will still be active, but the one shot timer
 		should now have stopped - however, at this time neither of the timers
@@ -851,7 +865,7 @@ static portTickType uxTick = ( portTickType ) -1;
 		a few ticks ago. */
 		xTimerStopFromISR( xISRAutoReloadTimer, NULL );
 	}	
-	else if( uxTick == ( 4 * xBasePeriod ) )
+	else if( uxTick == ( 4 * ( xBasePeriod - xMargin ) ) )
 	{
 		/* The auto reload timer is now stopped, and the one shot timer is
 		active, but at this time neither timer should have expired since the
@@ -885,7 +899,7 @@ static portTickType uxTick = ( portTickType ) -1;
 			configASSERT( xTestStatus );
 		}
 	}	
-	else if( uxTick == ( ( 8 * xBasePeriod ) + xMargin ) )
+	else if( uxTick == ( 8 * xBasePeriod ) )
 	{
 		/* The auto reload timer is now stopped, and the one shot timer has
 		already expired and then stopped itself.  Both callback counters should
@@ -905,7 +919,7 @@ static portTickType uxTick = ( portTickType ) -1;
 		/* Now reset the one shot timer. */
 		xTimerResetFromISR( xISROneShotTimer, NULL );
 	}	
-	else if( uxTick == ( 9 * xBasePeriod ) )
+	else if( uxTick == ( ( 9 * xBasePeriod ) - xMargin ) )
 	{
 		/* Only the one shot timer should be running, but it should not have
 		expired since the last test.  Check the callback counters have not
@@ -924,7 +938,7 @@ static portTickType uxTick = ( portTickType ) -1;
 		
 		xTimerResetFromISR( xISROneShotTimer, NULL );
 	}	
-	else if( uxTick == ( 10 * xBasePeriod ) )
+	else if( uxTick == ( ( 10 * xBasePeriod ) - ( 2 * xMargin ) ) )
 	{
 		/* Only the one shot timer should be running, but it should not have
 		expired since the last test.  Check the callback counters have not
@@ -943,7 +957,7 @@ static portTickType uxTick = ( portTickType ) -1;
 		
 		xTimerResetFromISR( xISROneShotTimer, NULL );
 	}
-	else if( uxTick == ( 11 * xBasePeriod ) )
+	else if( uxTick == ( ( 11 * xBasePeriod ) - ( 3 * xMargin ) ) )
 	{
 		/* Only the one shot timer should be running, but it should not have
 		expired since the last test.  Check the callback counters have not
@@ -962,7 +976,7 @@ static portTickType uxTick = ( portTickType ) -1;
 		
 		xTimerResetFromISR( xISROneShotTimer, NULL );
 	}	
-	else if( uxTick == ( ( 12 * xBasePeriod ) + xMargin ) )
+	else if( uxTick == ( ( 12 * xBasePeriod ) - ( 2 * xMargin ) ) )
 	{
 		/* Only the one shot timer should have been running and this time it
 		should have	expired.  Check its callback count has been incremented.