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Fix support for stepping maximum number of ticks

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This commit fixes support for tickless implementations that call
vTaskStepTick() with the maximum number of allowed ticks to step.

vTaskStepTick()
---------------
Function vTaskStepTick() provides a way for the tickless idle
implementation to account for ticks that elapse during tickless idle.
The maximum number of stepped ticks allowed is the number passed to
portSUPPRESS_TICKS_AND_SLEEP().  It is the number of ticks between
xTickCount and xNextTaskUnblockTime.

vTaskStepTick() is specifically intended for use with tickless idle,
so it always executes with the scheduler disabled.  For reference,
compare it with the more general function xTaskCatchUpTicks().

Without this Change
-------------------
Prior to this commit, if a task is supposed to wake at xTickCount ==
0xFFFFFFFF, then when tickless idle ends, function vTaskStepTick()
sets the tick to 0xFFFFFFFF but the task remains on the delayed list
because xTaskIncrementTick() does not execute.  One tick later,
xTaskIncrementTick() executes because it's time to increment xTickCount
to 0x00000000.  An assertion failure occurs in
taskSWITCH_DELAYED_LISTS() because the delayed task list is not
empty.  Other examples of valling vTaskStepTick() with the maximum
allowed number of ticks merely result in a task waking one tick late.

Default Tickless Implementations
--------------------------------
Note that the default tickless implementations never pass the maximum
allowed value to vTaskStepTick().  The default implementations use the
tick interrupt to finish the sleep and allow that one tick to be
counted normally via the tick ISR and xTaskIncrementTick().
This commit is contained in:
Jeff Tenney 2020-06-09 16:45:27 -07:00
parent 6199b72fbf
commit 3bcdee89c6
2 changed files with 15 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

2
include/task.h
View file

@ -2822,7 +2822,7 @@ void vTaskSetTaskNumber( TaskHandle_t xTask, const UBaseType_t uxHandle ) PRIVIL
* to date with the actual execution time by being skipped forward by a time
* equal to the idle period.
*/
void vTaskStepTick( const TickType_t xTicksToJump ) PRIVILEGED_FUNCTION;
void vTaskStepTick( TickType_t xTicksToJump ) PRIVILEGED_FUNCTION;
/*
* Only available when configUSE_TICKLESS_IDLE is set to 1.

15
tasks.c
View file

@ -2599,12 +2599,25 @@ implementations require configUSE_TICKLESS_IDLE to be set to a value other than
1. */
#if ( configUSE_TICKLESS_IDLE != 0 )
void vTaskStepTick( const TickType_t xTicksToJump )
void vTaskStepTick( TickType_t xTicksToJump )
{
/* Correct the tick count value after a period during which the tick
was suppressed. Note this does *not* call the tick hook function for
each stepped tick. */
configASSERT( ( xTickCount + xTicksToJump ) <= xNextTaskUnblockTime );
if( ( xTickCount + xTicksToJump ) == xNextTaskUnblockTime )
{
/* Arrange for xTickCount to reach xNextTaskUnblockTime in
xTaskIncrementTick() when the scheduler resumes. This ensures that
any delayed tasks are resumed at the correct time. */
configASSERT( uxSchedulerSuspended );
configASSERT( xTicksToJump != 0 );
taskENTER_CRITICAL();
xPendedTicks++;
taskEXIT_CRITICAL();
xTicksToJump--;
}
xTickCount += xTicksToJump;
traceINCREASE_TICK_COUNT( xTicksToJump );
}