Description
Before this change each task had a single direct to task notification value and state as described here: https://www.FreeRTOS.org/RTOS-task-notifications.html. After this change each task has an array of task notifications, so more than one task notification value and state per task. The new FreeRTOSConfig.h compile time constant configTASK_NOTIFICATION_ARRAY_ENTRIES sets the number of indexes in the array.
Each notification within the array operates independently - a task can only block on one notification within the array at a time and will not be unblocked by a notification sent to any other array index.
Task notifications were introduced as a light weight method for peripheral drivers to pass data and events to tasks without the need for an intermediary object such as a semaphore - for example, to unblock a task from an ISR when the operation of a peripheral completed. That use case only requires a single notification value. Their popularity and resultant expanded use cases have since made the single value a limitation - especially as FreeRTOS stream and message buffers themselves use the notification mechanism. This change resolves that limitation. Stream and message buffers still use the task notification at array index 0, but now application writers can avoid any conflict that might have with their own use of task notifications by using notifications at array indexes other than 0.
The pre-existing task notification API functions work in a backward compatible way by always using the task notification at array index 0. For each such function there is now an equivalent that is postfixed "Indexed" and takes an additional parameter to specify which index within the array it should operate upon. For example, xTaskNotify() is the original that only operates on array index 0. xTaskNotifyIndexed() is the new function that can operate on any array index.
Test Steps
The update is tested using the Win32 demo (PR to be created in the FreeRTOS/FreeRTOS github repo), which has been updated to build and run a new test file FreeRTOS/Demo/Common/Minimal/TaskNotifyArray.c. The tests in that file are in addition to, not a replacement for those in FreeRTOS/Demo/Common/Minimal/TaskNotify.c.
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Move the prototype and documentation for xTaskCatchUpTicks() into the correct place in the task.h header file (in the public documentation from the private documentation).
Rename the variable that holds the return value in xTaskCatchUpTicks() to more accurately represent its meaning.
An error on trace argument.
In "xTaskPriorityDisinherit", the disinherit priority should be "pxTCB->uxBasePriority".
And, in "vTaskPriorityDisinheritAfterTimeout", the disinherit priority should be "uxPriorityToUse", which might not be "pxTCB->uxBasePriority".
+ The idle task decides to enter sleep mode on the following line.
```
if( xExpectedIdleTime >= configEXPECTED_IDLE_TIME_BEFORE_SLEEP )
```
+ The scheduler is suspended, preventing any context switches.
[Potentially a tick interrupt could occur here. That could happen if other tasks executing consumed a lot of time since the above code line executed. If a tick interrupt occurs here the interrupt will be entered but the interrupt will not do anything other than increment xPendedTicks.]
+ The expected idle time is checked again. No context switches can occur now so the code will execute until the scheduler is unsuspended. Assuming configEXPECTED_IDLE_TIME_BEFORE_SLEEP is set to a sensible value, a tick interrupt won't occur for some time.
+ portSUPPRESS_TICKS_AND_SLEEP() is called.
+ The default implementation of the tickless function calls eTaskConfirmSleep() - which prior to this change does not return eAbortSleep even though xPendedTicks is not 0, and after this change does return eAbortSleep.
