Add option to set the core affinity for the Timer Svc Task on SMP systems

[sudeep-mohanty]

Title

Make Timer Service Task core affinity configurable

Description

This PR introduces the configTIMER_SERVICE_TASK_CORE_AFFINITY config option which allows a user to set the core affinity of the Timer Service Task on SMP systems. The motivation to have this feature comes from requests such as this and this on the ESP-IDF repository. It would be nice if the FreeRTOS-Kernel can support this natively.

Test Steps

N.A

Checklist:

• I have tested my changes. No regression in existing tests.
• I have modified and/or added unit-tests to cover the code changes in this Pull Request.

Related Issue

None

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[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (1b2b090) 93.66% compared to head (8c1a99a) 93.66%.

Additional details and impacted files

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##             main     #805   +/-   ##
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  Coverage   93.66%   93.66%           
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  Files           6        6           
  Lines        2526     2526           
  Branches      604      604           
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  Hits         2366     2366           
  Misses        107      107           
  Partials       53       53           

Flag	Coverage Δ
unittests	93.66% <100.00%> (ø)

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Files	Coverage Δ
timers.c	98.77% <100.00%> (ø)

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[archigup]

Hey, thanks for the PR!

Could the #if ( configNUMBER_OF_CORES == 1 ) be moved inwards to just around the task create functions? Seems the rest of the logic in the blocks are the same.

[sudeep-mohanty]

Thanks for the review @archigup. Updated as suggested.

[chinglee-iot]

@sudeep-mohanty
Thank you for creating the feedback. The issue in your description indicates that timer task is pinned to core 0 and blocked by higher priority tasks on core 0. As a result, the application watchdog callback can not be called within timeout. The alternative solution also suggests that allowing tasks to run on any core could be a better solution, which is the current setting for timer task. Therefore, this should not be an issue in FreeRTOS SMP.

On the other hand, user can consider to create another task with core affinity to serve application specific requirement instead of changing the affinity of timer task cause it may have effect on software timer service.

[sudeep-mohanty]

Thanks for the feedback @chinglee-iot. The idea here is to give users the flexibility of either pinning the timer task to a core or letting it run unpinned. Ofcourse, all issues with a lower priority task getting blocked by a higher priority task remain even on an SMP system irrespective of the task's core affinity, so IMO this PR shouldn't cause change to how the timer task runs in practice. A counter argument could be to let the timer task run on a separate core uninterrupted for a potentially more responsive timer service which is not possible today.

[sonarcloud]

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