Add support for FreeRTOS task notification arrays (IDFGH-7819)

[andrewteta]

The ESP-IDF FreeRTOS configuration does not support direct to task notifications at notification index > 0. This seems to only be a limitation of the FreeRTOSConfig.h file, which sets #define configTASK_NOTIFICATION_ARRAY_ENTRIES 1.

A clear and concise description of what you want to happen.
I think the cleanest solution would be to add a menuconfig option for FREERTOS_TASK_NOTIFICATION_ARRAY_ENTRIES to configure this value at compile time.

I changed the value in ~/esp/esp-idf/components/freertos/include/esp_additions/freertos/FreeRTOSConfig.h from 1 to 32 with no apparent issues.

[0xjakob]

@andrewteta I agree, this could be made configurable.

Please keep in mind, though, that according to the documentation in task.h, each notification value is 32 bits long. This means that in your case, you'll add 31 * 4 bytes * number of tasks in your system. You will fill up 1KB of memory with less than 10 FreeRTOS tasks, including the system tasks (esp_timer, esp_event, etc.).

[andrewteta]

Thanks for reminding me of that. I think depending on the application, though the low overhead of direct-to-task notifications could outweigh some of the other IPC mechanisms (queue, for example). With memory consumption in mind, for example, I could get away with only 3 or 4 notifications, so it should be configurable to any value (1-32). I would like to add the feature myself, but I don't really know where to start with the menuconfig build system. I've been digging into the workings of esp-idf for a long time now, though so with some guidance I could probably make a pull request. Thanks for getting back to me!

[0xjakob]

@andrewteta I think just making the option configurable should work like this: Instead of defining it to 1, you just set it to a Kconfig option, similar to the tick hook configuration in the same file you mentioned above:

#define configUSE_TICK_HOOK                             CONFIG_FREERTOS_USE_TICK_HOOK

Then you add the Kconfig option to the FreeRTOS Kconfig file, but without the CONFIG_ prefix.

The probably more difficult part is adding a unit test. If we support this option, we want to have a test that checks if increasing the size of the task notification array actually works at runtime. There might be some edge cases, too.

Anyways, a Pull Request will always be welcome. Once you submit it, just be prepared that we add additional unit tests if you haven't provided them yourself. This might take a while since it'll be holiday season soon, so fewer colleagues will be available to review and process PRs.

[TobiasUhmannVoss]

Has this been implemented? In my app I am using ESP-IDF 5.0.3 but I cannot see such an option in the config and I get a failed assertion assert failed: ulTaskGenericNotifyTake tasks.c:5533 (uxIndexToWait < 1) when trying to notify at index 1.

[0xjakob]

@TobiasUhmannVoss This feature is only available from IDF version v5.1. New features are usually not backported to older releases (see our Support Periods documentation for more information). Is it possible for you to update to that version?

[TobiasUhmannVoss]

@0xjakob Thanks for the info! Until recently, I couldn't use IDF 5.1 due to some compilation problem with the new gcc and my TensorFlow Lite component but I solved my problem using an event group instead of task notifications already.