doc: kernel: document general policy for Zephyr without threads #29338
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| * Non-sleeping delays e.g. :c:func:`k_busy_wait` | ||
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| * The system clock including :c:func:`k_uptime_get` |
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I think it would be worthwhile mentioning SYS_CLOCK_EXISTS here, because when no MT is often combined with no system clock
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OK, I'll have to look at that. Looks like SYS_CLOCK_EXISTS=n means nothing related to ticks is supported, including k_uptime_get(). So the only way to detect passage of time is k_cycle_get_32().
I guess this one goes too. The value of this feature to me is diminishing rapidly....
| * Applications that select :option:`CONFIG_UART_INTERRUPT_DRIVEN` may | ||
| work, depending on driver implementation. | ||
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| * Applications that select :option:`CONFIG_UART_ASYNC_API` may |
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I am not sure about this one. I always thought this actually required at least k_timer:
https://github.com/zephyrproject-rtos/zephyr/blob/master/drivers/serial/uart_nrfx_uarte.c#L830
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That's unfortunate. I wouldn't expect other SoC's to have that problem. I suppose we don't support that API, then.
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@nashif @andyross @andrewboie this addresses the documentation of the scope of |
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I've tweaked the text a little, and added more structure. I've also explicitly noted the requirement that Note that all this is preliminary, intended to capture high level requirements before reviewing the code to determine what can actually be supported based on existing use and target-specific capabilities. |
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| Subsystem Behavior Without Thread Support | ||
| ***************************************** | ||
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| The seconds below list driver and functional subsystems that are |
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s/seconds/sections/
| Functionality that will not work with :option:`CONFIG_MULTITHREADING` | ||
| includes but is not limited to: | ||
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| * :c:func:`k_sleep()` and any other API that causes a thread to |
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We should consider being explicit here, just like we are explicit above.
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Better would be to make progress on #18970 so we can just say "Any api that sleeps except if using the no-wait path".
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I'm not sure if the direction given was to list all API that meets the "sleeps" criteria (which I can't do until #18970 progresses to the point where we've identified that API), or to just refine the text to match what I said. So I did the latter.
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This provides the documentation of scope required as a stage towards removing deprecation for CONFIG_MULTITHREADING=n. The specific lists of what does work will follow as the code base is inspected and updated. Signed-off-by: Peter Bigot <[email protected]>
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This pull request has been marked as stale because it has been open (more than) 60 days with no activity. Remove the stale label or add a comment saying that you would like to have the label removed otherwise this pull request will automatically be closed in 14 days. Note, that you can always re-open a closed pull request at any time. |
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@pabigot if you are ok with that I would like to pick up this work and reopen PR as i would like to de-deprecate no multithreading support. |
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@nordic-krch it's yours. |
This provides the documentation of scope required as a stage towards removing deprecation for CONFIG_MULTITHREADING=n. The specific lists of what does work will follow as the code base is inspected and updated.
Addresses a gating item in #27415.