Xenomai - VxWorks Emulator - Implementation of taskWait()

MONTET Julien julien.montet at reseau.eseo.fr
Mon May 31 09:11:55 CEST 2021


Hello Philippe,

Thank you for your answer and all of your explainations !

I understand now the next steps I need to follow.

Regards,

Julien
________________________________
De : Philippe Gerum <rpm at xenomai.org>
Envoyé : dimanche 30 mai 2021 10:00
À : MONTET Julien <julien.montet at reseau.eseo.fr>
Cc : xenomai at xenomai.org <xenomai at xenomai.org>
Objet : Re: Xenomai - VxWorks Emulator - Implementation of taskWait()


MONTET Julien via Xenomai <xenomai at xenomai.org> writes:

> Hi the developers,
>
> I already succeeded to use Xenomai with API/libraires such as Alchemy and Posix.
> My goal is now to use the VxWorks API.
> I don't have any issue to include path/librairies but I am trying to use the function "taskWait" (used by VxWorks) that is not present in Xenomai-VxWorks.
> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.windriver.com%2Ffr-FR%2Fbundle%2Fvxworks_7_application_core_os_sr0630-enus%2Fpage%2FCORE%2FtaskLib.html%23taskWait&data=04%7C01%7Cjulien.montet%40reseau.eseo.fr%7Cf85369ae235840b9093a08d9234113bb%7C4d7ad1591265437ab9f62946247d5bf9%7C0%7C0%7C637579584692348260%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=12Vr5F7HQUaNjI2PUH%2FjGiVmLCQDCTuJgjnrzvQ370o%3D&reserved=0
> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fxenomai.org%2Fdocumentation%2Fxenomai-3%2Fhtml%2Fxeno3prm%2Finclude_2vxworks_2taskLib_8h_source.html&data=04%7C01%7Cjulien.montet%40reseau.eseo.fr%7Cf85369ae235840b9093a08d9234113bb%7C4d7ad1591265437ab9f62946247d5bf9%7C0%7C0%7C637579584692358215%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=om%2B3dyMdJMqMt%2FsrXdtBCXARoa7dPIkd0TWLx3hmVwI%3D&reserved=0
>
> I don't really know if this function is obvious or if a similar code could run on Xenomai.

taskWait() is roughly equivalent to pthread_join() with WAIT_FOREVER as
a timeout. Dealing with a valid timeout would be tricky though, since
POSIX does not provide support for this, neither does libcobalt for this
reason.

[Cobalt core]     <- kernel, implements syscalls from libcobalt.so
    ^
[libcobalt]       <- POSIX API (lib/cobalt)
    ^
[libcopperplate]  <- building blocks for non-POSIX APIs (common RTOS API patterns)
    ^
[VxWorks]         <- VxWorks emulation

There is no provision for join-with-timeout in either libcopperplate or
libcobalt at the moment. If your *libc is recent enough, you could
implement pthread_tryjoin() in libcobalt (lib/cobalt/thread.c) as a
variation of the existing pthread_join(), which would use the native
pthread_tryjoin(3) instead of pthread_join(3) to have the caller wait
for the thread to exit, finalizing the operation by a call to
cobalt_thread_join().

> Could you advise a way to implement something that looks like taskWait ?
> Could rt_task_wait_period<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fxenomai.org%2Fdocumentation%2Fxenomai-3%2Fhtml%2Fxeno3prm%2Fgroup__alchemy__task.html%23ga1645d3a072ef3cefeed3bcbb27dcf108&data=04%7C01%7Cjulien.montet%40reseau.eseo.fr%7Cf85369ae235840b9093a08d9234113bb%7C4d7ad1591265437ab9f62946247d5bf9%7C0%7C0%7C637579584692358215%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=BZNXcdami%2BxdXZ5kpOuSGA4jQlVwu6CxKIXPjNsVz30%3D&reserved=0> from Alchemy (task.h) be an interesting solution ?
>

No, this is not related. rt_task_wait_period() waits for the next wakeup
in a periodic timeline started by rt_task_set_periodic().

--
Philippe.


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