[Xenomai] Canonical way to differentiate between NPTL / Cobalt threads

[Xenomai] Canonical way to differentiate between NPTL / Cobalt threads

[Julien Blanc]

We're using a mix of regular NPTL posix threads and RT cobalt threads
in our application, using XDDP communication between them.

In a few places, we need to identify the calling context, ie, whether
we're being called from a cobalt RT thread or from a regular NPTL
thread, and act accordingly.

My understanding is that calling pthread_getschedparam and checking
that the returned policy is SCHED_FIFO does the job.

* is it correct ? Or are they some corner cases not covered by this
test ?
* is it the canonical way, or is there another one ? (maybe cheaper -
since this call will do two calls in case of a posix thread, there must
be a cheaper way to detect the running context).

Regards,

Julien

Re: [Xenomai] Canonical way to differentiate between NPTL / Cobalt threads

[Philippe Gerum]

On 03/28/2018 04:00 PM, Julien Blanc wrote:
> We're using a mix of regular NPTL posix threads and RT cobalt threads
> in our application, using XDDP communication between them.
> 
> In a few places, we need to identify the calling context, ie, whether
> we're being called from a cobalt RT thread or from a regular NPTL
> thread, and act accordingly.
> 
> My understanding is that calling pthread_getschedparam and checking
> that the returned policy is SCHED_FIFO does the job.
> 
> * is it correct ? Or are they some corner cases not covered by this
> test ?

A regular pthread undergoing the SCHED_FIFO policy would also match this
test, so this would work as long as SCHED_FIFO is exclusively used for
Cobalt threads.

> * is it the canonical way, or is there another one ? (maybe cheaper -
> since this call will do two calls in case of a posix thread, there must
> be a cheaper way to detect the running context).
> 
cobalt_thread_pid(pthread_t) from the internal support library would do
the job. A successful call would denote a cobalt thread, -ESRCH would
denote a regular (or invalid) pthread.

-- 
Philippe.

Re: [Xenomai] Canonical way to differentiate between NPTL / Cobalt threads

[Julien Blanc]

Le mercredi 28 mars 2018 à 16:16 +0200, Philippe Gerum a écrit :
> 
> cobalt_thread_pid(pthread_t) from the internal support library would
> do
> the job. A successful call would denote a cobalt thread, -ESRCH would
> denote a regular (or invalid) pthread.

Seems to work perfectly, thanks.

Regards,

Julien