Re: [Xenomai-help] Xenomai 2.0.1 - Posix Skin - implementing a periodic thread

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Paolo Gai wrote:
 > Dear all,
 > 
 > here is another small demo... this time of a periodic thread in POSIX.
 > 
 > It works under Xenomai, but it fails under Posix Real-Time.
 > 
 > The reason of the failure is the SIGUSR1 not being blocked by the main 
 > thread. If in main() the comments below the note "// REMOVE THE COMMENTS 
 > BELOW" are removed, then the signal is masked also in the main(), and as 
 > a result the POSIX version works.
 > 
 > The question I have is if the behavior in Xenomai (that is, not failing 
 > like the POSIX counterpart) is correct or not...

The answer is in section 2.4.2 of the standard, delivery of real-time
signals.

http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html#tag_02_04_02

real-time signals are marked pending to the process, not a particular
thread. So, Linux implementation is correct, Xenomai is incorrect.

When creating a timer with timer_create, Xenomai assume that signals
will be delivered to the thread which created the thread.

Linux supports an extension which allows timer notifications to be
delivered to a particular thread; set the sigev_notify member of the
sigevent structure to 
SIGEV_SIGNAL | SIGEV_THREAD_ID
and set the member _sigev_un._tid to the thread ID of the target thread.

-- 


					    Gilles Chanteperdrix.