rt_sleep() forever

Paolo Mantegazza mantegazza at aero.polimi.it
Fri Jun 9 10:49:34 CEST 2006

Malte Witt wrote:
> Hi,
> I am experiencing a problem with rt_sleep. I have a C++ project. I have a 
> couple of soft realtime threads and one hard realtime thread. One of the 
> soft realtime threads is writing some data into a piece of hardware which 
> is not time critcal BUT there is a minimum delay between the accesses. So 
> between the steps of the sequence I am using rt_sleep(nano2count(nanos)); 
> to ensure this minimum delay. Thread is initialized, memory is locked, 
> oneshot mode is set and timer is started.
> The problem now is: occasionally rt_sleep does not return after the given 
> period, but sleeps forever. Did anybody experience this before?
> I am using:
> - RTAI 3.3 (but not most current release I guess)
> - Kernel
> - All of the above is done in userspace using LXRT

As usual: can you reproduce it with a simple example?

As an alternative try to see what happens if your make you time hard 
real time and let the scheduler switch it back/forth soft when Linux is 


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