RTEMS semaphores - binary or counting by default?

Joel Sherrill joel.sherrill at OARcorp.com
Thu Nov 20 14:21:03 UTC 2003


Rickard Westman wrote:

> Hi,
> 
> I think I've found an inconsistency between the implementation and
> documentation for RTEMS 4.6.0pre5, concerning the default attributes for
> semaphores.  According to the documentation ("RTEMS C User's Guide,
> Edition 4.6.0pre5"), semaphores are binary by default.  This does not
> seem to agree with the defines in attr.h, however, where we have:
> 
> #define RTEMS_DEFAULT_ATTRIBUTES  0x00000000
> (...)
> #define RTEMS_COUNTING_SEMAPHORE      0x00000000
> #define RTEMS_BINARY_SEMAPHORE        0x00000010
> #define RTEMS_SIMPLE_BINARY_SEMAPHORE 0x00000020
> 
> This means that if RTEMS_DEFAULT_ATTRIBUTES is used (or some attribute
> symbol other than the above) you get a counting semaphore instead of the
> expected binary one.
> 

You are correct.  The documentation is incorrect.  I checked the CVS
history for attr.h back to about 1995 and binary was never the default.
I filed it as PR521.

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
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