Perhaps the current definition of a semaphore in
sem_overview.7 could be clearer.
A semaphore is an integer whose value is never allowed
to fall below zero.
What about the definition from the book [1]_ in the
section (2.2.5 Semaphores)?
[...] an integer variable to count the number of wakeups
saved for future use.
It is simple enough to be easy to understand. Kind of
self-explanatory.
Also, the whole "semaphore description" paragraph could be
rewritten. A proposal as an example:
Semaphore is a counter of its pending wakeups. A call to
sem_wait() consumes one wakeup (decrements counter). If
there is no wakeup to be consumed (counter equals zero)
sem_wait() blocks. sem_post() adds one wakeup (increments
counter).
or something like:
A semaphore is represented by an integer that stores the
number of semaphore's pending wakeups (i.e., the number
of calls to sem_wait() that won't block). [...]
Maybe I'm talking bullshit, but at least it's worth to
check it out.
.. [1] Operating systems: design and implementation; 1997;
Andrew S. Tanenbaum, Albert S. Woodhull; 2nd ed.
Cheers!
pasquali
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